ListView引發NullPointerException

Question

我有一個自定義的ListView（由bauerca DragSortListView）活動佈局和當我開始活動時，它會引發NullPointerException和關閉應用程序，但是當我在下次啓動此活動 - 它工作正常。我怎樣才能消除這個錯誤。 登錄

06-05 14:47:13.218: E/AndroidRuntime(498): FATAL EXCEPTION: main 
06-05 14:47:13.218: E/AndroidRuntime(498): java.lang.NullPointerException 
06-05 14:47:13.218: E/AndroidRuntime(498): at android.view.ViewGroup.addView(ViewGroup.java:1821) 
06-05 14:47:13.218: E/AndroidRuntime(498): at android.view.ViewGroup.addView(ViewGroup.java:1808) 
06-05 14:47:13.218: E/AndroidRuntime(498): at com.mobeta.android.dslv.DragSortListView$AdapterWrapper.getView(DragSortListView.java:739) 
06-05 14:47:13.218: E/AndroidRuntime(498): at android.widget.AbsListView.obtainView(AbsListView.java:1430) 
06-05 14:47:13.218: E/AndroidRuntime(498): at android.widget.ListView.makeAndAddView(ListView.java:1745) 
06-05 14:47:13.218: E/AndroidRuntime(498): at android.widget.ListView.fillDown(ListView.java:670) 
06-05 14:47:13.218: E/AndroidRuntime(498): at android.widget.ListView.fillFromTop(ListView.java:727) 
06-05 14:47:13.218: E/AndroidRuntime(498): at android.widget.ListView.layoutChildren(ListView.java:1584) 
06-05 14:47:13.218: E/AndroidRuntime(498): at com.mobeta.android.dslv.DragSortListView.layoutChildren(DragSortListView.java:2136) 
06-05 14:47:13.218: E/AndroidRuntime(498): at android.widget.AbsListView.onLayout(AbsListView.java:1260) 
06-05 14:47:13.218: E/AndroidRuntime(498): at android.view.View.layout(View.java:7175) 
06-05 14:47:13.218: E/AndroidRuntime(498): at android.widget.RelativeLayout.onLayout(RelativeLayout.java:912) 
06-05 14:47:13.218: E/AndroidRuntime(498): at android.view.View.layout(View.java:7175) 
06-05 14:47:13.218: E/AndroidRuntime(498): at android.widget.FrameLayout.onLayout(FrameLayout.java:338) 
06-05 14:47:13.218: E/AndroidRuntime(498): at android.view.View.layout(View.java:7175) 
06-05 14:47:13.218: E/AndroidRuntime(498): at android.widget.FrameLayout.onLayout(FrameLayout.java:338) 
06-05 14:47:13.218: E/AndroidRuntime(498): at android.view.View.layout(View.java:7175) 
06-05 14:47:13.218: E/AndroidRuntime(498): at android.view.ViewRoot.performTraversals(ViewRoot.java:1140) 
06-05 14:47:13.218: E/AndroidRuntime(498): at android.view.ViewRoot.handleMessage(ViewRoot.java:1859) 
06-05 14:47:13.218: E/AndroidRuntime(498): at android.os.Handler.dispatchMessage(Handler.java:99) 
06-05 14:47:13.218: E/AndroidRuntime(498): at android.os.Looper.loop(Looper.java:123) 
06-05 14:47:13.218: E/AndroidRuntime(498): at android.app.ActivityThread.main(ActivityThread.java:3683) 
06-05 14:47:13.218: E/AndroidRuntime(498): at java.lang.reflect.Method.invokeNative(Native Method) 
06-05 14:47:13.218: E/AndroidRuntime(498): at java.lang.reflect.Method.invoke(Method.java:507) 
06-05 14:47:13.218: E/AndroidRuntime(498): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839) 
06-05 14:47:13.218: E/AndroidRuntime(498): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597) 
06-05 14:47:13.218: E/AndroidRuntime(498): at dalvik.system.NativeStart.main(Native Method) 

適配器

private class OrderAdapter extends ArrayAdapter<Order>{ 
      public OrderAdapter(List<Order> list) { 
       super(MainActivity.this, R.layout.order_list_item,R.id.address,list); 
      } 
      public View getView(int position, View convertView, ViewGroup parent) { 
        View v = super.getView(position, convertView, parent); 
         TextView item=(TextView) v.findViewById(R.id.address); 
          TextView subitem=(TextView) v.findViewById(R.id.client); 
          item.setTextColor(Color.WHITE); 
          subitem.setTextColor(Color.WHITE); 
          item.setText(getItem(position).order_address); 
          subitem.setText(getItem(position).order_client); 

          TextView pos = (TextView) v.findViewById(R.id.pos_number); 
          pos.setText(String.valueOf(getItem(position).position_number)); 

          ImageView state = (ImageView) v.findViewById(R.id.checkItem); 
          state.setVisibility(View.VISIBLE); 
          if (getItem(position).order_status == 3) 
           state.setBackgroundResource(drawable.check_cancelled); 
          if (getItem(position).order_status == 2) 
           state.setBackgroundResource(drawable.check_checked); 
          if (getItem(position).order_status == 0) 
           state.setBackgroundResource(drawable.check_nb); 
          if (getItem(position).order_status == 1) 
          { 
           state.setVisibility(View.GONE); 
          } 
        return v; 

初始化

c_orders = new ArrayList<Order>(); 
adapter = new OrderAdapter(c_orders); 
myList=(DragSortListView)findViewById(R.id.dsvlist); 
myList.setAdapter(adapter); 
myList.setDropListener(onDrop); 
myList.setRemoveListener(onRemove); 
myList.setOnItemClickListener(listener); 

Answer 1

，而不是調用

View v = super.getView(position, convertView, parent); 

自行充氣視圖。

LayoutInflater inflater = (LayoutInflater) context 
       .getSystemService(Context.LAYOUT_INFLATER_SERVICE); 
view v = inflater.inflate(R.layout.your_layout_name, parent, false); 
. 
. 
. 
. 
. 

注意：您應該閱讀教程以瞭解「適配器如何工作？」和「什麼是提高列表視圖性能的最佳方法？」