Android 尝试从按键调用showDialog()方法时获取NullPointerException
每当在特定视图中按下按钮时,我试图显示一个自定义对话框。但是,每当我尝试切换到包含按钮的视图时,就会出现强制关闭错误。LogCat在我用来设置侦听器的方法上给了我一个NullPointerException,但是,我不确定是否有错误。我想这可能是对话框代码,但我已经将其写入了Android开发者网站的规范中 下面是按钮侦听器的方法:Android 尝试从按键调用showDialog()方法时获取NullPointerException,android,dialog,nullpointerexception,Android,Dialog,Nullpointerexception,每当在特定视图中按下按钮时,我试图显示一个自定义对话框。但是,每当我尝试切换到包含按钮的视图时,就会出现强制关闭错误。LogCat在我用来设置侦听器的方法上给了我一个NullPointerException,但是,我不确定是否有错误。我想这可能是对话框代码,但我已经将其写入了Android开发者网站的规范中 下面是按钮侦听器的方法: //Registers the listeners for the various buttons in the edit view private void re
//Registers the listeners for the various buttons in the edit view
private void registerButtonListenersAndSetDefaultText() {
mTimeButton.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
showDialog(TIME_PICKER_DIALOG);
}
});
updateTimeButtonText();
mDayButton.setOnClickListener(new View.OnClickListener() { //here is where
//the error is
//being thrown.
public void onClick(View v) {
showDialog(DAY_CHECKBOX_DIALOG);
}
});
}
以下是onCreateDialog()方法:
下面是showDayPicker()方法(我认为可能是这个方法导致了问题):
下面是日志:
10-19 20:23:57.191: ERROR/AndroidRuntime(293): FATAL EXCEPTION: main
10-19 20:23:57.191: ERROR/AndroidRuntime(293): java.lang.RuntimeException: Unable to start activity ComponentInfo{vt.nhw.android.easyringertoggle/vt.nhw.android.easyringertoggle.ScheduleEditActivity}: java.lang.NullPointerException
10-19 20:23:57.191: ERROR/AndroidRuntime(293): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2663)
10-19 20:23:57.191: ERROR/AndroidRuntime(293): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2679)
10-19 20:23:57.191: ERROR/AndroidRuntime(293): at android.app.ActivityThread.access$2300(ActivityThread.java:125)
10-19 20:23:57.191: ERROR/AndroidRuntime(293): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2033)
10-19 20:23:57.191: ERROR/AndroidRuntime(293): at android.os.Handler.dispatchMessage(Handler.java:99)
10-19 20:23:57.191: ERROR/AndroidRuntime(293): at android.os.Looper.loop(Looper.java:123)
10-19 20:23:57.191: ERROR/AndroidRuntime(293): at android.app.ActivityThread.main(ActivityThread.java:4627)
10-19 20:23:57.191: ERROR/AndroidRuntime(293): at java.lang.reflect.Method.invokeNative(Native Method)
10-19 20:23:57.191: ERROR/AndroidRuntime(293): at java.lang.reflect.Method.invoke(Method.java:521)
10-19 20:23:57.191: ERROR/AndroidRuntime(293): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868)
10-19 20:23:57.191: ERROR/AndroidRuntime(293): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626)
10-19 20:23:57.191: ERROR/AndroidRuntime(293): at dalvik.system.NativeStart.main(Native Method)
10-19 20:23:57.191: ERROR/AndroidRuntime(293): Caused by: java.lang.NullPointerException
10-19 20:23:57.191: ERROR/AndroidRuntime(293): at vt.nhw.android.easyringertoggle.ScheduleEditActivity.registerButtonListenersAndSetDefaultText(ScheduleEditActivity.java:52)
10-19 20:23:57.191: ERROR/AndroidRuntime(293): at vt.nhw.android.easyringertoggle.ScheduleEditActivity.onCreate(ScheduleEditActivity.java:39)
10-19 20:23:57.191: ERROR/AndroidRuntime(293): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
