[任务：创建一个后台任务以在应用程序停止/暂停时运行，该任务定期（3-7秒）执行HTTP请求并将响应信息存储在mysqlite中，并在需要时显示本地通知。
我已经创建了如下所示的后台服务，
[Service(Enabled = true)]
public class MyRequestService : Service
从MainActivity的意图开始，
public void StartMyRequestService()
{
var serviceToStart = new Intent(this, typeof(MyRequestService));
StartService(serviceToStart);
}
public void StopMyRequestService()
{
var serviceToStart = new Intent(this, typeof(MyRequestService));
StopService(serviceToStart);
}
protected override void OnPause()
{
base.OnPause();
StartMyRequestService();
}
protected override void OnDestroy()
{
base.OnDestroy();
StartMyRequestService();
}
protected override void OnResume()
{
base.OnResume();
StopMyRequestService();
}
在我的服务中，我使用了以下功能，
并且代码如下所示，
private Handler handler;
private Action runnable;
private bool isStarted
private WakeLock wakeLock;
public override void OnCreate()
{
base.OnCreate();
handler = new Handler();
runnable = new Action(() =>
{
DispatchNotificationThatAlarmIsGenerated("I'm running");
handler.PostDelayed(runnable, DELAY_BETWEEN_LOG_MESSAGES);
});
}
public override StartCommandResult OnStartCommand(Intent intent, StartCommandFlags flags, int startId)
{
if (isStarted)
{
// service is already started
}
else
{
CreateNotificationChannel();
DispatchNotificationThatServiceIsRunning();
handler.PostDelayed(runnable, DELAY_BETWEEN_LOG_MESSAGES);
isStarted = true;
PowerManager powerManager = (PowerManager)this.GetSystemService(Context.PowerService);
WakeLock wakeLock = powerManager.NewWakeLock(WakeLockFlags.Full, "Client Lock");
wakeLock.Acquire();
}
return StartCommandResult.Sticky;
}
public override void OnTaskRemoved(Intent rootIntent)
{
//base.OnTaskRemoved(rootIntent);
}
public override IBinder OnBind(Intent intent)
{
// Return null because this is a pure started service. A hybrid service would return a binder that would
// allow access to the GetFormattedStamp() method.
return null;
}
public override void OnDestroy()
{
// Stop the handler.
handler.RemoveCallbacks(runnable);
// Remove the notification from the status bar.
var notificationManager = (NotificationManager)GetSystemService(NotificationService);
notificationManager.Cancel(NOTIFICATION_SERVICE_ID);
isStarted = false;
wakeLock.Release();
base.OnDestroy();
}
private void CreateNotificationChannel()
{
//Notification Channel
NotificationChannel notificationChannel = new NotificationChannel(NOTIFICATION_CHANNEL_ID, NOTIFICATION_CHANNEL_NAME, NotificationImportance.Max);
notificationChannel.EnableLights(true);
notificationChannel.LightColor = Color.Red;
notificationChannel.EnableVibration(true);
notificationChannel.SetVibrationPattern(new long[] { 100, 200, 300, 400, 500, 400, 300, 200, 400 });
NotificationManager notificationManager = (NotificationManager)this.GetSystemService(Context.NotificationService);
notificationManager.CreateNotificationChannel(notificationChannel);
}
private void DispatchNotificationThatServiceIsRunning()
{
NotificationCompat.Builder builder = new NotificationCompat.Builder(this, NOTIFICATION_CHANNEL_ID)
.SetDefaults((int)NotificationDefaults.All)
.SetSmallIcon(Resource.Drawable.icon)
.SetVibrate(new long[] { 100, 200, 300, 400, 500, 400, 300, 200, 400 })
.SetSound(null)
.SetChannelId(NOTIFICATION_CHANNEL_ID)
.SetPriority(NotificationCompat.PriorityDefault)
.SetAutoCancel(false)
.SetContentTitle("Mobile")
.SetContentText("My service started")
.SetOngoing(true);
NotificationManagerCompat notificationManager = NotificationManagerCompat.From(this);
notificationManager.Notify(NOTIFICATION_SERVICE_ID, builder.Build());
}
private void DispatchNotificationThatAlarmIsGenerated(string message)
{
var intent = new Intent(this, typeof(MainActivity));
intent.AddFlags(ActivityFlags.ClearTop);
var pendingIntent = PendingIntent.GetActivity(this, 0, intent, PendingIntentFlags.OneShot);
Notification.Builder notificationBuilder = new Notification.Builder(this, NOTIFICATION_CHANNEL_ID)
.SetSmallIcon(Resource.Drawable.icon_round)
.SetContentTitle("Alarm")
.SetContentText(message)
.SetAutoCancel(true)
.SetContentIntent(pendingIntent);
var notificationManager = (NotificationManager)GetSystemService(NotificationService);
notificationManager.Notify(App.NOTIFICATION_ALARM, notificationBuilder.Build());
}
这只是一个示例，代码不会发出任何HTTP请求，也不能与实体，数据库连接等一起使用，它只是简单地每X秒发送一个新的通知。我应该看到的是，当应用程序关闭时，服务会启动并创建本机通知，这就是我所看到的。然后一段时间，我看到正在生成“警报”通知，然后我的服务通知被杀死，服务被处置，仅此而已。如果单击手机上的电源按钮以点亮屏幕，则会看到“警报”通知再次生效。我已经检查了几种具有不同Android操作系统（6、7和8）并且禁用了省电模式的移动设备，没有区别，服务通知被终止。问题是什么，我在做什么错？
提前感谢您的帮助或指导！
我认为您正在使用Foreground Services。
您应该通过StartForeground方法调度服务通知（前景通知）。
因此请尝试更改
private void DispatchNotificationThatServiceIsRunning()
{
NotificationCompat.Builder builder = new NotificationCompat.Builder(this, NOTIFICATION_CHANNEL_ID)
.SetDefaults((int)NotificationDefaults.All)
.SetSmallIcon(Resource.Drawable.icon)
.SetVibrate(new long[] { 100, 200, 300, 400, 500, 400, 300, 200, 400 })
.SetSound(null)
.SetChannelId(NOTIFICATION_CHANNEL_ID)
.SetPriority(NotificationCompat.PriorityDefault)
.SetAutoCancel(false)
.SetContentTitle("Mobile")
.SetContentText("My service started")
.SetOngoing(true);
NotificationManagerCompat notificationManager = NotificationManagerCompat.From(this);
notificationManager.Notify(NOTIFICATION_SERVICE_ID, builder.Build());
}
到
private void DispatchNotificationThatServiceIsRunning()
{
NotificationCompat.Builder builder = new NotificationCompat.Builder(this, NOTIFICATION_CHANNEL_ID)
.SetDefaults((int)NotificationDefaults.All)
.SetSmallIcon(Resource.Drawable.icon)
.SetVibrate(new long[] { 100, 200, 300, 400, 500, 400, 300, 200, 400 })
.SetSound(null)
.SetChannelId(NOTIFICATION_CHANNEL_ID)
.SetPriority(NotificationCompat.PriorityDefault)
.SetAutoCancel(false)
.SetContentTitle("Mobile")
.SetContentText("My service started")
.SetOngoing(true);
NotificationManagerCompat notificationManager = NotificationManagerCompat.From(this);
//dispatch foreground notification
StartForeground(NOTIFICATION_SERVICE_ID, builder.Build());
}