App Inventor will change to appinventorbeta.com

As a result of the recent changes to Google Labs and App Inventor, effective immediately, the URL for App Inventor will change from appinventor.googlelabs.com to appinventorbeta.com. This URL change WILL NOT have an impact on your projects stored in App Inventor. All data that you see in your appinventor.googlelabs.com account, as well as documentation and email forums will be available at appinventorbeta.com.




As Google announced on the App Inventor Announcement Forum, Google will end support for App Inventor and open source the code base at the end of this year. Additionally, in order to ensure the future success of App Inventor, Google has funded the establishment of aCenter for Mobile Learning at the MIT Media Lab, where MIT will be actively engaged in studying and extending App Inventor. This transition will happen at the end of 2011. At that time you will need to download your data from appinventorbeta.com in order to continue working with it in the open source instance of App Inventor. In the coming months we will send you detailed instructions on how to download your data.

path.addArc()

package com.exercise.AndroidDraw;



import android.app.Activity;

import android.content.Context;

import android.graphics.Canvas;

import android.graphics.Color;

import android.graphics.Paint;

import android.graphics.Path;

import android.graphics.RectF;

import android.os.Bundle;

import android.view.View;



public class AndroidDrawActivity extends Activity {



	/** Called when the activity is first created. */

    @Override

    public void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        setContentView(new MyView(this));

    }

    

    public class MyView extends View {



		public MyView(Context context) {

			super(context);

			// TODO Auto-generated constructor stub

		}



		@Override

		protected void onDraw(Canvas canvas) {

			// TODO Auto-generated method stub

			super.onDraw(canvas);



			

			float width = (float)getWidth();

			float height = (float)getHeight();

			float radius;

			

			if (width > height){

				radius = height/4;

			}else{

				radius = width/4;

			}



			Paint paint = new Paint();

			paint.setColor(Color.WHITE);

			paint.setStrokeWidth(5);	

			paint.setStyle(Paint.Style.STROKE);

			

			Path path = new Path();



			float center_x, center_y;

			center_x = width/4;

			center_y = height/4;

			final RectF oval = new RectF();

			oval.set(center_x - radius, 

					center_y - radius, 

					center_x + radius, 

					center_y + radius);

			path.addArc(oval, 0, 90);

			

			

			center_x = width/2;

			center_y = height/2;

			oval.set(center_x - radius, 

					center_y - radius, 

					center_x + radius, 

					center_y + radius);

			path.addArc(oval, -90, 180);

			

			center_x = width * 3/4;

			center_y = height * 3/4;

			oval.set(center_x - radius, 

					center_y - radius, 

					center_x + radius, 

					center_y + radius);

			path.addArc(oval, 0, 360);

			

			canvas.drawPath(path, paint);

			

		}



	}

}

Free ebook: Programming Windows Phone 7, by Charles Petzold

This book is a gift from the Windows Phone 7 team at Microsoft to the programming community. Showing you the basics of writing applications for Windows Phone 7 using the C# programming language with the Silverlight and XNA 2D frameworks.

You can download a PDF here (38.6 MB).
And, as of August 1, 2011, you can now download an EPUB version here and a MOBI version here.

Source: Microsoft Press - Free ebook: Programming Windows Phone 7, by Charles Petzold

canvas.drawRoundRect()

package com.exercise.AndroidDraw;



import android.app.Activity;

import android.content.Context;

import android.graphics.Canvas;

import android.graphics.Color;

import android.graphics.Paint;

import android.graphics.Path;

import android.graphics.RectF;

import android.os.Bundle;

import android.view.View;



public class AndroidDrawActivity extends Activity {



	/** Called when the activity is first created. */

    @Override

    public void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        setContentView(new MyView(this));

    }

    

    public class MyView extends View {



		public MyView(Context context) {

			super(context);

			// TODO Auto-generated constructor stub

		}



		@Override

		protected void onDraw(Canvas canvas) {

			// TODO Auto-generated method stub

			super.onDraw(canvas);



			

			float width = (float)getWidth();

			float height = (float)getHeight();

			float radius;

			

			if (width > height){

				radius = height/4;

			}else{

				radius = width/4;

			}



			Paint paint = new Paint();

			paint.setColor(Color.WHITE);

			paint.setStrokeWidth(5);	



			paint.setStyle(Paint.Style.FILL);

			float center_x, center_y;

			center_x = width/4;

			center_y = height/4;

			final RectF rect = new RectF();

			rect.set(center_x - radius, 

					center_y - radius, 

					center_x + radius, 

					center_y + radius);

			canvas.drawRoundRect(rect, 50, 50, paint);

			

			paint.setStyle(Paint.Style.STROKE);

			center_x = width/2;

			center_y = height/2;

			rect.set(center_x - radius, 

					center_y - radius, 

					center_x + radius, 

					center_y + radius);

			canvas.drawRoundRect(rect, 100, 50, paint);

			

			paint.setStyle(Paint.Style.STROKE);

			center_x = width * 3/4;

			center_y = height * 3/4;

			rect.set(center_x - radius, 

					center_y - radius, 

					center_x + radius, 

					center_y + radius);

			canvas.drawRoundRect(rect, 100, 100, paint);

			

		}



	}

}

canvas.drawArc()

package com.exercise.AndroidDraw;



import android.app.Activity;

import android.content.Context;

import android.graphics.Canvas;

import android.graphics.Color;

import android.graphics.Paint;

import android.graphics.Path;

import android.graphics.RectF;

import android.os.Bundle;

import android.view.View;



public class AndroidDrawActivity extends Activity {



	/** Called when the activity is first created. */

    @Override

    public void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        setContentView(new MyView(this));

    }

    

    public class MyView extends View {



		public MyView(Context context) {

			super(context);

