异常调度输入事件 - 空指针异常

Question

04-19 13:00:01.441    2331-2331/com.example.barun.myapplication E/InputEventReceiver﹕ Exception dispatching input event.
04-19 13:00:01.442    2331-2331/com.example.barun.myapplication E/MessageQueue-JNI﹕ Exception in MessageQueue callback: handleReceiveCallback
04-19 13:00:01.442    2331-2331/com.example.barun.myapplication E/MessageQueue-JNI﹕ java.lang.NullPointerException: Attempt to invoke virtual method 'boolean android.support.v7.internal.view.menu.MenuItemImpl.hasSubMenu()' on a null object reference
        at android.support.v7.internal.view.menu.ActionMenuItemView.onTouchEvent(ActionMenuItemView.java:135)
        at android.view.View.dispatchTouchEvent(View.java:8388)
        at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2430)
        at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2119)
        at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2430)
        at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2119)
        at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2430)
        at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2119)
        at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2430)
        at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2119)
        at com.android.internal.policy.impl.PhoneWindow$DecorView.superDispatchTouchEvent(PhoneWindow.java:2314)
        at com.android.internal.policy.impl.PhoneWindow.superDispatchTouchEvent(PhoneWindow.java:1692)
        at android.app.Activity.dispatchTouchEvent(Activity.java:2739)
        at com.android.internal.policy.impl.PhoneWindow$DecorView.dispatchTouchEvent(PhoneWindow.java:2275)
        at android.view.View.dispatchPointerEvent(View.java:8578)
        at android.view.ViewRootImpl$ViewPostImeInputStage.processPointerEvent(ViewRootImpl.java:4021)
        at android.view.ViewRootImpl$ViewPostImeInputStage.onProcess(ViewRootImpl.java:3887)
        at android.view.ViewRootImpl$InputStage.deliver(ViewRootImpl.java:3449)
        at android.view.ViewRootImpl$InputStage.onDeliverToNext(ViewRootImpl.java:3502)
        at android.view.ViewRootImpl$InputStage.forward(ViewRootImpl.java:3468)
        at android.view.ViewRootImpl$AsyncInputStage.forward(ViewRootImpl.java:3578)
        at android.view.ViewRootImpl$InputStage.apply(ViewRootImpl.java:3476)
        at android.view.ViewRootImpl$AsyncInputStage.apply(ViewRootImpl.java:3635)
        at android.view.ViewRootImpl$InputStage.deliver(ViewRootImpl.java:3449)
        at android.view.ViewRootImpl$InputStage.onDeliverToNext(ViewRootImpl.java:3502)
        at android.view.ViewRootImpl$InputStage.forward(ViewRootImpl.java:3468)
        at android.view.ViewRootImpl$InputStage.apply(ViewRootImpl.java:3476)
        at android.view.ViewRootImpl$InputStage.deliver(ViewRootImpl.java:3449)
        at android.view.ViewRootImpl.deliverInputEvent(ViewRootImpl.java:5701)
        at android.view.ViewRootImpl.doProcessInputEvents(ViewRootImpl.java:5675)
        at android.view.ViewRootImpl.enqueueInputEvent(ViewRootImpl.java:5646)
        at android.view.ViewRootImpl$WindowInputEventReceiver.onInputEvent(ViewRootImpl.java:5791)
        at android.view.InputEventReceiver.dispatchInputEvent(InputEventReceiver.java:185)
        at android.os.MessageQueue.nativePollOnce(Native Method)
        at android.os.MessageQueue.next(MessageQueue.java:143)
        at android.os.Looper.loop(Looper.java:122)
        at android.app.ActivityThread.main(ActivityThread.java:5221)
        at java.lang.reflect.Method.invoke(Native Method)
        at java.lang.reflect.Method.invoke(Method.java:372)
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:899)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694)
04-19 13:00:01.442    2331-2331/com.example.barun.myapplication D/AndroidRuntime﹕ Shutting down VM
04-19 13:00:01.442    2331-2331/com.example.barun.myapplication E/AndroidRuntime﹕ FATAL EXCEPTION: main
Process: com.example.barun.myapplication, PID: 2331
java.lang.NullPointerException: Attempt to invoke virtual method 'boolean android.support.v7.internal.view.menu.MenuItemImpl.hasSubMenu()' on a null object reference
        at android.support.v7.internal.view.menu.ActionMenuItemView.onTouchEvent(ActionMenuItemView.java:135)
        at android.view.View.dispatchTouchEvent(View.java:8388)
        at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2430)
        at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2119)
        at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2430)
        at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2119)
        at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2430)
        at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2119)
        at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2430)
        at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2119)
        at com.android.internal.policy.impl.PhoneWindow$DecorView.superDispatchTouchEvent(PhoneWindow.java:2314)
        at com.android.internal.policy.impl.PhoneWindow.superDispatchTouchEvent(PhoneWindow.java:1692)
        at android.app.Activity.dispatchTouchEvent(Activity.java:2739)
        at com.android.internal.policy.impl.PhoneWindow$DecorView.dispatchTouchEvent(PhoneWindow.java:2275)
        at android.view.View.dispatchPointerEvent(View.java:8578)
        at android.view.ViewRootImpl$ViewPostImeInputStage.processPointerEvent(ViewRootImpl.java:4021)
        at android.view.ViewRootImpl$ViewPostImeInputStage.onProcess(ViewRootImpl.java:3887)
        at android.view.ViewRootImpl$InputStage.deliver(ViewRootImpl.java:3449)
        at android.view.ViewRootImpl$InputStage.onDeliverToNext(ViewRootImpl.java:3502)
        at android.view.ViewRootImpl$InputStage.forward(ViewRootImpl.java:3468)
        at android.view.ViewRootImpl$AsyncInputStage.forward(ViewRootImpl.java:3578)
        at android.view.ViewRootImpl$InputStage.apply(ViewRootImpl.java:3476)
        at android.view.ViewRootImpl$AsyncInputStage.apply(ViewRootImpl.java:3635)
        at android.view.ViewRootImpl$InputStage.deliver(ViewRootImpl.java:3449)
        at android.view.ViewRootImpl$InputStage.onDeliverToNext(ViewRootImpl.java:3502)
        at android.view.ViewRootImpl$InputStage.forward(ViewRootImpl.java:3468)
        at android.view.ViewRootImpl$InputStage.apply(ViewRootImpl.java:3476)
        at android.view.ViewRootImpl$InputStage.deliver(ViewRootImpl.java:3449)
        at android.view.ViewRootImpl.deliverInputEvent(ViewRootImpl.java:5701)
        at android.view.ViewRootImpl.doProcessInputEvents(ViewRootImpl.java:5675)
        at android.view.ViewRootImpl.enqueueInputEvent(ViewRootImpl.java:5646)
        at android.view.ViewRootImpl$WindowInputEventReceiver.onInputEvent(ViewRootImpl.java:5791)
        at android.view.InputEventReceiver.dispatchInputEvent(InputEventReceiver.java:185)
        at android.os.MessageQueue.nativePollOnce(Native Method)
        at android.os.MessageQueue.next(MessageQueue.java:143)
        at android.os.Looper.loop(Looper.java:122)
        at android.app.ActivityThread.main(ActivityThread.java:5221)
        at java.lang.reflect.Method.invoke(Native Method)
        at java.lang.reflect.Method.invoke(Method.java:372)
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:899)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694)
04-19 13:00:03.580    2331-2331/com.example.barun.myapplication I/Process﹕ Sending signal. PID: 2331 SIG: 9

