Android - 使用 AnimatorSet 缩放动画
Android - Zoom animation using AnimatorSet
官方Zooming a View tutorial uses an AnimatorSet放大了一个View。随着视野的扩大，它会产生向下运动的错觉。稍后，AnimatorSet 简单地向后重放以创建缩小的错觉。
我需要实施的是与此完全相反的情况。我需要从展开的视图开始，然后向上移动将其缩小为较小的视图：
好像不能用例子里的反转码。该示例假定您首先放大视图并展开它，然后将其缩小回原始缩略图图标。
这是我到目前为止所尝试过的方法。我的 XML 布局是
<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="match_parent"
android:orientation="vertical"
android:background="#1999da">
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginTop="16dp"
android:orientation="horizontal"
android:layout_gravity="center"
android:gravity="center">
<!-- The final shrunk image -->
<ImageView
android:id="@+id/thumb_button_1"
android:layout_width="wrap_content"
android:layout_height="50dp"
android:layout_marginRight="1dp"
android:visibility="invisible"/>
</LinearLayout>
</LinearLayout>
<!-- The initial expanded image that needs to be shrunk -->
<ImageView
android:id="@+id/expanded_image"
android:layout_width="wrap_content"
android:layout_height="125dp"
android:layout_gravity="center"
android:src="@drawable/title_logo_expanded"
android:scaleType="centerCrop"/>
</FrameLayout>
这里是执行缩小操作的方法。我基本上已经尝试反转教程中的过程：
private void zoomImageFromThumbReverse(final View expandedImageView, int imageResId, final int duration) {
// If there's an animation in progress, cancel it immediately and proceed with this one.
if (mCurrentAnimator != null) {
mCurrentAnimator.cancel();
}
// Load the low-resolution "zoomed-out" image.
final ImageView thumbView = (ImageView) findViewById(R.id.thumb_button_1);
thumbView.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 container view (i.e. the FrameLayout), and the
// final bounds are the global visible rectangle of the thumbnail. 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).
findViewById(R.id.container).getGlobalVisibleRect(startBounds, globalOffset);
thumbView.getGlobalVisibleRect(finalBounds);
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 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 expanded-image and show the zoomed-out, thumbnail view. When the animation begins,
// it will position the zoomed-in view in the place of the thumbnail.
expandedImageView.setAlpha(0f);
thumbView.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).
thumbView.setPivotX(0f);
thumbView.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(thumbView, View.X, startBounds.left,
finalBounds.left))
.with(ObjectAnimator.ofFloat(thumbView, View.Y, startBounds.top,
finalBounds.top))
.with(ObjectAnimator.ofFloat(thumbView, View.SCALE_X, startScale, 1f))
.with(ObjectAnimator.ofFloat(thumbView, View.SCALE_Y, startScale, 1f));
//set.setDuration(mShortAnimationDuration);
set.setDuration(duration);
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-out image, it should zoom back down to the original bounds
// and show the thumbnail instead of the expanded image.
final float startScaleFinal = startScale;
thumbView.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(thumbView, View.X, startBounds.left))
.with(ObjectAnimator.ofFloat(thumbView, View.Y, startBounds.top))
.with(ObjectAnimator
.ofFloat(thumbView, View.SCALE_X, startScaleFinal))
.with(ObjectAnimator
.ofFloat(thumbView, View.SCALE_Y, startScaleFinal));
//set.setDuration(mShortAnimationDuration);
set.setDuration(duration);
set.setInterpolator(new DecelerateInterpolator());
set.addListener(new AnimatorListenerAdapter() {
@Override
public void onAnimationEnd(Animator animation) {
expandedImageView.setAlpha(1f);
thumbView.setVisibility(View.GONE);
mCurrentAnimator = null;
}
@Override
public void onAnimationCancel(Animator animation) {
expandedImageView.setAlpha(1f);
thumbView.setVisibility(View.GONE);
mCurrentAnimator = null;
}
});
set.start();
mCurrentAnimator = set;
}
});
}
我在onCreate()中调用这个方法如下：
final View expandedImageView = findViewById(R.id.expanded_image);
new Handler().postDelayed(new Runnable(){
public void run() {
zoomImageFromThumbReverse(expandedImageView, R.drawable.title_logo_min, 1000);
}}, 1000);
好吧，伙计们。它不工作。我不知道为什么。演示示例完美运行，那么为什么它不起作用？看看我是不是疯了告诉我。
谁能找出错误？或者指出我正确的方向？非常感谢所有帮助。
好的，我想你想要缩小图片和描述并向上移动。我无法理解您的代码，这对我来说太复杂了（我是菜鸟）。现在我已经使用以下代码完成了您想要的操作。首先我声明了一个带有图像视图的相对布局，这个相对布局将成为容器。我设置了初始宽度高度，但我们稍后会从代码中更改它。
