android关于轮询的一种解决方案

         前段时间，由于公司项目中某个功能需要用到轮询的操作，所以参考了网上的一些资料，做了一个demo。主要方案是：AlarmManager + BroadcastReceiver + Service

     首选需要获取AlarmManager,并包装要执行的服务： 

    /**
     * 开始轮询
     */
    public static void startPolling(Context context, int seconds, Class<?> cls, String action) {
        //获取AlarmManager系统服务
        AlarmManager manager = (AlarmManager) context
                .getSystemService(Context.ALARM_SERVICE);

        //包装需要执行Service的Intent
        Intent intent = new Intent(context, cls);
        intent.setAction(action);
        PendingIntent pendingIntent = PendingIntent.getService(context, 0,
                intent, PendingIntent.FLAG_UPDATE_CURRENT);

        //触发服务的起始时间
        long triggerAtTime = SystemClock.elapsedRealtime();

        //使用AlarmManger的setRepeating方法设置定期执行的时间间隔（seconds秒）和需要执行的Service
        manager.setRepeating(AlarmManager.ELAPSED_REALTIME, triggerAtTime,
                seconds * 1000, pendingIntent);
    }

    /**
     * 停止轮询服务
     */
    public static void stopPolling(Context context, Class<?> cls, String action) {
        AlarmManager manager = (AlarmManager) context
                .getSystemService(Context.ALARM_SERVICE);
        Intent intent = new Intent(context, cls);
        intent.setAction(action);
        PendingIntent pendingIntent = PendingIntent.getService(context, 0,
                intent, PendingIntent.FLAG_UPDATE_CURRENT);
        //取消正在执行的服务
        manager.cancel(pendingIntent);
    }

    然后我们需要在服务中执行获取数据的操作：

 @Override
    public int onStartCommand(Intent intent, int flags, int startId) {
       thread = new Thread(new Runnable() {
            @Override
            public void run() {
                Intent intent = new Intent();
                intent.setAction("CustomBroadcastReceiver");
                intent.putExtra("data",++i);
                sendBroadcast(intent);
            }
        });
        thread.start();
        return super.onStartCommand(intent, flags, startId);
    }

    在广播中，我定义了一个回调。广播接收到数据后，会执行回调，把数据传给activity：

 private Handler handler = new Handler() {
        @Override
        public void handleMessage(Message msg) {
            super.handleMessage(msg);
            if(auctionListener == null) {
                Toast.makeText(context,"监听器为空",Toast.LENGTH_SHORT).show();
                return;
            }else {
                auctionListener.onUpdataAction(msg.what);
            }
        }
    };

    @Override
    public void onReceive(Context context, Intent intent) {
        this.context = context;
        Message message = handler.obtainMessage();
        message.what = intent.getIntExtra("data",0);
        handler.sendMessage(message);
    }

    不过有一个问题，我明明在activity中设置了回调，仍然会执行监听器为空的操作，不明白为什么。知道的麻烦，回复一下，到底是什么原因？

    然后是在activity中调用：

<span style="font-size:14px;">   @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        textView = (TextView) findViewById(R.id.text);
        receiver = new CustomBroadcastReceiver();
        receiver.setOnAuctionListener(this);
        IntentFilter intentFilter = new IntentFilter(CustomBroadcastReceiver.ACTION);
        registerReceiver(receiver,intentFilter);
        PollingUtils.startPolling(this,1,MyService.class,MyService.ACTION);
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
        unregisterReceiver(receiver);
        PollingUtils.stopPolling(this,MyService.class,MyService.ACTION);
    }

    @Override
    public void onUpdataAction(int data) {
      textView.setText(data+"");
    }</span>