So how can you know when page is scrolled, and which page is currently visible? One approach is to implement OnPageChangeListener for the ViewPager. The onPageSelected(int position) method will be called when a new page becomes selected. But not the first page at start-up.
Example:
package com.example.androidviewpagerapp;
import android.support.v4.view.PagerAdapter;
import android.support.v4.view.ViewPager;
import android.support.v4.view.ViewPager.OnPageChangeListener;
import android.support.v7.app.ActionBarActivity;
import android.text.method.ScrollingMovementMethod;
import android.graphics.Color;
import android.graphics.Typeface;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.view.ViewGroup;
import android.view.ViewGroup.LayoutParams;
import android.widget.ImageView;
import android.widget.LinearLayout;
import android.widget.TextView;
import android.widget.Toast;
public class MainActivity extends ActionBarActivity {
ViewPager viewPager;
MyPagerAdapter myPagerAdapter;
TextView textMsg;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
textMsg = (TextView)findViewById(R.id.msg);
textMsg.setMovementMethod(new ScrollingMovementMethod());
viewPager = (ViewPager) findViewById(R.id.myviewpager);
myPagerAdapter = new MyPagerAdapter();
viewPager.setAdapter(myPagerAdapter);
viewPager.setOnPageChangeListener(myOnPageChangeListener);
}
OnPageChangeListener myOnPageChangeListener =
new OnPageChangeListener(){
@Override
public void onPageScrollStateChanged(int state) {
//Called when the scroll state changes.
}
@Override
public void onPageScrolled(int position,
float positionOffset, int positionOffsetPixels) {
//This method will be invoked when the current page is scrolled,
//either as part of a programmatically initiated smooth scroll
//or a user initiated touch scroll.
}
@Override
public void onPageSelected(int position) {
//This method will be invoked when a new page becomes selected.
textMsg.append("onPageSelected:" + position + "\n");
}};
private class MyPagerAdapter extends PagerAdapter {
int NumberOfPages = 5;
int[] res = { android.R.drawable.ic_dialog_alert,
android.R.drawable.ic_menu_camera,
android.R.drawable.ic_menu_compass,
android.R.drawable.ic_menu_directions,
android.R.drawable.ic_menu_gallery };
int[] backgroundcolor = { 0xFF101010, 0xFF202020, 0xFF303030,
0xFF404040, 0xFF505050 };
@Override
public int getCount() {
return NumberOfPages;
}
@Override
public boolean isViewFromObject(View view, Object object) {
return view == object;
}
@Override
public Object instantiateItem(ViewGroup container, int position) {
textMsg.append("instantiateItem:" + position + "\n");
TextView textView = new TextView(MainActivity.this);
textView.setTextColor(Color.WHITE);
textView.setTextSize(30);
textView.setTypeface(Typeface.DEFAULT_BOLD);
textView.setText(String.valueOf(position));
ImageView imageView = new ImageView(MainActivity.this);
imageView.setImageResource(res[position]);
LayoutParams imageParams = new LayoutParams(
LayoutParams.MATCH_PARENT, LayoutParams.MATCH_PARENT);
imageView.setLayoutParams(imageParams);
LinearLayout layout = new LinearLayout(MainActivity.this);
layout.setOrientation(LinearLayout.VERTICAL);
LayoutParams layoutParams = new LayoutParams(
LayoutParams.MATCH_PARENT, LayoutParams.MATCH_PARENT);
layout.setBackgroundColor(backgroundcolor[position]);
layout.setLayoutParams(layoutParams);
layout.addView(textView);
layout.addView(imageView);
final int page = position;
layout.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
Toast.makeText(MainActivity.this,
"Page " + page + " clicked", Toast.LENGTH_LONG)
.show();
}
});
container.addView(layout);
return layout;
}
@Override
public void destroyItem(ViewGroup container, int position, Object object) {
container.removeView((LinearLayout) object);
textMsg.append("destroyItem:" + position + "\n");
}
}
}
<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:orientation="vertical"
android:paddingBottom="@dimen/activity_vertical_margin"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
tools:context="com.example.androidviewpagerapp.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" />
<LinearLayout
android:layout_width="match_parent"
android:layout_height="100dp" >
<TextView
android:id="@+id/msg"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:gravity="bottom" />
</LinearLayout>
<android.support.v4.view.ViewPager
android:id="@+id/myviewpager"
android:layout_width="match_parent"
android:layout_height="match_parent" />
</LinearLayout>
Download the files.
Next:
- ViewPager auto scroll to the first, last or any page
1 comment:
OnPageChangeListener is deprecated it is replaced with addOnPageChangeListener Thanks For your answer
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