在使用FirebaseRecyclerAdapter填充

時遇到Firebase數據庫異常我在使用FirebaseRecyclerAdapter時遇到問題。在使用FirebaseRecyclerAdapter填充

的火力實時數據庫結構如下：

The structure displayed here is connected to the root of the database

什麼我想在這裏做， 僅獲得了關鍵的中存在的「MainGroup」部分數據的Firebase實時數據庫。

因此，要做到這一點，我創建了一個名爲RecyclerDataGetSetCLass 模型類和一個viewholder類名爲RecyclerDataGetSetClassViewHolder

，但我得到一個錯誤說

com.google.firebase.database。 DatabaseException：無法轉換對象 java.lang.String類型的輸入 com.example.talarir.mapproject.NonAdminClasses.RecyclerDataGetSetCLass

是

的活動類和其他java文件如下：

1）NonAdminACtivity.java //which contains the viewholder class

public class NonAdminACtivity extends AppCompatActivity implements View.OnClickListener { 
private FirebaseAuth mAuth; 
private FirebaseAuth.AuthStateListener mAuthListener; 

public Button saveLocationBtn,getLocationBtn; 
public RecyclerView nonAdminRecyclerView; 

private Boolean flag=false; 

private DatabaseReference mFirebaseDatabase; 
private FirebaseDatabase mFirebaseInstance; 

private DatabaseReference mFirebaseDatabase1; 
private FirebaseDatabase mFirebaseInstance1; 


@Override 
protected void onCreate(Bundle savedInstanceState) 
{ 
    super.onCreate(savedInstanceState); 
    setContentView(R.layout.activity_non_admin_activity); 


    mFirebaseInstance1 = FirebaseDatabase.getInstance(); 
    mFirebaseDatabase1 = mFirebaseInstance1.getReference("MainGroup"); 

    nonAdminRecyclerView= (RecyclerView) findViewById(R.id.recycler_view_fragment_one); 
    nonAdminRecyclerView.setHasFixedSize(true); 
    nonAdminRecyclerView.setLayoutManager(new LinearLayoutManager(this)); 

    mAuth = FirebaseAuth.getInstance(); 

    mAuthListener = new FirebaseAuth.AuthStateListener() { 
     @Override 
     public void onAuthStateChanged(@NonNull FirebaseAuth firebaseAuth) { 

      FirebaseUser user = firebaseAuth.getCurrentUser(); 

      if (user != null) { 
       // User is signed in 
       flag=true; 
       Log.d("CooActivity", "onAuthStateChanged:signed_in:" + user.getUid()); 
       Toast.makeText(getApplicationContext(),"done",Toast.LENGTH_SHORT).show(); 

      } 
      else 
      { 
       // User is signed out 
       Log.d("CooActivity", "onAuthStateChanged:signed_out"); 
       startActivity(new Intent(getApplicationContext(), LoginActivity.class)); 
       finish(); 

      } 

     } 
    }; 
} 

@Override 
public void onStart() 
{ 
    super.onStart(); 
    mAuth.addAuthStateListener(mAuthListener); 

    saveLocationBtn= (Button) findViewById(R.id.saveLocationOfUser); 
    saveLocationBtn.setOnClickListener(this); 
    getLocationBtn= (Button) findViewById(R.id.getLocationOfUser); 
    getLocationBtn.setOnClickListener(this); 

    FirebaseRecyclerAdapter<RecyclerDataGetSetCLass,RecyclerDataGetSetClassViewHolder> firebaseRecyclerAdapter=new FirebaseRecyclerAdapter<RecyclerDataGetSetCLass, RecyclerDataGetSetClassViewHolder>(
      RecyclerDataGetSetCLass.class, 
      R.layout.each_list_non_admin, 
      RecyclerDataGetSetClassViewHolder.class, 
      mFirebaseDatabase1 
    ) { 
     @Override 
     protected void populateViewHolder(RecyclerDataGetSetClassViewHolder viewHolder, RecyclerDataGetSetCLass model, int position) 
     { 
      viewHolder.setMainGroupName(model.getMainGroupName()); 
     } 
    }; 

    nonAdminRecyclerView.setAdapter(firebaseRecyclerAdapter); 

