错误与firebaselistadapter

Question

大厅：

public class Lobby extends AppCompatActivity implements View.OnClickListener{ 
    private TextView text; 
    private Button add; 
    public FirebaseListAdapter<LobbysName> adapterList; 
    final Context context=this; 

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

     text=(TextView)findViewById(R.id.listtext); 

     add=(Button)findViewById(R.id.add_lobby); 
     add.setOnClickListener(this); 

     readLobby(); 
    } 

    @Override 
    public void onClick(View view) { 
     //???????? ??? ? ????? dialog_add.xml, ??????? ???????? ??? ??????????? ????: 
     LayoutInflater li=LayoutInflater.from(context); 
     View dialog=li.inflate(R.layout.dialog_add,null); 

     //??????? AlertDialog 
     AlertDialog.Builder mDialogBuilder = new AlertDialog.Builder(context); 

     //??????????? dialog_add.xml ??? ?????? AlertDialog: 
     mDialogBuilder.setView(dialog); 

     //??????????? ??????????? ???? ??? ????? ?????? ? ???????? ???????: 
     final EditText userInput = (EditText) dialog.findViewById(R.id.input_text); 

     //??????????? ????????? ? ?????????? ????: 
     mDialogBuilder 
       .setCancelable(false) 
       .setPositiveButton("OK", 
         new DialogInterface.OnClickListener() { 
          public void onClick(DialogInterface dialog,int id) { 
           //?????? ????? ? ?????????? ? ?????? ????? ?? ???????? ??????: 
           addNewLobby(userInput.getText().toString()); 
          } 
         }) 
       .setNegativeButton("??????", 
         new DialogInterface.OnClickListener() { 
          public void onClick(DialogInterface dialog, int id) { 
           dialog.cancel(); 
          } 
         }); 
     //??????? AlertDialog: 
     AlertDialog alertDialog = mDialogBuilder.create(); 

     //? ?????????? ???: 
     alertDialog.show(); 

    } 
    public void addNewLobby(String name){ 
     FirebaseDatabase.getInstance().getReference().child("lobby").push() 
       .setValue(new LobbysName(name, 
         FirebaseAuth.getInstance().getCurrentUser().getEmail())); 
     Toast.makeText(getApplicationContext(),"?????? ?????????",Toast.LENGTH_SHORT).show(); 
    } 

    public void readLobby(){ 

     final ListView list=(ListView)findViewById(R.id.list_lobby); 

     /*--------------??????????? ?????? ????? ?????--------------------*/ 
     list.post(new Runnable() { 
      @Override 
      public void run() { 
       list.setSelection(list.getCount() - 1); 
      } 
     }); 
//ERORS THIS------------------------------------- 
     adapterList = new FirebaseListAdapter<LobbysName>(this, LobbysName.class, R.layout.itemlobby, FirebaseDatabase.getInstance().getReference().child("lobby")) { 
      @Override 
      protected void populateView(View v, LobbysName model, int position) { 
       text.setText(model.getName()); 
      } 
     }; 
     list.setAdapter(adapterList); 
    } 

    @Override 
    public boolean onCreateOptionsMenu(Menu menu) { 
     getMenuInflater().inflate(R.menu.main, menu); 
     return true; 
    } 

    @Override 
    public boolean onOptionsItemSelected(MenuItem item) { 
     switch (item.getItemId()) { 
      case R.id.settings_item_1: 
       finish(); 
       startActivity(new Intent(getApplicationContext(),Add_User.class)); 

      case R.id.settings_item_2: 
       Toast.makeText(getApplicationContext(), 
         "?????", Toast.LENGTH_LONG).show(); 
     } 
     return super.onOptionsItemSelected(item); 
    } 

    @Override 
    public void onBackPressed() { 
     finish(); 
     startActivity(new Intent(getApplicationContext(),Sign_in.class)); 
    } 
} 

