我正在为具有自定义列表的 ListView 编写自定义适配器。
显然,我必须编写getView
函数。所以这是我的代码:
/*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,程序因 NullPointer 异常而崩溃。
这是我的崩溃报告:
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)
当然,布局和项目本身存在......
有什么想法吗?
更新:当我在调试时查看变量时,我发现它vi
没有被夸大(vi == null
),为什么?