通用域名格式。谷歌。火力基地。数据库DatabaseException:无法转换java类型的对象。字符串输入com。测验便秘。最后的问题条目

Question

我正在构建一个社交应用程序，可以从firebase中保存和检索数据。但我发现了这个错误

com.google.firebase.database.数据库异常：无法将类型java.lang.字符串的对象转换为类型com.test.consti.last.在com.google.android.gms.internal.zzear.zzb（未知来源）在com.google.android.gms.internal.zzear.zza（未知来源）在com.google.firebase.database.DataSnapshot.get值（未知来源）在com.test.consti.last.FirebasHelper.fetch数据（FirebasHelper.java:28）在com.test.consti.last.FirebasHelper.access0美元（FirebasHelper.java:17）在com.test.consti.last.FirebasHelper$1.onChildAdded（Firebaseelper.java:36）在com.google.android.gms.internal.zzdri.zza（未知来源）在com.google.android.gms.internal.zzdwu.zzbvb（未知来源）在com.google.android.gms.internal.zzdxa.run（未知来源）在android.os.Handler. handleCallback（Handler. java： 730）在android. os.在android. os.在android. app.ActivityThread. main（ActivityThread. java： 5419）在java. lang.反射。方法。方法调用（方法. java： 525）在com. android. interal. os。ZygoteInit$method odAndArgsCaller. run（ZygoteInit. java： 1046）在com. android. interal. os。在dalvik. system上的ZygoteInit. main（ZygoteInit. java： 862）。NativeStart. main（本机方法）

这是我的消防员助手。我要从firebase数据库中检索数据（仅限于“问题”儿童内容）

public class FirebaseHelper {
 DatabaseReference db;
 Boolean saved=null;
 ArrayList<QuestionEntry> questionEntries =new ArrayList<>();
public FirebaseHelper(DatabaseReference db)  {
    this.db=db;
    }
private void fetchData (DataSnapshot dataSnapshot){
questionEntries.clear();
for (DataSnapshot ds :dataSnapshot.getChildren()){
//There is the error
    QuestionEntry questionEntry = ds.getValue(QuestionEntry.class);
    questionEntries.add(questionEntry);
}
}
public ArrayList<QuestionEntry> retreive (){
db.addChildEventListener(new ChildEventListener() {
    @Override
    public void onChildAdded(DataSnapshot dataSnapshot, String s) {
        fetchData(dataSnapshot);
    }

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

    @Override
    public void onChildRemoved(DataSnapshot dataSnapshot) {

    }

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

    }

    @Override
    public void onCancelled(DatabaseError databaseError) {

    }
});
return questionEntries;
}

那么这就是问卷调查

public class QuestionEntry {
public String question_title;

public String question_id;
public   String tag_id;
public   String tag_name;
public   String question_content;
public String question_date;
public    String question_username;
public String interet;


public QuestionEntry(){

}

public void setQuestion_title(String question_title) {
    this.question_title = question_title;
}

public void setQuestion_id(String question_id) {
    this.question_id = question_id;
}

public void setTag_id(String tag_id) {
    this.tag_id = tag_id;
}

public void setTag_name(String tag_name) {
    this.tag_name = tag_name;
}

public void setQuestion_content(String question_content) {
    this.question_content = question_content;
}

public void setQuestion_date(String question_date) {
    this.question_date = question_date;
}

public void setQuestion_username(String question_username) {
    this.question_username = question_username;
}

public void setInteret(String interet) {
    this.interet = interet;
}

public String getQuestion_title() {
    return question_title;
}

public String getQuestion_id() {
    return question_id;
}

public String getTag_id() {
    return tag_id;
}

public String getTag_name() {
    return tag_name;
}

public String getQuestion_content() {
    return question_content;
}



public String getQuestion_username() {
    return question_username;
}

public String getInteret() {
    return interet;
}

public String getQuestion_date() {
    return question_date;
}
}

这是我的firebase数据库结构这是我的活动

这是我的活动

    public class Actu extends Fragment {
    public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
        v = inflater.inflate(R.layout.activity_actu, container, false);
        lv = (ListView) v.findViewById(R.id.actu_rv);
        db = FirebaseDatabase.getInstance().getReference("Questions");
        helper = new FirebaseHelper(db);
        adapter = new QuestionAdapter(getContext(),helper.retreive());
        lv.setAdapter(adapter);


        return v;        }
}

我已经将内容发布到firebase

Answer 1

将fetchData方法更改为：

private void fetchData (DataSnapshot dataSnapshot){
questionEntries.clear();
QuestionEntry questionEntry = dataSnapshot.getValue(QuestionEntry.class);
questionEntries.add(questionEntry);
 }

for循环在nodequestions的子节点中循环，由于子节点包含字符串，因此您将得到该错误。