<RelativeLayout
android:id="@+id/container"
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"
android:paddingBottom="@dimen/activity_vertical_margin"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
tools:context=".MainActivity">
<ImageView
android:id="@+id/imageView"
android:layout_width="400dp"
android:layout_height="200dp"
android:layout_centerHorizontal="true"
android:scaleType="fitXY"
android:src="@drawable/my_image"/>
</RelativeLayout>
现在，在 Activity 中，我为布局更改设置了一个侦听器，以便我可以获得容器的实际大小。然后设置 ImageView 的布局。
public class MainActivity extends Activity {
ImageView im;
RelativeLayout container;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
Logger.init().hideThreadInfo().setMethodCount(0);
setContentView(R.layout.activity_main);
im = (ImageView) findViewById(R.id.imageView);
container = (RelativeLayout) findViewById(R.id.container);
container.getViewTreeObserver().addOnGlobalLayoutListener(new ViewTreeObserver.OnGlobalLayoutListener() {
@Override
public void onGlobalLayout() {
setInitialPos();
container.getViewTreeObserver().removeOnGlobalLayoutListener(this);
}
});
}
int width;
int height;
int topMargin;
private void setInitialPos() {
Logger.e("container: " + container.getWidth() + " x " + container.getHeight());
width = container.getWidth();
height = 400;
RelativeLayout.LayoutParams layoutParams = (RelativeLayout.LayoutParams) im.getLayoutParams();
layoutParams.width = width;
layoutParams.height = height;
topMargin = (container.getHeight() - height) / 2;
layoutParams.topMargin = topMargin;
im.setLayoutParams(layoutParams);
startAnimation();
}
我们必须在这里设置三样东西的动画，width、height 和 topMargin（用于定位）。因此，我为动画师的初始位置声明了三个变量，并在初始布局设置上计算它们。现在我们需要同时为这三个变量设置动画，这很容易。
private void startAnimation() {
AnimatorSet animator = new AnimatorSet();
Animator widthAnimator = ObjectAnimator.ofInt(this, "width", width, 200);
widthAnimator.setInterpolator(new LinearInterpolator());
Animator heightAnimator = ObjectAnimator.ofInt(this, "height", height, 100);
heightAnimator.setInterpolator(new LinearInterpolator());
Animator marginAnimator = ObjectAnimator.ofInt(this, "topMargin", topMargin, 0);
marginAnimator.setInterpolator(new LinearInterpolator());
animator.playTogether(widthAnimator, heightAnimator, marginAnimator);
animator.setDuration(3000);
animator.start();
}
public void setWidth(int w) {
RelativeLayout.LayoutParams layoutParams = (RelativeLayout.LayoutParams) im.getLayoutParams();
layoutParams.width = w;
im.setLayoutParams(layoutParams);
}
public void setHeight(int h) {
RelativeLayout.LayoutParams layoutParams = (RelativeLayout.LayoutParams) im.getLayoutParams();
layoutParams.height = h;
im.setLayoutParams(layoutParams);
}
public void setTopMargin(int m) {
RelativeLayout.LayoutParams layoutParams = (RelativeLayout.LayoutParams) im.getLayoutParams();
layoutParams.topMargin = m;
im.setLayoutParams(layoutParams);
}
}
这是我最终使用的解决方案：
private void applyAnimation(final View startView, final View finishView, long duration) {
float scalingFactor = ((float)finishView.getHeight())/((float)startView.getHeight());
ScaleAnimation scaleAnimation = new ScaleAnimation(1f, scalingFactor,
1f, scalingFactor,
Animation.RELATIVE_TO_SELF, 0.5f,
Animation.RELATIVE_TO_SELF, 0.5f);
scaleAnimation.setDuration(duration);
scaleAnimation.setInterpolator(new AccelerateDecelerateInterpolator());
Display display = getWindowManager().getDefaultDisplay();
int H;
if(Build.VERSION.SDK_INT >= 13){
Point size = new Point();
display.getSize(size);
H = size.y;
}
else{
H = display.getHeight();
}
float h = ((float)finishView.getHeight());
float verticalDisplacement = (-(H/2)+(3*h/4));
TranslateAnimation translateAnimation = new TranslateAnimation(Animation.ABSOLUTE, 0,
Animation.ABSOLUTE, 0,
Animation.ABSOLUTE, 0,
Animation.ABSOLUTE, verticalDisplacement);
translateAnimation.setDuration(duration);
translateAnimation.setInterpolator(new AccelerateDecelerateInterpolator());
AnimationSet animationSet = new AnimationSet(false);
animationSet.addAnimation(scaleAnimation);
animationSet.addAnimation(translateAnimation);
animationSet.setFillAfter(false);
startView.startAnimation(animationSet);
}
