Beginning in Android 3.0 (API level 11), you have more control on how and when to use layers with the View.setLayerType() method. This API takes two parameters: the type of layer you want to use and an optional Paint object that describes how the layer should be composited... ... ... A view can use one of three layer types:
- LAYER_TYPE_NONE: The view is rendered normally and is not backed by an off-screen buffer. This is the default behavior.
- LAYER_TYPE_HARDWARE: The view is rendered in hardware into a hardware texture if the application is hardware accelerated. If the application is not hardware accelerated, this layer type behaves the same as LAYER_TYPE_SOFTWARE.
- LAYER_TYPE_SOFTWARE: The view is rendered in software into a bitmap.
You can disable hardware acceleration for an individual view at runtime with the following code:
Note: You currently cannot enable hardware acceleration at the view level. View layers have other functions besides disabling hardware acceleration.
reference: http://developer.android.com/guide/topics/graphics/hardware-accel.html#controlling
myView.setLayerType(View.LAYER_TYPE_SOFTWARE, null);
Note: You currently cannot enable hardware acceleration at the view level. View layers have other functions besides disabling hardware acceleration.
reference: http://developer.android.com/guide/topics/graphics/hardware-accel.html#controlling
To varify if a View is Hardware Accelerated, we can call myView.isHardwareAccelerated() and/or Canvas.isHardwareAccelerated().
- View.isHardwareAccelerated() returns true if the View is attached to a hardware accelerated window.
- Canvas.isHardwareAccelerated() returns true if the Canvas is hardware accelerated
reference: http://developer.android.com/guide/topics/graphics/hardware-accel.html#determining
Also have to be noticed is when hardware accelerated, some operation is unsupported, depends on API levels. That's why we have to disable Hardware Acceleration.
reference: http://developer.android.com/guide/topics/graphics/hardware-accel.html#unsupported
MainActivity.java
package com.example.androiddrawpath;
import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.widget.CompoundButton;
import android.widget.CompoundButton.OnCheckedChangeListener;
import android.widget.RadioButton;
import android.widget.SeekBar;
import android.widget.SeekBar.OnSeekBarChangeListener;
import android.widget.TextView;
public class MainActivity extends Activity {
SeekBar radiusBar;
MyView myView;
SeekBar ptBar;
TextView textPt;
final static int MIN_PT = 3;
RadioButton optLayerTypeNone, optLayerTypeSoftware, optLayerTypeHardware;
TextView textLayerInfo;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
radiusBar = (SeekBar) findViewById(R.id.radiusbar);
myView = (MyView) findViewById(R.id.myview);
float defaultRatio = (float) (radiusBar.getProgress())
/ (float) (radiusBar.getMax());
myView.setShapeRadiusRatio(defaultRatio);
radiusBar.setOnSeekBarChangeListener(radiusBarOnSeekBarChangeListener);
textPt = (TextView)findViewById(R.id.pttext);
ptBar = (SeekBar)findViewById(R.id.ptbar);
ptBar.setOnSeekBarChangeListener(ptBarOnSeekBarChangeListener);
optLayerTypeNone = (RadioButton)findViewById(R.id.typeNone);
optLayerTypeSoftware = (RadioButton)findViewById(R.id.typeSoftware);
optLayerTypeHardware = (RadioButton)findViewById(R.id.typeHardware);
textLayerInfo = (TextView)findViewById(R.id.typeinfo);
myView.passElements(textLayerInfo);
myView.setLayerType(View.LAYER_TYPE_SOFTWARE, null);
optLayerTypeNone.setOnCheckedChangeListener(optLayerTypeOnCheckedChangeListener);
optLayerTypeSoftware.setOnCheckedChangeListener(optLayerTypeOnCheckedChangeListener);
optLayerTypeHardware.setOnCheckedChangeListener(optLayerTypeOnCheckedChangeListener);
};
OnCheckedChangeListener optLayerTypeOnCheckedChangeListener =
new OnCheckedChangeListener(){
@Override
public void onCheckedChanged(CompoundButton buttonView,
boolean isChecked) {
if(optLayerTypeNone.isChecked()){
myView.setLayerType(View.LAYER_TYPE_NONE, null);
}else if(optLayerTypeSoftware.isChecked()){
myView.setLayerType(View.LAYER_TYPE_SOFTWARE, null);
}else{
myView.setLayerType(View.LAYER_TYPE_HARDWARE, null);
}
myView.invalidate();
}};
OnSeekBarChangeListener radiusBarOnSeekBarChangeListener =
new OnSeekBarChangeListener() {
@Override
public void onProgressChanged(SeekBar seekBar, int progress,
boolean fromUser) {
float ratio = (float) (radiusBar.getProgress())
/ (float) (radiusBar.getMax());
myView.setShapeRadiusRatio(ratio);
myView.invalidate();
}
@Override
public void onStartTrackingTouch(SeekBar seekBar) {}
@Override
public void onStopTrackingTouch(SeekBar seekBar) {}
};
OnSeekBarChangeListener ptBarOnSeekBarChangeListener =
new OnSeekBarChangeListener() {
@Override
public void onProgressChanged(SeekBar seekBar, int progress,
boolean fromUser) {
int pt = progress + MIN_PT;
textPt.setText("number of point in polygon: " + String.valueOf(pt));
