我正在对 Android L 中的共享元素转换进行一些基本探索。我设置的简单示例有一个在活动转换期间从屏幕顶部转换到屏幕底部的图像视图，并且我已经延长了转换持续时间所以我可以看到工作正常。到目前为止，我遇到了两个问题，试图了解共享元素转换是如何工作的。
1) 仅使用 Enter/Return 转换时（Exit/Reenter 设置为 null）。输入过渡很好，但是当按下后退按钮时，视图会动画一段时间，停止，然后重新出现在最终位置。似乎与这个问题相似，但我已将所有 Exist/Reenter 转换设置为 null，所以不确定它为什么会发生。
2) 仅使用 Exit/Reenter 转换时（Enter/Return 设置为 null）。什么都没有发生，视图在屏幕上向下转换，就像它遵循默认的输入转换（300 毫秒持续时间）一样，当按下返回时，视图会弹回其原始位置。
如何使用退出/重新进入过渡？
这是我的代码：
activity_main.xml
<RelativeLayout 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:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
android:paddingBottom="@dimen/activity_vertical_margin" tools:context=".MainActivity">
<ImageView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:id="@+id/imageView"
android:src="@drawable/ic_launcher"
android:layout_alignParentTop="true"
android:layout_centerHorizontal="true" />
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Animate!"
android:id="@+id/button"
android:layout_centerVertical="true"
android:layout_alignParentStart="true" />
</RelativeLayout>
activity_second.xml
<ImageView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:id="@+id/imageView2"
android:src="@drawable/ic_launcher"
android:layout_alignParentBottom="true"
android:layout_centerHorizontal="true" />
MainActivity.java
public class MainActivity extends Activity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
getWindow().requestFeature(Window.FEATURE_CONTENT_TRANSITIONS);
getWindow().requestFeature(Window.FEATURE_ACTIVITY_TRANSITIONS);
getWindow().setAllowEnterTransitionOverlap(false);
getWindow().setAllowReturnTransitionOverlap(false);
getWindow().setSharedElementExitTransition(exitTransition());
getWindow().setSharedElementReenterTransition(reenterTransition());
//getWindow().setSharedElementExitTransition(null);
//getWindow().setSharedElementReenterTransition(null);
setContentView(R.layout.activity_main);
final View iView = findViewById(R.id.imageView);
iView.setTransitionName("image");
final Button button = (Button)findViewById(R.id.button);
button.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Intent intent = new Intent(MainActivity.this, SecondActivity.class);
ActivityOptions options = ActivityOptions
.makeSceneTransitionAnimation(MainActivity.this, iView, "image");
startActivity(intent, options.toBundle());
}
});
}
private Transition exitTransition() {
ChangeBounds bounds = new ChangeBounds();
bounds.setInterpolator(new BounceInterpolator());
bounds.setDuration(2000);
return bounds;
}
private Transition reenterTransition() {
ChangeBounds bounds = new ChangeBounds();
bounds.setInterpolator(new OvershootInterpolator());
bounds.setDuration(2000);
return bounds;
}
}
SecondActivity.java
public class SecondActivity extends Activity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
getWindow().requestFeature(Window.FEATURE_CONTENT_TRANSITIONS);
getWindow().requestFeature(Window.FEATURE_ACTIVITY_TRANSITIONS);
getWindow().setAllowEnterTransitionOverlap(false);
getWindow().setAllowReturnTransitionOverlap(false);
//getWindow().setSharedElementEnterTransition(enterTransition());
//getWindow().setSharedElementReturnTransition(returnTransition());
getWindow().setSharedElementEnterTransition(null);
getWindow().setSharedElementReturnTransition(null);
setContentView(R.layout.activity_second);
final View iView = findViewById(R.id.imageView2);
iView.setTransitionName("image");
}
@Override
public void onBackPressed() {
super.onBackPressed();
finishAfterTransition();
}
private Transition enterTransition() {
ChangeBounds bounds = new ChangeBounds();
bounds.setDuration(2000);
return bounds;
}
private Transition returnTransition() {
ChangeBounds bounds = new ChangeBounds();
bounds.setInterpolator(new DecelerateInterpolator());
bounds.setDuration(2000);
return bounds;
}
}