Android实现图片点击预览效果(zoom动画)

public class ZoomActivity extends FragmentActivity {
 // 保存下当前动画类，以便可以随时结束动画
 private Animator mCurrentAnimator;
 //系统的短时长动画持续时间（单位ms）
 // 对于不易察觉的动画或者频繁发生的动画
 // 这个动画持续时间是最理想的
 private int mShortAnimationDuration;
 @Override
 protected void onCreate(Bundle savedInstanceState) {
  super.onCreate(savedInstanceState);
  setContentView(R.layout.activity_zoom);
  // 给ImageButton设置点击事件
  final View thumb1View = findViewById(R.id.thumb_button_1);
  thumb1View.setOnClickListener(new View.OnClickListener() {
   @Override
   public void onClick(View view) {
  //执行zoom动画方法
    zoomImageFromThumb(thumb1View, R.drawable.image1);
   }
  });
  //取回系统默认的短时长动画持续时间
  mShortAnimationDuration = getResources().getInteger(
android.R.integer.config_shortAnimTime);
 }
 ...
}

private void zoomImageFromThumb(final View thumbView, int imageResId) {
 // 如果有动画在执行，立即取消，然后执行现在这个动画
 if (mCurrentAnimator != null) {
 mCurrentAnimator.cancel();
 }
 // 加载高分辨率的图片
 final ImageView expandedImageView = (ImageView) findViewById(
  R.id.expanded_image);
 expandedImageView.setImageResource(imageResId);
 // 计算开始和结束位置的图片范围
 final Rect startBounds = new Rect();
 final Rect finalBounds = new Rect();
 final Point globalOffset = new Point();
 // 开始的范围就是ImageButton的范围，
 // 结束的范围是容器（FrameLayout）的范围
 // getGlobalVisibleRect(Rect)得到的是view相对于整个硬件屏幕的Rect
 // 即绝对坐标，减去偏移，获得动画需要的坐标，即相对坐标
 // getGlobalVisibleRect(Rect,Point)中，Point获得的是view在它在
 // 父控件上的坐标与在屏幕上坐标的偏移
 thumbView.getGlobalVisibleRect(startBounds);
 findViewById(R.id.container)
  .getGlobalVisibleRect(finalBounds, globalOffset);
 startBounds.offset(-globalOffset.x, -globalOffset.y);
 finalBounds.offset(-globalOffset.x, -globalOffset.y);
 // Adjust the start bounds to be the same aspect ratio as the final
 // bounds using the "center crop" technique. This prevents undesirable
 // stretching during the animation. Also calculate the start scaling
 // factor (the end scaling factor is always 1.0).
 // 下面这段逻辑其实就是保持纵横比
 float startScale;
 // 如果结束图片的宽高比比开始图片的宽高比大
 // 就是结束时“视觉上”拉宽了（压扁了）图片
 if ((float) finalBounds.width() / finalBounds.height()
  > (float) startBounds.width() / startBounds.height()) {
 // Extend start bounds horizontally
 startScale = (float) startBounds.height() / finalBounds.height();
 float startWidth = startScale * finalBounds.width();
 float deltaWidth = (startWidth - startBounds.width()) / 2;
 startBounds.left -= deltaWidth;
 startBounds.right += deltaWidth;
 } else {
 // Extend start bounds vertically
 startScale = (float) startBounds.width() / finalBounds.width();
 float startHeight = startScale * finalBounds.height();
 float deltaHeight = (startHeight - startBounds.height()) / 2;
 startBounds.top -= deltaHeight;
 startBounds.bottom += deltaHeight;
 }
 // Hide the thumbnail and show the zoomed-in view. When the animation
 // begins, it will position the zoomed-in view in the place of the
 // thumbnail.
 // 隐藏小的图片，展示大的图片。当动画开始的时候，
 // 要把大的图片发在小的图片的位置上
 //小的设置透明
 thumbView.setAlpha(0f);
 //大的可见
 expandedImageView.setVisibility(View.VISIBLE);
 // Set the pivot point for SCALE_X and SCALE_Y transformations
 // to the top-left corner of the zoomed-in view (the default
 // is the center of the view).
 expandedImageView.setPivotX(0f);
 expandedImageView.setPivotY(0f);
 // Construct and run the parallel animation of the four translation and
 // scale properties (X, Y, SCALE_X, and SCALE_Y).
 AnimatorSet set = new AnimatorSet();
 set
  .play(ObjectAnimator.ofFloat(expandedImageView, View.X,
   startBounds.left, finalBounds.left))
  .with(ObjectAnimator.ofFloat(expandedImageView, View.Y,
   startBounds.top, finalBounds.top))
  .with(ObjectAnimator.ofFloat(expandedImageView, View.SCALE_X,
  startScale, 1f)).with(ObjectAnimator.ofFloat(expandedImageView,
   View.SCALE_Y, startScale, 1f));
 set.setDuration(mShortAnimationDuration);
 set.setInterpolator(new DecelerateInterpolator());
 set.addListener(new AnimatorListenerAdapter() {
 @Override
 public void onAnimationEnd(Animator animation) {
  mCurrentAnimator = null;
 }
 @Override
 public void onAnimationCancel(Animator animation) {
  mCurrentAnimator = null;
 }
 });
 set.start();
 mCurrentAnimator = set;
 // Upon clicking the zoomed-in image, it should zoom back down
 // to the original bounds and show the thumbnail instead of
 // the expanded image.
 // 再次点击返回小的图片，就是上面扩大的反向动画。即预览完成
 final float startScaleFinal = startScale;
 expandedImageView.setOnClickListener(new View.OnClickListener() {
 @Override
 public void onClick(View view) {
  if (mCurrentAnimator != null) {
  mCurrentAnimator.cancel();
  }
  // Animate the four positioning/sizing properties in parallel,
  // back to their original values.
  AnimatorSet set = new AnimatorSet();
  set.play(ObjectAnimator
   .ofFloat(expandedImageView, View.X, startBounds.left))
   .with(ObjectAnimator
    .ofFloat(expandedImageView,
     View.Y,startBounds.top))
   .with(ObjectAnimator
    .ofFloat(expandedImageView,
View.SCALE_X, startScaleFinal))
   .with(ObjectAnimator
    .ofFloat(expandedImageView,
View.SCALE_Y, startScaleFinal));
  set.setDuration(mShortAnimationDuration);
  set.setInterpolator(new DecelerateInterpolator());
  set.addListener(new AnimatorListenerAdapter() {
  @Override
  public void onAnimationEnd(Animator animation) {
   thumbView.setAlpha(1f);
   expandedImageView.setVisibility(View.GONE);
   mCurrentAnimator = null;
  }
  @Override
  public void onAnimationCancel(Animator animation) {
   thumbView.setAlpha(1f);
   expandedImageView.setVisibility(View.GONE);
   mCurrentAnimator = null;
  }
  });
  set.start();
  mCurrentAnimator = set;
 }
 });
}