关于asynctask的通知无法正常工作并且广播接收器

Question

我总是收到此错误，我是广播接收者的新手，对通知的经验很少，但是每次我调用Asynctask并在postExecute上调用通知时，都会得到此错误。我整天都在努力寻找解决方案，但似乎找不到解决方案。

Ps：：使用通知在不使用broadcastReceiver的情况下也可以正常工作，但是我想使用它，因此即使应用程序是封闭的应用程序也可以保持用户更新。

public class CSVStringToListConverter implements Converter<String, List<Integer>> {

@Autowired
private Errors errors;

@Override
public List<Integer> convert(String arg0) {
    List<Integer> list = new ArrayList<Integer>();
    for (String s : arg0.split(",")) {
        try {
            list.add(Integer.parseInt(s));
        } catch (NumberFormatException e) {
            list = Collections.emptyList();
            errors.rejectValue("fieldName", "fieldName.invalid", "Invalid integer in list");
        }
    }

    return list;
}}

在这里我的MainActivity

11-03 16:09:06.482 29073-29073/com.example.jade.messaging E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.jade.messaging, PID: 29073
java.lang.NullPointerException: Attempt to invoke virtual method 'android.content.ContentResolver android.content.Context.getContentResolver()' on a null object reference
    at android.content.ContextWrapper.getContentResolver(ContextWrapper.java:102)
    at android.app.PendingIntent.getActivity(PendingIntent.java:306)
    at android.app.PendingIntent.getActivity(PendingIntent.java:272)
    at com.example.jade.messaging.MainActivity.sendOnChannel1(MainActivity.java:77)
    at com.example.jade.messaging.MainActivity$getTemp.onPostExecute(MainActivity.java:306)
    at com.example.jade.messaging.MainActivity$getTemp.onPostExecute(MainActivity.java:240)
    at android.os.AsyncTask.finish(AsyncTask.java:651)
    at android.os.AsyncTask.access$500(AsyncTask.java:180)
    at android.os.AsyncTask$InternalHandler.handleMessage(AsyncTask.java:668)
    at android.os.Handler.dispatchMessage(Handler.java:102)
    at android.os.Looper.loop(Looper.java:148)
    at android.app.ActivityThread.main(ActivityThread.java:7409)
    at java.lang.reflect.Method.invoke(Native Method)
    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1230)
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1120)

这是我的广播接收器

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    handler = new Handler();
    createNotificationChannels();
    notificationManager = NotificationManagerCompat.from(this);
    stopAlarm();
}
private void createNotificationChannels() {
    try {
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
            NotificationChannel channel1 = new NotificationChannel(
                    CHANNEL_1_ID,
                    "Channel 1",
                    NotificationManager.IMPORTANCE_HIGH
            );
            channel1.setDescription("This is Channel 1");

            NotificationManager manager = getSystemService(NotificationManager.class);
            if (manager != null) {
                manager.createNotificationChannel(channel1);
            }
        }
    } catch (Exception e) {
        e.printStackTrace();
    }
}
public void sendOnChannel1() {
    String title = "Notif";

    Intent intent = new Intent(this, MainActivity.class);
    intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK | 
    Intent.FLAG_ACTIVITY_CLEAR_TASK);   
    //this is where I get the null pointer and if I remove this I get the error at the .build   
    pendingIntent1 = PendingIntent.getActivity(this, 1, intent, 0); 

    Notification notification = new NotificationCompat.Builder(this, CHANNEL_1_ID)
            .setSmallIcon(R.drawable.ic_launcher_foreground)
            .setContentTitle(title)
            .setContentText(message)
            .setPriority(NotificationCompat.PRIORITY_HIGH)
            .setCategory(NotificationCompat.CATEGORY_MESSAGE)
            .setContentIntent(pendingIntent1)
            .setVibrate(new long[0])
            .setAutoCancel(true)
            .build();

    notificationManager.notify(1, notification);
}

然后我在其中调用的方法将在主活动上运行MainActivity activity = new MainActivity(); @Override public void onReceive(Context arg0, Intent arg1) { // For our recurring task, we'll just display a message activity.getValue(); } ，在执行后将运行notif。

AsyncTask代码：

AsyncTask

我在asyctask上使用了弱引用，这就是为什么有活动的原因。在每个代码上。仅当我在asynctask上调用notif时，并且如果我在broadcastreceiver类上调用notif方法时，我的应用程序才会崩溃，我会收到有关存储数据的全局类的错误。说它为空。

请帮助