ColorAnimationView 实现了滑动Viewpager 时背景色动态变化的过渡效果

用法在注释中：

import android.animation.Animator;
import android.animation.ArgbEvaluator;
import android.animation.ObjectAnimator;
import android.animation.ValueAnimator;
import android.content.Context;
import android.support.v4.view.ViewPager;
import android.util.AttributeSet;
import android.view.View;

/*
 * ColorAnimationView 实现了滑动 Viewpager 的时候背景色动态变化的过渡效果
 * 
 * ColorAnimationView colorAnimationView = (ColorAnimationView) findViewById(R.id.ColorAnimationView);
		ViewPager viewPager = (ViewPager) findViewById(R.id.viewPager);
		viewPager.setAdapter(adpter);
		colorAnimationView.setmViewPager(viewPager, resource.length);
        colorAnimationView.setOnPageChangeListener(new ViewPager.OnPageChangeListener() {
            @Override
            public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {
                Log.e("TAG","onPageScrolled");
            }

            @Override
            public void onPageSelected(int position) {
                Log.e("TAG","onPageSelected");
            }

            @Override
            public void onPageScrollStateChanged(int state) {
                Log.e("TAG","onPageScrollStateChanged");
            }
        });
        
        
    <FrameLayout 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"
         tools:context="cn.taurusxi.guidebackgroundcoloranimation.sample.SampleActivity">

	    <com.*.ColorAnimationView
	        android:id="@+id/ColorAnimationView"
	        android:layout_width="match_parent"
	        android:layout_height="match_parent"/>
	
	    <android.support.v4.view.ViewPager
	        android:id="@+id/viewPager"
	        android:padding="30dp"
	        android:layout_width="match_parent"
	        android:layout_height="match_parent"/>

	</FrameLayout>
 * @author Administrator
 *
 */
public class ColorAnimationView extends View
		implements ValueAnimator.AnimatorUpdateListener, Animator.AnimatorListener {
	private static final int RED = 0xffFF8080;
	private static final int BLUE = 0xff8080FF;
	private static final int WHITE = 0xffffffff;
	private static final int GREEN = 0xff80ff80;
	private static final int DURATION = 3000;
	ValueAnimator colorAnim = null;

	private PageChangeListener mPageChangeListener;

	ViewPager.OnPageChangeListener onPageChangeListener;

	public void setOnPageChangeListener(ViewPager.OnPageChangeListener onPageChangeListener) {
		this.onPageChangeListener = onPageChangeListener;
	}



	/**
	 * 这是你唯一需要关心的方法
	 * @param mViewPager  你必须在设置 Viewpager 的 Adapter 这后，才能调用这个方法。
	 * @param count   ,viewpager孩子的数量
	 * @param colors int... colors ，你需要设置的颜色变化值~~ 如何你传人 空，那么触发默认设置的颜色动画
	 * */
	/**
	 * This is the only method you need care about.
	 * @param mViewPager  ,you need set the adpater before you call this.
	 * @param count   ,this param set the count of the viewpaper's child
	 * @param colors ,this param set the change color use (int... colors),
	 *               so,you could set any length if you want.And by default.
	 *               if you set nothing , don't worry i have already creat
	 *               a default good change color!
	 * */
	public void setmViewPager(ViewPager mViewPager, int count, int... colors) {
//		this.mViewPager = mViewPager;
		if (mViewPager.getAdapter() == null) {
			throw new IllegalStateException(
					"ViewPager does not have adapter instance.");
		}
		mPageChangeListener.setViewPagerChildCount(count);

		mViewPager.setOnPageChangeListener(mPageChangeListener);
		if (colors.length == 0) {
			createDefaultAnimation();
		} else {
			createAnimation(colors);
		}

	}

	public ColorAnimationView(Context context) {
		this(context, null, 0);

	}

	public ColorAnimationView(Context context, AttributeSet attrs) {
		this(context, attrs, 0);
	}

	public ColorAnimationView(Context context, AttributeSet attrs, int defStyleAttr) {
		super(context, attrs, defStyleAttr);
		mPageChangeListener = new PageChangeListener();
	}

	private void seek(long seekTime) {
		if (colorAnim == null) {
			createDefaultAnimation();
		}
		colorAnim.setCurrentPlayTime(seekTime);
	}

	private void createAnimation(int... colors) {
		if (colorAnim == null) {
			colorAnim = ObjectAnimator.ofInt(this,
					"backgroundColor", colors);
			colorAnim.setEvaluator(new ArgbEvaluator());
			colorAnim.setDuration(DURATION);
			colorAnim.addUpdateListener(this);
		}
	}

	private void createDefaultAnimation() {
		colorAnim = ObjectAnimator.ofInt(this,
				"backgroundColor", WHITE, RED, BLUE, GREEN, WHITE);
		colorAnim.setEvaluator(new ArgbEvaluator());
		colorAnim.setDuration(DURATION);
		colorAnim.addUpdateListener(this);
	}

	@Override public void onAnimationStart(Animator animation) {

	}

	@Override public void onAnimationEnd(Animator animation) {
	}

	@Override public void onAnimationCancel(Animator animation) {

	}

	@Override public void onAnimationRepeat(Animator animation) {

	}

	@Override public void onAnimationUpdate(ValueAnimator animation) {
		invalidate();
//		long playtime = colorAnim.getCurrentPlayTime();
	}

	private class PageChangeListener
			implements ViewPager.OnPageChangeListener {

		private int viewPagerChildCount;

		public void setViewPagerChildCount(int viewPagerChildCount) {
			this.viewPagerChildCount = viewPagerChildCount;
		}

		public int getViewPagerChildCount() {
			return viewPagerChildCount;
		}

		@Override public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {

			int count = getViewPagerChildCount() - 1;
			if (count != 0) {
				float length = (position + positionOffset) / count;
				int progress = (int) (length * DURATION);
				ColorAnimationView.this.seek(progress);
			}
			// call the method by default
            if (onPageChangeListener!=null){
                onPageChangeListener.onPageScrolled(position,positionOffset,positionOffsetPixels);
            }

		}

		@Override public void onPageSelected(int position) {
            if (onPageChangeListener!=null) {
                onPageChangeListener.onPageSelected(position);
            }
		}

		@Override public void onPageScrollStateChanged(int state) {
            if (onPageChangeListener!=null) {
                onPageChangeListener.onPageScrollStateChanged(state);
            }
		}
	}
}