Question

当我返回Fragment时，我有2个可重用的方法来恢复y RecyclerView中项目的位置。它适用于我的其他碎片。但是我有一个带有灵活空间的片段，图像为scrolling-techniques-behavior，在NestedScrollView中有一个RecyclerView。我无法获得位置和偏移量。我可以从适配器获得位置。但是当我尝试恢复位置时，没有任何反应，它总是显示顶部项目。

public static void storeRecyclerViewListPosition(Activity activity, final RecyclerView recyclerView, String identifier) {
        Log.i(TAG, "storeRecyclerViewListPosition: " + identifier);
        SharedPreferences preferences = PreferenceManager.getDefaultSharedPreferences(activity);

        View firstChild = recyclerView.getChildAt(0);
        if (firstChild != null) {
            int firstVisiblePosition = recyclerView.getChildAdapterPosition(firstChild);
            int offset = firstChild.getTop();

            Log.d(TAG, "storeRecyclerViewListPosition: " + identifier + "_position: " + firstVisiblePosition);
            Log.d(TAG, "storeRecyclerViewListPosition: " + identifier + "_offset: " + offset);

            preferences.edit()
                    .putInt(identifier + "_position", firstVisiblePosition)
                    .putInt(identifier + "_offset", offset)
                    .apply();
        }
    }


public static void restoreRecyclerViewListPosition(Activity activity, final RecyclerView recyclerView, final String identifier) {
        Log.i(TAG, "restoreRecyclerViewListPosition: " + identifier);

        final SharedPreferences preferences = PreferenceManager.getDefaultSharedPreferences(activity);
        Log.d(TAG, "storeRecyclerViewListPosition: " + identifier + "_position: " + preferences.getInt(identifier + "_position", 0));
        Log.d(TAG, "storeRecyclerViewListPosition: " + identifier + "_offset: " + preferences.getInt(identifier + "_offset", 0));

        recyclerView.scrollToPosition(preferences.getInt(identifier + "_position", 0));
        new Handler().postDelayed(new Runnable() {
            @Override
            public void run() {
                recyclerView.scrollBy(0, - preferences.getInt(identifier + "_offset", 0));
            }
        }, 500);
    }

Answer 1

你在做什么基本上是这样的：

int firstVisiblePosition = recyclerView.getChildAdapterPosition(recyclerView.getChildAt(0));

如标题所示，这与此相同：

int firstVisiblePosition = 0;

相反，你应该这样做：

int firstVisiblePosition = ((LinearLayoutManager) recyclerView.getLayoutManager()).findFirstCompletelyVisibleItemPosition();

也适用于GridLayoutManager。

我相应地采用了你的方法并对它们进行了一些编辑。这对我有用：

@Override
protected void onPause() {
    storeRecyclerViewListPosition();
    super.onPause();
}

@Override
protected void onResume() {
    restoreRecyclerViewListPosition();
    super.onResume();
}

public void storeRecyclerViewListPosition() {
    SharedPreferences preferences = PreferenceManager.getDefaultSharedPreferences(this);
    int firstVisiblePosition = ((LinearLayoutManager) recyclerView.getLayoutManager()).findFirstVisibleItemPosition();
    preferences.edit().putInt("position", firstVisiblePosition).apply();
}


public void restoreRecyclerViewListPosition() {
    final SharedPreferences preferences = PreferenceManager.getDefaultSharedPreferences(this);
    recyclerView.smoothScrollToPosition(preferences.getInt("position", 0));
}

NestedScrollView recyclelerView.scrollToPosition中的RecyclerView为0

1 个答案: