4) set for each view of your FragmentStatPagerAdapter a tag that corresponds to drawable index that you declared in the LayerDrawable. for example when you open the app FragmentA is showing so its tag must correspond to upper drawable that is 2 (beginning from 0). last page tag must be 0 corresponds to lowest drawable.

5）改变每个视图的功能绘制 transformPage

5) change drawable of each view at the function transformPage

6），用于将按钮使用 RelativeLayout的。 为了在上面放置按钮的所有视图中使用 RelativeLayout的。购买儿童放置在Z轴上较高。你可以看到它在code：

6) for adding the button use RelativeLayout. In order to place buttons on top of all views use RelativeLayout. Later children are placing higher on the Z axis. You can see it in the code:

现在让我们看看code：

now lets see code:

MainActivity

MainActivity

public class MainActivity extends FragmentActivity {

    ViewPager viewPager=null;
    int numberOfViewPagerChildren = 3;
    int lastIndexOfViewPagerChildren = numberOfViewPagerChildren - 1;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        viewPager = (ViewPager) findViewById(R.id.pager);
        viewPager.setAdapter(new MyAdapter(getSupportFragmentManager()));

        final LayerDrawable background = (LayerDrawable) viewPager.getBackground();

        background.getDrawable(0).setAlpha(0); // this is the lowest drawable
        background.getDrawable(1).setAlpha(0);
        background.getDrawable(2).setAlpha(255); // this is the upper one 

        viewPager.setPageTransformer(true, new ViewPager.PageTransformer() {
            @Override
            public void transformPage(View view, float position) {

                int index = (Integer) view.getTag();
                Drawable currentDrawableInLayerDrawable;
                currentDrawableInLayerDrawable = background.getDrawable(index);

                if(position <= -1 || position >= 1) {
                    currentDrawableInLayerDrawable.setAlpha(0);
                } else if( position == 0 ) {
                    currentDrawableInLayerDrawable.setAlpha(255);
                } else { 
                    currentDrawableInLayerDrawable.setAlpha((int)(255 - Math.abs(position*255)));
                }

            }
        });


        }
    class MyAdapter extends FragmentStatePagerAdapter
    {

        public MyAdapter(FragmentManager fm) {
            super(fm);
        }

        @Override
        public Fragment getItem(int i) {
            Fragment fragment=null;
            if(i==0)
            {
                fragment=new FragmentA();
            }
            if(i==1)
            {
                fragment=new FragmentB();
            }
            if(i==2)
            {
                fragment=new FragmentC();
            }
            return fragment;
        }

        @Override
        public int getCount() {
            return numberOfViewPagerChildren;
        }

        @Override
        public boolean isViewFromObject(View view, Object object) {
            if(object instanceof FragmentA){
                view.setTag(2);
            }
            if(object instanceof FragmentB){
                view.setTag(1);
            }
            if(object instanceof FragmentC){
                view.setTag(0);
            }
            return super.isViewFromObject(view, object);
        }        
    }

}

activity_main.xml

activity_main.xml

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent" >

    <android.support.v4.view.ViewPager
        android:id="@+id/pager"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:background="@drawable/layerdrawable" >
    </android.support.v4.view.ViewPager>

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_alignParentBottom="true"
        android:orientation="horizontal"
        android:layout_marginBottom="48dip" >

        <Button
            android:layout_width="0dip"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:text="Sign in"
            android:layout_margin="16dip"
            android:background="#2ec6e4"
            android:textColor="#FFFFFF" />

        <Button
            android:layout_width="0dip"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:text="Join us"
            android:background="#2ec6e4"
            android:layout_margin="16dip"
            android:textColor="#FFFFFF"
            />
    </LinearLayout>

</RelativeLayout>

LayerDrawable

LayerDrawable

<?xml version="1.0" encoding="utf-8"?>
<layer-list xmlns:android="http://schemas.android.com/apk/res/android" >

    <item>
        <bitmap
            android:id="@+id/Idofbg3"
            android:gravity="fill"
            android:src="@drawable/bg3" />
    </item>
    <item>
        <bitmap
            android:id="@+id/Idofbg2"
            android:gravity="fill"
            android:src="@drawable/bg2" />
    </item>
    <item>
        <bitmap
            android:id="@+id/Idofbg1"
            android:gravity="fill"
            android:src="@drawable/bg1" />
    </item>

</layer-list>

对于懒惰的人谁只是不想申报片段：

for lazy people who just do not want to declare fragments:

碎裂

public class FragmentA extends Fragment {
    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        View v = inflater.inflate(R.layout.fragment_a,container,false);

        return v;
    }
}

fragment_a.xml

fragment_a.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent" android:layout_height="match_parent"
    android:id="@+id/FragmentA"
     android:background="@android:color/transparent">


    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:textAppearance="?android:attr/textAppearanceLarge"
        android:text="This is Fragment A"
        android:textColor="#FFFFFF"
        android:id="@+id/textView"  
        android:gravity="center"
        android:layout_alignParentTop="true"
        android:layout_alignParentLeft="true"
        android:layout_alignParentRight="true"
        android:layout_alignParentBottom="true" />
</RelativeLayout>