我们在这个案例模仿上篇博客中的DepthPageTransformer动画效果吧。我们自己定义两种动画。一个Scale动画和一个Translate动画，使两个动画交替一起运行就能够模仿出DepthPageTransformer这种平移缩放的动画效果出来，代码非常easy，不单独贴出了。以下有完整的代码的。

public class ViewPagerWithTransformer extends ViewPager {

	// 左边的View

	private View mLeftView;

	// 右边的View

	private View mRightView;

	// 平移动画的梯度值

	private float mTranslate;

	// 缩放动画的梯度值

	private float mScale;

	// 最小缩放比例

	private static final float MIN_SCALE = 0.6f;

	// 保存ViewPager上View的对象

	private Map<Integer, View> mViewCache = new HashMap<Integer, View>();

	/**

	 * 设置View的缓存

	 *

	 * @param position

	 * @param viewCache

	 */

	public void setViewCache(Integer position, View viewCache) {

		mViewCache.put(position, viewCache);

	}

	/**

	 * 从View的缓存集合中移除指定position的View

	 *

	 * @param position

	 */

	public void removeViewCache(Integer position) {

		mViewCache.remove(position);

	}

	public ViewPagerWithTransformer(Context context, AttributeSet attrs) {

		super(context, attrs);

		// TODO Auto-generated constructor stub

	}

	@Override

	protected void onPageScrolled(int position, float offset, int offsetPixels) {

		super.onPageScrolled(position, offset, offsetPixels);

		mLeftView = mViewCache.get(position);

		mRightView = mViewCache.get(position + 1);

		animStack(mLeftView, mRightView, offset, offsetPixels);

	}

	private void animStack(View left, View right, float offset, int offsetPixels) {

		// TODO Auto-generated method stub

		if (right != null) {

			// 从第0页——》到第1页，offset:0~1。缩放比例mScale:0.6~1

			mScale = (1 - MIN_SCALE) * offset + MIN_SCALE;

			//平移的距离

			mTranslate = -getWidth() - getPageMargin() + offsetPixels;

			//使用NineOldAndroids编写属性动画

			ViewHelper.setScaleX(right, mScale);

			ViewHelper.setScaleY(right, mScale);

			ViewHelper.setTranslationX(right, mTranslate);

		}

		if (left != null) {

			// 左边的页永远在最上面

			left.bringToFront();

		}

	}

}

在布局文件里申明，activity_main.xml

<RelativeLayout 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" >

    <com.example.viewpagerwithtransformeranim.ViewPagerWithTransformer

        android:id="@+id/viewpager"

        android:layout_width="match_parent"

        android:layout_height="match_parent" >

    </com.example.viewpagerwithtransformeranim.ViewPagerWithTransformer>

</RelativeLayout>

在Activity中使用这个控件。MainActivity.java

public class MainActivity extends Activity {

	private int[] imgRes = new int[] { R.drawable.guide_image1, R.drawable.guide_image2, R.drawable.guide_image3 };

	private List<ImageView> imgList = new ArrayList<ImageView>();

	private ViewPagerWithTransformer mViewPager;

	@Override

	protected void onCreate(Bundle savedInstanceState) {

		super.onCreate(savedInstanceState);

		requestWindowFeature(Window.FEATURE_NO_TITLE);

		setContentView(R.layout.activity_main);

		mViewPager = (ViewPagerWithTransformer) findViewById(R.id.viewpager);

		mViewPager.setAdapter(new PagerAdapter() {

			@Override

			public boolean isViewFromObject(View arg0, Object arg1) {

				return arg0 == arg1;

			}

			@Override

			public int getCount() {

				return imgRes.length;

			}

			@Override

			public Object instantiateItem(ViewGroup container, int position) {

				ImageView mImageView = new ImageView(MainActivity.this);

				mImageView.setBackgroundResource(imgRes[position]);

				mImageView.setScaleType(ScaleType.CENTER_CROP);

				imgList.add(mImageView);

				//给ViewPager设置View缓存

				mViewPager.setViewCache(position, mImageView);

				container.addView(mImageView);

				return mImageView;

			}

			@Override

			public void destroyItem(ViewGroup container, int position, Object object) {

				//移除ViewPager的View缓存

				mViewPager.removeViewCache(position);

				container.removeView(imgList.get(position));

			}

		});

	}

}

好，所有源代码在上面了，注意一下，在给ViewPager设置的适配器PagerAdapter里面重写instantiateItem方法时。一定要记得调用mViewPager.setViewCache(position, mImageView)方法，给ViewPager设置View缓存。然后在重写destroyItem方法中调用mViewPager.removeViewCache(position)方法移除View缓存。