Android 8.1 or 9.0 Error when clicking on connect

[hamzology]

When I have compiled an apk and tried to run on android 8.0 it was working fine but when I installed the same apk in my android 9.0 and then click on connect vpn button it is crashing and giving the below error:

Fatal Exception: android.app.RemoteServiceException: Bad notification for startForeground: java.lang.RuntimeException: invalid channel for service notification: Notification(channel=null pri=0 contentView=null vibrate=null sound=null tick defaults=0x0 flags=0x14a color=0x00000000 category=service actions=2 vis=PRIVATE)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2082)
at android.os.Handler.dispatchMessage(Handler.java:109)
at android.os.Looper.loop(Looper.java:207)
at android.app.ActivityThread.main(ActivityThread.java:7539)
at java.lang.reflect.Method.invoke(Method.java)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:524)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:958)

[i-build-web-apps]

In OpenVPNService.java, add the following method:

@RequiresApi(api = Build.VERSION_CODES.O)
private String createNotificationChannel(String channelId, String channelName){
    NotificationChannel chan = new NotificationChannel(channelId, channelName, NotificationManager.IMPORTANCE_DEFAULT);
    chan.setLightColor(Color.BLUE) ;
    chan.setLockscreenVisibility(Notification.VISIBILITY_PRIVATE);
    NotificationManager service = (NotificationManager) getSystemService(Context.NOTIFICATION_SERVICE);
    service.createNotificationChannel(chan);
    return channelId ;
}

Then replace:

    android.app.Notification.Builder nbuilder = new Notification.Builder(this);

with:

    String channelID = "" ;
    android.app.Notification.Builder nbuilder ;
    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
        channelID = createNotificationChannel("my_service", "My Background Service") ;
        nbuilder = new Notification.Builder(this, channelID);
    }
    else
        nbuilder = new Notification.Builder(this);