Android实现定时功能，闹钟+前台服务

1.首先在MainActitvty里的Onclick启动服务

    @Override
    public void onClick(View view) {
        switch (view.getId()) {
            case R.id.start_server:
                Intent startIntent = new Intent(this, MyService.class);
                startService(startIntent);
                break;
            case R.id.stop_server:
                Intent stopIntent = new Intent(this, MyService.class);
                stopService(stopIntent);
                break;
            default:
                break;
        }

    }

然后在Myservice里面添加下面的内容
在Oncreate方法里面,也就是服务第一次创建的时候加入下面代码

    @Override
    public void onCreate() {
        super.onCreate();
        if (android.os.Build.VERSION.SDK_INT >= android.os.Build.VERSION_CODES.O) {
            NotificationManager notificationManager = (NotificationManager) getSystemService(Context.NOTIFICATION_SERVICE);
            NotificationChannel channel = null;
            channel = new NotificationChannel("sid", getString(R.string.app_name), NotificationManager.IMPORTANCE_HIGH); //sid标示可以改为别的
            notificationManager.createNotificationChannel(channel);
            Notification notification = new Notification.Builder(getApplicationContext(), "sid").build();
            startForeground(1, notification); //开启前台服务模式，会在通知的位置弹出一个框。
        }

    }

然后在OnStartCommand里面添加下面代码

    @Override
    public int onStartCommand(Intent intent, int flags, int startId) {
        new Thread(new Runnable() {
            @Override
            public void run() {
                    //这里写要运行的代码

        }).start();
        AlarmManager manager = (AlarmManager) getSystemService(ALARM_SERVICE);
        int interval = 30 * 1000; //30s 运行一次
        long triggerTime = SystemClock.elapsedRealtime() + interval; //系统开机到现在的毫秒数+延迟执行时间
        Intent i = new Intent(this, MyService.class);
        PendingIntent pi = PendingIntent.getService(this, 0, i, 0);
        manager.set(AlarmManager.ELAPSED_REALTIME_WAKEUP, triggerTime, pi);
        return super.onStartCommand(intent, flags, startId);
    }

如果服务被销毁了想重新拉起，可以修改OnDestory代码如下

    @Override
    public void onDestroy() {
        super.onDestroy();
        Log.d("cxa", "MyService---->onDestroy，前台service被杀死");
        // 重启自己
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
            getApplicationContext().startForegroundService(new Intent(getApplicationContext(), MyService.class));
        } else {
            getApplicationContext().startService(new Intent(getApplicationContext(), MyService.class));
        }
    }