Android 背景图片轮播

package com.example.test;


import android.animation.ValueAnimator;
import android.annotation.TargetApi;
import android.content.Context;
import android.graphics.Canvas;
import android.graphics.drawable.Drawable;
import android.os.Build;
import android.util.AttributeSet;
import android.view.View;
import android.view.animation.LinearInterpolator;


@TargetApi(Build.VERSION_CODES.ICE_CREAM_SANDWICH)
public class AutoPlayView extends View {
Drawable mDrawableLeft, mDrawableRight;
int drawableWidth, drawableHeight;
ValueAnimator valueAnimator;


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


private void init() {
mDrawableLeft = getResources().getDrawable(R.drawable.ic_launcher);
drawableWidth = Utils.getScreenWith(getContext());
drawableHeight = mDrawableLeft.getMinimumHeight();
mDrawableLeft.setBounds(0, 0, drawableWidth, drawableHeight);


mDrawableRight = getResources().getDrawable(R.drawable.ic_launcher);
mDrawableRight.setBounds(drawableWidth, 0, drawableWidth * 2,
drawableHeight);
}


@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
int wdMode = MeasureSpec.getMode(widthMeasureSpec);
int hdMode = MeasureSpec.getMode(heightMeasureSpec);
// 测量布局大小，默认为屏幕的宽，图片的高
if (wdMode == MeasureSpec.EXACTLY && hdMode == MeasureSpec.EXACTLY) {
super.onMeasure(widthMeasureSpec, heightMeasureSpec);
} else {
int wd = MeasureSpec.makeMeasureSpec(
Utils.getScreenWith(getContext()),
MeasureSpec.EXACTLY);
int hd = MeasureSpec.makeMeasureSpec(drawableHeight,
MeasureSpec.EXACTLY);
setMeasuredDimension(wd, hd);
}
}


@Override
protected void onDraw(Canvas canvas) {
// 思路：左边一张图，右边隐藏一张图，不停的scrollto
mDrawableLeft.draw(canvas);
mDrawableRight.draw(canvas);
}


public void startPlay() {
// 一张图片的宽的移动距离，即可视觉上达到不停的在滚动
valueAnimator = ValueAnimator.ofInt(0, drawableWidth);
valueAnimator.setInterpolator(new LinearInterpolator());
valueAnimator.setRepeatCount(-1);
valueAnimator.setDuration(2000);
valueAnimator.setRepeatMode(ValueAnimator.RESTART);
valueAnimator
.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {
@Override
public void onAnimationUpdate(ValueAnimator animation) {
int value = (Integer) animation.getAnimatedValue();
scrollTo(value, 0);
}
});
valueAnimator.start();
}


public void stopPlay() {
if (valueAnimator != null && valueAnimator.isRunning()
&& valueAnimator.isStarted()) {
valueAnimator.cancel();
}
}
}