对话框解除动画不适用

Question

我有一个DialogFragment，其唯一的子节点是StackView。在父片段中单击按钮时，将启动该对话框。

我尝试通过getWindow（）。setWindowAnimations（）向片段添加动画但由于某种原因它无法正常工作。

我采用的方法是为Window的decorView设置动画：

public class TrailerDialogFragment extends DialogFragment {

    private static final String VIDEOS_EXTRA = "videos extra";

    private List<Video> mVideos = new ArrayList<>();

    @BindView(R.id.stack_view)
    StackView mStackView;

    @Override
    public void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        List<Video> videos = getArguments().getParcelableArrayList(VIDEOS_EXTRA);
        if (videos != null) {mVideos.addAll(videos);}
    }

    public static TrailerDialogFragment newInstance(List<Video> videos) {
        Bundle bundle = new Bundle();
        ArrayList<Video> arrayList = new ArrayList<>();
        arrayList.addAll(videos);
        bundle.putParcelableArrayList(VIDEOS_EXTRA, arrayList);
        TrailerDialogFragment fragment = new TrailerDialogFragment();
        fragment.setArguments(bundle);
        return fragment;
    }


    @Nullable
    @Override
    public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container,
                             @Nullable Bundle savedInstanceState) {
        View rootView = inflater.inflate(R.layout.dialog_stackview, container, false);

        ButterKnife.bind(this, rootView);
        mStackView.setAdapter(new VideoAdapter(mVideos));

        return rootView;
    }

    @NonNull
    @Override
    public Dialog onCreateDialog(Bundle savedInstanceState) {
        Dialog dialog = super.onCreateDialog(savedInstanceState);
        dialog.getWindow().setBackgroundDrawable(new ColorDrawable(Color.TRANSPARENT));
        return dialog;
    }

    @Override
    public void onStart() {
        super.onStart();
        final View decorView = getDialog()
                .getWindow()
                .getDecorView();

        ObjectAnimator scaleDown = ObjectAnimator.ofPropertyValuesHolder(decorView,
                PropertyValuesHolder.ofFloat("scaleX", 0.0f, 1.0f),
                PropertyValuesHolder.ofFloat("scaleY", 0.0f, 1.0f),
                PropertyValuesHolder.ofFloat("alpha", 0.0f, 1.0f));
        scaleDown.setDuration(500);
        scaleDown.start();
    }

    @Override
    public void onCancel(DialogInterface dialog) {
        final View decorView = getDialog()
                .getWindow()
                .getDecorView();

        ObjectAnimator scaleDown = ObjectAnimator.ofPropertyValuesHolder(decorView,
                PropertyValuesHolder.ofFloat("scaleX", 1.0f, 0.0f),
                PropertyValuesHolder.ofFloat("scaleY", 1.0f, 0.0f),
                PropertyValuesHolder.ofFloat("alpha", 1.0f, 0.0f));
        scaleDown.setDuration(500);
        scaleDown.start();
        super.onCancel(dialog);
    }

    private static class VideoAdapter extends BaseAdapter {

        List<Video> mVideos = new ArrayList<>();

        public VideoAdapter(List<Video> videos) {
            mVideos.addAll(videos);
        }

        @Override
        public int getCount() {
            return mVideos.size();
        }

        @Override
        public Object getItem(int i) {
            return mVideos.get(i);
        }

        @Override
        public long getItemId(int i) {
            return 0;
        }

        @Override
        public View getView(int i, View view, ViewGroup viewGroup) {
            View resultView;
            if (view == null) {
                resultView = LayoutInflater.from(viewGroup.getContext()).inflate(
                        R.layout.dummy_view, viewGroup, false);
            } else  {
                resultView = view;
            }
            TextView tv = (TextView) resultView.findViewById(R.id.trailer_title);
            ImageView image = (ImageView) resultView.findViewById(R.id.trailer_image);

            tv.setText(mVideos.get(i).name());
            ViewUtil.loadThumbnail(mVideos.get(i).key(), resultView.getContext(), image);
            return resultView;
        }
    }
}

当我单击对话框片段外部时，会触发onCancel回调，但由于某种原因，动画无法播放。 DialogFragment只是消失了。

你知道为什么会这样吗？