看起来您缺少Build.VERSION_CODE.O和更高版本https://developer.android.com/develop/ui/views/notifications/channels的通知通道

if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
            int importance = NotificationManager.IMPORTANCE_LOW;
            NotificationChannel notificationChannel = new NotificationChannel(channelId, channelName, importance);
            notificationManager.createNotificationChannel(notificationChannel);

            // Make notification show big text.
            NotificationCompat.BigTextStyle bigTextStyle = new NotificationCompat.BigTextStyle();
            bigTextStyle.setBigContentTitle(title);
            bigTextStyle.bigText(notificationText);
            // Set big text style.
            builder.setStyle(bigTextStyle);
        } else {
            builder.setContentTitle(title);
            builder.setContentText(notificationText);
        }

下面的香奈儿链接和下面提供的例子沿着把我弄晕了。

if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
            int importance = NotificationManager.IMPORTANCE_LOW;
            NotificationChannel notificationChannel = new NotificationChannel(channelId, channelName, importance);
            notificationManager.createNotificationChannel(notificationChannel);

            // Make notification show big text.
            NotificationCompat.BigTextStyle bigTextStyle = new NotificationCompat.BigTextStyle();
            bigTextStyle.setBigContentTitle(title);
            bigTextStyle.bigText(notificationText);
            // Set big text style.
            builder.setStyle(bigTextStyle);
        } else {
            builder.setContentTitle(title);
            builder.setContentText(notificationText);
        }

这个链接使它更清楚。notification channel is not sending notifications它基本上100%的罚款，他只是忘了调用函数createNotificationChannel（）之前创建通知。

对于Android 8及更高版本，您需要创建通知通道，在通知构建器之前写入，并将相同的通道ID传递给NotificationCompat.Builder
复制/粘贴：

public void createNotification(Context ctx) {
    createNotificationChannel();

    SharedPreferences settings = ctx.getApplicationContext().getSharedPreferences(ContactsContract.CommonDataKinds.StructuredName.DISPLAY_NAME, 0);
    String contactName = settings.getString("curName", String.valueOf(0));
    String contactEmail = settings.getString("contactEmail", String.valueOf(0));
    String contactNumber = settings.getString("curPhone", String.valueOf(0));
    String dueAmount = String.valueOf(settings.getInt("amountDue", 0));

    NotificationCompat.Builder builder = new NotificationCompat.Builder(ctx, "CHANNEL_ID");
    builder.setSmallIcon(R.drawable.myanlogo);
    Intent intent = new Intent(Intent.ACTION_VIEW, Uri.parse("https://www.journaldev.com/"));
    PendingIntent pendingIntent = PendingIntent.getActivity(ctx, 0, intent, PendingIntent.FLAG_UPDATE_CURRENT | PendingIntent.FLAG_IMMUTABLE);
    builder.setContentIntent(pendingIntent);
    builder.setLargeIcon(BitmapFactory.decodeResource(ctx.getResources(), R.mipmap.ic_launcher));
    builder.setContentTitle("LETTING YOU KNOW");
    builder.setContentText("Your notification content here.");

    NotificationManager notificationManager = (NotificationManager) ctx.getSystemService(NOTIFICATION_SERVICE);
    notificationManager.notify(1, builder.build());
}

我已更新此行NotificationCompat.Builder builder = new NotificationCompat.Builder(ctx, "CHANNEL_ID");

JAVA语言

private void createNotificationChannel() {
    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
        NotificationChannel notificationChannel = new NotificationChannel("CHANNEL_ID", "Updates", NotificationManager.IMPORTANCE_DEFAULT);
        NotificationManager notificationManager = (NotificationManager) getSystemService(NOTIFICATION_SERVICE);
        notificationManager.createNotificationChannel(notificationChannel);
    }
}

Kotlin

private fun createNotificationChannel() {
    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
        val importance = NotificationManager.IMPORTANCE_DEFAULT
        val notificationChannel = NotificationChannel("CHANNEL_ID", "Updates", NotificationManager.IMPORTANCE_DEFAULT)
        val notificationManager = getSystemService(NOTIFICATION_SERVICE) as NotificationManager
        notificationManager.createNotificationChannel(notificationChannel)
    }
}