我正在尝试将 Firebase 支持的 RecyclerView 集成到 React Native 应用程序中。对于硬编码数据,它运行良好,但是在插入动态加载的行并在 RecyclerView.Adapter 上调用 notifyItemInserted() 或 notifyDataSetChanged() 时,RecyclerView 本身不会反射(reflect)更改。这表现为一个初始的空白 View ,直到应用程序的刷新按钮被点击,这具有从 React Native 端重新渲染 RecyclerView 的唯一效果,或者直到滚动或屏幕方向改变。
在阅读了本网站上关于不涉及 React Native 的类似问题的十几个或更多问题并尝试了大多数常见解决方案后,我怀疑这个问题与 React Native 特别相关。
鉴于 React Native 的 ListView 实现的持续性能问题,找到解决方案可能对许多人有所帮助。
public class PostsAdapter extends RecyclerView.Adapter<PostsAdapter.ViewHolder> {
ArrayList<Post> mDataset;
public PostsAdapter(ArrayList<Post> list){
mDataset = list;
}
public static class ViewHolder extends RecyclerView.ViewHolder {
public LinearLayout mPostView;
public ViewHolder(LinearLayout v) {
super(v);
mPostView = v;
}
}
@Override
public PostsAdapter.ViewHolder onCreateViewHolder(ViewGroup parent,
int viewType) {
LinearLayout v = (LinearLayout) LayoutInflater.from(parent.getContext())
.inflate(R.layout.post, parent, false);
ViewHolder vh = new ViewHolder(v);
return vh;
}
@Override
public void onBindViewHolder(ViewHolder holder, int position) {
TextView tv = (TextView) holder.mPostView.findViewById(R.id.title);
tv.setText(mDataset.get(position).title);
}
@Override
public int getItemCount() {
return mDataset.size();
}
}
public class RNPostsViewManager extends SimpleViewManager{
private ArrayList<Post> mDataset = new ArrayList<>();
public static final String REACT_CLASS = "AndroidPostsView";
private RecyclerView mRecyclerView;
private PostsAdapter mAdapter;
private RecyclerView.LayoutManager mLayoutManager;
private DatabaseReference mDatabase;
private Query initialDataQuery;
private ChildEventListener initialDataListener;
@Override
public String getName() {
return REACT_CLASS;
}
@UiThread
public void addPost (Post p){
mDataset.add(p);
mAdapter.notifyItemInserted(mDataset.size()-1);
}
@Override
public RecyclerView createViewInstance( ThemedReactContext context) {
mAdapter = new PostsAdapter(mDataset);
mRecyclerView = new RecyclerView(context){
@Override
protected void onAttachedToWindow() {
super.onAttachedToWindow();
initialDataQuery.addChildEventListener(initialDataListener);
}
};
mLayoutManager = new LinearLayoutManager(context.getCurrentActivity(), LinearLayoutManager.VERTICAL, false);
DividerItemDecoration mDecoration = new DividerItemDecoration(context, 1);
mDecoration.setDrawable(ContextCompat.getDrawable(context.getCurrentActivity(), R.drawable.sep));
mRecyclerView.setLayoutManager(mLayoutManager);
mRecyclerView.addItemDecoration(mDecoration);
mRecyclerView.setItemAnimator(new DefaultItemAnimator());
mRecyclerView.setAdapter(mAdapter);
mDatabase = FirebaseDatabase.getInstance().getReference();
initialDataQuery = mDatabase.child("wp-posts").orderByChild("unixPostDate").limitToFirst(100);
initialDataListener = new ChildEventListener() {
@Override
public void onChildAdded(DataSnapshot dataSnapshot, String previousChildName) {
Post p = dataSnapshot.getValue(Post.class);
addPost(p);
}
@Override
public void onChildChanged(DataSnapshot dataSnapshot, String previousChildName) {
}
@Override
public void onChildRemoved(DataSnapshot dataSnapshot) {
}
@Override
public void onChildMoved(DataSnapshot dataSnapshot, String previousChildName) {
}
@Override
public void onCancelled(DatabaseError databaseError) {
}
};
return mRecyclerView;
}
}
// layout file post.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:background="@android:color/background_light"
android:clickable="true"
android:focusable="true"
android:gravity="center_vertical"
android:orientation="horizontal"
android:padding="10dp"
android:weightSum="1">
<Button
android:id="@+id/button"
style="@style/Widget.AppCompat.Button.Small"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginRight="20dp"
android:background="@android:drawable/ic_menu_more"
android:gravity="center_vertical" />
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_gravity="fill_vertical"
android:orientation="horizontal"
android:weightSum="1">
<TextView
android:id="@+id/title"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_gravity="fill_vertical"
android:layout_weight="1"
android:gravity="top"
android:text="TextView"
android:textColor="@color/title"
android:textStyle="bold" />
</LinearLayout>
</LinearLayout>
最佳答案
问题是当 RecyclerView
是原生 UI 组件时,requestLayout
无法正常工作。
以下 hack 解决了所有这些问题:
我现在覆盖 RecyclerView
中的 requestLayout
方法。
然后在任何 notify*
方法,甚至 scrollToPosition
调用或任何调用重新布局的方法之前,我允许我的自定义 requestLayout
方法强制重新布局。
最终结果是这样的:
private boolean mRequestedLayout = false;
public void aMethodThatUpdatesStuff(int indexToUpdate, ReadableMap updatedChild) {
final SPAdapter adapter = (SPAdapter) getAdapter();
mRequestedLayout = false;
adapter.updateDataAtIndex(indexToUpdate, updatedChild); // <-- this runs notifyItemChanged inside
}
@Override
public void requestLayout() {
super.requestLayout();
// We need to intercept this method because if we don't our children will never update
// Check https://stackoverflow.com/questions/49371866/recyclerview-wont-update-child-until-i-scroll
if (!mRequestedLayout) {
mRequestedLayout = true;
this.post(new Runnable() {
@SuppressLint("WrongCall")
@Override
public void run() {
mRequestedLayout = false;
layout(getLeft(), getTop(), getRight(), getBottom());
onLayout(false, getLeft(), getTop(), getRight(), getBottom());
}
});
}
}
关于android - React Native 中的 RecyclerView : notifyItemInserted() and notifyDataSetChanged() have no effect,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/44868899/