myView.setNumberOfPoint(pt);
myView.invalidate();
}
@Override
public void onStartTrackingTouch(SeekBar seekBar) {}
@Override
public void onStopTrackingTouch(SeekBar seekBar) {}
};
}
MyView.java
package com.example.androiddrawpath;
import android.content.Context;
import android.graphics.Canvas;
import android.util.AttributeSet;
import android.view.View;
import android.widget.TextView;
public class MyView extends View {
MyShape myShape;
float ratioRadius;
int numberOfPoint = 3; //default
//corresponding to UI element
TextView textLayerInfo;
public MyView(Context context) {
super(context);
initMyView();
}
public MyView(Context context, AttributeSet attrs) {
super(context, attrs);
initMyView();
}
public MyView(Context context, AttributeSet attrs, int defStyleAttr) {
super(context, attrs, defStyleAttr);
initMyView();
}
public void initMyView(){
myShape = new MyShape();
}
@Override
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
long starting = System.nanoTime();
int w = getWidth();
int h = getHeight();
if((w==0) || (h==0)){
return;
}
float x = (float)w/2.0f;
float y = (float)h/2.0f;
float radius;
if(w > h){
radius = h * ratioRadius;
}else{
radius = w * ratioRadius;
}
myShape.setPolygon(x, y, radius, numberOfPoint);
canvas.drawPath(myShape.getPath(), myShape.getPaint());
long end = System.nanoTime();
String info = "myView.isHardwareAccelerated() = " + isHardwareAccelerated() + "\n"
+ "canvas.isHardwareAccelerated() = " + canvas.isHardwareAccelerated() + "\n"
+ "processing time (reference only) : " + String.valueOf(end - starting) + " (ns)";
textLayerInfo.setText(info);
}
public void setShapeRadiusRatio(float ratio){
ratioRadius = ratio;
}
public void setNumberOfPoint(int pt){
numberOfPoint = pt;
}
public void passElements(TextView textLayerInfo){
this.textLayerInfo = textLayerInfo;
}
}
MyShape.java
package com.example.androiddrawpath;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.Path;
public class MyShape {
private Paint paint;
private Path path;
public MyShape() {
paint = new Paint();
paint.setColor(Color.BLUE);
paint.setStrokeWidth(3);
paint.setStyle(Paint.Style.STROKE);
path = new Path();
}
public void setCircle(float x, float y, float radius, Path.Direction dir){
path.reset();
path.addCircle(x, y, radius, dir);
}
public void setPolygon(float x, float y, float radius, int numOfPt){
double section = 2.0 * Math.PI/numOfPt;
path.reset();
path.moveTo(
(float)(x + radius * Math.cos(0)),
(float)(y + radius * Math.sin(0)));
for(int i=1; i<numOfPt; i++){
path.lineTo(
(float)(x + radius * Math.cos(section * i)),
(float)(y + radius * Math.sin(section * i)));
}
path.close();
}
public Path getPath(){
return path;
}
public Paint getPaint(){
return paint;
}
}
/res/layout/activity_main.xml
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:paddingBottom="@dimen/activity_vertical_margin"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
android:orientation="vertical"
tools:context="com.example.androiddrawpath.MainActivity" >
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="center_horizontal"
android:autoLink="web"
android:text="http://android-er.blogspot.com/"
android:textStyle="bold" />
<TextView
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="radius(%)"/>
<SeekBar
android:id="@+id/radiusbar"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:max="100"
android:progress="50" />
<TextView
android:id="@+id/pttext"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="number of point in polygon: 3"/>
<SeekBar
android:id="@+id/ptbar"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:max="10"
android:progress="0" />
<RadioGroup
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:orientation="horizontal">
<RadioButton android:id="@+id/typeNone"
android:layout_width="0dp"
android:layout_weight="1"
android:layout_height="wrap_content"
android:text="LAYER_TYPE_NONE"/>
<RadioButton android:id="@+id/typeSoftware"
android:layout_width="0dp"
android:layout_weight="1"
android:layout_height="wrap_content"
android:text="LAYER_TYPE_SOFTWARE"/>
<RadioButton android:id="@+id/typeHardware"
android:layout_width="0dp"
android:layout_weight="1"
android:layout_height="wrap_content"
android:text="LAYER_TYPE_HARDWARE"/>
</RadioGroup>
<RelativeLayout
android:layout_width="match_parent"
android:layout_height="match_parent">
<TextView
android:id="@+id/typeinfo"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_alignParentBottom="true" />
<com.example.androiddrawpath.MyView
android:id="@+id/myview"
android:layout_width="match_parent"
android:layout_height="match_parent" />
</RelativeLayout>
</LinearLayout>
In order to call setLayerType(int layerType, Paint paint), View.isHardwareAccelerated() and Canvas.isHardwareAccelerated (), android:minSdkVersion in AndroidManifest.xml have to be set ="11" in .
Download the files.More examples of Draw Path on canvas of custom View.
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