这里的关键因素是TranslateAnimation参数中toYDelta的值：
toYDelta = (-(H/2)+(3*h/4));
理解为什么这有效是最主要的。剩下的就简单了。
官方Zooming a View tutorial uses an AnimatorSet放大了一个View。随着视野的扩大，它会产生向下运动的错觉。稍后，AnimatorSet 简单地向后重放以创建缩小的错觉。
这是我到目前为止所尝试过的方法。我的 XML 布局是
<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="match_parent"
android:orientation="vertical"
android:background="#1999da">
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginTop="16dp"
android:orientation="horizontal"
android:layout_gravity="center"
android:gravity="center">
<!-- The final shrunk image -->
<ImageView
android:id="@+id/thumb_button_1"
android:layout_width="wrap_content"
android:layout_height="50dp"
android:layout_marginRight="1dp"
android:visibility="invisible"/>
</LinearLayout>
</LinearLayout>
<!-- The initial expanded image that needs to be shrunk -->
<ImageView
android:id="@+id/expanded_image"
android:layout_width="wrap_content"
android:layout_height="125dp"
android:layout_gravity="center"
android:src="@drawable/title_logo_expanded"
android:scaleType="centerCrop"/>
</FrameLayout>
这里是执行缩小操作的方法。我基本上已经尝试反转教程中的过程：
private void zoomImageFromThumbReverse(final View expandedImageView, int imageResId, final int duration) {
// If there's an animation in progress, cancel it immediately and proceed with this one.
if (mCurrentAnimator != null) {
mCurrentAnimator.cancel();
}
// Load the low-resolution "zoomed-out" image.
final ImageView thumbView = (ImageView) findViewById(R.id.thumb_button_1);
thumbView.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 container view (i.e. the FrameLayout), and the
// final bounds are the global visible rectangle of the thumbnail. 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).
findViewById(R.id.container).getGlobalVisibleRect(startBounds, globalOffset);
thumbView.getGlobalVisibleRect(finalBounds);
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 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 expanded-image and show the zoomed-out, thumbnail view. When the animation begins,
// it will position the zoomed-in view in the place of the thumbnail.
expandedImageView.setAlpha(0f);
thumbView.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).
thumbView.setPivotX(0f);
thumbView.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(thumbView, View.X, startBounds.left,
finalBounds.left))
.with(ObjectAnimator.ofFloat(thumbView, View.Y, startBounds.top,
finalBounds.top))
.with(ObjectAnimator.ofFloat(thumbView, View.SCALE_X, startScale, 1f))
.with(ObjectAnimator.ofFloat(thumbView, View.SCALE_Y, startScale, 1f));
//set.setDuration(mShortAnimationDuration);
set.setDuration(duration);
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-out image, it should zoom back down to the original bounds
// and show the thumbnail instead of the expanded image.
final float startScaleFinal = startScale;
thumbView.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(thumbView, View.X, startBounds.left))
.with(ObjectAnimator.ofFloat(thumbView, View.Y, startBounds.top))
.with(ObjectAnimator
.ofFloat(thumbView, View.SCALE_X, startScaleFinal))
.with(ObjectAnimator
.ofFloat(thumbView, View.SCALE_Y, startScaleFinal));
//set.setDuration(mShortAnimationDuration);
set.setDuration(duration);
set.setInterpolator(new DecelerateInterpolator());
set.addListener(new AnimatorListenerAdapter() {
@Override
public void onAnimationEnd(Animator animation) {
expandedImageView.setAlpha(1f);
thumbView.setVisibility(View.GONE);
mCurrentAnimator = null;
}
@Override
public void onAnimationCancel(Animator animation) {
expandedImageView.setAlpha(1f);
thumbView.setVisibility(View.GONE);
mCurrentAnimator = null;
}
});
set.start();
mCurrentAnimator = set;
}
});
}
我在onCreate()中调用这个方法如下：
final View expandedImageView = findViewById(R.id.expanded_image);
new Handler().postDelayed(new Runnable(){
public void run() {
zoomImageFromThumbReverse(expandedImageView, R.drawable.title_logo_min, 1000);
}}, 1000);
好吧，伙计们。它不工作。我不知道为什么。演示示例完美运行，那么为什么它不起作用？看看我是不是疯了告诉我。
谁能找出错误？或者指出我正确的方向？非常感谢所有帮助。
好的，我想你想要缩小图片和描述并向上移动。我无法理解您的代码，这对我来说太复杂了（我是菜鸟）。现在我已经使用以下代码完成了您想要的操作。首先我声明了一个带有图像视图的相对布局，这个相对布局将成为容器。我设置了初始宽度高度，但我们稍后会从代码中更改它。
<RelativeLayout
android:id="@+id/container"
