平移和缩放布局 Animation Android 中的问题

Question

I have the view with layout below.

What I want is moving View B to the position of View A and at the same time move RelativeLayout C up with the same height of View B. The two actions will be done with the animations. Like the picture shown below.

I am using ObjectAnimation to implement this feature, but when I am using the

    float viewBY = viewB.getTranslationY();
    ObjectAnimator viewBMoveUp
                = ObjectAnimator.ofFloat(viewB, "translationY",
                viewBY, viewBY - viewB.getHeight());

    float layoutCCurrentY = layoutC.getY();
    ObjectAnimator layoutCMoveUp
            = ObjectAnimator.ofFloat(layoutC, "Y",
            layoutCCurrentY, layoutCCurrentY - viewB.getHeight());
    AnimatorSet animSet = new AnimatorSet();
        animSet.play(viewBMoveUp).with(layoutCMoveUp);
        animSet.setDuration(150);
        animSet.start();

I find the LayoutC's bottom is also up with viewB.getHeight(), which is not I expected. Like the picture below:

So anybody can help about this?

Answer 1

One simpler way to achieve the expected result is to use animateLayoutChanges attribute in the parent layout.

<!-- Defines whether changes in layout (caused by adding and removing items) should cause 
a LayoutTransition to run. When this flag is set to true, a default LayoutTransition object 
will be set on the ViewGroup container and default animations will run when these layout 
changes occur.-->
<attr name="animateLayoutChanges" format="boolean" />

With this, you don't need to manually animate each movement. When you set viewA visibility to View.GONE , the parent layout will fade out viewA and translate position of viewB and layoutC .

<RelativeLayout
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:animateLayoutChanges="true">

    <View
        android:id="@+id/viewA"
        android:layout_width="match_parent"
        android:layout_height="60dp" />

    <View
        android:id="@+id/viewB"
        android:layout_width="match_parent"
        android:layout_height="60dp"
        android:layout_below="@+id/viewA" />

    <RelativeLayout
        android:id="@+id/layoutC"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_below="@+id/viewB"
        android:layout_alignParentBottom="true">

    </RelativeLayout>

</RelativeLayout>