Question

我正在构建一个社交应用，它将保存并从firebase中检索数据。但是我收到了这个错误

com.google.firebase.database.DatabaseException：无法转换对象类型java.lang.String以键入com.test.consti.last.QuestionEntry 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.getValue（未知来源）在 com.test.consti.last.FirebaseHelper.fetchData（FirebaseHelper.java:28）在 com.test.consti.last.FirebaseHelper.access $ 000（FirebaseHelper.java:17）在 com.test.consti.last.FirebaseHelper $ 1.onChildAdded（FirebaseHelper.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.Handler.dispatchMessage（Handler.java:92）在android.os.Looper.loop（Looper.java:176）在android.app.ActivityThread.main（ActivityThread.java:5419） at java.lang.reflect.Method.invokeNative（Native Method）在java.lang.reflect.Method.invoke（Method.java:525）在 com.android.internal.os.ZygoteInit $ MethodAndArgsCaller.run（ZygoteInit.java:1046）在com.android.internal.os.ZygoteInit.main（ZygoteInit.java:862）在dalvik.system.NativeStart.main（本地方法）

这是我的FirebaseHelper。我可以从firebase数据库中检索数据（仅限＃34;问题＆＃34;孩子的内容）

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;
}

然后这是QuestionEntry

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;
}
}

this is my firebase database structure 这是我的Acticity

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循环遍历节点questions的子节点，并且由于子节点包含字符串，您将收到该错误。

com.google.firebase.database.DatabaseException：无法将java.lang.String类型的对象转换为com.test.consti.last.QuestionEntry

1 个答案: