正如Android文档中所述：
https://developer.android.com/preview/features/notification-channels.html
如果您以Android O为目标并在未指定有效通知通道的情况下发布通知，则无法发布通知，并且系统会记录错误。
要解决此问题，您需要创建NotificationChannel。

NotificationManager mNotificationManager = (NotificationManager) getSystemService(Context.NOTIFICATION_SERVICE);

// The id of the channel.
String id = "my_channel_01";

// The user-visible name of the channel.
CharSequence name = getString(R.string.channel_name);

// The user-visible description of the channel.
String description = getString(R.string.channel_description);

int importance = NotificationManager.IMPORTANCE_LOW;

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

// Configure the notification channel.
mChannel.setDescription(description);

mChannel.enableLights(true);
// Sets the notification light color for notifications posted to this
// channel, if the device supports this feature.
mChannel.setLightColor(Color.RED);

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

mNotificationManager.createNotificationChannel(mChannel);

然后按如下方式将其分配给通知：

mNotificationManager = (NotificationManager)getSystemService(Context.NOTIFICATION_SERVICE);

// Sets an ID for the notification, so it can be updated.
int notifyID = 1;

// The id of the channel.
String CHANNEL_ID = "my_channel_01";

// Create a notification and set the notification channel.
Notification notification = new Notification.Builder(MainActivity.this)
    .setContentTitle("New Message")
    .setContentText("You've received new messages.")
    .setSmallIcon(R.drawable.ic_notify_status)
    .setChannelId(CHANNEL_ID)
    .build();

// Issue the notification.
mNotificationManager.notify(id, notification);

更新日期：

如果您想使用NotificationCompat，下面是一个简单的示例：

NotificationCompat.Builder mBuilder;
mBuilder = new NotificationCompat.Builder(getApplicationContext())
    .setSmallIcon(R.mipmap.ic_launcher_icon)
    .setContentTitle("Title")
    .setContentText("Text")
    .setOngoing(true)
    .setChannelId(id);

事实上，您必须使用Notification Builder，以便通过setChannelId（）设置通道ID;

吐司和Logcat上的消息谈到了您应该注意的两个项目，它们的顺序是：

1. NotificationChannel mChannel = new NotificationChannel(id, name, importance);
2. builder = new NotificationCompat.Builder(this, id);
   通知管理器通知管理器和通知通道mChannel也只创建一次。
   通知需要设置程序：

builder.setContentTitle() // required  
       .setSmallIcon()    // required 
       .setContentText()  // required

请参阅On Android 8.1 API 27 notification does not display中的示例。

容易的

companion object {
    private val TAG = simpleClassName

    // The id of the channel.
    private val channelId = "my_channel_01"
    private val notifyID: Int = 1
    private val importance = NotificationManagerCompat.IMPORTANCE_DEFAULT
}

val mChannel = NotificationChannelCompat.Builder(channelId, importance).apply {
    setName("channel name") // Must set! Don't remove
    setDescription("channel description")
    setLightsEnabled(true)
    setLightColor(Color.RED)
    setVibrationEnabled(true)
    setVibrationPattern(longArrayOf(100, 200, 300, 400, 500, 400, 300, 200, 400))
}.build()

NotificationManagerCompat.from(context).createNotificationChannel(mChannel)
val notification: Notification = NotificationCompat.Builder(context, channelId)
    .setSmallIcon(R.drawable.ic_launcher_foreground)
    .setContentTitle(sender)
    .setContentText(body)
    .build()
NotificationManagerCompat.from(context).notify(notifyID, notification)