如何在其他活动的后按中保留“回收者"视图的滚动位置? [英] How to retain the scrolled position of a Recycler view on back press from another activity?

问题描述

我看到了许多与此主题相关的问题，但是没有一个问题对我有帮助.我的RecyclerView使用的是 StaggeredGridLayout (显示卡片). 每个CardView都会打开一个新活动，我面临的问题是，在该新活动上按一下后，RecyclerView会滚动回到顶部.我希望它保留以前的滚动位置.

I saw many related questions about this topic, but none of them helped me. I am using a StaggeredGridLayout for my RecyclerView (showing cards). Every CardView opens a new activity, the problem I am facing is that on back press from that new activity, the RecyclerView scrolls back to the top. I want it to retain the previously scrolled position.

这是我现在用来设置布局的内容:

rv.setLayoutManager(new StaggeredGridLayoutManager(2, StaggeredGridLayoutManager.VERTICAL));
rv.setHasFixedSize(true);

任何适合新手的可行解决方案?

Any proper working solution for a newbie?

   @Override
 protected void onResume() {
     super.onResume();
    if (listState != null) {
        rvlayout.onRestoreInstanceState(listState);
    }
      initializeData();

 }

布局:

RecyclerView.LayoutManager rvlayout = new StaggeredGridLayoutManager(2, StaggeredGridLayoutManager.VERTICAL);

和initializeData:

and initializeData :

 public void initializeData() {

    rv.setLayoutManager(rvlayout);
    rv.setHasFixedSize(true);
    persons.clear();

    c = db.rawQuery(SELECT_SQL, null);
    c.moveToFirst();

    if (!c.moveToFirst())
    return;


    while (!c.isLast()) {
        id = c.getString(0);
        names = c.getString(1);
        age = c.getString(2);
        persons.add(new Person(id,names,age));
        c.moveToNext();
    }

    adapter = new RVAdapter(persons);
    rv.setAdapter(adapter);

}

推荐答案

正确的方法是保存RecyclerView滚动位置的状态并在活动"之间进行切换时将其还原.

The proper way to do it is to save the state of RecyclerView scroll position and restore it while switching between Activities.

protected void onSaveInstanceState(Bundle state) {
    super.onSaveInstanceState(state);

    state.putParcelable(LIST_STATE_KEY, layoutManager.onSaveInstanceState());
}

2.要检索数据，请重写onRestoreInstanceState()

protected void onRestoreInstanceState(Bundle state) {
    super.onRestoreInstanceState(state);

    Parcelable listState = state.getParcelable(LIST_STATE_KEY);
}

3.最后用onResume()方法更新LayoutManager

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

    if (listState != null) {
        layoutManager.onRestoreInstanceState(listState);
    }
}

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