Android ViewPager实现动画切换效果

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
  android:id="@+id/view_pager_box"
  android:layout_width="match_parent"
  android:layout_height="match_parent"
  android:orientation="horizontal" >

  <android.support.v4.view.ViewPager
    android:id="@+id/viewpager"
    android:layout_margin="10dp"
    android:layout_width="wrap_content"
    android:layout_height="120dp" />

</LinearLayout>

import android.app.Activity;
import android.os.Bundle;
import android.support.v4.view.PagerAdapter;
import android.support.v4.view.ViewPager;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ImageView;
import android.widget.ImageView.ScaleType;

public class MainActivity extends Activity {

  private ViewPager viewPager;
  private int[] imageIds = new int[]{R.drawable.pic1,R.drawable.pic2,R.drawable.pic3,R.drawable.pic4,R.drawable.pic5,};
  @Override
  protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    viewPager = (ViewPager) findViewById(R.id.viewpager);

    viewPager.setOffscreenPageLimit(3); //设置内存中预加载页面数

    viewPager.setPageTransformer(true, new DepthPageTransformer()); //设置页面切换过渡动画

    viewPager.setAdapter(new PagerAdapter() {

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

      @Override
      public int getCount() {
        return imageIds.length;
      }

      @Override
      public Object instantiateItem(ViewGroup container, int position) {
        ImageView imageView = new ImageView(MainActivity.this);
        imageView.setScaleType(ScaleType.CENTER_CROP);
        imageView.setImageResource(imageIds[position]);
        imageView.setTag(position); //设置标记
        container.addView(imageView);
        return imageView;
      }

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

import android.support.v4.view.ViewPager;
import android.view.View;

public class DepthPageTransformer implements ViewPager.PageTransformer {

  private static final float MIN_SCALE = 0.75f;

  @Override
  public void transformPage(View view, float position) {

    android.util.Log.i("yuminfeng", "====view:" + view.getTag()  + ",position:" + position);

    int pageWidth = view.getWidth();

    if (position < -1) { // [-Infinity,-1) 
      // This page is way off-screen to the left.
      view.setAlpha(0);

    } else if (position <= 0) { // [-1,0]
      // Use the default slide transition when moving to the left page
      view.setAlpha(1);
      view.setTranslationX(0);
      view.setScaleX(1);
      view.setScaleY(1);

    } else if (position <= 1) { // (0,1]
      // Fade the page out.
      view.setAlpha(1 - position);

      // Counteract the default slide transition
      view.setTranslationX(pageWidth * -position);

      // Scale the page down (between MIN_SCALE and 1)
      float scaleFactor = MIN_SCALE + (1 - MIN_SCALE) * (1 - Math.abs(position));
      view.setScaleX(scaleFactor);
      view.setScaleY(scaleFactor);

    } else { // (1,+Infinity]
      // This page is way off-screen to the right.
      view.setAlpha(0);
    }
  }

}

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
  android:id="@+id/view_pager_box"
  android:layout_width="match_parent"
  android:layout_height="160dp"
  android:gravity="center"
  android:clipChildren="false"
  android:orientation="horizontal" >

  <android.support.v4.view.ViewPager
    android:id="@+id/viewpager"
    android:layout_width="match_parent"
    android:layout_margin="30dp"
    android:layout_height="120dp" />

</LinearLayout>

import android.support.v4.view.ViewPager;
import android.view.View;

public class AlphaScaleTransformer implements ViewPager.PageTransformer {

  private static final float DEFAULT_MIN_ALPHA = 0.5f;
  private float mMinAlpha = DEFAULT_MIN_ALPHA;
  private static final float DEFAULT_MIN_SCALE = 0.85f;
  private float mMinScale = DEFAULT_MIN_SCALE;
  public static final float DEFAULT_CENTER = 0.5f;

  @Override
  public void transformPage(View view, float position) {
    int pageWidth = view.getWidth();
    int pageHeight = view.getHeight();

    view.setScaleX(0.999f);// hack
    view.setPivotY(pageHeight / 2);
    view.setPivotX(pageWidth / 2);

    if (position < -1) { // [-Infinity,-1)
      view.setAlpha(mMinAlpha);
      view.setScaleX(mMinScale);
      view.setScaleY(mMinScale);
      view.setPivotX(pageWidth);

    } else if (position <= 1) { // [-1,1]

      if (position < 0) // [0，-1]
      { // [1,min]
        float factor = mMinAlpha + (1 - mMinAlpha) * (1 + position);
        float scaleFactor = (1 + position) * (1 - mMinScale) + mMinScale;

        view.setAlpha(factor);
        view.setScaleX(scaleFactor);
        view.setScaleY(scaleFactor);
        view.setPivotX(pageWidth * (DEFAULT_CENTER + (DEFAULT_CENTER * -position)));

      } else// [1，0]
      {
        // [min,1]
        float factor = mMinAlpha + (1 - mMinAlpha) * (1 - position);
        float scaleFactor = (1 - position) * (1 - mMinScale) + mMinScale;

        view.setAlpha(factor);
        view.setScaleX(scaleFactor);
        view.setScaleY(scaleFactor);
        view.setPivotX(pageWidth * ((1 - position) * DEFAULT_CENTER));

      }
    } else { // (1,+Infinity]
      view.setAlpha(mMinAlpha);
      view.setPivotX(0);
      view.setScaleX(mMinScale);
      view.setScaleY(mMinScale);
    }
  }
}