			// TODO Auto-generated constructor stub

		}



		@Override

		protected void onDraw(Canvas canvas) {

			// TODO Auto-generated method stub

			super.onDraw(canvas);



			

			float width = (float)getWidth();

			float height = (float)getHeight();

			float radius;

			

			if (width > height){

				radius = height/4;

			}else{

				radius = width/4;

			}

			

			Path path = new Path();

			path.addCircle(width/2, 

					height/2, radius, 

					Path.Direction.CW);

			

			Paint paint = new Paint();

			paint.setColor(Color.WHITE);

			paint.setStrokeWidth(5);	



			paint.setStyle(Paint.Style.FILL);

			float center_x, center_y;

			center_x = width/2;

			center_y = height/4;

			final RectF oval = new RectF();

			oval.set(center_x - radius, 

					center_y - radius, 

					center_x + radius, 

					center_y + radius);

			canvas.drawArc(oval, 90, 270, true, paint);

			

			paint.setStyle(Paint.Style.STROKE);

			center_x = width/2;

			center_y = height/2;

			oval.set(center_x - radius, 

					center_y - radius, 

					center_x + radius, 

					center_y + radius);

			canvas.drawArc(oval, 90, 270, true, paint);

			

			paint.setStyle(Paint.Style.STROKE);

			center_x = width/2;

			center_y = height * 3/4;

			oval.set(center_x - radius, 

					center_y - radius, 

					center_x + radius, 

					center_y + radius);

			canvas.drawArc(oval, 90, 270, false, paint);

			

		}



	}

}

Canvas.drawTextOnPath on circle path

package com.exercise.AndroidDraw;



import android.app.Activity;

import android.content.Context;

import android.graphics.Canvas;

import android.graphics.Color;

import android.graphics.Paint;

import android.graphics.Path;

import android.os.Bundle;

import android.view.View;



public class AndroidDrawActivity extends Activity {



	/** Called when the activity is first created. */

    @Override

    public void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        setContentView(new MyView(this));

    }

    

    public class MyView extends View {



		public MyView(Context context) {

			super(context);

			// TODO Auto-generated constructor stub

		}



		@Override

		protected void onDraw(Canvas canvas) {

			// TODO Auto-generated method stub

			super.onDraw(canvas);



			float width = (float)getWidth();

			float height = (float)getHeight();

			float radius;

			

			if (width > height){

				radius = height/4;

			}else{

				radius = width/4;

			}

			

			Path path = new Path();

			path.addCircle(width/2, 

					height/2, radius, 

					Path.Direction.CW);

			

			Paint paint = new Paint();

			paint.setColor(Color.WHITE);

			paint.setStrokeWidth(5);

			paint.setStyle(Paint.Style.STROKE);

			paint.setTextSize(37);

			

			canvas.drawTextOnPath(

					"Android-er http://android-er.blogspot.com/", 

					path, 0, 0, 

					paint);

			

			paint.setColor(Color.GREEN);

			paint.setStyle(Paint.Style.FILL);

			canvas.drawTextOnPath("Android-er http://android-er.blogspot.com/", 

					path, 0, 0, 

					paint);

		}

	}

}

drawPath() on Canvas

package com.exercise.AndroidDraw;



import android.app.Activity;

import android.content.Context;

import android.graphics.Canvas;

import android.graphics.Color;

import android.graphics.Paint;

import android.graphics.Path;

import android.os.Bundle;

import android.view.View;



public class AndroidDrawActivity extends Activity {



	/** Called when the activity is first created. */

  @Override

  public void onCreate(Bundle savedInstanceState) {

      super.onCreate(savedInstanceState);

      setContentView(new MyView(this));

  }



  public class MyView extends View {

  	

  	class Pt{

  		float x, y;

  		

  		Pt(float _x, float _y){

  			x = _x;

  			y = _y;

  		}

  	}

  	

  	Pt[] myPath = { new Pt(100, 100),

  					new Pt(200, 200),

  					new Pt(200, 500),

  					new Pt(400, 500),

  					new Pt(400, 200)

  					};



		public MyView(Context context) {

			super(context);

			// TODO Auto-generated constructor stub

		}



		@Override

		protected void onDraw(Canvas canvas) {

			// TODO Auto-generated method stub

			super.onDraw(canvas);



			

			Paint paint = new Paint();

			paint.setColor(Color.WHITE);

			paint.setStrokeWidth(3);

			paint.setStyle(Paint.Style.STROKE);

			Path path = new Path();

			

			path.moveTo(myPath[0].x, myPath[0].y);

			for (int i = 1; i < myPath.length; i++){

				path.lineTo(myPath[i].x, myPath[i].y);

			}

			canvas.drawPath(path, paint);

			

		}



	}

}

Example of drawing on View

package com.exercise.AndroidDraw;



import android.app.Activity;

import android.content.Context;

import android.graphics.Canvas;

import android.graphics.Color;

import android.graphics.Paint;

import android.os.Bundle;

import android.view.View;



public class AndroidDrawActivity extends Activity {



	/** Called when the activity is first created. */

  @Override

  public void onCreate(Bundle savedInstanceState) {

      super.onCreate(savedInstanceState);

      setContentView(new MyView(this));

  }



  public class MyView extends View {



		public MyView(Context context) {

			super(context);

			// TODO Auto-generated constructor stub

		}



		@Override

		protected void onDraw(Canvas canvas) {

			// TODO Auto-generated method stub

			super.onDraw(canvas);

			

			int width = getWidth();

			int height = getHeight();

			int radius;

			

			if (width > height){

				radius = height/2;

			}else{

				radius = width/2;

			}

			

			Paint paint = new Paint();

			paint.setStyle(Paint.Style.FILL);

			

			paint.setColor(Color.RED);

			canvas.drawPaint(paint);

			paint.setColor(Color.BLUE);

			canvas.drawCircle(width/2, height/2, radius, paint);

		}



	}

}

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The new release of Android 3 brings the full power of Android to tablet computing and this hands-on guide offers an introduction to developing tablet applications using this new Android release. Veteran author Wei-Meng Lee explains how Android 3 is specifically optimized for tablet computing and he details Android's tablet-specific functions. Beginning with the basics, this book moves at a steady pace to provide everything you need to know to begin successfully developing your own Android tablet applications.

