Android：listview崩溃

Question

我正在使用android listview，它的工作非常好。我的实施如下

ListView listview = (ListView)findViewById(R.id.list);
setListAdapter(new ArrayAdapter<String>(MyIncidentActivity.this,
    R.layout.row_incident, R.id.label_incident, db_results));

现在我引入了onItemClickListener，如下所示，应用程序无故崩溃。

listview.setOnItemClickListener(new OnItemClickListener() {

            @Override
            public void onItemClick(AdapterView<?> arg0, View arg1, int arg2,
                    long arg3) {
                // TODO Auto-generated method stub

            }
        });

logcat的

08-12 14:44:40.105: ERROR/AndroidRuntime(14525): FATAL EXCEPTION: main
08-12 14:44:40.105: ERROR/AndroidRuntime(14525): java.lang.RuntimeException: Unable to start activity ComponentInfo{a.b/a.b.MyIncidentActivity}: java.lang.NullPointerException
08-12 14:44:40.105: ERROR/AndroidRuntime(14525):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1647)
08-12 14:44:40.105: ERROR/AndroidRuntime(14525):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1663)
08-12 14:44:40.105: ERROR/AndroidRuntime(14525):     at android.app.ActivityThread.access$1500(ActivityThread.java:117)
08-12 14:44:40.105: ERROR/AndroidRuntime(14525):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:931)
08-12 14:44:40.105: ERROR/AndroidRuntime(14525):     at android.os.Handler.dispatchMessage(Handler.java:99)
08-12 14:44:40.105: ERROR/AndroidRuntime(14525):     at android.os.Looper.loop(Looper.java:123)
08-12 14:44:40.105: ERROR/AndroidRuntime(14525):     at android.app.ActivityThread.main(ActivityThread.java:3683)
08-12 14:44:40.105: ERROR/AndroidRuntime(14525):     at java.lang.reflect.Method.invokeNative(Native Method)
08-12 14:44:40.105: ERROR/AndroidRuntime(14525):     at java.lang.reflect.Method.invoke(Method.java:507)
08-12 14:44:40.105: ERROR/AndroidRuntime(14525):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
08-12 14:44:40.105: ERROR/AndroidRuntime(14525):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
08-12 14:44:40.105: ERROR/AndroidRuntime(14525):     at dalvik.system.NativeStart.main(Native Method)
08-12 14:44:40.105: ERROR/AndroidRuntime(14525): Caused by: java.lang.NullPointerException
08-12 14:44:40.105: ERROR/AndroidRuntime(14525):     at a.b.MyIncidentActivity.onCreate(MyIncidentActivity.java:50)
08-12 14:44:40.105: ERROR/AndroidRuntime(14525):     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
08-12 14:44:40.105: ERROR/AndroidRuntime(14525):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1611)
08-12 14:44:40.105: ERROR/AndroidRuntime(14525):     ... 11 more

有人可以帮我找出原因。我迷失了这个错误。在同一个应用程序内同样的实现工作正常，但不知道为什么它不工作。

Answer 1

您使用的代码

setListAdapter(adapter);

表示您使用的是ListActivity，在使用ListActivity时，您的列表如下：

listView = this.getListView();

或者您可以使用

listView = this.findViewById(android.R.id.list);

你正在使用

listView = this.findViewById(R.id.list);

如果ListActivity出现错误，则无法找到ListView并导致NullPointerException。

Answer 2

试试这样。

Public class ABCD implements OnItemClickListener{
          ListView listview;//class varible

           listview = (ListView)findViewById(R.id.list);
           setListAdapter(new ArrayAdapter<String>(MyIncidentActivity.this,
           R.layout.row_incident, R.id.label_incident, db_results));
           listview.setOnItemClickListener(this);

        @Override
    public void onItemClick(AdapterView<?> arg0, View arg1, int arg2, long arg3) {
        // TODO Auto-generated method stub

    }

}