在我的例子中，这是因为我们试图在没有指定NotificationChannel的情况下发布通知:

public static final String NOTIFICATION_CHANNEL_ID_SERVICE = "com.mypackage.service";
public static final String NOTIFICATION_CHANNEL_ID_TASK = "com.mypackage.download_info";

public void initChannel(){
    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
        NotificationManager nm = (NotificationManager) getSystemService(NOTIFICATION_SERVICE);
        nm.createNotificationChannel(new NotificationChannel(NOTIFICATION_CHANNEL_ID_SERVICE, "App Service", NotificationManager.IMPORTANCE_DEFAULT));
        nm.createNotificationChannel(new NotificationChannel(NOTIFICATION_CHANNEL_ID_INFO, "Download Info", NotificationManager.IMPORTANCE_DEFAULT));
    }
}

放置上述代码的最佳位置是Application类中的onCreate()方法，因此我们只需要声明一次:

public class App extends Application {

    @Override
    public void onCreate() {
        super.onCreate();
        initChannel();
    }
}

在我们设置好这些之后，我们可以使用通知和我们刚刚指定的channelId:

Intent i = new Intent(this, MainActivity.class);
i.setFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP | Intent.FLAG_ACTIVITY_SINGLE_TOP);
PendingIntent pi = PendingIntent.getActivity(this, 0, i, PendingIntent.FLAG_UPDATE_CURRENT);
NotificationCompat.Builder builder = new NotificationCompat.Builder(this, NOTIFICATION_CHANNEL_ID_INFO);
            .setContentIntent(pi)
            .setWhen(System.currentTimeMillis())
            .setContentTitle("VirtualBox.exe")
            .setContentText("Download completed")
            .setSmallIcon(R.mipmap.ic_launcher);

然后，我们可以使用它来发布通知:

int notifId = 45;
NotificationManager nm = (NotificationManager) getSystemService(NOTIFICATION_SERVICE);
nm.notify(notifId, builder.build());

如果你想使用它作为前台服务的通知:

startForeground(notifId, builder.build());

这可能是旧的，但是，以防有人有和我一样的情况。 出于某种原因，在Android 11 OnePlus Nord上

Notification.Builder().Build()

崩溃了,

NotificationCompat.Builder().Build()

工作很好。 考虑迁移到androidx.core.app.NotificationCompat。

Java解决方案(Android 9.0, API 28)

在你的Service类中，添加这个:

@Override
public void onCreate(){
    super.onCreate();
    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O)
        startMyOwnForeground();
    else
        startForeground(1, new Notification());
}

private void startMyOwnForeground(){
    String NOTIFICATION_CHANNEL_ID = "com.example.simpleapp";
    String channelName = "My Background Service";
    NotificationChannel chan = new NotificationChannel(NOTIFICATION_CHANNEL_ID, channelName, NotificationManager.IMPORTANCE_NONE);
    chan.setLightColor(Color.BLUE);
    chan.setLockscreenVisibility(Notification.VISIBILITY_PRIVATE);
    NotificationManager manager = (NotificationManager) getSystemService(Context.NOTIFICATION_SERVICE);
    assert manager != null;
    manager.createNotificationChannel(chan);

    NotificationCompat.Builder notificationBuilder = new NotificationCompat.Builder(this, NOTIFICATION_CHANNEL_ID);
    Notification notification = notificationBuilder.setOngoing(true)
            .setSmallIcon(R.drawable.icon_1)
            .setContentTitle("App is running in background")
            .setPriority(NotificationManager.IMPORTANCE_MIN)
            .setCategory(Notification.CATEGORY_SERVICE)
            .build();
    startForeground(2, notification);
}

更新:android 9.0馅饼(api 28)

将此权限添加到您的AndroidManifest.xml文件中:

<uses-permission android:name="android.permission.FOREGROUND_SERVICE" />

这对我很管用。在我的服务类中，我为android 8.1创建了通知通道，如下所示:

public class Service extends Service {

    public static final String NOTIFICATION_CHANNEL_ID_SERVICE = "com.package.MyService";
    public static final String NOTIFICATION_CHANNEL_ID_INFO = "com.package.download_info";

    @Override
    public void onCreate() {

        super.onCreate();
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
            NotificationManager nm = (NotificationManager) getSystemService(NOTIFICATION_SERVICE);
            nm.createNotificationChannel(new NotificationChannel(NOTIFICATION_CHANNEL_ID_SERVICE, "App Service", NotificationManager.IMPORTANCE_DEFAULT));
            nm.createNotificationChannel(new NotificationChannel(NOTIFICATION_CHANNEL_ID_INFO, "Download Info", NotificationManager.IMPORTANCE_DEFAULT));
        } else {
            Notification notification = new Notification();
            startForeground(1, notification);
        }
    }
}

注意:创建要为Build.VERSION创建通知的通道。SDK_INT >= Build.VERSION_CODES.O

这是我的解决方案

private static final int NOTIFICATION_ID = 200;
private static final String CHANNEL_ID = "myChannel";
private static final String CHANNEL_NAME = "myChannelName";

private void startForeground() {

    final NotificationCompat.Builder mBuilder = new NotificationCompat.Builder(
            getApplicationContext(), CHANNEL_ID);

    Notification notification;



        notification = mBuilder.setTicker(getString(R.string.app_name)).setWhen(0)
                .setOngoing(true)
                .setContentTitle(getString(R.string.app_name))
                .setContentText("Send SMS gateway is running background")
                .setSmallIcon(R.mipmap.ic_launcher)
                .setShowWhen(true)
                .build();

        NotificationManager notificationManager = (NotificationManager) getApplication().getSystemService(Context.NOTIFICATION_SERVICE);

        //All notifications should go through NotificationChannel on Android 26 & above
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
            NotificationChannel channel = new NotificationChannel(CHANNEL_ID,
                    CHANNEL_NAME,
                    NotificationManager.IMPORTANCE_DEFAULT);
            notificationManager.createNotificationChannel(channel);

        }
        notificationManager.notify(NOTIFICATION_ID, notification);

    }

希望对大家有所帮助:)

如果你正在使用VPN库，这些代码将是有帮助的，我把它放在onCreate(savedInstanceState: Bundle?)

 NotificationChannelManager.createNotificationChannelIfNeeded(
            activity,
            channelName = "Chanel Name",
            channelDescription = "Channel description"
        )