Android 数据未从Firebase插入ArrayList

我正在尝试将Firebase节点的数据添加到ArrayList对象中。但是数据没有填充到我的ArrayList对象中，当调用onPostExecute（）时，我得到的ArrayList大小为0

如何将Firebase节点添加到ArrayList中

我的android代码

public class FirebaseSyncContacts extends AsyncTask<Void,Void,Void> {

    Map<String,String > contacts;
    ArrayList<FirebaseUserModel> userModelObjects;
    Context context;
    public FirebaseSyncContacts(Context context,Map<String,String>contacts)
    {

        this.context=context;
        this.contacts=contacts;
        userModelObjects=new ArrayList<>();

    }

    protected void onPreExecute() {
        Log.i("app","Syncing started");
    }

    protected Void doInBackground(Void... voids) {

        DatabaseReference rootRef = FirebaseDatabase.getInstance().getReference().child("Users");
        rootRef.addListenerForSingleValueEvent(new ValueEventListener() {
            public void onDataChange(DataSnapshot dataSnapshot) {
                for(Map.Entry<String, String> singleContact: contacts.entrySet()) {
                    if (dataSnapshot.hasChild(singleContact.getKey())) {
                        Log.i("app", "Present: " + singleContact.getKey());
                        userModelObjects.add(dataSnapshot.getValue(FirebaseUserModel.class));
                    }
                    else {
                        Log.i("app", "Absent: " + singleContact.getKey());
                        userModelObjects.add(dataSnapshot.getValue(FirebaseUserModel.class));
                    }
                }
            }

            public void onCancelled(DatabaseError databaseError) {
                Log.i("app","failed to connect: "+databaseError.getMessage());
            }
        });

        return null;
    }

    protected void onPostExecute(Void aVoid) {
        Log.i("app","total contacts added: "+userModelObjects.size()); // always getting 0 
}
}

火基结构

-Users
    -ContactNo
                -fname
                -lname
                -gender
                -isInstalled
                -day
                -month
                -year

预期结果： 它应该将每个联系人号码节点添加到userModelObjects ArrayList中，并返回onPostExecute（）ArrayList的总大小，即添加的联系人总数

实际结果： onPostExecute（）之后返回的大小为0，即未添加任何对象

编辑 我收到了每个联系人的警告 W/ClassMapper:在com.demo.example.Firebase.FirebaseUserModel类上找不到91987654321的setter/字段

---

我已删除ASyncTask，但仍遇到此问题。

将类名从：

public class FirebaseUserModel {....

到

for循环变为：

for( DataSnapshot snapShot: dataSnapshot.getChildren()) {

 ContactNo userModel = snapShot.getValue(ContactNo.class);
 userModelObjects.add(userModel);


}

更新

-Users
    -ContactNo
                -fname
                -lname
                -gender
                -isInstalled
                -day
                -month
                -year

首先，正如我所说的，您不需要asyncTask，因此只要在您希望的任何地方使用以下代码，因为firebase为您处理后台线程：

//In your activity, do this directly:
DatabaseReference rootRef = FirebaseDatabase.getInstance().getReference().child("Users");
rootRef.addListenerForSingleValueEvent(new ValueEventListener() {
public void onDataChange(DataSnapshot dataSnapshot) {

for(DataSnapshot snapShot: dataSnapshot.getChildren()) {

ContactNo userModel = snapShot.getValue(ContactNo.class);
userModelObjects.add(userModel);
}
}

 public void onCancelled(DatabaseError databaseError) {
Log.i("app","failed to connect: "+databaseError.getMessage());
}
});

这一定是你的新课

public class ContactNo {

//make sure that these names are exactly like the keys in your database
private String fname,lname,gender;

//note if isInstalled is supposed to be a boolean, then make it a boolean and not an int 
private int isInstalled,day,month,year;

public ContactNo() { }

public ContactNo(String fname,String lname,String gender,int isInstalled,int day,int month,int year)
{

    this.fname=fname;
    this.lname=lname;
    this.gender=gender;
    this.isInstalled=isInstalled;
    this.day=day;
    this.month=month;
    this.year=year;
}

---

}

我认为您不需要asyncTask。这个问题是由asyncTask引起的吗？如何知道任务在没有AsyncTask的情况下完成？您不需要AsyncTask，因为firebase快照侦听器已经是一段异步代码。它正在后台监听，当您查询中的文档更新时将触发。这里要做的是在异步任务中设置一个异步任务。好的。现在我已经删除了ASyncTask，但仍然遇到同样的问题。如何解决此问题。实际上ContactNo是用户联系人号码，每次添加新联系人时，它都会发生变化。对于每个联系人号码，我都会收到此警告：W/ClassMapper:No setter/field for 91987654321在com.demo.example.Firebase.firebaseUserModel类中找到。您可以在doInBackground（）中修改我的代码吗每个循环的方法？因为我在将我的每个地图键与firebase进行比较时被卡住了

public class ContactNo {

//make sure that these names are exactly like the keys in your database
private String fname,lname,gender;

//note if isInstalled is supposed to be a boolean, then make it a boolean and not an int 
private int isInstalled,day,month,year;

public ContactNo() { }

public ContactNo(String fname,String lname,String gender,int isInstalled,int day,int month,int year)
{

    this.fname=fname;
    this.lname=lname;
    this.gender=gender;
    this.isInstalled=isInstalled;
    this.day=day;
    this.month=month;
    this.year=year;
}