Question

我有第二个活动在onCreate（）中调用的以下方法。

它从第一个活动通过Serializable获取一个对象，并根据它创建一个列表，更改对象并将其发送回第一个活动。

这样可以正常工作，但如果我向第一个活动发回未更改的对象，则在尝试在第二个活动中创建列表时会崩溃。

private void createLectureListView() {

    ListView lecListView = (ListView) findViewById(R.id.lectureListView);

    Intent i = getIntent();
    mod = (Module)i.getSerializableExtra("moduleObject");

    lectureList = new ArrayList<Lecture>();

    if (mod.lectureArrayList!=null) lectureList=mod.lectureArrayList;

    listAdapter = new ArrayAdapter<Lecture>(this,android.R.layout.simple_list_item_1, lectureList);

    lecListView.setAdapter(listAdapter);
}

这是一个例外：

Caused by: java.lang.NullPointerException

[编辑]还添加了其他位。这是Activity1中的一个：

private void registerClickCallback() {
    ListView listView1 = (ListView) findViewById(R.id.listView1);
    listView1.setOnItemClickListener(new AdapterView.OnItemClickListener() {
        @Override
        public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
            Intent myIntent = new Intent(MenuActivity.this, LectureNotes.class);
            //pass the module object we are selecting
            myIntent.putExtra("moduleObject",modulesInfo.get(position));
            pos = position;

            startActivityForResult(myIntent,1);
        }
    });
}

第一个ACtivity中的onActivityResult方法。

@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
    super.onActivityResult(requestCode, resultCode, data);
    if (requestCode == 1) {
        if(resultCode == RESULT_OK){
            mod = (Module)data.getSerializableExtra("moduleObject");
            if (mod!=modulesInfo.get(pos))
                modulesInfo.set(pos,mod);
        }
    }
}

[EDIT2]堆栈跟踪

12-12 08:56:37.041    4143-4143/com.example.learnorizeapp E/AndroidRuntime﹕ FATAL EXCEPTION: main
    java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.learnorizeapp/com.example.learnorizeapp.LectureNotes}: java.lang.NullPointerException
            at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2180)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2230)
            at android.app.ActivityThread.access$600(ActivityThread.java:141)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1234)
            at android.os.Handler.dispatchMessage(Handler.java:99)
            at android.os.Looper.loop(Looper.java:137)
            at android.app.ActivityThread.main(ActivityThread.java:5041)
            at java.lang.reflect.Method.invokeNative(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:511)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
            at dalvik.system.NativeStart.main(Native Method)
     Caused by: java.lang.NullPointerException
            at com.example.learnorizeapp.LectureNotes.createLectureListView(LectureNotes.java:59)
            at com.example.learnorizeapp.LectureNotes.onCreate(LectureNotes.java:28)
            at android.app.Activity.performCreate(Activity.java:5104)
            at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1080)
            at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2144)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2230)
            at android.app.ActivityThread.access$600(ActivityThread.java:141)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1234)
            at android.os.Handler.dispatchMessage(Handler.java:99)
            at android.os.Looper.loop(Looper.java:137)
            at android.app.ActivityThread.main(ActivityThread.java:5041)
            at java.lang.reflect.Method.invokeNative(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:511)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
            at dalvik.system.NativeStart.main(Native Method)
12-12 08:56:37.057      459-709/system_process W/ActivityManager﹕ Force finishing activity com.example.learnorizeapp/.LectureNotes
12-12 08:56:37.057      459-709/system_process W/ActivityManager﹕ Force finishing activity com.example.learnorizeapp/.MenuActivity

Answer 1

讲座有一个问题在做一些不同的场景时，例如点击一个按钮但没有点击另一个，它返回null。

通过Serializable崩溃发送对象

1 个答案: