Android實現圖片點擊預覽效果(zoom動畫)

<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
 android:id="@+id/container"
 android:layout_width="match_parent"
 android:layout_height="match_parent">
 <LinearLayout android:layout_width="match_parent"
  android:layout_height="wrap_content"
  android:orientation="vertical"
  android:padding="16dp">
  <ImageButton
   android:id="@+id/thumb_button_1"
   android:layout_width="100dp"
   android:layout_height="75dp"
   android:layout_marginRight="1dp"
   android:src="@drawable/thumb1"
   android:scaleType="centerCrop"
android:contentDescription="@string/description_image_1" />
 </LinearLayout>
 <!-- 這個不可見的ImageView持有上面的ImageButton zoom后的圖片版本。
 動畫沒有發生之前，它占據了整個屏幕。動畫開始，這個View從上面
 ImageButton的范圍變化到他自己最終的范圍。
   -->
 <ImageView
  android:id="@+id/expanded_image"
  android:layout_width="match_parent"
  android:layout_height="match_parent"
  android:visibility="invisible"
android:contentDescription="@string/description_zoom_touch_close" />

</FrameLayout>

public class ZoomActivity extends FragmentActivity {
 // 保存下當前動畫類，以便可以隨時結束動畫
 private Animator mCurrentAnimator;
 //系統的短時長動畫持續時間（單位ms）
 // 對于不易察覺的動畫或者頻繁發生的動畫
 // 這個動畫持續時間是最理想的
 private int mShortAnimationDuration;
 @Override
 protected void onCreate(Bundle savedInstanceState) {
  super.onCreate(savedInstanceState);
  setContentView(R.layout.activity_zoom);
  // 給ImageButton設置點擊事件
  final View thumb1View = findViewById(R.id.thumb_button_1);
  thumb1View.setOnClickListener(new View.OnClickListener() {
   @Override
   public void onClick(View view) {
  //執行zoom動畫方法
    zoomImageFromThumb(thumb1View, R.drawable.image1);
   }
  });
  //取回系統默認的短時長動畫持續時間
  mShortAnimationDuration = getResources().getInteger(
android.R.integer.config_shortAnimTime);
 }
 ...
}

private void zoomImageFromThumb(final View thumbView, int imageResId) {
 // 如果有動畫在執行，立即取消，然后執行現在這個動畫
 if (mCurrentAnimator != null) {
 mCurrentAnimator.cancel();
 }
 // 加載高分辨率的圖片
 final ImageView expandedImageView = (ImageView) findViewById(
  R.id.expanded_image);
 expandedImageView.setImageResource(imageResId);
 // 計算開始和結束位置的圖片范圍
 final Rect startBounds = new Rect();
 final Rect finalBounds = new Rect();
 final Point globalOffset = new Point();
 // 開始的范圍就是ImageButton的范圍，
 // 結束的范圍是容器（FrameLayout）的范圍
 // getGlobalVisibleRect(Rect)得到的是view相對于整個硬件屏幕的Rect
 // 即絕對坐標，減去偏移，獲得動畫需要的坐標，即相對坐標
 // getGlobalVisibleRect(Rect,Point)中，Point獲得的是view在它在
 // 父控件上的坐標與在屏幕上坐標的偏移
 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).
 // 下面這段邏輯其實就是保持縱橫比
 float startScale;
 // 如果結束圖片的寬高比比開始圖片的寬高比大
 // 就是結束時“視覺上”拉寬了（壓扁了）圖片
 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.
 // 隱藏小的圖片，展示大的圖片。當動畫開始的時候，
 // 要把大的圖片發在小的圖片的位置上
 //小的設置透明
 thumbView.setAlpha(0f);
 //大的可見
 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.
 // 再次點擊返回小的圖片，就是上面擴大的反向動畫。即預覽完成
 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;
 }
 });
}