android - 如何在屏幕旋转时保持RecyclerView的滚动位置

我正在用gridlayoutmanager填充recyclerview。现在我想保存屏幕旋转时的滚动位置。
我尝试使用onSaveInstanceState和onRestoreInstanceState（）来执行此操作，如本文所示：
How to save RecyclerView's scroll position using RecyclerView.State?
以下是我的代码：

@Override
protected void onSaveInstanceState(Bundle outState) {
    Log.e(TAG, "onSaveInstanceState");
    super.onSaveInstanceState(outState);
    outState.putParcelable(KEY_INSTANCE_STATE_RV_POSITION,
    gridLayoutManager.onSaveInstanceState());
 }


@Override
protected void onRestoreInstanceState(Bundle savedInstanceState) {

    Log.e(TAG, "onRestoreInstanceState");
    super.onRestoreInstanceState(savedInstanceState);
    if (savedInstanceState!= null){
        Parcelable savedState =
    savedInstanceState.getParcelable(KEY_INSTANCE_STATE_RV_POSITION);

        movieAdapter.addAll(movieItemList);
        if (savedState!= null){
            gridLayoutManager.onRestoreInstanceState(savedState);
        }
    }
}


//this is my movieAdapter.addAll() method

public void addAll(List<MovieItem>items){

    movieItems = items;
}


//This is the method to get lists of movies from ViewModel Class

private void loadFavMovies() {
    FavViewModel favViewModel =
    ViewModelProviders.of(MainActivity.this).get(FavViewModel.class);
    favViewModel.getFavListLiveData().observe(MainActivity.this, new
    Observer<List<FavlistItem>>() {
        @Override
        public void onChanged(List<FavlistItem> favlistItems) {
            if (!favlistItems.isEmpty()) {
                loadingIndicator.setVisibility(View.GONE);
                movieRecycler.setVisibility(View.GONE);
                favRecycler.setVisibility(View.VISIBLE);
                favAdapter.setFavlistItems(favlistItems);
                Toast.makeText(getApplicationContext(), "Swipe Left Or
       Right To remove Item",Toast.LENGTH_SHORT).show();
               }else {
                loadingIndicator.setVisibility(View.GONE);
                Toast.makeText(getApplicationContext(), "No Favorite
      Movies",Toast.LENGTH_SHORT).show();
            }
        }
    });
}

这是此项目的github链接https://github.com/harshabhadra/Movies-Mela

最佳答案

这样做的一个方法是停止在方向改变时重新创建活动。您可以将其添加到清单中的活动中。

android:configChanges="orientation|screenSize"

但这并不总是一个好的实践，所以另一个选择是在退出onSaveInstanceState之前保存适配器位置，然后使用onCreate滚动到scrollToPosition中的那个位置。所以，举个例子，你可以按照下面的思路做一些事情。

    @Override
    public void onSaveInstanceState(Bundle savedInstanceState) {
      savedInstanceState.putInt("position", mRecyclerView.getAdapterPosition()); // get current recycle view position here.
      //your other code
      super.onSaveInstanceState(savedInstanceState);
    }

    @Override
    protected void onCreate(Bundle savedInstanceState) {
      super.onCreate(savedInstanceState);
      //your other code
      if(savedInstanceState != null){
        // scroll to existing position which exist before rotation.

  mRecyclerView.scrollToPosition(savedInstanceState.getInt("position"));
      }
   }