• Serves as a full-color, hands-on introduction to developing tablet applications with the new Android 3
• Offers a helpful overview of Android 3 programming for tablets
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• Highlights ways to build the Android user interface for tablets, create location-based services, publish Android applications, use Eclipse for Android development, and employ the Android emulator

Beginning Android Tablet Application Development is an ideal starting point for getting started with using Android 3 to develop tablet applications.

From the Back Cover

A full-color introduction to Android tablet development

The new release of Android 3 brings the full power of Android to tablet computing! This hands-on guide offers first-time and new Android programmers a fast-paced introduction to developing tablet applications using the new Android release. Veteran author Wei-Meng Lee begins by explaining how to install the necessary tools and write the customary "hello world" application. He then quickly moves on to cover the various components of an Android tablet application. You'll quickly get up to speed with Android 3 as you build a selection of sample tablet projects that will help you to successfully develop your own Android tablet applications.

Beginning Android Tablet Application Development:

• Builds a versatile Android UI using fragments to dynamically populate activities

• Displays commonly used functions using Action Bar items

• Examines the Android user interface and helps you gain an understanding of the components of a screen

• Shows how to create location-based services applications

• Details how to build a location-monitoring application

• Helps you create a sample application and walks you through the steps of publishing your app on the Android market

• Discusses using Eclipse for Android development and using the Android simulator

Get file info

Example of getting file info, such as path, last modified Date Time.

package com.exercise.AndroidFile;



import java.io.File;

import java.util.Date;



import android.app.Activity;

import android.os.Bundle;

import android.widget.TextView;



public class AndroidFileActivity extends Activity {

	

    /** Called when the activity is first created. */

    @Override

    public void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        setContentView(R.layout.main);

        

        TextView info = (TextView)findViewById(R.id.info);

        

        File file = new File("/sdcard/test.txt");



        String AbsolutePath = file.getAbsolutePath();

        String Path = file.getPath();

        String Parent = file.getParent();

        String Name = file.getName();

        long lastModified = file.lastModified();

        Date lastModifiedDate = new Date(lastModified);

        

        info.setText(

        		"AbsolutePath: " + AbsolutePath + "\n" +

        		"Path: " + Path + "\n" +

        		"Parent: " + Parent + "\n" +

        		"Name: " + Name + "\n" +

        		"lastModified: " + lastModified + "\n" +

        		"lastModifiedDate: " + lastModifiedDate

        		);

        

    }

}

Set hint text of EditText

android:hint set hint text to display when the EditText is empty. The hint text will disappear once user enter any text.

<EditText 

    android:layout_width="fill_parent"

    android:layout_height="wrap_content"

    android:hint="Hint Text:" />

Return result to onActivityResult()

To return result to onActivityResult() of calling activity, we can use the method setResult().

main activity

package com.exercise.AndroidResult;



import android.app.Activity;

import android.content.Intent;

import android.os.Bundle;

import android.view.View;

import android.widget.Button;

import android.widget.TextView;



public class AndroidResultActivity extends Activity {

	

	final static int REQ_CODE = 1;

	

	TextView tvResultCode;

	

    /** Called when the activity is first created. */

    @Override

    public void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        setContentView(R.layout.main);

        

        tvResultCode = (TextView)findViewById(R.id.resultcode);

        

        Button btnStartActivity2 = (Button)findViewById(R.id.startactivity2);

        btnStartActivity2.setOnClickListener(new Button.OnClickListener(){



			@Override

			public void onClick(View arg0) {

				// TODO Auto-generated method stub

				Intent intent = new Intent(AndroidResultActivity.this, Activity2.class);

				startActivityForResult(intent, REQ_CODE);

			}});

    }



	@Override

	protected void onActivityResult(int requestCode, int resultCode, Intent data) {

		// TODO Auto-generated method stub

		if(requestCode == REQ_CODE){

			if (resultCode == RESULT_OK){

				tvResultCode.setText("RESULT_OK");

			}else if(resultCode == RESULT_CANCELED){

				tvResultCode.setText("RESULT_CANCELED");

			}

		}

	}

}

main.xml

<?xml version="1.0" encoding="utf-8"?>

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"

    android:orientation="vertical"

    android:layout_width="fill_parent"

    android:layout_height="fill_parent"

    >

<TextView  

    android:layout_width="fill_parent" 

    android:layout_height="wrap_content" 

    android:text="@string/hello"

    />

<Button

    android:id="@+id/startactivity2"

    android:layout_width="fill_parent" 

    android:layout_height="wrap_content" 

    android:text="Start Activity 2"

    />

<TextView

    android:id="@+id/resultcode"

    android:layout_width="fill_parent" 

    android:layout_height="wrap_content" 

    />

</LinearLayout>

Sub-activity

package com.exercise.AndroidResult;



import android.app.Activity;

import android.content.Intent;

import android.os.Bundle;

import android.view.View;

import android.widget.Button;



public class Activity2 extends Activity {



	@Override

	protected void onCreate(Bundle savedInstanceState) {

		// TODO Auto-generated method stub

		super.onCreate(savedInstanceState);

		setContentView(R.layout.main2);

		

		Button btnReturnOK = (Button)findViewById(R.id.returnOK);

		btnReturnOK.setOnClickListener(new Button.OnClickListener(){



			@Override

			public void onClick(View v) {

				// TODO Auto-generated method stub

				Intent i = new Intent();

				setResult(RESULT_OK, i);

				finish();

