java - 致命异常 onItemClick 监听器

Question

情况是当我选择其中一个列表项时。它将在下一个 Activity 中显示该项目的详细信息。

我尝试使用 onItemClick 监听器从选定的 ListItem 获取值。我在点击该项目时遇到错误 [FATAL EXCEPTION]。

请帮助我。

这是 ScheduleFragment.java 的一部分

public class ScheduleFragment extends Fragment {
 /* other activity */

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState)
{
    View rootView = inflater.inflate(R.layout.fragment_schedule, container, false);

myListView = (ListView) rootView.findViewById(R.id.list);

    // on selecting single subject
    myListView.setOnItemClickListener(new OnItemClickListener() {

        @Override
        public void onItemClick(AdapterView<?> parent, View view,
                int position, long id) {
            // getting values from selected ListItem
            String matrix_id = ((ListView) view.findViewById(R.id.list)).getText()
                    .toString();

            // Starting new intent
            Intent in = new Intent(getActivity().getApplicationContext(),
                    SingleSubject.class);

            // sending matrix id to next activity
            in.putExtra(TAG_MATRIX_ID, matrix_id);

            // starting new activity and expecting some response back
            startActivityForResult(in, 100);
        }
    });

这是 SingleSubject.java

public class SingleSubject extends Activity {

    @Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.single_subject);


    // getting subject details from intent
    Intent i = getIntent();

    // getting matrix_id from intent
    matrix_id = i.getStringExtra(TAG_MATRIX_ID);

    // Getting complete matrix_id details in background thread
    new GetSubjectDetails().execute();


}

这个single_subject.xml

<!-- Name Label -->
<TextView android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:text="Name"
    android:paddingLeft="10dip"
    android:paddingRight="10dip"
    android:paddingTop="10dip"
    android:textSize="17dip"/>

<!-- Input Name -->
<EditText android:id="@+id/inputName"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:layout_margin="5dip"
    android:layout_marginBottom="15dip"
    android:singleLine="true"/>

<!-- Email Label -->
<TextView android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:text="Email"
    android:paddingLeft="10dip"
    android:paddingRight="10dip"
    android:paddingTop="10dip"
    android:textSize="17dip"/>

<!-- Input Email -->
<EditText android:id="@+id/inputEmail" 
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:layout_margin="5dip"
    android:layout_marginBottom="15dip"
    android:singleLine="true"/>

这是fragment_schedule.xml

 <ListView
    android:id="@+id/list"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"/>

这是日志错误。

03-25 14:40:49.808: W/dalvikvm(10182): threadid=1: thread exiting with uncaught exception (group=0x40d09930)
03-25 14:40:49.854: E/AndroidRuntime(10182): FATAL EXCEPTION: main
03-25 14:40:49.854: E/AndroidRuntime(10182): java.lang.NullPointerException
03-25 14:40:49.854: E/AndroidRuntime(10182):    at com.ultra.esc.ScheduleFragment$1.onItemClick(ScheduleFragment.java:95)
03-25 14:40:49.854: E/AndroidRuntime(10182):    at android.widget.AdapterView.performItemClick(AdapterView.java:298)
03-25 14:40:49.854: E/AndroidRuntime(10182):    at android.widget.AbsListView.performItemClick(AbsListView.java:1100)
03-25 14:40:49.854: E/AndroidRuntime(10182):    at android.widget.AbsListView$PerformClick.run(AbsListView.java:2749)
03-25 14:40:49.854: E/AndroidRuntime(10182):    at android.widget.AbsListView$1.run(AbsListView.java:3423)
03-25 14:40:49.854: E/AndroidRuntime(10182):    at android.os.Handler.handleCallback(Handler.java:725)
03-25 14:40:49.854: E/AndroidRuntime(10182):    at android.os.Handler.dispatchMessage(Handler.java:92)
03-25 14:40:49.854: E/AndroidRuntime(10182):    at android.os.Looper.loop(Looper.java:137)
03-25 14:40:49.854: E/AndroidRuntime(10182):    at android.app.ActivityThread.main(ActivityThread.java:5039)
03-25 14:40:49.854: E/AndroidRuntime(10182):    at java.lang.reflect.Method.invokeNative(Native Method)
03-25 14:40:49.854: E/AndroidRuntime(10182):    at java.lang.reflect.Method.invoke(Method.java:511)
03-25 14:40:49.854: E/AndroidRuntime(10182):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
03-25 14:40:49.854: E/AndroidRuntime(10182):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
03-25 14:40:49.854: E/AndroidRuntime(10182):    at dalvik.system.NativeStart.main(Native Method)

Answer 1

您在为适配器扩展的布局中没有 ListView

 String matrix_id = ((ListView) view.findViewById(R.id.list)).getText()
                .toString();

因此，上述初始化为您提供了 NullpointerExcpetion。

猜测工作:

我可以从我回答的上一个问题中猜出你的问题( ClassCastException: android.widget.TextView cannot be cast to android.widget.ListView )。您在适配器中使用 id R.id.matrix_id 和 R.id.name 膨胀的布局具有 TextView。但为了确认您可以发布您的适配器代码。

复制您之前的问题

 ListAdapter adapter = new SimpleAdapter(
                       getActivity(), subjectList,
                    R.layout.all_subject, new String[] { TAG_MATRIX_ID,
                            TAG_NAME},
                    new int[] { R.id.matrix_id, R.id.name });

您可以使用 getTag 和 setTag 来避免按照 laalto 的建议再次初始化 View

 String matrix_id = ((TextView) view.findViewById(R.id.matrix_id)).getText()
                .toString();

 String name = ((TextView) view.findViewById(R.id.name)).getText()
                .toString();