android工作室中的Recycler视图存在问题-仅偶尔出现

Question

我已经按照教程为我的应用程序创建了一个回收视图我不工作，因为它只是偶尔在视野中显示任何东西似乎没有任何犯罪或理由。。。

回收的布局

<?xml version="1.0" encoding="utf-8"?> 
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"    
android:id="@+id/parent_layout"
android:layout_width="match_parent"
android:layout_height="80dp">
<TextView
android:id="@+id/text_value"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:gravity="center_vertical"
android:text="Test"
android:textColor="#000000"
android:textSize="18sp" />
</LinearLayout>

带有回收视图的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="match_parent"
android:orientation="vertical">
<androidx.recyclerview.widget.RecyclerView
android:layout_width="match_parent"
android:layout_height="match_parent"
android:id="@+id/recycler_view_accounts"/>
</LinearLayout>

RecyclerViewAdapter类

public class RecyclerViewAdapterAccounts extends RecyclerView.Adapter<RecyclerViewAdapterAccounts.ViewHolder> {
private ArrayList<String> mlist;
private Context mContext;
public RecyclerViewAdapterAccounts(ArrayList<String> list, Context context) {
mlist = list;
mContext = context;
}
@NonNull
@Override
public RecyclerViewAdapterAccounts.ViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.layout_listitem, parent, false);
return new ViewHolder(view);
}
@Override
public void onBindViewHolder(@NonNull RecyclerViewAdapterAccounts.ViewHolder holder, final int position) {
holder.accountName.setText(mlist.get(position));
holder.parent_layout.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Toast.makeText(mContext, mlist.get(position), Toast.LENGTH_LONG).show();
}
});
}
@Override
public int getItemCount() {
return mlist.size();
}
public class ViewHolder extends RecyclerView.ViewHolder{
TextView accountName;
LinearLayout parent_layout;
public ViewHolder(@NonNull View itemView) {
super(itemView);
accountName = itemView.findViewById(R.id.text_value);
parent_layout = itemView.findViewById(R.id.parent_layout);
}
}
}

相关的onCreate活动

@Override
protected void onCreate(@Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_manage_accounts);
initAccounts();
RecyclerView recyclerView = findViewById(R.id.recycler_view_accounts);
RecyclerViewAdapterAccounts adapter = new RecyclerViewAdapterAccounts(accounts, this);
recyclerView.setAdapter(adapter);
recyclerView.setLayoutManager(new LinearLayoutManager(this));
adapter.notifyDataSetChanged();
}

虽然没有显示，但我可以测试initAccounts((是否按原样填充数组我还可以看到onCreateViewHolder和onBindViewHolder没有被称为

有什么建议吗？？？

编辑：这是initAccounts

private void initAccounts() {
DatabaseReference userRef = 
FirebaseDatabase.getInstance().getReference().child("users");
userRef.addListenerForSingleValueEvent(new ValueEventListener() {
@Override
public void onDataChange(@NonNull DataSnapshot snapshot) {
Iterator<DataSnapshot> children = snapshot.getChildren().iterator();
while (children.hasNext()) {
DataSnapshot child = children.next();
String[] parts = child.getValue().toString().split(",");
String role = parts[0].replace('{', ' ');
String msg = child.getKey() + ": " + role;
accounts.add(msg);
}
}
@Override
public void onCancelled(@NonNull DatabaseError error) {
}
});

}

Answer 1

这里的问题是向accounts添加对象，但没有将更改通知适配器。对代码进行以下更改。若要在onCreate()内部设置适配器，请仅使用。

private RecyclerViewAdapterAccounts adapter;
@Override
protected void onCreate(@Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_manage_accounts);
initAccounts();
RecyclerView recyclerView = findViewById(R.id.recycler_view_accounts);
recyclerView.setLayoutManager(new LinearLayoutManager(this));
adapter = new RecyclerViewAdapterAccounts(accounts, this);
recyclerView.setAdapter(adapter);
}

现在在RecyclerViewAdapterAccounts中创建一个方法，在适配器中添加元素；

public void addAll(ArratList<String> list){
mlist.clear();// To clear list if thats the case
mlist.addAll(list);
notifyDataSetChanged();
}

现在，您可以在一个转到适配器中添加所有元素。

public void onDataChange(@NonNull DataSnapshot snapshot) {
ArrayList<String> dataList=new ArrayList<>();
Iterator<DataSnapshot> children = snapshot.getChildren().iterator();
while (children.hasNext()) {
DataSnapshot child = children.next();
String[] parts = child.getValue().toString().split(",");
String role = parts[0].replace('{', ' ');
String msg = child.getKey() + ": " + role;
dataList.add(msg);
}
adapter.addAll(dataList);
}