} 

public static class RecyclerDataGetSetClassViewHolder extends RecyclerView.ViewHolder 
{ 
    View mView; 
    public RecyclerDataGetSetClassViewHolder(View itemView) { 
     super(itemView); 
     mView=itemView; 
    } 

    public void setMainGroupName(String mainGroupName) 
    { 
     TextView textView= (TextView) mView.findViewById(R.id.textViewRecyclerViewNonAdmin); 
     textView.setText(mainGroupName); 
    } 
} 

@Override 
public void onStop() { 
    super.onStop(); 
    if (mAuthListener != null) { 
     mAuth.removeAuthStateListener(mAuthListener); 
    } 
} 

@Override 
protected void onDestroy() { 
    FirebaseAuth.getInstance().signOut(); 
    super.onDestroy(); 
} 

@Override 
public void onClick(View v) 
{ 
    if (v.getId()==R.id.saveLocationOfUser) 
    { 
     if (flag) 
     { 
      saveUserLocation_NonAdminActivity(); 
     } 
     else 
     { 
      Toast.makeText(this,"firebase not ready",Toast.LENGTH_SHORT).show(); 
     } 
    } 
    if (v.getId()==R.id.getLocationOfUser) 
    { 
     retrieveUserLocation_NonAdminActivity(); 
    } 
} 

private void retrieveUserLocation_NonAdminActivity() 
{ 
    CreationOfUserClass creationOfUserClass=new CreationOfUserClass(this); 
    creationOfUserClass.retrieveUserDataFromFireBase(mFirebaseDatabase,mFirebaseInstance); 
} 

private void saveUserLocation_NonAdminActivity() 
{ 

    FirebaseUser user=FirebaseAuth.getInstance().getCurrentUser(); 
    final CreationOfUserClass creationOfUserClass=new CreationOfUserClass(this); 
    creationOfUserClass.createUsers(user, mFirebaseDatabase,mFirebaseInstance); 
} 
}

2）RecyclerDataGetSetCLass //The model class

public class RecyclerDataGetSetCLass 
{ 
private String mainGroupName; 

public RecyclerDataGetSetCLass() 
{ 
} 

public RecyclerDataGetSetCLass(String mainGroupName) 
{ 
    this.mainGroupName=mainGroupName; 
} 

public String getMainGroupName() { 
    return mainGroupName; 
} 

public void setMainGroupName(String mainGroupName) { 
    this.mainGroupName = mainGroupName; 
} 
}

3）activity_non_admin_activity.xml

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" 
xmlns:tools="http://schemas.android.com/tools" 
android:id="@+id/activity_non_admin_activity" 
android:layout_width="match_parent" 
android:layout_height="match_parent" 
android:orientation="vertical" 
tools:context="com.example.talarir.mapproject.NonAdminACtivity"> 


<Button 
    android:text="SaveLocation" 
    android:layout_width="match_parent" 
    android:layout_height="wrap_content" 
    android:id="@+id/saveLocationOfUser" /> 

<Button 
    android:text="getLocation" 
    android:layout_width="match_parent" 
    android:layout_height="wrap_content" 
    android:id="@+id/getLocationOfUser" /> 

<LinearLayout 
    android:layout_width="match_parent" 
    android:layout_height="match_parent" 
    android:orientation="vertical"> 

    <android.support.v7.widget.RecyclerView 
     android:id="@+id/recycler_view_fragment_one" 
     android:scrollbars="vertical" 
     android:layout_width="match_parent" 
     android:layout_height="match_parent"> 
    </android.support.v7.widget.RecyclerView> 

</LinearLayout> 

</LinearLayout>

4）each_list_non_admin.xml //the layout to be inflated for each recycler list element

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" 
    android:layout_width="match_parent" 
    android:layout_height="60dp" 
    xmlns:card_view="http://schemas.android.com/tools"> 

<android.support.v7.widget.CardView 
    android:id="@+id/card_view" 
    android:layout_gravity="center" 
    android:layout_width="fill_parent" 
    android:layout_height="100dp" 
    android:layout_margin="5dp" 
    card_view:cardCornerRadius="2dp" 
    card_view:contentPadding="10dp"> 

    <TextView 
     android:layout_width="match_parent" 
     android:layout_height="match_parent" 
     android:id="@+id/textViewRecyclerViewNonAdmin"/> 

