自定義適配器中的NullPointerException getView

Question

我正在爲具有自定義列表的ListView編寫自定義適配器。

顯然，我必須寫getView函數。所以這裏是我的代碼：

/*1*/ public View getView(int position, View convertView, ViewGroup parent) { 
/*2*/ View vi = convertView; 
/*3*/ if (convertView == null) 
/*4*/  vi = inflater.inflate(R.layout.result_list_item, null); 
/*5*/ 
/*6*/ TextView title = (TextView) vi.findViewById(R.id.tvTitle); 
/*7*/ TextView subtitle = (TextView) vi.findViewById(R.id.tvSubTitle); 
/*8*/ ImageView image = (ImageView) vi.findViewById(R.id.imageView1); 
/*9*/ 
/*10*/ title.setText(data.get(position).getDescription().toString()); 
/*11*/ subtitle.setText(data.get(position).getDate().toString()); 
/*12*/ String img = "http://someLink/" + data.get(position).getId() + "a_t.jpg"; 
/*13*/ imageLoader.DisplayImage(img, image); 
/*14*/ return vi; 
/*15*/ } 

但是，我注意到在第6行程序崩潰與NullPointer異常。

這裏是我的崩潰報告：

04-18 09:33:32.745: E/AndroidRuntime(2209): FATAL EXCEPTION: main 
04-18 09:33:32.745: E/AndroidRuntime(2209): java.lang.NullPointerException 
04-18 09:33:32.745: E/AndroidRuntime(2209):  at com.package.mojo.NoPicAdapter.getView(NoPicAdapter.java:46) 
04-18 09:33:32.745: E/AndroidRuntime(2209):  at android.widget.AbsListView.obtainView(AbsListView.java:1554) 
04-18 09:33:32.745: E/AndroidRuntime(2209):  at android.widget.ListView.measureHeightOfChildren(ListView.java:1264) 
04-18 09:33:32.745: E/AndroidRuntime(2209):  at android.widget.ListView.onMeasure(ListView.java:1175) 
04-18 09:33:32.745: E/AndroidRuntime(2209):  at android.view.View.measure(View.java:8366) 
04-18 09:33:32.745: E/AndroidRuntime(2209):  at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:3138) 
04-18 09:33:32.745: E/AndroidRuntime(2209):  at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1017) 
04-18 09:33:32.745: E/AndroidRuntime(2209):  at android.widget.LinearLayout.measureVertical(LinearLayout.java:386) 
04-18 09:33:32.745: E/AndroidRuntime(2209):  at android.widget.LinearLayout.onMeasure(LinearLayout.java:309) 
04-18 09:33:32.745: E/AndroidRuntime(2209):  at android.view.View.measure(View.java:8366) 
04-18 09:33:32.745: E/AndroidRuntime(2209):  at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:3138) 
04-18 09:33:32.745: E/AndroidRuntime(2209):  at android.widget.FrameLayout.onMeasure(FrameLayout.java:250) 
04-18 09:33:32.745: E/AndroidRuntime(2209):  at android.view.View.measure(View.java:8366) 
04-18 09:33:32.745: E/AndroidRuntime(2209):  at android.widget.LinearLayout.measureVertical(LinearLayout.java:531) 
04-18 09:33:32.745: E/AndroidRuntime(2209):  at android.widget.LinearLayout.onMeasure(LinearLayout.java:309) 
04-18 09:33:32.745: E/AndroidRuntime(2209):  at android.view.View.measure(View.java:8366) 
04-18 09:33:32.745: E/AndroidRuntime(2209):  at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:3138) 
04-18 09:33:32.745: E/AndroidRuntime(2209):  at android.widget.FrameLayout.onMeasure(FrameLayout.java:250) 
04-18 09:33:32.745: E/AndroidRuntime(2209):  at android.view.View.measure(View.java:8366) 
04-18 09:33:32.745: E/AndroidRuntime(2209):  at android.view.ViewRoot.performTraversals(ViewRoot.java:847) 
04-18 09:33:32.745: E/AndroidRuntime(2209):  at android.view.ViewRoot.handleMessage(ViewRoot.java:1868) 
04-18 09:33:32.745: E/AndroidRuntime(2209):  at android.os.Handler.dispatchMessage(Handler.java:99) 
04-18 09:33:32.745: E/AndroidRuntime(2209):  at android.os.Looper.loop(Looper.java:123) 
04-18 09:33:32.745: E/AndroidRuntime(2209):  at android.app.ActivityThread.main(ActivityThread.java:3691) 
04-18 09:33:32.745: E/AndroidRuntime(2209):  at java.lang.reflect.Method.invokeNative(Native Method) 
04-18 09:33:32.745: E/AndroidRuntime(2209):  at java.lang.reflect.Method.invoke(Method.java:507) 
04-18 09:33:32.745: E/AndroidRuntime(2209):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:847) 
04-18 09:33:32.745: E/AndroidRuntime(2209):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:605) 
04-18 09:33:32.745: E/AndroidRuntime(2209):  at dalvik.system.NativeStart.main(Native Method) 

當然

，佈局和項目本身存在...

有什麼想法？

更新：當我在調試時查看變量時，我看到vi沒有被充氣（vi == null），爲什麼？

Answer 1

更改此：

vi = inflater.inflate(R.layout.result_list_item, null); 

要這樣：

vi = inflater.inflate(R.layout.result_list_item, parent, false); 

---

這是您的適配器應該如何：

public class NoPicAdapter extends ArrayAdapter<NewAndCalendar> { 

    private ArrayList<NewAndCalendar> data; 
    private Activity mActivity; 
    private LayoutInflater inflater = null; 

    public NoPicAdapter(Activity a, ArrayList<NewAndCalendar> d) { 
     super(a, R.layout.no_pic_list_item, d); 
     mActivity = a; 
     data = d; 
     inflater = (LayoutInflater) mActivity 
       .getSystemService(Context.LAYOUT_INFLATER_SERVICE); 
    } 


    @Override 
    public View getView(int position, View convertView, ViewGroup parent) { 
     View vi = convertView; 
     if (vi == null) 
      vi = inflater.inflate(R.layout.no_pic_list_item, parent, false); 
     TextView title = (TextView) vi.findViewById(R.id.noPicTitle); 
     TextView subtitle = (TextView) vi.findViewById(R.id.noPicSubtitle); 

     title.setText(data.get(position).getmTitle()); 
     subtitle.setText(data.get(position).getmPubDate()); 

     return vi; 
    } 

} 

Answer 2

你初始化吹氣？如果沒有初始化它。

inflater = getLayoutInflater(); 

或

inflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE); 

Answer 3

嘗試此

VI = LayoutInflater.from（mActivity）.inflate（R.layout.result_list_item，NULL）;

如果mActivity是您從創建此適配器的對象的活動傳遞的Activity上下文。