RecyclerView存储/还原活动之间的状态

Question

我正在将ListViews迁移到RecyclerViews。对于列表视图，我使用了此处介绍的通用技术来存储和恢复活动之间的滚动位置。如何使用RecyclerViews进行相同操作？在RecyclerView.onSaveInstanceState()似乎有protected访问权限，因此无法直接使用。

Answer 1

好吧，所以回答我自己的问题。据我了解，由于它们已经将布局代码和视图回收代码（即名称）分离了，因此负责保持布局状态（并恢复其状态）的组件现在已LayoutManager在您的recyclerview中使用。

因此，要存储状态，请使用相同的模式，但要在布局管理器而不是recyclerview上：

protected void onSaveInstanceState(Bundle state) {

     super.onSaveInstanceState(state);

     // Save list state

     mListState = mLayoutManager.onSaveInstanceState();

     state.putParcelable(LIST_STATE_KEY, mListState);

}

恢复状态onRestoreInstanceState()：

protected void onRestoreInstanceState(Bundle state) {

    super.onRestoreInstanceState(state);

    // Retrieve list state and list/item positions

    if(state != null)

        mListState = state.getParcelable(LIST_STATE_KEY);

}

然后更新LayoutManager（我在中做onResume()）：

@Override

protected void onResume() {

    super.onResume();

    if (mListState != null) {

        mLayoutManager.onRestoreInstanceState(mListState);

    }

}

Answer 2

我找到了一个更好的解决方案 -该解决方案具有以下优点：

RecyclerView状态会在手机旋转时保存和恢复

RecyclerView状态在通过RecyclerView 返回活动时得以保存和恢复（在显示其他活动时未销毁该状态-这意味着onRestoreInstanceState()不称为!!）

码

public class ActivityItemList extends AppCompatActivity

{

    private final String KEY_RECYCLER_STATE = "recycler_state";

    private RecyclerView mRecyclerView;

    private static Bundle mBundleRecyclerViewState;

    @Override

    protected void onCreate(Bundle savedInstanceState)

    {

        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_list);//set to whatever layout name you have

        mRecyclerView = (RecyclerView) findViewById(R.id.recycler_view);//set to whatever view id you use

        // don't forget to set your adapter

    }

    @Override

    protected void onPause()

    {

        super.onPause();

        // save RecyclerView state

        mBundleRecyclerViewState = new Bundle();

        Parcelable listState = mRecyclerView.getLayoutManager().onSaveInstanceState();

        mBundleRecyclerViewState.putParcelable(KEY_RECYCLER_STATE, listState);

    }

    @Override

    protected void onResume()

    {

        super.onResume();

        // restore RecyclerView state

        if (mBundleRecyclerViewState != null) {

            Parcelable listState = mBundleRecyclerViewState.getParcelable(KEY_RECYCLER_STATE);

            mRecyclerView.getLayoutManager().onRestoreInstanceState(listState);

        }

    }

}

Answer 3

那是我的解决方案，它可以还原项目和RecyclerView的位置

1）在onSaveInstanceState方法中保存回收者视图状态

@Override

protected void onSaveInstanceState(Bundle outState) {

    Parcelable listState = myRecyclerView.getLayoutManager().onSaveInstanceState();

    // putting recyclerview position

    outState.putParcelable(SAVED_RECYCLER_VIEW_STATUS_ID, listState);

    // putting recyclerview items

    outState.putParcelableArrayList(SAVED_RECYCLER_VIEW_DATASET_ID,mDataset);

    super.onSaveInstanceState(outState);

}

2）在onCreate方法中检查savedInstanceState Bundle

@Override

    protected void onCreate(@Nullable Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        if (savedInstanceState==null){

            getRemoteData(); // No saved data, get data from remote

        }else{

            restorePreviousState(); // Restore data found in the Bundle

        }

    }

3）如果屏幕已旋转，请还原回收者视图数据

public void restorePreviousState(){

    // getting recyclerview position

    mListState = mSavedInstanceState.getParcelable(SAVED_RECYCLER_VIEW_STATUS_ID);

    // getting recyclerview items

    mDataset = mSavedInstanceState.getParcelableArrayList(SAVED_RECYCLER_VIEW_DATASET_ID);

    // Restoring adapter items

    mAdapter.setItems(mDataset);

    // Restoring recycler view position

    mRvMedia.getLayoutManager().onRestoreInstanceState(mListState);

}