10-19 20:23:57.191: ERROR/AndroidRuntime(293): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2627)
10-19 20:23:57.191: ERROR/AndroidRuntime(293): ... 11 more
顺便说一句,我之前已经发布过这个问题,但是实际的问题主体变得复杂,所以我删除并重新发布了。谢谢你的帮助 您如何获得对这些对象的引用?像这样的
mTimeButton = (Button)findViewById(R.id.timeBtn);
如果是,你什么时候做?如果在进行findViewById()调用时视图不在屏幕上,它将向您返回null
发布你的onCreate方法,你会更容易弄清楚到底发生了什么
编辑:还向引发异常的行添加注释。因为我们不知道哪一个是52。你确定
mTimeButton
和mDayButton
引用的是按钮吗?您的问题出现在onCreate
上,而不是showDialog
。错误发生在第32行。如果双击在vt.nhw.android.easyringertoggle.ScheduleEditActivity.registerButtonListenersAndSetDefaultText(ScheduleEditActivity.java:52)上告诉您的logcat错误,您将看到代码中没有行号的错误。堆栈跟踪指向ScheduleEditActivity.java的第52行
我正在引用对象mTimeButton和mDayButton,格式为:mTimeButton=(Button)findViewById(R.id.time_Button)
,我在onCreate()中执行此操作我刚刚发现,似乎我没有在onCreate()方法中正确地形成按钮引用。谢谢你在这件小事上的帮助。
10-19 20:23:57.191: ERROR/AndroidRuntime(293): FATAL EXCEPTION: main
10-19 20:23:57.191: ERROR/AndroidRuntime(293): java.lang.RuntimeException: Unable to start activity ComponentInfo{vt.nhw.android.easyringertoggle/vt.nhw.android.easyringertoggle.ScheduleEditActivity}: java.lang.NullPointerException
10-19 20:23:57.191: ERROR/AndroidRuntime(293): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2663)
10-19 20:23:57.191: ERROR/AndroidRuntime(293): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2679)
10-19 20:23:57.191: ERROR/AndroidRuntime(293): at android.app.ActivityThread.access$2300(ActivityThread.java:125)
10-19 20:23:57.191: ERROR/AndroidRuntime(293): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2033)
10-19 20:23:57.191: ERROR/AndroidRuntime(293): at android.os.Handler.dispatchMessage(Handler.java:99)
10-19 20:23:57.191: ERROR/AndroidRuntime(293): at android.os.Looper.loop(Looper.java:123)
10-19 20:23:57.191: ERROR/AndroidRuntime(293): at android.app.ActivityThread.main(ActivityThread.java:4627)
10-19 20:23:57.191: ERROR/AndroidRuntime(293): at java.lang.reflect.Method.invokeNative(Native Method)
10-19 20:23:57.191: ERROR/AndroidRuntime(293): at java.lang.reflect.Method.invoke(Method.java:521)
10-19 20:23:57.191: ERROR/AndroidRuntime(293): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868)
10-19 20:23:57.191: ERROR/AndroidRuntime(293): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626)
10-19 20:23:57.191: ERROR/AndroidRuntime(293): at dalvik.system.NativeStart.main(Native Method)
10-19 20:23:57.191: ERROR/AndroidRuntime(293): Caused by: java.lang.NullPointerException
10-19 20:23:57.191: ERROR/AndroidRuntime(293): at vt.nhw.android.easyringertoggle.ScheduleEditActivity.registerButtonListenersAndSetDefaultText(ScheduleEditActivity.java:52)
10-19 20:23:57.191: ERROR/AndroidRuntime(293): at vt.nhw.android.easyringertoggle.ScheduleEditActivity.onCreate(ScheduleEditActivity.java:39)
10-19 20:23:57.191: ERROR/AndroidRuntime(293): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
10-19 20:23:57.191: ERROR/AndroidRuntime(293): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2627)
10-19 20:23:57.191: ERROR/AndroidRuntime(293): ... 11 more
mTimeButton = (Button)findViewById(R.id.timeBtn);