			}});

		

		Button btnReturnCancel = (Button)findViewById(R.id.returnCancel);

		btnReturnCancel.setOnClickListener(new Button.OnClickListener(){



			@Override

			public void onClick(View v) {

				// TODO Auto-generated method stub

				Intent i = new Intent();

				setResult(RESULT_CANCELED, i);

				finish();

			}});

		

	}



}

<?xml version="1.0" encoding="utf-8"?>

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"

    android:orientation="vertical"

    android:layout_width="fill_parent"

    android:layout_height="fill_parent"

    >

<TextView  

    android:layout_width="fill_parent" 

    android:layout_height="wrap_content" 

    android:text="@string/hello"

    />

<Button

    android:id="@+id/returnOK"

    android:layout_width="fill_parent" 

    android:layout_height="wrap_content" 

    android:text="return OK"

    />

<Button

    android:id="@+id/returnCancel"

    android:layout_width="fill_parent" 

    android:layout_height="wrap_content" 

    android:text="return Cancel"

    />

</LinearLayout>

More on the example of custom widget view

Modify onDraw() of MyWidgetView.java on last exercise to add more funny text on the custom widget view.

package com.exercise.AndroidWidgetView;



import android.content.Context;

import android.graphics.Canvas;

import android.graphics.Color;

import android.graphics.Paint;

import android.graphics.Path;

import android.graphics.RectF;

import android.util.AttributeSet;

import android.view.View;



public class MyWidgetView extends View {

	

	final int MIN_WIDTH = 300;

	final int MIN_HEIGHT = 150;

	final int DEFAULT_COLOR = Color.WHITE;

	int _color;

	

	final int STROKE_WIDTH = 2;



	public MyWidgetView(Context context) {

		super(context);

		// TODO Auto-generated constructor stub

		init();

	}



	public MyWidgetView(Context context, AttributeSet attrs) {

		super(context, attrs);

		// TODO Auto-generated constructor stub

		init();

	}



	public MyWidgetView(Context context, AttributeSet attrs, int defStyle) {

		super(context, attrs, defStyle);

		// TODO Auto-generated constructor stub

		init();

	}

	

	private void init(){

		setMinimumWidth(MIN_WIDTH);

		setMinimumHeight(MIN_HEIGHT);

		_color = DEFAULT_COLOR;

	}



	@Override

	protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {

		// TODO Auto-generated method stub

		super.onMeasure(getSuggestedMinimumWidth(), getSuggestedMinimumHeight());

	}



	@Override

	protected void onDraw(Canvas canvas) {

		// TODO Auto-generated method stub

		

		Paint paint = new Paint();

		paint.setColor(_color);

		paint.setStrokeWidth(STROKE_WIDTH);

		canvas.drawRect(5, 5, getWidth()-5, getHeight()-5, paint);

		

		Path path;

		path = new Path();

		paint.setColor(Color.GRAY);

		paint.setTextSize(25);

		path.addArc(new RectF(25, 25, getWidth()-25, getHeight()-25), 180, 90);

		canvas.drawTextOnPath("Hello", path, 0, 0, paint);

		path = new Path();

		path.addArc(new RectF(25, 25, getWidth()-25, getHeight()-25), 0, 90);

		canvas.drawTextOnPath("Android-er", path, 0, 0, paint);

	}

	

	public void setColor(int color){

		_color = color;

	}

	

}

A example of custom widget view

MyWidgetView.java, our custom widget view.

package com.exercise.AndroidWidgetView;



import android.content.Context;

import android.graphics.Canvas;

import android.graphics.Color;

import android.graphics.Paint;

import android.util.AttributeSet;

import android.view.View;



public class MyWidgetView extends View {

	

	final int MIN_WIDTH = 200;

	final int MIN_HEIGHT = 50;

	final int DEFAULT_COLOR = Color.WHITE;

	int _color;

	

	final int STROKE_WIDTH = 2;



	public MyWidgetView(Context context) {

		super(context);

		// TODO Auto-generated constructor stub

		init();

	}



	public MyWidgetView(Context context, AttributeSet attrs) {

		super(context, attrs);

		// TODO Auto-generated constructor stub

		init();

	}



	public MyWidgetView(Context context, AttributeSet attrs, int defStyle) {

		super(context, attrs, defStyle);

		// TODO Auto-generated constructor stub

		init();

	}

	

	private void init(){

		setMinimumWidth(MIN_WIDTH);

		setMinimumHeight(MIN_HEIGHT);

		_color = DEFAULT_COLOR;

	}



	@Override

	protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {

		// TODO Auto-generated method stub

		super.onMeasure(getSuggestedMinimumWidth(), getSuggestedMinimumHeight());

	}



	@Override

	protected void onDraw(Canvas canvas) {

		// TODO Auto-generated method stub

		

		Paint paint = new Paint();

		paint.setColor(_color);

		paint.setStrokeWidth(STROKE_WIDTH);

		canvas.drawRect(5, 5, getWidth()-5, getHeight()-5, paint);

	}

	

	public void setColor(int color){

		_color = color;

	}

	

}

main.xml, the layout with our custom widget view

<?xml version="1.0" encoding="utf-8"?>

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"

   android:orientation="vertical"

   android:layout_width="fill_parent"

   android:layout_height="fill_parent"

   >

<TextView 

   android:layout_width="fill_parent"

   android:layout_height="wrap_content"

   android:text="@string/hello"

   />

<com.exercise.AndroidWidgetView.MyWidgetView

	android:id = "@+id/mywidget_01"

   android:layout_width="fill_parent"

   android:layout_height="wrap_content"

   android:layout_margin="5dp"

