创建 PendingIntent 时的 Nullpointer答案

【问题标题】：Nullpointer at creating PendingIntent创建 PendingIntent 时的 Nullpointer
【发布时间】：2013-08-07 20:58:25
【问题描述】：

我在Intent alarmIntent = new Intent(this, MyNotification.class); 得到一个空指针，但我不知道如何解决这个问题.. 我希望有人能帮助我..

应该做的是每天 9 点设置闹钟，这样我就可以在包含 BroadcastReceiver 的 MyNotification 类中设置通知。

下面是我所有的代码：

调用 AlarmManager 类（来自 MainActivity）：

Alarm setAlarm = new Alarm();
        setAlarm.setRecurringAlarm();

我要设置AlarmManager的类（Alarm.class）：

public class Alarm extends Activity {
public void setRecurringAlarm() {

    Log.i("Alarm", "Setting Recurring Alarm");

    Calendar updateTime = Calendar.getInstance();

    updateTime.set(Calendar.HOUR, 7);
    updateTime.set(Calendar.MINUTE, 0);
    updateTime.set(Calendar.SECOND, 0);

    Intent alarmIntent = new Intent(this, MyNotification.class);
    PendingIntent recurringDownload = PendingIntent.getBroadcast(this, 0, alarmIntent, PendingIntent.FLAG_CANCEL_CURRENT);
    AlarmManager alarms = (AlarmManager) getSystemService(Context.ALARM_SERVICE);
    alarms.cancel(recurringDownload);
    alarms.setInexactRepeating(AlarmManager.RTC, updateTime.getTimeInMillis(), AlarmManager.INTERVAL_DAY , recurringDownload);
}

}

Logcat 输出：

08-07 22:43:38.079: E/AndroidRuntime(21476): FATAL EXCEPTION: main
08-07 22:43:38.079: E/AndroidRuntime(21476): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.weatherclothes/com.weatherclothes.MainActivity}: java.lang.NullPointerException
08-07 22:43:38.079: E/AndroidRuntime(21476):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2355)
08-07 22:43:38.079: E/AndroidRuntime(21476):    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2391)
08-07 22:43:38.079: E/AndroidRuntime(21476):    at android.app.ActivityThread.access$600(ActivityThread.java:151)
08-07 22:43:38.079: E/AndroidRuntime(21476):    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1335)
08-07 22:43:38.079: E/AndroidRuntime(21476):    at android.os.Handler.dispatchMessage(Handler.java:99)
08-07 22:43:38.079: E/AndroidRuntime(21476):    at android.os.Looper.loop(Looper.java:155)
08-07 22:43:38.079: E/AndroidRuntime(21476):    at android.app.ActivityThread.main(ActivityThread.java:5493)
08-07 22:43:38.079: E/AndroidRuntime(21476):    at java.lang.reflect.Method.invokeNative(Native Method)
08-07 22:43:38.079: E/AndroidRuntime(21476):    at java.lang.reflect.Method.invoke(Method.java:511)
08-07 22:43:38.079: E/AndroidRuntime(21476):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1028)
08-07 22:43:38.079: E/AndroidRuntime(21476):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:795)
08-07 22:43:38.079: E/AndroidRuntime(21476):    at dalvik.system.NativeStart.main(Native Method)
08-07 22:43:38.079: E/AndroidRuntime(21476): Caused by: java.lang.NullPointerException
08-07 22:43:38.079: E/AndroidRuntime(21476):    at android.content.ComponentName.<init>(ComponentName.java:75)
08-07 22:43:38.079: E/AndroidRuntime(21476):    at android.content.Intent.<init>(Intent.java:3655)
08-07 22:43:38.079: E/AndroidRuntime(21476):    at com.weatherclothes.Alarm.setRecurringAlarm(Alarm.java:23)
08-07 22:43:38.079: E/AndroidRuntime(21476):    at com.weatherclothes.MainActivity.onCreate(MainActivity.java:58)
08-07 22:43:38.079: E/AndroidRuntime(21476):    at android.app.Activity.performCreate(Activity.java:5066)
08-07 22:43:38.079: E/AndroidRuntime(21476):    at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1101)
08-07 22:43:38.079: E/AndroidRuntime(21476):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2311)
08-07 22:43:38.079: E/AndroidRuntime(21476):    ... 11 more

【问题讨论】：

在创建 PendingIntent pi 之前检查您的上下文是否为空
哇哈哈，上下文确实为空。知道如何解决吗？
只要使用上下文 mContext = this;
现在我这样做了：但我仍然得到同样的错误......：S Context mContext = this; if (mContext != null) { PendingIntent pi = PendingIntent.getService(mContext, 0, new Intent(mContext, MyNotification.class), PendingIntent.FLAG_UPDATE_CURRENT); AlarmManager am = (AlarmManager) mContext .getSystemService(Context.ALARM_SERVICE); am.setRepeating(AlarmManager.RTC, calendar.getTimeInMillis(), AlarmManager.INTERVAL_DAY, pi); }
在创建alarmIntent 时尝试Alarm.this（即className.this）而不是使用this。看看这是否有效。

标签： android android-intent nullpointerexception alarmmanager null-pointer

【解决方案1】：

只是想知道，你为什么要这样做，而不是把 setRecurringAlarm() 方法放在你的 MainActivity 中？

您只是在创建警报活动的实例，并在其上调用方法。我真的不认为有必要在额外的活动中这样做。

只是猜测，但可能在没有正确启动的情况下将警报活动用作上下文可能会导致 NullPointerException。

【讨论】：