Java RecyclerView未显示收到的数据
我从Firebase(在线数据存储)获取数据,但不知怎的,在我的适配器类中,数据集是[]。然而,当我使用同一个类传入20个随机事件时,它工作得非常好。这是代码 片段类:Java RecyclerView未显示收到的数据,java,android,fragment,firebase,android-recyclerview,Java,Android,Fragment,Firebase,Android Recyclerview,我从Firebase(在线数据存储)获取数据,但不知怎的,在我的适配器类中,数据集是[]。然而,当我使用同一个类传入20个随机事件时,它工作得非常好。这是代码 片段类: @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); myFirebaseRef = new Firebase("http..."); initListItems();
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
myFirebaseRef = new Firebase("http...");
initListItems();
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_products, container, false);
// Inflate the layout for this fragment
mRecyclerView = (RecyclerView) rootView.findViewById(R.id.list);
mRecyclerView.setLayoutManager(new LinearLayoutManager(getActivity().getApplicationContext()));
mAdapter = new MyAdapter(mDataset);
mRecyclerView.setAdapter(mAdapter);
return rootView;
}
// Get the data from Firebase and set it to List
private void initListItems() {
// Attach an listener to read the data at our posts reference
myFirebaseRef.addValueEventListener(new ValueEventListener() {
@Override
public void onDataChange(DataSnapshot snapshot) {
System.out.println("There are " + snapshot.getChildrenCount() + "children");
for (DataSnapshot postSnapshot : snapshot.getChildren()) {
title = postSnapshot.child("name").getValue().toString();
description = postSnapshot.child("description").getValue().toString();
location = postSnapshot.child("location").getValue().toString();
//This displays the information so it is properly reading data in
System.out.println("title: " + title +
"description" + description + "location" + location);
mDataset.add(new ListItem(title, description, location, 0.00, 0.00));
}
}
});
// If i remove the above code and just put this, the recycleview displays this information
for (int i = 0; i<20; i++) {
String name ="This is element #" + i;
mDataset.add(new ListItem(name, "description", "location", 0.00, 0.00));
}
}
@覆盖
创建时的公共void(Bundle savedInstanceState){
super.onCreate(savedInstanceState);
myFirebaseRef=新Firebase(“http…”);
initListItems();
}
@凌驾
创建视图上的公共视图(布局、充气机、视图组容器、,
Bundle savedInstanceState){
视图根视图=充气机。充气(R.layout.fragment\u产品,容器,假);
//为该碎片膨胀布局
mRecyclerView=(RecyclerView)rootView.findviewbyd(R.id.list);
setLayoutManager(新的LinearLayoutManager(getActivity().getApplicationContext());
mAdapter=新的MyAdapter(mDataset);
mRecyclerView.setAdapter(mAdapter);
返回rootView;
}
//从Firebase获取数据并将其设置为List
私有void initListItems(){
//附加一个侦听器来读取我们的posts引用中的数据
myFirebaseRef.addValueEventListener(新的ValueEventListener(){
@凌驾
公共无效onDataChange(数据快照快照){
System.out.println(“有”+snapshot.getChildrenCount()+“子项”);
对于(DataSnapshot postSnapshot:snapshot.getChildren()){
title=postSnapshot.child(“name”).getValue().toString();
description=postSnapshot.child(“description”).getValue().toString();
location=postSnapshot.child(“location”).getValue().toString();
//这将显示信息,以便正确读取中的数据
System.out.println(“标题:”+标题+
“说明”+说明+“位置”+位置);
添加(新列表项(标题、描述、位置,0.00、0.00));
}
}
});
//如果我删除了上面的代码并将其放入,recycleview将显示此信息
对于(int i=0;i在onCreate
中,您可以异步获取数据-这可能需要一些时间。与此同时,程序流继续运行,您在onCreateView
中设置了回收器,但这发生在您获得数据响应之前,因此您的mDataset
仍然没有值。在您得到结果并将其放入mDataset
,但我看不到您将更改通知RecyclerView
的地方
因此,您必须将RecyclerView
的设置推迟到真正获得结果之后,或者在获得数据集更新后通知RecyclerView
。这是正确的,因此在onDataChange
中,在mDataset.add()之后再调用notifyDataSetChanged()
。请注意,我们正在为FirebaseUI添加一个RecycleView适配器来为您解决这个问题:(0.2应该完成RecycleWebAdapter合同,它现在在一个分支上)。非常感谢您。我所要做的就是在mDataset.add(新启动(标题、说明、位置、0.00、0.00))之后添加mAdapter.notifyDataSetChanged();
public class MyAdapter extends RecyclerView.Adapter<MyAdapter.ViewHolder> {
private static final String TAG = "MyAdapter";
private List<ListItem> mDataSet;
/**
* Provide a reference to the type of views that you are using (custom ViewHolder)
*/
public static class ViewHolder extends RecyclerView.ViewHolder {
private final TextView textView;
private final ImageView imageView;
private final TextView textViewLocation;
public ViewHolder(View v) {
super(v);
// Define click listener for the ViewHolder's View.
v.setOnClickListener(new View.OnClickListener() {
...
});
textView = (TextView) v.findViewById(R.id.startupName);
textViewLocation = (TextView) v.findViewById((R.id.startupLocation));
imageView = (ImageView) v.findViewById(R.id.startupImage);
}
public TextView getTextView() {
return textView;
}
public TextView getTextViewLocation() {
return textViewLocation;
}
public ImageView getImageView() {
return imageView;
}
}
// When I try to send the data received from Firebase, it prints out [ ] but if i use the random data I created, it works
public MyAdapter(List<ListItem> dataSet) {
System.out.println("THE DATASET IS " + dataSet);
mDataSet = dataSet;
}
// Create new views (invoked by the layout manager)
@Override
public ViewHolder onCreateViewHolder(ViewGroup viewGroup, int viewType) {
// Create a new view.
View v = LayoutInflater.from(viewGroup.getContext())
.inflate(R.layout.row_item, viewGroup, false);
return new ViewHolder(v);
}
// Replace the contents of a view (invoked by the layout manager)
@Override
public void onBindViewHolder(ViewHolder viewHolder, final int position) {
Log.d(TAG, "Element " + position + " set.");
// Get element from your dataset at this position and replace the contents of the view with that element
...
}
// Return the size of your dataset (invoked by the layout manager)
@Override
public int getItemCount() {
return mDataSet == null ? 0 : mDataSet.size();
}
}