   />

<com.exercise.AndroidWidgetView.MyWidgetView

	android:id = "@+id/mywidget_02"

   android:layout_width="50dp"

   android:layout_height= "50dp"

   android:layout_margin="5dp"

   />

<com.exercise.AndroidWidgetView.MyWidgetView

	android:id = "@+id/mywidget_03"

   android:layout_width="50dp"

   android:layout_height= "50dp"

   android:layout_margin="5dp"

   />

</LinearLayout>

main code

package com.exercise.AndroidWidgetView;



import android.app.Activity;

import android.graphics.Color;

import android.os.Bundle;



public class AndroidWidgetViewActivity extends Activity {

	

	MyWidgetView myWidget_01, myWidget_02, myWidget_03;

	

   /** Called when the activity is first created. */

   @Override

   public void onCreate(Bundle savedInstanceState) {

       super.onCreate(savedInstanceState);

       setContentView(R.layout.main);

      

       myWidget_01 = (MyWidgetView)findViewById(R.id.mywidget_01);

       myWidget_02 = (MyWidgetView)findViewById(R.id.mywidget_02);

       myWidget_03 = (MyWidgetView)findViewById(R.id.mywidget_03);

       myWidget_02.setColor(Color.RED);

       myWidget_03.setBackgroundColor(Color.GREEN);

       myWidget_03.setColor(Color.BLUE);

   }

}

next:
- More on the example of custom widget view

Google to Acquire Motorola Mobility

Supercharging Android: Google to Acquire Motorola Mobility

The acquisition of Motorola will increase competition by strengthening Google’s patent portfolio, which will enable Google to better protect Android from anti-competitive threats from Microsoft, Apple and other companies.

Source: Official Google Blog: Supercharging Android: Google to Acquire Motorola Mobility

Encodes characters in the given string as '%'-escaped octets using the UTF-8 scheme

The android.net.Uri class provide a method encode() to encode characters in the given string as '%'-escaped octets using the UTF-8 scheme. Leaves letters ("A-Z", "a-z"), numbers ("0-9"), and unreserved characters ("_-!.~'()*") intact. Encodes all other characters.

example:

        String src = "ABC def";

        String dest = Uri.encode(src);

It convert "ABC def" to "ABC%20def"

Pro Android Python with SL4A

Pro Android Python with SL4A is for programmers and hobbyists who want to write apps for Android devices without having to learn Java first. Paul Ferrill leads you from installing the Scripting Layer for Android (SL4A) to writing small scripts, to more complicated and interesting projects, and finally to uploading and packaging your programs to an Android device.

Android runs scripts in many scripting languages, but Python, Lua, and Beanshell are particularly popular. Most programmers know more than one programming language, so that they have the best tool for whatever task they want to accomplish. Pro Android Python with SL4A explores the world of Android scripting by introducing you to the most important open-source programming languages that are available on Android-based hardware.

Pro Android Python with SL4A starts by exploring the Android software development kit and then shows you how to set up an Eclipse-based Android development environment. You then approach the world of Android programming by using Beanshell, which runs on the Dalvik, and learning how to write small programs to administer an Android device.

Next, discover how Lua, a lightweight language perfectly suited for scripting on smaller devices, can work with Android. Lua can be used for small but important tasks, like SMS encryption and synchronizing photos with flickr.

Last, but certainly not least, you will discover the world of Python scripting for SL4A, and the power contained within the full range of Python modules that can combine with the Android SDK. You'll learn to write small location-aware apps to get you started, but by the end of this book, you'll find yourself writing fully GUI-fied applications running on the Android desktop!

Pro Android Python with SL4A is rounded out with a chapter on distributing and packaging scripts, a skill that you'll find very useful as you reach out to a wider audience with your programs.

What you’ll learn

• Understand the SL4A
• Explore the Android software development kit
• Write scripts to administer an Android phone
• Write and execute full Python and applications
• Learn how to write simple apps using Facades
• Explore the full Android development process, from development to packaging

Html-encode string using TextUtils.htmlEncode()

In order to convert string to html format, we can use htmlEncode() method of TextUtils class.

package com.exercise.AndroidHtmlEncode;



import android.app.Activity;

import android.os.Bundle;

import android.text.TextUtils;

import android.widget.TextView;



public class AndroidHtmlEncodeActivity extends Activity {

    /** Called when the activity is first created. */

    @Override

    public void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        setContentView(R.layout.main);

        

        TextView textSrc = (TextView)findViewById(R.id.src);

        TextView textDest = (TextView)findViewById(R.id.dest);

        

        String src = "example: <activity>";

        String dest = TextUtils.htmlEncode(src);

        

        textSrc.setText(src);

        textDest.setText(dest);

    }

}

Get Time Zone of location, from web service of www.geonames.org

The GeoNames geographical database covers all countries and contains over eight million placenames that are available for download free of charge.

Using GeoNames WebServices, we can get time zone of any location. For example, the query:
http://api.geonames.org/timezoneJSON?formatted=true&lat=40.75649&lng=-73.98626&username=demo

return the time zone of the location of lat:40.75649 lng:-73.98626 (Nex York).

{

 "time": "2011-08-10 10:07",

 "countryName": "United States",

 "sunset": "2011-08-10 20:01",

 "rawOffset": -5,

 "dstOffset": -4,

 "countryCode": "US",

 "gmtOffset": -5,

 "lng": -73.98626,

 "sunrise": "2011-08-10 06:00",

 "timezoneId": "America/New_York",

 "lat": 40.75649

}

Please note that the parameter 'username' needs to be passed with each request. The username for your application can be registered here.

