如何迭代DataSnapshot？

Question

我正在尝试迭代联系人节点的子节点. .

但是我的ListArray contacts只是部分填充.前两个条目按预期填充数组(从Logcat输出),但第三个条目无法填充数组.这是MainActivity.java:

public class MainActivity extends AppCompatActivity {
TextView stringTextView;

@Override
protected void onCreate(@Nullable Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    stringTextView = (TextView)findViewById(R.id.textView2);

    FirebaseDatabase firebaseDatabase= FirebaseDatabase.getInstance().getInstance();
    DatabaseReference dbRef= firebaseDatabase.getReference("County/Dublin");

    dbRef.addValueEventListener(new ValueEventListener() {
        @Override
        public void onDataChange(DataSnapshot dataSnapshot) {

            DataSnapshot contactSnapshot = dataSnapshot.child("contacts");
            Iterable<DataSnapshot> contactChildren = contactSnapshot.getChildren();
            ArrayList<Contact> contacts= new ArrayList<>();

            for (DataSnapshot contact : contactChildren) {
                Contact c = contact.getValue(Contact.class);
                Log.d("contact:: ", c.name + " " + c.number);
                contacts.add(c);
            }
        }

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

和模型类Contact.java:

public class Contact {
public String name;
public String number;

public Contact() {
}


public Contact(String name, String number) {
    this.name = name;
    this.number = number;
}
}

为什么我ListArray没有完全填充？

UPDATE

以下是我对建议的代码示例所做的事情:

@Override
        public void onDataChange(DataSnapshot dataSnapshot) {
            ArrayList<String> names= new ArrayList<>();
            for(DataSnapshot ds : dataSnapshot.getChildren()) {
                String name = ds.child("name").getValue(String.class);
                names.add(name);
                String number = ds.child("number").getValue(String.class);
                Log.d("TAG", name);
            }
            for(int i=0; i < names.size(); i++){

                stringTextView.setText(stringTextView.getText() + names
                        .get(i) + " , ");
            }
        }

数组仍然没有填充,也没有显示到屏幕上.

Answer 1

请使用此代码:

DatabaseReference rootRef = FirebaseDatabase.getInstance().getReference();
DatabaseReference ref = rootRef.child("County").child("Dublin").child("contacts");
ValueEventListener eventListener = new ValueEventListener() {
    @Override
    public void onDataChange(DataSnapshot dataSnapshot) {
        ArrayList<String> names= new ArrayList<>();
        for(DataSnapshot ds : dataSnapshot.getChildren()) {
            String name = ds.child("name").getValue(String.class);
            names.add(name);
            String number = ds.child("number").getValue(String.class);
            Log.d("TAG", name + " / " + number);
        }
        for(String name : names) {
            TextView stringTextView = (TextView) findViewById(R.id.string_text_view);
            stringTextView.setText(stringTextView.getText().toString() + name + " , ");
        }
    }

    @Override
    public void onCancelled(DatabaseError databaseError) {}
};
ref.addListenerForSingleValueEvent(eventListener);

你的输出将是:

ger / 0213
paddy / 3345556
jeff / 55555

因此,拥有这些数据,您可以将它添加到ArrayList,显示它,用它做你想做的事情.