将值从 Firebase 添加到回收视图适配器不会显示在应用中

Question

我正试图从Firebase数据库返回键和值，并将其插入RecycleView适配器，但这些值不会显示在应用程序中。

我无论如何都无法理解。

我试着在Toast中显示值，结果成功了，但为什么不将值插入RecycleView适配器中呢？

这就是代码。

public class test extends AppCompatActivity {
TextView textView;
Button button;
String phone;
String n;
String a;
FirebaseAuth mAuth;
MyRecyclerViewAdapter adapter;
ArrayList<String> info;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_test);

Bundle b = new Bundle();
b = getIntent().getExtras();
phone = b.getString("number");
textView = findViewById(R.id.textV);
button = findViewById(R.id.signoutButton);
mAuth = FirebaseAuth.getInstance();
textView.setText(textView.getText().toString() + " as " + phone);

info = new ArrayList<>();

FirebaseDatabase myRef = FirebaseDatabase.getInstance();
DatabaseReference sRef = myRef.getReference("users");
sRef.addValueEventListener(new ValueEventListener() {

@Override
public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
for (DataSnapshot childSnap : dataSnapshot.getChildren()) {
if (childSnap.getKey().equals(phone)) {
for (DataSnapshot c : childSnap.getChildren()) {
n = c.getKey();
a = c.getValue().toString();
info.add(n);
info.add(a);

}

}

}
}
@Override
public void onCancelled(@NonNull DatabaseError databaseError) {
}
});

RecyclerView recyclerView = findViewById(R.id.rvInfo);
recyclerView.setLayoutManager(new LinearLayoutManager(this));
adapter = new MyRecyclerViewAdapter(this, info);
adapter.setClickListener(new MyRecyclerViewAdapter.ItemClickListener() {
@Override
public void onItemClick(View view, int position) {
Toast.makeText(test.this, "You clicked " + adapter.getItem(position) + " on row number " + position, Toast.LENGTH_SHORT).show();
}
});
recyclerView.setAdapter(adapter);

}
}

Answer 1

您可以使用以下代码获得

sRef.addValueEventListener(new ValueEventListener() {

@Override
public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
for (DataSnapshot childSnap : dataSnapshot.getChildren()) {
if (childSnap.getKey().equals(phone)) {
for (DataSnapshot c : childSnap.getChildren()) {
n = c.getKey();
a = c.getValue().toString();
info.add(n);
info.add(a);
}
}
}
notifyDataSetChanged();
}
@Override
public void onCancelled(@NonNull DatabaseError databaseError) {
}
});

你必须在从燃烧库中填充ArrayList之后添加notifyDataSetChanged();。因为从firebase加载数据需要时间。在从firebase填充ArrayList之前，您的适配器已初始化。