我正在按照 Youtube 视频教程学习 Android 应用程序开发，该教程基本上列出了我所有扩展 ListActivity 类的应用程序活动。按照该说明，每当我从列表中选择活动时，我都会收到此错误，应用程序会说"不幸的是，我的应用程序已停止"。在堆栈溢出上搜索了很多，但对这种空异常错误没有疑问

'boolean android.support.v7.internal.view.menu.MenuItemImpl.hasSubMenu（）' on a null object reference（）'

下面是我的代码，

public class Menu extends ListActivity {
    String classes[] = {"MainActivity","example1","example2","example3","example4","example5","example6"};
    @Override
    protected void onCreate(Bundle savedInstanceState){
        super.onCreate(savedInstanceState);
        setListAdapter(new ArrayAdapter<String>(Menu.this,R.layout.abc_action_menu_item_layout ,classes));
    }
    @Override
    protected void onListItemClick(ListView l, View v, int position, long id){
        super.onListItemClick(l, v, position, id);
        String cheese = classes[position];
        try {
            Class ourClass = Class.forName("com.example.barun.myapplication."+cheese);
            Intent ourIntent = new Intent(Menu.this,ourClass);
            startActivity(ourIntent);
        }catch(ClassNotFoundException e){
            e.printStackTrace();
        }
    }
}

让我知道所需的任何进一步信息。谢谢，提前。

Answer 1

问题出在这一行

setListAdapter(new ArrayAdapter<String>(Menu.this,R.layout.abc_action_menu_item_layout, classes));

您正在使用此视图android.support.v7.internal.view.menu.ActionMenuItemView 来自 abc_action_menu_item_layout 作为您的值。动作栏相关的东西。

溶液：而是创建一个布局 （TextView） 将视图 ID 设置为 @android:id/text1
simple_layout.xml

<?xml version="1.0" encoding="utf-8"?>
<TextView xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@android:id/text1"
    android:layout_width="match_parent"
    android:layout_height="match_parent" />

像这样创建适配器

setListAdapter(new ArrayAdapter<String>(Menu.this, R.layout.simple_ayout, classes));

Answer 2

空指针异常错误意味着您正在执行的操作返回"null"值。

仔细检查您的日志，您可以看到日志告诉您错误在第 135 行，在名为 ActionMenuItemView.java 的类中。

(ActionMenuItemView.java:135)

你能给我你在那行写的代码吗？

那里可能有问题。