We can modify the exercise of "Parse JSON returned from Flickr Services" to parse the result to get the time zone.

package com.exercise.AndroidTimeZone;



import java.io.BufferedReader;

import java.io.IOException;

import java.io.InputStream;

import java.io.InputStreamReader;

import java.io.Reader;



import org.apache.http.HttpEntity;

import org.apache.http.client.ClientProtocolException;

import org.apache.http.client.HttpClient;

import org.apache.http.client.methods.HttpGet;

import org.apache.http.impl.client.DefaultHttpClient;

import org.json.JSONException;

import org.json.JSONObject;



import android.app.Activity;

import android.os.Bundle;

import android.view.View;

import android.widget.Button;

import android.widget.EditText;

import android.widget.TextView;



public class AndroidTimeZoneActivity extends Activity {

	

	TextView textTimeZone;

	EditText inputLat, inputLon;

	Button buttonGetTimeZone;

	

	final static String DEFAULT_LAT = "40.75649";

	final static String DEFAULT_LON = "-73.98626";



   /** Called when the activity is first created. */

   @Override

   public void onCreate(Bundle savedInstanceState) {

       super.onCreate(savedInstanceState);

       setContentView(R.layout.main);

      

       textTimeZone = (TextView)findViewById(R.id.timezone);

       inputLat = (EditText)findViewById(R.id.lat);

       inputLat.setText(DEFAULT_LAT);

       inputLon = (EditText)findViewById(R.id.lon);

       inputLon.setText(DEFAULT_LON);

       buttonGetTimeZone = (Button)findViewById(R.id.getTimeZone);

       buttonGetTimeZone.setOnClickListener(buttonGetTimeZoneOnClickistener);

      

   }

  

   Button.OnClickListener buttonGetTimeZoneOnClickistener

   = new Button.OnClickListener(){



		@Override

		public void onClick(View v) {

			// TODO Auto-generated method stub

			

			String lat = inputLat.getText().toString();

			String lon = inputLon.getText().toString();

			

			String rqsurl = "http://api.geonames.org/timezoneJSON?formatted=true"

					+ "&lat=" + lat

					+ "&lng=" + lon

					+ "&username=demo";

			

			String jsonResult = QueryGeonames(rqsurl);

			String parsedResult = ParseJSON(jsonResult);

			textTimeZone.setText(parsedResult);

		}};

		

		private String QueryGeonames(String q){

			

			String qResult = null;

			HttpClient httpClient = new DefaultHttpClient();

			HttpGet httpGet = new HttpGet(q);

			

	        try {

	        	HttpEntity httpEntity = httpClient.execute(httpGet).getEntity();

	        	

	        	if (httpEntity != null){

	        		InputStream inputStream = httpEntity.getContent();

	        	    Reader in = new InputStreamReader(inputStream);

	        	    BufferedReader bufferedreader = new BufferedReader(in);

	        	    StringBuilder stringBuilder = new StringBuilder();

	        	   

	        	    String stringReadLine = null;

	        	   

	        	    while ((stringReadLine = bufferedreader.readLine()) != null) {

	        	    	stringBuilder.append(stringReadLine + "\n");	

	        	    }

	        	   

	        	    qResult = stringBuilder.toString();   

	        	}	

	        } catch (ClientProtocolException e) {

	        	// TODO Auto-generated catch block

	        	e.printStackTrace();	

	        } catch (IOException e) {

	        	// TODO Auto-generated catch block

	        	e.printStackTrace();	

	        }

			

			return qResult;

		}

		    

		

		private String ParseJSON(String json){

			

			String jResult = null;

			

			try {

				JSONObject JsonObject = new JSONObject(json);

				

				jResult = "\n"

						+ "lat: " + JsonObject.getString("lat") + "\n"

						+ "lng: " + JsonObject.getString("lng") + "\n"

						+ "countryName: " + JsonObject.getString("countryName") + "\n"

						+ "countryCode: " + JsonObject.getString("countryCode") + "\n"

						+ "timezoneId: " + JsonObject.getString("timezoneId") + "\n"

						+ "rawOffset: " + JsonObject.getString("rawOffset") + "\n"

						+ "dstOffset: " + JsonObject.getString("dstOffset") + "\n"

						+ "gmtOffset: " + JsonObject.getString("gmtOffset") + "\n";

				

			} catch (JSONException e) {

				// TODO Auto-generated catch block

				e.printStackTrace();	

			}

			

			return jResult;	

		}		       

}

Layout, main.xml

<?xml version="1.0" encoding="utf-8"?>

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"

   android:orientation="vertical"

   android:layout_width="fill_parent"

   android:layout_height="fill_parent"

   >

<TextView 

   android:layout_width="fill_parent"

   android:layout_height="wrap_content"

   android:text="@string/hello"

   />

<TextView

   android:layout_width="fill_parent"

   android:layout_height="wrap_content"

   android:text="lat"

   />

<EditText

   android:id="@+id/lat"

   android:layout_width="fill_parent"

   android:layout_height="wrap_content"

   />

<TextView

   android:layout_width="fill_parent"

   android:layout_height="wrap_content"

   android:text="lon"

   />

<EditText

   android:id="@+id/lon"

   android:layout_width="fill_parent"

   android:layout_height="wrap_content"

   />

<Button

   android:id="@+id/getTimeZone"

   android:layout_width="fill_parent"

   android:layout_height="wrap_content"

   android:text="Get Time Zone from geonames.org"

   />

<TextView 

   android:id="@+id/timezone"

   android:layout_width="fill_parent"

   android:layout_height="wrap_content"

   />

</LinearLayout>

Please remember you you have to modify AndroidManifest.xml to grant permission of "android.permission.INTERNET".


Download the files.

