原文

概要

本课程演示如何执行触摸缩放动画，这对诸如照片库等应用程序可以将视图从缩略图动画化为充满屏幕的全尺寸图像。

以下是触摸缩放动画看起来像展开图像缩略图以填充屏幕：
视频地址：https://developer.android.com/training/animation/anim_zoom.mp4

如果你想跳过并看到一个完整的工作示例，请参阅 GitHub上android-WearSpeakerSample项目中的 UIAnimation类

创建视图

创建一个布局文件，其中包含要放大的内容的大小版本。以下示例创建一个ImageButton可点击的图像缩略图，并ImageView显示该图像的放大视图：

<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"><ImageButtonandroid: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><!-- This initially-hidden ImageView will hold the expanded/zoomed version ofthe images above. Without transformations applied, it takes up the entirescreen. To achieve the "zoom" animation, this view's bounds are animatedfrom the bounds of the thumbnail button above, to its final laid-outbounds.--><ImageViewandroid: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>

设置缩放动画

应用布局后，设置触发缩放动画的事件处理程序。以下示例将添加一个View.OnClickListener以ImageButton在用户单击图像按钮时执行缩放动画：

public class ZoomActivity extends FragmentActivity {// Hold a reference to the current animator,// so that it can be canceled mid-way.private Animator mCurrentAnimator;// The system "short" animation time duration, in milliseconds. This// duration is ideal for subtle animations or animations that occur// very frequently.private int mShortAnimationDuration;@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_zoom);// Hook up clicks on the thumbnail views.final View thumb1View = findViewById(R.id.thumb_button_1);thumb1View.setOnClickListener(new View.OnClickListener() {@Overridepublic void onClick(View view) {zoomImageFromThumb(thumb1View, R.drawable.image1);}});// Retrieve and cache the system's default "short" animation time.mShortAnimationDuration = getResources().getInteger(android.R.integer.config_shortAnimTime);}...
}

放大视图

适当时，您现在需要从正常大小的视图动画到缩放视图。一般来说，您需要从正常大小的视图的边界到较大视图的边界进行动画处理。以下方法向您展示了如何通过执行以下操作来实现从图像缩略图放大到放大视图的缩放动画：

• 将高分辨率图像分配给隐藏的“放大”（放大）ImageView。为简单起见，以下示例在UI线程上加载大图像资源。您需要在单独的线程中进行加载以防止在UI线程上阻塞，然后在UI线程上设置位图。理想情况下，位图不应该大于屏幕尺寸。
• 计算的开始和结束范围ImageView。
• 动画四个位置和大小的属性X，Y（SCALE_X和SCALE_Y）同时，从起始边界到结束边界。这四个动画被添加到一个AnimatorSet以便它们可以同时启动。
• 通过运行类似的动画缩小范围，但当用户在放大图像时触摸屏幕时反过来缩小。您可以通过向图像添加a View.OnClickListener来实现ImageView。点击后， ImageView最小化为图像缩略图的大小，并将其可见性设置GONE为隐藏。

private void zoomImageFromThumb(final View thumbView, int imageResId) {// If there's an animation in progress, cancel it// immediately and proceed with this one.if (mCurrentAnimator != null) {mCurrentAnimator.cancel();}// Load the high-resolution "zoomed-in" image.final ImageView expandedImageView = (ImageView) findViewById(R.id.expanded_image);expandedImageView.setImageResource(imageResId);// Calculate the starting and ending bounds for the zoomed-in image.// This step involves lots of math. Yay, math.final Rect startBounds = new Rect();final Rect finalBounds = new Rect();final Point globalOffset = new Point();// The start bounds are the global visible rectangle of the thumbnail,// and the final bounds are the global visible rectangle of the container// view. Also set the container view's offset as the origin for the// bounds, since that's the origin for the positioning animation// properties (X, Y).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).float startScale;if ((float) finalBounds.width() / finalBounds.height()> (float) startBounds.width() / startBounds.height()) {// Extend start bounds horizontallystartScale = (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 verticallystartScale = (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.thumbView.setAlpha(0f);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() {@Overridepublic void onAnimationEnd(Animator animation) {mCurrentAnimator = null;}@Overridepublic 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.final float startScaleFinal = startScale;expandedImageView.setOnClickListener(new View.OnClickListener() {@Overridepublic 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() {@Overridepublic void onAnimationEnd(Animator animation) {thumbView.setAlpha(1f);expandedImageView.setVisibility(View.GONE);mCurrentAnimator = null;}@Overridepublic void onAnimationCancel(Animator animation) {thumbView.setAlpha(1f);expandedImageView.setVisibility(View.GONE);mCurrentAnimator = null;}});set.start();mCurrentAnimator = set;}});
}

Lastest Update：2018.04.25

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