簡單的ListView在Android上使用Firebase。問題與JSON

Question

我想在列表視圖中顯示一個簡單的名單列表。但我無法弄清楚如何。我想我將無法使用模態類，因爲JSON中的所有值將具有相同的屬性，稱爲學生。在火力點我JSON數據看起來像這樣的firebse

{ 
"physicsClass":{ 
    "students":["John","Frank","Allen"] 
}, 
"chemistryClass":{ 
    "students":["Gillen","Jason","David East"] 
} 
} 

當我運行了它與下面的錯誤日誌崩潰：

com.google.firebase.database.DatabaseException: Failed to convert value of type java.util.ArrayList to String 
at com.google.android.gms.internal.zzaix.zzaC(Unknown Source) 
at com.google.android.gms.internal.zzaix.zzb(Unknown Source) 
at com.google.android.gms.internal.zzaix.zza(Unknown Source) 
at com.google.firebase.database.DataSnapshot.getValue(Unknown Source) 
at com.firebase.ui.database.FirebaseListAdapter.parseSnapshot(FirebaseListAdapter.java:113) 
at com.firebase.ui.database.FirebaseListAdapter.getItem(FirebaseListAdapter.java:102) 
at com.firebase.ui.database.FirebaseListAdapter.getView(FirebaseListAdapter.java:130) 
at android.widget.AbsListView.obtainView(AbsListView.java:2346) 
at android.widget.ListView.measureHeightOfChildren(ListView.java:1281) 
at android.widget.ListView.onMeasure(ListView.java:1188) 
at android.view.View.measure(View.java:18794) 
at android.widget.RelativeLayout.measureChildHorizontal(RelativeLayout.java:715) 
at android.widget.RelativeLayout.onMeasure(RelativeLayout.java:461) 
at android.view.View.measure(View.java:18794) 
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5951) 
at android.widget.FrameLayout.onMeasure(FrameLayout.java:194) 
at android.support.v7.widget.ContentFrameLayout.onMeasure(ContentFrameLayout.java:135) 
at android.view.View.measure(View.java:18794) 
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5951) 
at android.support.v7.widget.ActionBarOverlayLayout.onMeasure(ActionBarOverlayLayout.java:391) 
at android.view.View.measure(View.java:18794) 
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5951) 
at android.widget.FrameLayout.onMeasure(FrameLayout.java:194) 
at android.view.View.measure(View.java:18794) 
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5951) 
at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1465) 
at android.widget.LinearLayout.measureVertical(LinearLayout.java:748) 
at android.widget.LinearLayout.onMeasure(LinearLayout.java:630) 
at android.view.View.measure(View.java:18794) 
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5951) 
at android.widget.FrameLayout.onMeasure(FrameLayout.java:194) 
at com.android.internal.policy.PhoneWindow$DecorView.onMeasure(PhoneWindow.java:2643) 
at android.view.View.measure(View.java:18794) 
at android.view.ViewRootImpl.performMeasure(ViewRootImpl.java:2100) 
at android.view.ViewRootImpl.measureHierarchy(ViewRootImpl.java:1216) 
at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1452) 
at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1107) 
at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:6013) 
at android.view.Choreographer$CallbackRecord.run(Choreographer.java:858) 
at android.view.Choreographer.doCallbacks(Choreographer.java:670) 
at android.view.Choreographer.doFrame(Choreographer.java:606) 
at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:844) 
at android.os.Handler.handleCallback(Handler.java:739) 
at android.os.Handler.dispatchMessage(Handler.java:95) 
at android.os.Looper.loop(Looper.java:148) 
at android.app.ActivityThread.main(ActivityThread.java:5417) 
at java.lang.reflect.Method.invoke(Native Method) 
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726) 
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616) 

推薦列表視圖實現上述數據的任何其他方式/回收者視圖。

我正在使用firebase-ui sdk在列表視圖中顯示數據。下面是代碼

DatabaseReference ref = FirebaseDatabase.getInstance().getReference(); 
DatabaseReference sezRef = ref.child("physics"); 
studentList = (ListView)findViewById(R.id.studentList); 
firebaseListAdapter = new FirebaseListAdapter<String>(this,String.class,android.R.layout.simple_list_item_1,phyRef) { 
       @Override 
       protected void populateView(View v, String model, int position) { 
        TextView textView = (TextView)v.findViewById(android.R.id.text1); 
        textView.setText(model); 
       } 
      };studentList.setAdapter(firebaseListAdapter); 

Answer 1

錯誤Failed to convert value of type意味着，當你找回你從火力地堡快照對象，你嘗試獲得信息作爲String但在快照中的數據實際上是一個ArrayList。這就是Firebase拋出DatabaseException的原因。