ViewPager onFocus / onUnFocus listener use ViewGroup

activity_main.xml

<android.support.v4.view.ViewPager
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/main_viewpager"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"/>

MainActivity.java

package com.example.showsky.test;

import android.app.Activity;
import android.content.Context;
import android.graphics.Color;
import android.os.Bundle;
import android.support.v4.view.ViewPager;
import android.util.Log;
import android.view.View;

import java.util.ArrayList;
import java.util.List;


public class MainActivity extends Activity {

    private final static String TAG = "MainActivity";
    private Context context = null;
    private TestPagerAdapter testPagerAdapter = null;
    private ViewPager viewPager = null;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        Log.i(TAG, "onCreate");
        context = this;
        if (testPagerAdapter == null) {
            testPagerAdapter = new TestPagerAdapter();
        }
        setContentView(R.layout.activity_main);

        viewPager = (ViewPager) findViewById(R.id.main_viewpager);
        viewPager.setAdapter(testPagerAdapter);
    }

    @Override
    protected void onResume() {
        super.onResume();
        Log.i(TAG, "onResume");
    }

    @Override
    protected void onPause() {
        super.onPause();
        Log.i(TAG, "onPause");
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
        Log.i(TAG, "onDestroy");
    }

    private class TestPagerAdapter extends ViewGroupPagerAdapter {

        private List<Integer> colors = new ArrayList<Integer>();

        public TestPagerAdapter() {
            colors.add(Color.BLACK);
            colors.add(Color.RED);
            colors.add(Color.GREEN);
            colors.add(Color.BLUE);
            colors.add(Color.CYAN);
            colors.add(Color.MAGENTA);
            colors.add(Color.YELLOW);
        }

        @Override
        public int getCount() {
            return colors.size();
        }

        @Override
        public View getItem(int position) {
            TestViewGroup view = new TestViewGroup(context);
            view.index = position;
            view.setBackgroundColor(colors.get(position));
            return view;
        }
    }
}

TestViewGroup.java

package com.example.showsky.test;

import android.content.Context;
import android.util.AttributeSet;
import android.util.Log;
import android.view.ViewGroup;

/**
 * Created by showsky on 14/11/11.
 */
public class TestViewGroup extends ViewGroup implements ViewGroupPagerAdapter.ViewGroupPagerListener {

    private final static String TAG = "TestViewGroup";
    public int index = 0;

    public TestViewGroup(Context context) {
        super(context);
    }

    public TestViewGroup(Context context, AttributeSet attrs) {
        super(context, attrs);
    }

    public TestViewGroup(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);
    }

    @Override
    protected void onLayout(boolean changed, int l, int t, int r, int b) {
    }

    @Override
    protected void onAttachedToWindow() {
        super.onAttachedToWindow();
        Log.d(TAG, "Index: " + index + " onAttachedToWindow");
    }

    @Override
    protected void onDetachedFromWindow() {
        super.onDetachedFromWindow();
        Log.d(TAG, "Index: " + index + " onDetachedFromWindow");
    }

    @Override
    public void onFocus() {
        Log.d(TAG, "Index: " + index + " onFocus");
    }

    @Override
    public void onUnFocus() {
        Log.d(TAG, "Index: " + index + " onUnFocus");
    }
}

ViewGroupPagerAdapter.java

package com.example.showsky.test;

import android.support.v4.view.PagerAdapter;
import android.view.View;
import android.view.ViewGroup;

/**
 * Created by showsky on 14/11/11.
 */
public abstract class ViewGroupPagerAdapter extends PagerAdapter {

    private final static String TAG = "ViewGroupPagerAdapter";
    private View currentView = null;

    public interface ViewGroupPagerListener {

        public void onFocus();
        public void onUnFocus();
    }

    @Override
    public void setPrimaryItem(ViewGroup container, int position, Object object) {
        super.setPrimaryItem(container, position, object);
        View view = (View) object;
        if (view != currentView) {
            if (currentView != null && currentView instanceof ViewGroupPagerListener) {
                ((ViewGroupPagerListener) currentView).onUnFocus();
            }
            if (view != null && view instanceof ViewGroupPagerListener) {
                ((ViewGroupPagerListener) view).onFocus();
            }
            currentView = view;
        }
    }

    public abstract View getItem(int position);

    @Override
    public Object instantiateItem(ViewGroup container, int position) {
        View view = getItem(position);
        container.addView(view);
        return view;
    }

    @Override
    public void destroyItem(ViewGroup container, int position, Object object) {
        container.removeView((View) object);
    }

    @Override
    public boolean isViewFromObject(View view, Object object) {
        return (view == object);
    }

    public View getCurrentView() {
        return currentView;
    }
}