TransitionManager scene animation behavior with root layout - transition

Question

I'm testing out the Android Kit Kat transition feature. When the transition happens, the margins of the root layout are getting padded. I find this behavior strange.
The source
public class MainActivity extends ActionBarActivity {
Button btn;
TextView txt;
#TargetApi(Build.VERSION_CODES.KITKAT)
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
txt = (TextView)findViewById(R.id.text);
btn = (Button)findViewById(R.id.btn);
btn.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
ViewGroup root = (ViewGroup)findViewById(R.id.root);
Scene scene = Scene.getSceneForLayout(root, R.layout.activity_main2, MainActivity.this);
TransitionManager.go(scene);
}
});
}
...
}
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"
android:id="#+id/root"
tools:context="com.sebouh00.test.scenes.MainActivity">
<Button android:id="#+id/btn"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Click me"
android:layout_marginBottom="12dp"/>
<TextView
android:id="#+id/text"
android:layout_below="#id/btn"
android:text="#string/hello_world"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:textSize="18dp"/>
</RelativeLayout>
activity_main2.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"
android:id="#+id/root"
tools:context="com.sebouh00.test.scenes.MainActivity">
<Button android:id="#+id/btn"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Click me"
android:layout_marginBottom="12dp"/>
<ImageView
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_below="#id/btn"
android:id="#+id/img"
android:src="#drawable/flag"
android:layout_marginBottom="12dp"/>
<TextView
android:id="#+id/text"
android:layout_below="#id/img"
android:text="#string/hello_world"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:textSize="18dp"/>
</RelativeLayout>
Results in this unless I remove the paddings from activity_main2.xml
Any ideas why?

Answer 1

It's because the View produced by inflating activity_main2 gets inserted into the Scene's root, i.e. your R.id.root RelativeLayout, so the padding from R.id.root is still applied.