如何从Firebase检索ListView中的数据 [英] How can Retrieve data in ListView from Firebase

问题描述

您能帮我解决这个问题吗，我尝试在Listview的firebase中显示数据，但不显示任何内容！

Can you help me in this problem, I try to display data from in firebase in Listview, but Not Display anything!

ListView listView;
FirebaseDatabase firebaseDatabase;
DatabaseReference databaseReference;
ArrayList<String> arrayList = new ArrayList<>();

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_fairbase_list);

    firebaseDatabase=FirebaseDatabase.getInstance();
    databaseReference= firebaseDatabase.getReference("Users");


    listView=(ListView) findViewById(R.id.list);
    final ArrayAdapter<String>  arrayAdapter= new ArrayAdapter<String>(this ,android.R.layout.simple_list_item_1,arrayList);
    listView.setAdapter(arrayAdapter);
    Toast.makeText(this, "ok", Toast.LENGTH_SHORT).show();
    databaseReference.addChildEventListener(new ChildEventListener() {
        @Override
        public void onChildAdded(DataSnapshot dataSnapshot, String s) {
            String value=dataSnapshot.getValue(String.class);
            arrayList.add(value);
            arrayAdapter.notifyDataSetChanged();

        }

}

推荐答案

public class MainActivity extends AppCompatActivity{
 ListView listView;
    FirebaseDatabase firebaseDatabase;
    DatabaseReference databaseReference;
    ArrayList<String> arrayList = new ArrayList<>();
     ArrayAdapter<String> arrayAdapter;

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);

firebaseDatabase = FirebaseDatabase.getInstance();
databaseReference = firebaseDatabase.getReference("Users");


listView = (ListView) findViewById(R.id.lists);

Toast.makeText(this, "ok", Toast.LENGTH_SHORT).show();
databaseReference.addChildEventListener(new ChildEventListener() {
    @Override
    public void onChildAdded(DataSnapshot dataSnapshot, String s) {
        String value=dataSnapshot.getValue(String.class);
        arrayList.add(value);
        arrayAdapter = new ArrayAdapter<String>(MainActivity.this, android.R.layout.simple_list_item_1, arrayList);
        listView.setAdapter(arrayAdapter);

    }

    @Override
    public void onChildChanged(DataSnapshot dataSnapshot, String s) {

    }

    @Override
    public void onChildRemoved(DataSnapshot dataSnapshot) {

    }

    @Override
    public void onChildMoved(DataSnapshot dataSnapshot, String s) {

    }

    @Override
    public void onCancelled(DatabaseError databaseError) {

    }
});

 }}

此侦听器实际上用于列表，因此它不是来自侦听器的. 另外，由于用户未通过身份验证，因此您需要将数据库中的规则更改为:-

This listener is actually used for lists, so its not from the listener. Also since the user is not authenticated you need to change the rules in your database to :-

 {
"rules": {
   ".read": "true",
   ".write": "true"
 }
}

这篇关于如何从Firebase检索ListView中的数据的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！