</android.support.v7.widget.CardView> 
</RelativeLayout>

錯誤日誌如下：

com.google.firebase.database.DatabaseException: Can't convert object of type java.lang.String to type com.example.talarir.mapproject.NonAdminClasses.RecyclerDataGetSetCLass 
        at com.google.android.gms.internal.zzbtg.zze(Unknown Source) 
        at com.google.android.gms.internal.zzbtg.zzb(Unknown Source) 
        at com.google.android.gms.internal.zzbtg.zza(Unknown Source) 
        at com.google.firebase.database.DataSnapshot.getValue(Unknown Source) 
        at com.firebase.ui.database.FirebaseRecyclerAdapter.parseSnapshot(FirebaseRecyclerAdapter.java:151) 
        at com.firebase.ui.database.FirebaseRecyclerAdapter.getItem(FirebaseRecyclerAdapter.java:140) 
        at com.firebase.ui.database.FirebaseRecyclerAdapter.onBindViewHolder(FirebaseRecyclerAdapter.java:183) 
        at android.support.v7.widget.RecyclerView$Adapter.onBindViewHolder(RecyclerView.java:6308) 
        at android.support.v7.widget.RecyclerView$Adapter.bindViewHolder(RecyclerView.java:6341) 
        at android.support.v7.widget.RecyclerView$Recycler.tryBindViewHolderByDeadline(RecyclerView.java:5287) 
        at android.support.v7.widget.RecyclerView$Recycler.tryGetViewHolderForPositionByDeadline(RecyclerView.java:5550) 
        at android.support.v7.widget.RecyclerView$Recycler.getViewForPosition(RecyclerView.java:5392) 
        at android.support.v7.widget.RecyclerView$Recycler.getViewForPosition(RecyclerView.java:5388) 
        at android.support.v7.widget.LinearLayoutManager$LayoutState.next(LinearLayoutManager.java:2149) 
        at android.support.v7.widget.LinearLayoutManager.layoutChunk(LinearLayoutManager.java:1533) 
        at android.support.v7.widget.LinearLayoutManager.fill(LinearLayoutManager.java:1496) 
        at android.support.v7.widget.LinearLayoutManager.onLayoutChildren(LinearLayoutManager.java:593) 
        at android.support.v7.widget.RecyclerView.dispatchLayoutStep2(RecyclerView.java:3535) 
        at android.support.v7.widget.RecyclerView.dispatchLayout(RecyclerView.java:3264) 
        at android.support.v7.widget.RecyclerView.consumePendingUpdateOperations(RecyclerView.java:1633) 
        at android.support.v7.widget.RecyclerView$1.run(RecyclerView.java:341) 
        at android.view.Choreographer$CallbackRecord.run(Choreographer.java:871) 
        at android.view.Choreographer.doCallbacks(Choreographer.java:683) 
        at android.view.Choreographer.doFrame(Choreographer.java:616) 
        at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:857) 
        at android.os.Handler.handleCallback(Handler.java:751) 
        at android.os.Handler.dispatchMessage(Handler.java:95) 
        at android.os.Looper.loop(Looper.java:154) 
        at android.app.ActivityThread.main(ActivityThread.java:6209) 
        at java.lang.reflect.Method.invoke(Native Method) 
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:865) 
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:755) 
D/AppTracker: App Event: crash 
I/Process: Sending signal. PID: 29821 SIG: 9 
Application terminated.

請幫助我通過這個問題來獲得。

來源

2017-02-27 Ravi teja Talari

您顯示的每個項目的值都是單個字符串（-K....）。你試圖從價值中讀取整個課程，而這根本行不通。

final FirebaseRecyclerAdapter<RecyclerDataGetSetCLass,RecyclerDataGetSetClassViewHolder> firebaseRecyclerAdapter=new FirebaseRecyclerAdapter<RecyclerDataGetSetCLass, RecyclerDataGetSetClassViewHolder>(
     String.class, 
     R.layout.each_list_non_admin, 
     RecyclerDataGetSetClassViewHolder.class, 
     mFirebaseDatabase1 
) { 
    @Override 
    protected void populateViewHolder(RecyclerDataGetSetClassViewHolder viewHolder, String model, int position) 
    { 
     String key = adapter.getRef(position).getKey(); 
     viewHolder.setMainGroupName(key); 
    } 
};

在這段代碼中，我查看了正在顯示的項目的關鍵字，這可能是您要查找的值。

來源

2017-02-27 15:33:56

非常感謝！ :) –

在使用FirebaseRecyclerAdapter填充

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