我正在对Android L中的共享元素过渡进行一些基础探索。我设置了一个简单的示例，其中在活动转换期间，图像视图从屏幕顶部向底部平移，并延长了过渡持续时间，以便我可以看到它们的工作情况。尝试理解共享元素过渡的工作原理时，我遇到了两个问题。
1)仅使用Enter/Return过渡（Exit/Reenter设置为null）时。进入过渡很好，但当按下返回按钮时，视图会动画一段时间，然后停止，最后重新出现在最终位置。似乎类似于这个问题，但我已将所有Exist/Reenter转换设置为null，所以不知道为什么会发生这种情况。
2)仅使用Exit/Reenter过渡（Enter/Return设置为null）时。什么也没有发生，视图沿着默认的进入过渡（300ms持续时间）向下转换，当按下返回键时，视图会弹回到其原始位置。
如何使用Exit/Reenter过渡？
这里是我的代码：
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;
}
}
Fragment转换。也许其他人可以给出一个好的答案... - Alex Lockwood