Android：创建上下文菜单时出现异常

在点击ActionBar菜单选项后，我试图“转到”浮动上下文菜单。但我甚至无法加载该应用程序，因为在启动它之前，我遇到了一个异常。 我正在尝试使用以下简单代码：

indexActivity.java

     protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);

            setContentView(R.layout.activity_index);
            registerForContextMenu(findViewById(R.id.action_share));
(...)

那我有

    public void onCreateContextMenu(ContextMenu menu, View v,
                                        ContextMenu.ContextMenuInfo menuInfo) {
            super.onCreateContextMenu(menu, v, menuInfo);
            menu.setHeaderTitle("Context Menu");
(...)

menu.xml:

<menu xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    tools:context=".IndexActivity">

    <item android:id="@+id/action_settings"
        android:title="@string/action_settings"
        android:orderInCategory="100"
        app:showAsAction="never" />

    <item android:id="@+id/action_share"
        android:title="@string/action_share"
        android:orderInCategory="100"
        app:showAsAction="never" />

java.lang.RuntimeException: Unable to start activity ComponentInfo{com.converter.android.converter/com.converter.android.converter.IndexActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'int android.view.View.getId()' on a null object reference
            at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2298)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2360)
            at android.app.ActivityThread.access$800(ActivityThread.java:144)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1278)
            at android.os.Handler.dispatchMessage(Handler.java:102)
            at android.os.Looper.loop(Looper.java:135)
            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)
     Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'int android.view.View.getId()' on a null object reference
            at com.converter.android.converter.IndexActivity.onCreate(IndexActivity.java:33)
            at android.app.Activity.performCreate(Activity.java:5933)
            at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1105)
            at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2251)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2360)
            at android.app.ActivityThread.access$800(ActivityThread.java:144)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1278)
            at android.os.Handler.dispatchMessage(Handler.java:102)
            at android.os.Looper.loop(Looper.java:135)

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你试过注释registerForContextMenu吗？@user2875404，是的…注释我也不例外…但是在这种情况下，我无法创建上下文菜单..当然。。一种解决方法是将这个东西变成一个按钮，然后从那里调用onCreateContextMenu（）。这不是最好的方法，但事实上这是我一直在做的事情hahacan你也可以发布xml布局文件吗？@mt0s假设layout.xml与此问题有关吗？那是因为我没有做任何与此相关的改变。我只更改了menu.xml，添加了新项（我用menu.xml更新了这篇文章）和java文件。