类LobbysName：

public class LobbysName { 
    private String name; 
    private String id; 


    public LobbysName(String name, String id) { 

     this.name = name; 
     this.id = id; 
    } 
    public LobbysName() { 

    } 

    public String getName() { 
     return name; 
    } 

    public void setName(String name) { 
     this.name = name; 
    } 

    public String getId() { 
     return id; 
    } 

    public void setId(String id) { 
     this.id = id; 
    } 
} 

致命异常：主要：

Process: com.example.shcherbuk96.example2firebase, PID: 4434 
java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.TextView.setText(java.lang.CharSequence)' on a null object reference 
    **at com.example.shcherbuk96.example2firebase.TreeActivity.Lobby$4.populateView(Lobby.java:107) 
    at com.example.shcherbuk96.example2firebase.TreeActivity.Lobby$4.populateView(Lobby.java:104)** 
    at com.firebase.ui.database.FirebaseListAdapter.getView(FirebaseListAdapter.java:140) 
    at android.widget.AbsListView.obtainView(AbsListView.java:2362) 
    at android.widget.ListView.makeAndAddView(ListView.java:1970) 
    at android.widget.ListView.fillDown(ListView.java:704) 
    at android.widget.ListView.fillFromTop(ListView.java:765) 
    at android.widget.ListView.layoutChildren(ListView.java:1716) 
    at android.widget.AbsListView.onLayout(AbsListView.java:2161) 
    at android.view.View.layout(View.java:17523) 
    at android.view.ViewGroup.layout(ViewGroup.java:5612) 
    at android.widget.RelativeLayout.onLayout(RelativeLayout.java:1079) 
    at android.view.View.layout(View.java:17523) 
    at android.view.ViewGroup.layout(ViewGroup.java:5612) 
    at android.widget.FrameLayout.layoutChildren(FrameLayout.java:323) 
    at android.widget.FrameLayout.onLayout(FrameLayout.java:261) 
    at android.view.View.layout(View.java:17523) 
    at android.view.ViewGroup.layout(ViewGroup.java:5612) 
    at android.support.v7.widget.ActionBarOverlayLayout.onLayout(ActionBarOverlayLayout.java:437) 
    at android.view.View.layout(View.java:17523) 
    at android.view.ViewGroup.layout(ViewGroup.java:5612) 
    at android.widget.FrameLayout.layoutChildren(FrameLayout.java:323) 
    at android.widget.FrameLayout.onLayout(FrameLayout.java:261) 
    at android.view.View.layout(View.java:17523) 
    at android.view.ViewGroup.layout(ViewGroup.java:5612) 
    at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1741) 
    at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1585) 
    at android.widget.LinearLayout.onLayout(LinearLayout.java:1494) 
    at android.view.View.layout(View.java:17523) 
    at android.view.ViewGroup.layout(ViewGroup.java:5612) 
    at android.widget.FrameLayout.layoutChildren(FrameLayout.java:323) 
    at android.widget.FrameLayout.onLayout(FrameLayout.java:261) 
    at com.android.internal.policy.DecorView.onLayout(DecorView.java:724) 
    at android.view.View.layout(View.java:17523) 
    at android.view.ViewGroup.layout(ViewGroup.java:5612) 
    at android.view.ViewRootImpl.performLayout(ViewRootImpl.java:2342) 
    at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:2069) 
    at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1246) 
    at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:6301) 
    at android.view.Choreographer$CallbackRecord.run(Choreographer.java:871) 
    at android.view.Choreographer.doCallbacks(Choreographer.java:683) 
    at android.view.Choreographer.doFrame(Choreographer.java:619) 
    at android.view.Choreographer$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:6077) 
    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) 

Answer 1

从populateView()方法删除此行：

text.setText(model.getName()); 

替换：

TextView txt = (TextView) v.findViewById(android.R.id.listtext); 
txt.setText((model.getName()); 

Answer 2

问题就在这里：

text=(TextView)findViewById(R.id.listtext); 

这是null因为你Activity使用R.layout.activity_lobby，而不是项目的布局。

如果你想使用项目布局使用populateView方法：

TextView textItem = (TextView) v.findViewById(R.id.listtext); 
textItem.setText((model.getName());