如果你得到这个错误应该注意2项并且他们订购：

> NotificationChannel mChannel = new NotificationChannel(id,name,importance);

> builder = new NotificationCompat.Builder(context,id);

NotificationManager notifManager和NotificationChannel mChannel也只创建一次.

通知需要设置者：

> builder.setContentTitle()//必需

> .setSmallIcon()//必需

> .setContentText()//必需

见例子：

private NotificationManager notifManager;

public void createNotification(String aMessage,Context context) {

final int NOTIFY_ID = 0; // ID of notification

String id = context.getString(R.string.default_notification_channel_id); // default_channel_id

String title = context.getString(R.string.default_notification_channel_title); // Default Channel

Intent intent;

PendingIntent pendingIntent;

NotificationCompat.Builder builder;

if (notifManager == null) {

notifManager = (NotificationManager)context.getSystemService(Context.NOTIFICATION_SERVICE);

}

if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {

int importance = NotificationManager.IMPORTANCE_HIGH;

NotificationChannel mChannel = notifManager.getNotificationChannel(id);

if (mChannel == null) {

mChannel = new NotificationChannel(id,title,importance);

mChannel.enableVibration(true);

mChannel.setVibrationPattern(new long[]{100,200,300,400,500,400});

notifManager.createNotificationChannel(mChannel);

}

builder = new NotificationCompat.Builder(context,id);

intent = new Intent(context,MainActivity.class);

intent.setFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP | Intent.FLAG_ACTIVITY_SINGLE_TOP);

pendingIntent = PendingIntent.getActivity(context,intent,0);

builder.setContentTitle(aMessage) // required

.setSmallIcon(android.R.drawable.ic_popup_reminder) // required

.setContentText(context.getString(R.string.app_name)) // required

.setDefaults(Notification.DEFAULT_ALL)

.setAutoCancel(true)

.setContentIntent(pendingIntent)

.setTicker(aMessage)

.setVibrate(new long[]{100,400});

}

else {

builder = new NotificationCompat.Builder(context,400})

.setPriority(Notification.PRIORITY_HIGH);

}

Notification notification = builder.build();

notifManager.notify(NOTIFY_ID,notification);

}