Get time zone where currently running, using TimeZone.getDefault()

The method TimeZone.getDefault() returns the user's preferred time zone.

example:

        TextView textTimeZone = (TextView)findViewById(R.id.timezone);

        

        TimeZone timezone = TimeZone.getDefault();

        String TimeZoneName = timezone.getDisplayName();

		int TimeZoneOffset = timezone.getRawOffset()/(60 * 60 * 1000);

		

		textTimeZone.setText("My Time Zone\n" + 

				TimeZoneName + " : " +String.valueOf(TimeZoneOffset));

Related Post:
- Get Installed Time Zone

Get Installed Time Zone

The java.util.TimeZone class represents a time zone, primarily used for configuring a Calendar or SimpleDateFormat instance.

The method getAvailableIDs() returns the system's installed time zone IDs. Any of these IDs can be passed to getTimeZone() to lookup the corresponding time zone instance.

package com.exercise.AndroidTimeZone;



import java.util.TimeZone;



import android.app.Activity;

import android.os.Bundle;

import android.view.View;

import android.widget.AdapterView;

import android.widget.AdapterView.OnItemSelectedListener;

import android.widget.ArrayAdapter;

import android.widget.Spinner;

import android.widget.TextView;



public class AndroidTimeZoneActivity extends Activity {

	

	Spinner spinnerAvailableID;

	TextView textTimeZone;

	

	ArrayAdapter<String> idAdapter;

	

   /** Called when the activity is first created. */

   @Override

   public void onCreate(Bundle savedInstanceState) {

       super.onCreate(savedInstanceState);

       setContentView(R.layout.main);

      

       spinnerAvailableID = (Spinner)findViewById(R.id.availableID);

       textTimeZone = (TextView)findViewById(R.id.timezone);

      

       String[] idArray = TimeZone.getAvailableIDs();

       idAdapter = new ArrayAdapter<String>(this, android.R.layout.simple_spinner_item, idArray);

       idAdapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);

       spinnerAvailableID.setAdapter(idAdapter);

      

       spinnerAvailableID.setOnItemSelectedListener(new OnItemSelectedListener(){



			@Override

			public void onItemSelected(AdapterView<?> parent, View view,

					int position, long id) {

				// TODO Auto-generated method stub

				String selectedId = (String)(parent.getItemAtPosition(position));

				TimeZone timezone = TimeZone.getTimeZone(selectedId);		

				

				String TimeZoneName = timezone.getDisplayName();

				int TimeZoneOffset = timezone.getRawOffset()/(60 * 60 * 1000);

				

				textTimeZone.setText(TimeZoneName + " : " +String.valueOf(TimeZoneOffset));

			}



			@Override

			public void onNothingSelected(AdapterView<?> arg0) {

				// TODO Auto-generated method stub

				

			}});

   }

}

<?xml version="1.0" encoding="utf-8"?>

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"

   android:orientation="vertical"

   android:layout_width="fill_parent"

   android:layout_height="fill_parent"

   >

<TextView 

   android:layout_width="fill_parent"

   android:layout_height="wrap_content"

   android:text="@string/hello"

   />

<Spinner

   android:id="@+id/availableID"

   android:layout_width="fill_parent"

   android:layout_height="wrap_content"

	/>

<TextView 

   android:id="@+id/timezone"

   android:layout_width="fill_parent"

   android:layout_height="wrap_content"

   />

</LinearLayout>

Related Post:
- Get time zone where currently running, using TimeZone.getDefault()

Prevent restart when the screen orientation has changed, by android:configChanges

Refer to the last exercise "Activity will be re-started when screen orientation changed"; if you don't want the activity re-start when the screen orientation has changed, you can set android:configChanges in AndroidManifest.xml, and handle the event manually by overriding the callback method onConfigurationChanged().



Please notce that it's not reommended by Google- Note: Using this attribute should be avoided and used only as a last-resort. Please read Handling Runtime Changes for more information about how to properly handle a restart due to a configuration change.

override onConfigurationChanged()

package com.exercise.AndroidOrientation;

import android.app.Activity;
import android.content.pm.ActivityInfo;
import android.content.res.Configuration;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.Toast;

public class AndroidOrientationActivity extends Activity {
 
 String msg = "Default without changed";
 
   /** Called when the activity is first created. */
   @Override
   public void onCreate(Bundle savedInstanceState) {
       super.onCreate(savedInstanceState);
       setContentView(R.layout.main);
      
       Button buttonSetPortrait = (Button)findViewById(R.id.setPortrait);
       Button buttonSetLandscape = (Button)findViewById(R.id.setLandscape);
       Button buttonSetUnspecified = (Button)findViewById(R.id.setUnspecified);
       Button buttonShowMsg = (Button)findViewById(R.id.showMsg);
      
       buttonSetPortrait.setOnClickListener(new Button.OnClickListener(){

   @Override
   public void onClick(View arg0) {
    // TODO Auto-generated method stub
    setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_PORTRAIT);
   }});
      
       buttonSetLandscape.setOnClickListener(new Button.OnClickListener(){

   @Override
   public void onClick(View arg0) {
    // TODO Auto-generated method stub
    setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_LANDSCAPE);
   }});
      
       buttonSetUnspecified.setOnClickListener(new Button.OnClickListener(){

   @Override
   public void onClick(View arg0) {
    // TODO Auto-generated method stub
    setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_UNSPECIFIED);
   }});
      
       buttonShowMsg.setOnClickListener(new Button.OnClickListener(){

   @Override
   public void onClick(View arg0) {
    // TODO Auto-generated method stub
    Toast.makeText(AndroidOrientationActivity.this,
            "msg:\n" + msg,
            Toast.LENGTH_LONG).show();
   }});
      
