分类

• 按绑定方式划分
  1>绑定Service
  2>非绑定Service
• 按Service类型划分
  1>后台服务，Android开发中多数用后台Service，这种Service的优先级比较低，当系统内存不足，会被回收
  2>前台服务，就是Service和Notification关联，用户可见的服务，不会因为内存不足而被回收，简单理解就是音乐播放器的通知栏弹窗

后台服务

• 启动方式
  1> 非绑定Service启动

                startService(new Intent().setClass(ServiceDemoActivity.this,NoBindService.class));

2>绑定Service启动

                Intent intent = new Intent().setClass(ServiceDemoActivity.this, BindService.class);
                    bindService(intent,connect,BIND_AUTO_CREATE);

绑定Service需要创建connect，实现Activity和Service的连接

    private BindService.MyBinder mService = null;

    //Service的连接
    private ServiceConnection connect = new ServiceConnection() {
        @Override
        public void onServiceConnected(ComponentName componentName, IBinder iBinder) {
            mService  = (BindService.MyBinder) iBinder;
            mService.methodInBindServiceUsedByActivity();
        }

        @Override
        public void onServiceDisconnected(ComponentName componentName) {

        }
    };

前台服务

• 创建 ,跟后台Service创建方式一样，写个Service类继承自Service

public class FrontService extends Service {
    @Nullable
    @Override
    public IBinder onBind(Intent intent) {
        return null;
    }

    @Override
    public int onStartCommand(Intent intent, int flags, int startId) {
        return super.onStartCommand(intent, flags, startId);
    }

    @Override
    public void onDestroy() {
        super.onDestroy();
    }
}

• 构建通知消息
  在Service的onCreate中添加如下代码构建Notification

   @Override
    public void onCreate() {
        super.onCreate();
        // 创建通知
        Bitmap largeIcon = BitmapFactory.decodeResource(getResources(),R.drawable.test1);
        NotificationManager notificationManager = (NotificationManager) getSystemService(Context.NOTIFICATION_SERVICE);
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O){
            NotificationChannel channel = new NotificationChannel("channel_id","前台通知",NotificationManager.IMPORTANCE_DEFAULT);
            notificationManager.createNotificationChannel(channel);
        }

        Notification notification = new NotificationCompat.Builder(this,"channel_id")
                                        .setContentTitle("标题")
                                        .setContentText("内容")
                                        .setLargeIcon(largeIcon)
                                        .setSmallIcon(R.drawable.ic_launcher)
                                        .build();
        Log.d(TAG, "onStartCommand: 前台服务启动");
        /**
         * 开启前台服务
         * @parame1是服务的唯一标识
         * @param2是通知
         */
        startForeground(1, notification);
    }