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"
android:paddingBottom="@dimen/activity_vertical_margin"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
tools:context=".MainActivity">
<ImageView
android:id="@+id/imageView"
android:layout_width="400dp"
android:layout_height="200dp"
android:layout_centerHorizontal="true"
android:scaleType="fitXY"
android:src="@drawable/my_image"/>
</RelativeLayout>
现在，在 Activity 中，我为布局更改设置了一个侦听器，以便我可以获得容器的实际大小。然后设置 ImageView 的布局。
public class MainActivity extends Activity {
ImageView im;
RelativeLayout container;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
Logger.init().hideThreadInfo().setMethodCount(0);
setContentView(R.layout.activity_main);
im = (ImageView) findViewById(R.id.imageView);
container = (RelativeLayout) findViewById(R.id.container);
container.getViewTreeObserver().addOnGlobalLayoutListener(new ViewTreeObserver.OnGlobalLayoutListener() {
@Override
public void onGlobalLayout() {
setInitialPos();
container.getViewTreeObserver().removeOnGlobalLayoutListener(this);
}
});
}
int width;
int height;
int topMargin;
private void setInitialPos() {
Logger.e("container: " + container.getWidth() + " x " + container.getHeight());
width = container.getWidth();
height = 400;
RelativeLayout.LayoutParams layoutParams = (RelativeLayout.LayoutParams) im.getLayoutParams();
layoutParams.width = width;
layoutParams.height = height;
topMargin = (container.getHeight() - height) / 2;
layoutParams.topMargin = topMargin;
im.setLayoutParams(layoutParams);
startAnimation();
}
我们必须在这里设置三样东西的动画，width、height 和 topMargin（用于定位）。因此，我为动画师的初始位置声明了三个变量，并在初始布局设置上计算它们。现在我们需要同时为这三个变量设置动画，这很容易。
private void startAnimation() {
AnimatorSet animator = new AnimatorSet();
Animator widthAnimator = ObjectAnimator.ofInt(this, "width", width, 200);
widthAnimator.setInterpolator(new LinearInterpolator());
Animator heightAnimator = ObjectAnimator.ofInt(this, "height", height, 100);
heightAnimator.setInterpolator(new LinearInterpolator());
Animator marginAnimator = ObjectAnimator.ofInt(this, "topMargin", topMargin, 0);
marginAnimator.setInterpolator(new LinearInterpolator());
animator.playTogether(widthAnimator, heightAnimator, marginAnimator);
animator.setDuration(3000);
animator.start();
}
public void setWidth(int w) {
RelativeLayout.LayoutParams layoutParams = (RelativeLayout.LayoutParams) im.getLayoutParams();
layoutParams.width = w;
im.setLayoutParams(layoutParams);
}
public void setHeight(int h) {
RelativeLayout.LayoutParams layoutParams = (RelativeLayout.LayoutParams) im.getLayoutParams();
layoutParams.height = h;
im.setLayoutParams(layoutParams);
}
public void setTopMargin(int m) {
RelativeLayout.LayoutParams layoutParams = (RelativeLayout.LayoutParams) im.getLayoutParams();
layoutParams.topMargin = m;
im.setLayoutParams(layoutParams);
}
}
这是我最终使用的解决方案：
private void applyAnimation(final View startView, final View finishView, long duration) {
float scalingFactor = ((float)finishView.getHeight())/((float)startView.getHeight());
ScaleAnimation scaleAnimation = new ScaleAnimation(1f, scalingFactor,
1f, scalingFactor,
Animation.RELATIVE_TO_SELF, 0.5f,
Animation.RELATIVE_TO_SELF, 0.5f);
scaleAnimation.setDuration(duration);
scaleAnimation.setInterpolator(new AccelerateDecelerateInterpolator());
Display display = getWindowManager().getDefaultDisplay();
int H;
if(Build.VERSION.SDK_INT >= 13){
Point size = new Point();
display.getSize(size);
H = size.y;
}
else{
H = display.getHeight();
}
float h = ((float)finishView.getHeight());
float verticalDisplacement = (-(H/2)+(3*h/4));
TranslateAnimation translateAnimation = new TranslateAnimation(Animation.ABSOLUTE, 0,
Animation.ABSOLUTE, 0,
Animation.ABSOLUTE, 0,
Animation.ABSOLUTE, verticalDisplacement);
translateAnimation.setDuration(duration);
translateAnimation.setInterpolator(new AccelerateDecelerateInterpolator());
AnimationSet animationSet = new AnimationSet(false);
animationSet.addAnimation(scaleAnimation);
animationSet.addAnimation(translateAnimation);
animationSet.setFillAfter(false);
startView.startAnimation(animationSet);
}
这里的关键因素是TranslateAnimation参数中toYDelta的值：
toYDelta = (-(H/2)+(3*h/4));
理解为什么这有效是最主要的。剩下的就简单了。