Question

我尝试将我的应用程序连接到Firebase数据库，但每当我启动显示问题的代码时

这是我的主要活动

public class MainActivity extends AppCompatActivity {






    private static final String TAG = "ViewDatabase";

    private FirebaseDatabase mFirebaseDatabase;
    private DatabaseReference myRef;
protected void onCreate(@Nullable Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    mFirebaseDatabase = FirebaseDatabase.getInstance();
    myRef = mFirebaseDatabase.getReference("Discount/Business");



    myRef.addValueEventListener(new ValueEventListener() {
        @Override
        public void onDataChange(DataSnapshot dataSnapshot) {
            for(DataSnapshot ds : dataSnapshot.getChildren()){
                UserInformation uInfo = new UserInformation();
                uInfo.setAltro(ds.child("Altro").getValue(UserInformation.class).getAltro());
                uInfo.setCognome(ds.child("Cognome").getValue(UserInformation.class).getCognome());
                uInfo.setInformazioni(ds.child("Informazioni").getValue(UserInformation.class).getInformazioni());
                uInfo.setNome(ds.child("Nome").getValue(UserInformation.class).getNome());


                Log.d(TAG, "showData: Altro: " + uInfo.getAltro());
                Log.d(TAG, "showData: Cognome: " + uInfo.getCognome());
                Log.d(TAG, "showData: Informazioni: " + uInfo.getInformazioni());
                Log.d(TAG, "showData: Nome: " + uInfo.getNome());





            }
        }

        @Override
        public void onCancelled(DatabaseError databaseError) {

        }
    });

}

这是我的用户类

public class UserInformation {
private String Altro;
private String Cognome;
private String Informazioni;
private String Nome;



public UserInformation(){

}

public String getAltro() {
    return Altro;
}

public void setAltro(String altro) {
    Altro = altro;
}

public String getCognome() {
    return Cognome;
}

public void setCognome(String cognome) {
    Cognome = cognome;
}

public String getInformazioni() {
    return Informazioni;
}

public void setInformazioni(String informazioni) {
    Informazioni = informazioni;
}


public String getNome() {
    return Nome;
}

public void setNome(String nome) {
    Nome = nome;
}

My firebase database

和我的日志错误

11-14 10:59:55.016 2909-2909/com.app8 E/AndroidRuntime: FATAL EXCEPTION: main
                                                        Process: com.app8, PID: 2909
                                                        com.google.firebase.database.DatabaseException: Can't convert object of type java.lang.Long to type com.app8.UserInformation
                                                            at com.google.android.gms.internal.zzbqi.zze(Unknown Source)
                                                            at com.google.android.gms.internal.zzbqi.zzb(Unknown Source)
                                                            at com.google.android.gms.internal.zzbqi.zza(Unknown Source)
                                                            at com.google.firebase.database.DataSnapshot.getValue(Unknown Source)
                                                            at com.app8.MainActivity$1.onDataChange(MainActivity.java:41)
                                                            at com.google.android.gms.internal.zzbmz.zza(Unknown Source)
                                                            at com.google.android.gms.internal.zzbnz.zzYj(Unknown Source)
                                                            at com.google.android.gms.internal.zzboc$1.run(Unknown Source)
                                                            at android.os.Handler.handleCallback(Handler.java:751)
                                                            at android.os.Handler.dispatchMessage(Handler.java:95)
                                                            at android.os.Looper.loop(Looper.java:154)
                                                            at android.app.ActivityThread.main(ActivityThread.java:6119)
                                                            at java.lang.reflect.Method.invoke(Native Method)
                                                            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:886)
                                                            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:776)

这是我第一次使用Firebase，我已经看到了与该主题相关的其他问题，但我无法弄清楚如何使其工作，我希望你能帮助我。

感谢您的帮助，我们非常感谢任何建议

Answer 1

要从数据库中获取这些值，请使用以下代码：

DatabaseReference rootRef = FirebaseDatabase.getInstance().getReference();
DatabaseReference businessRef = rootRef.child("Discount").child("Business");
ValueEventListener eventListener = new ValueEventListener() {
    @Override
    public void onDataChange(DataSnapshot dataSnapshot) {
        for(DataSnapshot ds : dataSnapshot.getChildren()) {
            String altro = ds.child("Altro").getValue(String.class);
            String cognome = ds.child("Cognome").getValue(String.class);
            String informazioni = ds.child("Informazioni").getValue(String.class);
            String nome = ds.child("Nome").getValue(String.class);
            Log.d("TAG", altro + " / " + cognome + " / " + informazioni + " / " + nome);
        }
    }

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

作为建议，根据cu Java Naming Conventions将来使用所有字段。

Answer 2

你能在下面试试。

UserInformation uiFromSnapShot = ds.getValue（UserInformation.class）; uInfo.setXXX（uiFromSnapShot.getXXX）;

Answer 3

我弄清楚了此错误的实际原因。我刚才也遇到了这个问题。我了解到，firebase数据库中发生了某种垃圾数据收集。

解决方案：打开Firebase控制台->转到数据库->删除所有数据库数据->从手机上卸载应用程序->重新安装->错误已解决！！

快乐编码！

无法将java.lang.Long类型的对象转换为类型

3 个答案: