NPE上holder.rightCaret.setOnClickListener（新OnClickListener（））

Question

錯誤日誌：

06-28 12:07:38.227: E/AndroidRuntime(1199): FATAL EXCEPTION: main 
06-28 12:07:38.227: E/AndroidRuntime(1199): java.lang.NullPointerException 
06-28 12:07:38.227: E/AndroidRuntime(1199):  at com.innoventes.cpea.view.DashboardAdapter.getView(DashboardAdapter.java:55) 
06-28 12:07:38.227: E/AndroidRuntime(1199):  at android.widget.AbsListView.obtainView(AbsListView.java:1409) 
06-28 12:07:38.227: E/AndroidRuntime(1199):  at android.widget.ListView.makeAndAddView(ListView.java:1745) 
06-28 12:07:38.227: E/AndroidRuntime(1199):  at android.widget.ListView.fillSpecific(ListView.java:1290) 
06-28 12:07:38.227: E/AndroidRuntime(1199):  at android.widget.ListView.layoutChildren(ListView.java:1576) 
06-28 12:07:38.227: E/AndroidRuntime(1199):  at android.widget.AbsListView.onLayout(AbsListView.java:1260) 
06-28 12:07:38.227: E/AndroidRuntime(1199):  at android.view.View.layout(View.java:7175) 
06-28 12:07:38.227: E/AndroidRuntime(1199):  at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1254) 
06-28 12:07:38.227: E/AndroidRuntime(1199):  at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1130) 
06-28 12:07:38.227: E/AndroidRuntime(1199):  at android.widget.LinearLayout.onLayout(LinearLayout.java:1047) 
06-28 12:07:38.227: E/AndroidRuntime(1199):  at android.view.View.layout(View.java:7175) 
06-28 12:07:38.227: E/AndroidRuntime(1199):  at android.widget.FrameLayout.onLayout(FrameLayout.java:338) 
06-28 12:07:38.227: E/AndroidRuntime(1199):  at android.view.View.layout(View.java:7175) 
06-28 12:07:38.227: E/AndroidRuntime(1199):  at android.widget.FrameLayout.onLayout(FrameLayout.java:338) 
06-28 12:07:38.227: E/AndroidRuntime(1199):  at android.view.View.layout(View.java:7175) 
06-28 12:07:38.227: E/AndroidRuntime(1199):  at android.view.ViewRoot.performTraversals(ViewRoot.java:1140) 
06-28 12:07:38.227: E/AndroidRuntime(1199):  at android.view.ViewRoot.handleMessage(ViewRoot.java:1859) 
06-28 12:07:38.227: E/AndroidRuntime(1199):  at android.os.Handler.dispatchMessage(Handler.java:99) 
06-28 12:07:38.227: E/AndroidRuntime(1199):  at android.os.Looper.loop(Looper.java:130) 
06-28 12:07:38.227: E/AndroidRuntime(1199):  at android.app.ActivityThread.main(ActivityThread.java:3683) 
06-28 12:07:38.227: E/AndroidRuntime(1199):  at java.lang.reflect.Method.invokeNative(Native Method) 
06-28 12:07:38.227: E/AndroidRuntime(1199):  at java.lang.reflect.Method.invoke(Method.java:507) 
06-28 12:07:38.227: E/AndroidRuntime(1199):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839) 
06-28 12:07:38.227: E/AndroidRuntime(1199):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597) 
06-28 12:07:38.227: E/AndroidRuntime(1199):  at dalvik.system.NativeStart.main(Native Method) 

我的適配器：

public class DashboardAdapter extends ArrayAdapter<ProductModel>{ 

Context context; 
List<ProductModel> item; 

public DashboardAdapter(Context context, int resourceId,List<ProductModel> items) 
{ 
    super(context, resourceId, items); 
    this.context = context; 
    this.item = items; 
} 
/*private view holder class*/ 
private class ViewHolder 
{ 
    ImageButton rightCaret; 
    TextView txtTitle; 
} 
public View getView(int position, View convertView, ViewGroup parent) 
{ 
    ViewHolder holder = new ViewHolder(); 
    ProductModel rowItem = getItem(position); 
    LayoutInflater mInflater = (LayoutInflater) context.getSystemService(Activity.LAYOUT_INFLATER_SERVICE); 
    if (convertView == null) 
    { 
     convertView = mInflater.inflate(R.layout.dashboard_item,parent,false); 
     holder = new ViewHolder(); 
     holder.txtTitle = (TextView) convertView.findViewById(R.id.dashboardItem_description); 
     holder.rightCaret = (ImageButton) convertView.findViewById(R.id.rightCaretDash);    
     holder.rightCaret.setTag(position); 
     holder.txtTitle.setText(rowItem.getProductTitle()); 
     convertView.setTag(holder); 
     holder.rightCaret.setClickable(true); 
     holder.rightCaret.setId(position); 
     DashboardAdapter.this.notifyDataSetChanged();    
    } 
    holder.rightCaret.setOnClickListener(new View.OnClickListener() 
    {    
    public void onClick(final View view) 
     {     
      Integer index = (Integer) view.getTag(); 
      String header = item.get(index).toString(); 
      Intent intent = new Intent(context,ListProduct.class); 
      intent.putExtra("value",header); 
      intent.setFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP); 
      context.startActivity(intent); 
      notifyDataSetChanged();          
     } 

    }); 

    convertView.setClickable(true); 
    return convertView; 
} 

}

當我調試時，rightCaret的ImageButton爲空。請幫助我不知道如何走得更遠。

Answer 1

if (convertView == null) { 
    //your code.. 
    convertView.setTag(holder); 
} else 
    holder = (ViewHolder) convertView.getTag(); 

您創建一個新的ViewHolder隨時getView()被調用，但其場不initalized。