这是我的数据:
{
"users" : {
"00c49c66-7ac8-9a48-7c4541d8bac6" : {
"email" : "d@gmail.com",
"gender" : "m",
"name" : "deepak",
"user_id" : "00c49c66-7ac8-9a48-7c4541d8bac6"
},
"1cb9c1de-1fcf-a2cc-bf78c84e03c8" : {
"email" : "e@gmail.com",
"gender" : "f",
"name" : "ekta",
"user_id" : "1cb9c1de-1fcf-a2cc-bf78c84e03c8"
},
"38211c3f-6c48-8987-0c698b9b9b52" : {
"email" : "c@gmail.com",
"gender" : "m",
"name" : "chirag",
"user_id" : "38211c3f-6c48-8987-0c698b9b9b52"
},
"a536cf1f-419f-9658-cfb5f5a8ec78" : {
"email" : "a@gmail.com",
"gender" : "m",
"name" : "aniket",
"user_id" : "a536cf1f-419f-9658-cfb5f5a8ec78"
},
"c80d828d-48d7-a79a-9cc558cd1960" : {
"email" : "b@gmail.com",
"gender" : "f",
"name" : "bhakti",
"user_id" : "c80d828d-48d7-a79a-9cc558cd1960"
}
}
}
现在我要获取“性别”为“ m”的“名称”和“ id”
请任何人告诉我如何从Android客户端向Firebase触发这样的查询。
我尝试了firebase和其他一些链接提供的教程,但没有通过。
大多数解决方案都在Javascript中,而Firebase的Java API中则需要Android。
我试过了
public class ActivityHome extends Activity {
String strLoggedInUserID;
TextView tvData;
Firebase fbRef = new Firebase("https://myurl.com/users");
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_home);
tvData = (TextView) findViewById(R.id.tvData);
Query queryRef = fbRef.orderByChild("gender").equalTo("m");
Bundle extras = getIntent().getExtras();
strLoggedInUserID = extras.getString("userID");
fbRef.addValueEventListener(new ValueEventListener() {
@Override
public void onDataChange(DataSnapshot dataSnapshot) {
}
@Override
public void onCancelled(FirebaseError firebaseError) {
}
});
queryRef.addChildEventListener(new ChildEventListener() {
@Override
public void onChildAdded(DataSnapshot dataSnapshot, String s) {
//long longChildCount = dataSnapshot.getChildrenCount();
// tvData.setText(dataSnapshot).toString();
tvData.setText(s);
}
@Override
public void onChildChanged(DataSnapshot dataSnapshot, String s) {
//tvData.setText(s);
}
@Override
public void onChildRemoved(DataSnapshot dataSnapshot) {
}
@Override
public void onChildMoved(DataSnapshot dataSnapshot, String s) {
}
@Override
public void onCancelled(FirebaseError firebaseError) {
}
});
}
}
最佳答案
您的查询代码看起来正确,但是您不打印用户。
由于您要添加ChildEventListener
,因此将为每个孩子调用它:
queryRef.addChildEventListener(new ChildEventListener() {
@Override
public void onChildAdded(DataSnapshot dataSnapshot, String s) {
//long longChildCount = dataSnapshot.getChildrenCount();
// tvData.setText(dataSnapshot).toString();
tvData.setText(s);
}
dataSnapshot
参数包含有关单个用户的信息。要打印其密钥,名称和电子邮件:queryRef.addChildEventListener(new ChildEventListener() {
@Override
public void onChildAdded(DataSnapshot dataSnapshot, String s) {
System.out.println(dataSnapshot.key());
System.out.println(dataSnapshot.child("name").getValue());
System.out.println(dataSnapshot.child("email").getValue());
}
或者,您可以使用
ValueEventListener
一次收听所有孩子。private static class User {
String email;
String gender;
String name;
@JsonProperty("user_id")
String userId;
public String getEmail() { return email; }
public String getGender() { return gender; }
public String getName() { return name; }
public String getUserId() { return userId; }
}
queryRef.addValueEventListener(new ValueEventListener() {
@Override
public void onDataChange(DataSnapshot dataSnapshot) {
for (DataSnapshot child: dataSnapshot.getChildren()) {
User user = child.getValue(User.class);
System.out.println(user.getEmail());
}
}
@Override
public void onCancelled(FirebaseError firebaseError) {
}
});
在最后一个代码片段中,我还使用一个
User
类从DataSnapshot
获取数据。随着应用程序的增长,这比不断调用DataSnapshot.child()
更方便。section on reading data in the Firebase documentation中对此进行了介绍。