Android LayoutAnimation不生效

Pixel + Android 10 + Android Studio 3.5.3

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent">
    <GridView android:id="@+id/gv"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:horizontalSpacing="@dimen/spacing"
        android:verticalSpacing="@dimen/spacing"
        android:listSelector="@color/transparent"
        android:layoutAnimation="@anim/layout_anim"
        android:numColumns="auto_fit"/>
    <Button android:id="@+id/add_data"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@string/app_name"/>
</RelativeLayout>

<gridLayoutAnimation xmlns:android="http://schemas.android.com/apk/res/android"
    android:rowDelay="50%"
    android:columnDelay="40%"
    android:directionPriority="none"
    android:direction="top_to_bottom|left_to_right"
    android:animation="@anim/anim"/>

<?xml version="1.0" encoding="utf-8"?>
<set xmlns:android="http://schemas.android.com/apk/res/android" android:duration="600">
    <translate android:fromYDelta="50%p" android:toYDelta="0"/>
    <alpha android:fromAlpha="0.0" android:toAlpha="1.0" />
</set>

public class Test extends Activity {
    private GridAdapter mGrideAdapter;
    private GridView grid;
    private List<String> mDatas = new ArrayList<>();
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_test);
        grid = (GridView) findViewById(R.id.gv);
        mDatas.addAll(getData());
        mGrideAdapter = new GridAdapter();
        grid.setAdapter(mGrideAdapter);
        Button addData = (Button)findViewById(R.id.add_data);
        addData.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                addData();
                mGrideAdapter.notifyDataSetChanged();
            }
        });
    }
    private List<String> getData() {
        List<String> data = new ArrayList<String>();
        for (int i = 1;i<15;i++){
            data.add("DATA "+i);
        }
        return data;
    }
    public void addData(){
        mDatas.addAll(mDatas);
        //mGrideAdapter.notifyDataSetChanged();
    }
    public class GridAdapter extends BaseAdapter {
        public View getView(int position, View view, ViewGroup parent) {
            Item item;
            if(view != null && view.getTag() != null){
                item = (Item)view.getTag();
            }else{
                item = new Item();
                view = getLayoutInflater().inflate(R.layout.item_cover, null, false);
                item.cover = (ImageView)view.findViewById(R.id.ivCover);
                item.title = (TextView)view.findViewById(R.id.title);
            }
            item.title.setText(mDatas.get(position));
            return view;
        }
        class Item {
            ImageView cover;
            TextView title;
        }
        public final int getCount() {
            return mDatas.size();
        }
        public final Object getItem(int position) {
            return null;
        }
        public final long getItemId(int position) {
            return position;
        }
    }
}

// When set, dispatchDraw() will run the layout animation and unset the flag
  private static final int FLAG_RUN_ANIMATION = 0x8;
    @Override
    protected void dispatchDraw(Canvas canvas) {
        //...
        if ((flags & FLAG_RUN_ANIMATION) != 0 && canAnimate()) {
            final boolean buildCache = !isHardwareAccelerated();
            for (int i = 0; i < childrenCount; i++) {
                final View child = children[i];
                if ((child.mViewFlags & VISIBILITY_MASK) == VISIBLE) {
                    final LayoutParams params = child.getLayoutParams();
                    attachLayoutAnimationParameters(child, params, i, childrenCount);
                    bindLayoutAnimation(child);
                }
            }
            final LayoutAnimationController controller = mLayoutAnimationController;
            if (controller.willOverlap()) {
                mGroupFlags |= FLAG_OPTIMIZE_INVALIDATE;
            }
            controller.start();
    //清除标识, 后续不再执行LayoutAnimation
            mGroupFlags &= ~FLAG_RUN_ANIMATION;
            mGroupFlags &= ~FLAG_ANIMATION_DONE;
            if (mAnimationListener != null) {
                mAnimationListener.onAnimationStart(controller.getAnimation());
            }
        }
        //...
    }
    /**
     * Runs the layout animation. Calling this method triggers a relayout of
     * this view group.
     */
    public void startLayoutAnimation() {
        if (mLayoutAnimationController != null) {
            mGroupFlags |= FLAG_RUN_ANIMATION;
            requestLayout();
        }
    }
    /**
     * Schedules the layout animation to be played after the next layout pass
     * of this view group. This can be used to restart the layout animation
     * when the content of the view group changes or when the activity is
     * paused and resumed.
     */
    public void scheduleLayoutAnimation() {
        mGroupFlags |= FLAG_RUN_ANIMATION;
    }