Question

我试图在我的Activity中实例化一个Dialog。

public void createOptionsMenu() {
    Log.e("ActivityContext null?","" + myActivity.this);
    myOptionsDialog = new Dialog(myActivity.this); //throwsNPE
    myOptionsDialog.setContentView(R.layout.options_dialog);
    myOptionsDialog.show();
}

由于您可以在上面看到Log.e，我知道我的activity-context不是空的！

12-21 15:17:15.466: E/ActivityContext null?(3774): com.android.myproject.myActivity@41fd9af0
12-21 15:17:15.469: E/AndroidRuntime(3774): java.lang.NullPointerException

我认为问题在于我从另一个只有createOptionsMenu()来自ApplicationContext的班级拨打myActivity。如果是这样，我如何在不将ActivityContext传递给调用createOptionsMenu的其他类的情况下创建我的Dialog。

感谢任何帮助。

更新

12-21 15:17:15.469: E/AndroidRuntime(3774): FATAL EXCEPTION: main 12-21 15:17:15.469: E/AndroidRuntime(3774): java.lang.NullPointerException 12-21 15:17:15.469: E/AndroidRuntime(3774): at android.content.ContextWrapper.getApplicationInfo(ContextWrapper.java:140) 12-21 15:17:15.469: E/AndroidRuntime(3774): at android.view.ContextThemeWrapper.getTheme(ContextThemeWrapper.java:103) 12-21 15:17:15.469: E/AndroidRuntime(3774): at android.app.Dialog.<init>(Dialog.java:154) 12-21 15:17:15.469: E/AndroidRuntime(3774): at android.app.Dialog.<init>(Dialog.java:131) 12-21 15:17:15.469: E/AndroidRuntime(3774): at com.android.myproject.myActivity.createOptionsMenu(myActivity.java:798) 12-21 15:17:15.469: E/AndroidRuntime(3774): at com.android.myproject.WorkerClass$2.onItemLongClick(WorkerClass.java:448) 12-21 15:17:15.469: E/AndroidRuntime(3774): at android.widget.AbsListView.performLongPress(AbsListView.java:2883) 12-21 15:17:15.469: E/AndroidRuntime(3774): at android.widget.AbsListView$CheckForLongPress.run(AbsListView.java:2833) 12-21 15:17:15.469: E/AndroidRuntime(3774): at android.os.Handler.handleCallback(Handler.java:725) 12-21 15:17:15.469: E/AndroidRuntime(3774): at android.os.Handler.dispatchMessage(Handler.java:92) 12-21 15:17:15.469: E/AndroidRuntime(3774): at android.os.Looper.loop(Looper.java:153) 12-21 15:17:15.469: E/AndroidRuntime(3774): at android.app.ActivityThread.main(ActivityThread.java:5338) 12-21 15:17:15.469: E/AndroidRuntime(3774): at java.lang.reflect.Method.invokeNative(Native Method) 12-21 15:17:15.469: E/AndroidRuntime(3774): at java.lang.reflect.Method.invoke(Method.java:511) 12-21 15:17:15.469: E/AndroidRuntime(3774): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:833) 12-21 15:17:15.469: E/AndroidRuntime(3774): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:600) 12-21 15:17:15.469: E/AndroidRuntime(3774): at dalvik.system.NativeStart.main(Native Method)

实例化活动：

myActivity myActivity_ = new myActivity();
                WeakReference<myActivity> myWeakActivity = new WeakReference<myActivity>(myActivity_);
                myWeakActivity.get().createOptionsMenu();

Answer 1

问题在于背景。当我创建一个新的活动对象时，旧的活动不是有效的＆＃34;内部＆＃34;新的对象。

解决方法是简单地将Activity-Context传递给createOptionsMenu，然后执行此操作：

MyActivity myActivity_ = (MyActivity) context;

然后你可以参考你真正想要的资源。

希望它对某人有帮助。

实例化对话框时的NPE

1 个答案: