Android 广播通知 NullPointerException on tentent Extra.

Question

我需要在每天 8：30 在我的任务管理器中发出有关任务的通知。

这是我来自活动的代码：

public final static String INTENT_LIST_FOR_NOTIFICATION = "tasks for notification";
private void setUserNotifications() {
long targetTime = targetCalendar.getTimeInMillis();
long currentTime = targetCalendar.getTimeInMillis();
Intent intent = new Intent(this, MyScheduledReceiver.class);
intent.putExtra(INTENT_LIST_FOR_NOTIFICATION, taskArrayList);
PendingIntent pendingIntent = PendingIntent.getBroadcast(this, 0, intent, PendingIntent.FLAG_CANCEL_CURRENT);
if (currentTime >= targetTime) {
targetCalendar.add(Calendar.DAY_OF_MONTH, 1);
targetTime = targetCalendar.getTimeInMillis();
alarmManager.setRepeating(AlarmManager.RTC_WAKEUP, targetTime, AlarmManager.INTERVAL_DAY, pendingIntent);
}
else {
alarmManager.setRepeating(AlarmManager.RTC_WAKEUP, targetTime, AlarmManager.INTERVAL_DAY, pendingIntent);
}
}

在我的广播接收器中，我有此代码

public class MyScheduledReceiver extends BroadcastReceiver {
@Override
public void onReceive(Context context, Intent intent) {
Intent scheduledIntent = new Intent(context, MainActivity.class);
scheduledIntent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
PendingIntent contentIntent = PendingIntent.getActivity(context, 0,
scheduledIntent, 0);
NotificationManager notificationManager = (NotificationManager) context
.getSystemService(Context.NOTIFICATION_SERVICE);
ArrayList<MyTask> arrayList = (ArrayList<MyTask>) intent.getSerializableExtra(MainActivity.INTENT_LIST_FOR_NOTIFICATION);
for (int i = 0; i < arrayList.size(); i++) {
Notification notification = new Notification.Builder(context)
.setContentIntent(contentIntent)
.setContentTitle(arrayList.get(i).getmTaskName()) 
.setSmallIcon(R.mipmap.ic_launcher)
.setTicker("")
.setWhen(System.currentTimeMillis()).setAutoCancel(true)
.build();
notificationManager.notify(arrayList.get(i).getTaskId(), notification);
}
}
}

但是我对数组列表有问题。后

ArrayList<MyTask> arrayList = (ArrayList<MyTask>) intent.getSerializableExtra(MainActivity.INTENT_LIST_FOR_NOTIFICATION);

它是空的，并且在字符串中有空指针异常

for (int i = 0; i < arrayList.size(); i++) {

以下是例外：

java.lang.RuntimeException: Unable to start receiver java.lang.NullPointerException: Attempt to invoke virtual method 'int java.util.ArrayList.size()' on a null object reference
at android.app.ActivityThread.handleReceiver(ActivityThread.java:3018)
at android.app.ActivityThread.-wrap18(ActivityThread.java)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1544)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:154)
at android.app.ActivityThread.main(ActivityThread.java:6077)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:866)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:756)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'int java.util.ArrayList.size()' on a null object reference
at com.example.user1.testtaskmanager.MyScheduledReceiver.onReceive(MyScheduledReceiver.java:25)
at android.app.ActivityThread.handleReceiver(ActivityThread.java:3011)
at android.app.ActivityThread.-wrap18(ActivityThread.java)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1544)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:154)
at android.app.ActivityThread.main(ActivityThread.java:6077)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:866)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:756)

注意：它仅在 API 24 及下一个版本上。Api 23 和以前的工作正常。  

Answer 1

发送

intent.putStringArrayListExtra(MainActivity.INTENT_LIST_FOR_NOTIFICATION,taskArrayList)

接收

intent.getStringArrayListExtra(MainActivity.INTENT_LIST_FOR_NOTIFICATION)