       Toast.makeText(AndroidOrientationActivity.this,
         "onCreate\n" + msg,
         Toast.LENGTH_LONG).show();
      
       msg = "Changed!";
   }

 @Override
 public void onConfigurationChanged(Configuration newConfig) {
  // TODO Auto-generated method stub
  super.onConfigurationChanged(newConfig);
  Toast.makeText(AndroidOrientationActivity.this,
         "onConfigurationChanged\n" + msg,
         Toast.LENGTH_LONG).show();
 }
}

set android:configChanges in AndroidManifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
     package="com.exercise.AndroidOrientation"
     android:versionCode="1"
     android:versionName="1.0">
   <uses-sdk android:minSdkVersion="4" />

   <application android:icon="@drawable/icon" android:label="@string/app_name">
       <activity android:name=".AndroidOrientationActivity"
                 android:label="@string/app_name"
                 android:configChanges="orientation">
           <intent-filter>
               <action android:name="android.intent.action.MAIN" />
               <category android:name="android.intent.category.LAUNCHER" />
           </intent-filter>
       </activity>

   </application>
</manifest>

Activity will be re-started when screen orientation changed

The code listed here show the default behavior of Android application; it will will destroyed and re-created once screen orientation changed.

package com.exercise.AndroidOrientation;

import android.app.Activity;
import android.content.pm.ActivityInfo;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.Toast;

public class AndroidOrientationActivity extends Activity {

String msg = "Default without changed";

   /** Called when the activity is first created. */
   @Override
   public void onCreate(Bundle savedInstanceState) {
       super.onCreate(savedInstanceState);
       setContentView(R.layout.main);
      
       Button buttonSetPortrait = (Button)findViewById(R.id.setPortrait);
       Button buttonSetLandscape = (Button)findViewById(R.id.setLandscape);
       Button buttonSetUnspecified = (Button)findViewById(R.id.setUnspecified);
       Button buttonShowMsg = (Button)findViewById(R.id.showMsg);
      
       buttonSetPortrait.setOnClickListener(new Button.OnClickListener(){

  @Override
  public void onClick(View arg0) {
   // TODO Auto-generated method stub
   setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_PORTRAIT);
  }});
      
       buttonSetLandscape.setOnClickListener(new Button.OnClickListener(){

  @Override
  public void onClick(View arg0) {
   // TODO Auto-generated method stub
   setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_LANDSCAPE);
  }});
      
       buttonSetUnspecified.setOnClickListener(new Button.OnClickListener(){

  @Override
  public void onClick(View arg0) {
   // TODO Auto-generated method stub
   setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_UNSPECIFIED);
  }});
      
       buttonShowMsg.setOnClickListener(new Button.OnClickListener(){

  @Override
  public void onClick(View arg0) {
   // TODO Auto-generated method stub
   Toast.makeText(AndroidOrientationActivity.this,
           "msg:\n" + msg,
           Toast.LENGTH_LONG).show();
  }});
      
       Toast.makeText(AndroidOrientationActivity.this,
         "onCreate\n" + msg,
         Toast.LENGTH_LONG).show();
      
       msg = "Changed!";
   }

}

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
   android:orientation="vertical"
   android:layout_width="fill_parent"
   android:layout_height="fill_parent"
   >
<TextView 
   android:layout_width="fill_parent"
   android:layout_height="wrap_content"
   android:text="@string/hello"
   />
<Button
android:id="@+id/setPortrait" 
   android:layout_width="fill_parent"
   android:layout_height="wrap_content"
   android:text="Set Portrait"
   />
<Button
android:id="@+id/setLandscape" 
   android:layout_width="fill_parent"
   android:layout_height="wrap_content"
   android:text="Set Landscape"
   />
<Button
android:id="@+id/setUnspecified" 
   android:layout_width="fill_parent"
   android:layout_height="wrap_content"
   android:text="Auto Orientation"
   />
<Button
android:id="@+id/showMsg" 
   android:layout_width="fill_parent"
   android:layout_height="wrap_content"
   android:text="Show msg"
   />
</LinearLayout>

next:

- Prevent restart when the screen orientation has changed, by android:configChanges

- onSaveInstanceState() and onRestoreInstanceState()

Set Screen orientation programmatically

By calling setRequestedOrientation() method, we can set screen orientation programmatically.

package com.exercise.AndroidOrientation;

import android.app.Activity;
import android.content.pm.ActivityInfo;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;

public class AndroidOrientationActivity extends Activity {
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        
        Button buttonSetPortrait = (Button)findViewById(R.id.setPortrait);
        Button buttonSetLandscape = (Button)findViewById(R.id.setLandscape);
        
        buttonSetPortrait.setOnClickListener(new Button.OnClickListener(){

   @Override
   public void onClick(View arg0) {
    // TODO Auto-generated method stub
    setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_PORTRAIT);
   }});
        
        buttonSetLandscape.setOnClickListener(new Button.OnClickListener(){

   @Override
   public void onClick(View arg0) {
    // TODO Auto-generated method stub
    setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_LANDSCAPE);
   }});
    }
}

Related:
- Activity will be re-started when screen orientation changed

View PDF file by starting activity with intent of ACTION_VIEW

By starting activity with intent of ACTION_VIEW, for "application/pdf", we can ask the installed PDF ready to open PDF file from our app.

package com.exercise.AndroidReadPDF;

import java.io.File;

import android.app.Activity;
import android.content.Intent;
import android.net.Uri;
import android.os.Bundle;

public class AndroidReadPDFActivity extends Activity {
   /** Called when the activity is first created. */
   @Override
   public void onCreate(Bundle savedInstanceState) {
       super.onCreate(savedInstanceState);
       setContentView(R.layout.main);
      
       String path = "/sdcard/AndroidUsersGuide-2.3.4.pdf";
       File targetFile = new File(path);
       Uri targetUri = Uri.fromFile(targetFile);
      
       Intent intent;
       intent = new Intent(Intent.ACTION_VIEW);
       intent.setDataAndType(targetUri, "application/pdf");
      
       startActivity(intent);
   }
}