的Wi-Fi扫描没有广播接收器？ [英] Wi-Fi scanning without broadcast receiver?

问题描述

我创建的Wi-Fi扫描仪。它会不断扫描可用的Wi-Fi网络。但我的问题是，如果我可以实际运行的扫描需要为什么会正是广播接收机（调用 startScan（）每x秒计时器），并不会产生广播接收器收到相同的结果？

I have created wi-fi scanner. It continually scans for available wi-fi networks. But my question is why would exactly broadcast receiver is needed if i can actually run scanning (invoke startScan() with timer every x seconds) and receive the same results without creating broadcast receiver?

这是广播接收器code在的onCreate（）方法：

This is broadcast receiver code in onCreate() method:

i = new IntentFilter();
i.addAction(WifiManager.SCAN_RESULTS_AVAILABLE_ACTION);
receiver = new BroadcastReceiver(){
    public void onReceive(Context c, Intent i){
      WifiManager w = (WifiManager) c.getSystemService(Context.WIFI_SERVICE);
      List<ScanResult> l = w.getScanResults();
      for (ScanResult r : l) {
         // do smth with results
      }
      // log results
    }
};

在扫描方法，它扫描按钮后调用pressed我有：

In scanning method, which is invoked after scan button is pressed I have:

timer = new Timer(true);
timer.schedule(new WifiTimerTask(), 0, scanningInterval);
registerReceiver(receiver, i );

其中， WifiTimerTask 是

publlic class WifiTimerTask extends TimerTask{
    @Override
     public void run(){
         wifi = (WifiManager) getSystemService(Context.WIFI_SERVICE);
         if (wifi.isWifiEnabled()) {
            wifi.startScan();
            List<ScanResult> sc = wifi.getScanResults(); 
            for (ScanResult r : l) {
               // do smth with results
            }
           // log results
          }
     }
}

问题关键是，可以在不 registerReceiver进行了扫描（接收器，I）。但是，只有当 scanningInterval 大于2秒时，那么接收 scanresults和 startScan（）不同步。我的意思是 startScan（）结果不会改变，直到接收将得到新的结果。与此同时，在logcat中，我得到错误/参考wpa_supplicant（5837）进行的扫描动作... 。好像是2秒，虽然最低扫描间隔。请纠正我，如果我的假设是错误的。

And the point is that scanning can be performed without registerReceiver(receiver,i). However only if scanningInterval is lower than 2s, then receiver scanresults and startScan() are not synchronized. By that I mean startScan() results do not change until receiver will get new results. Meanwhile in logCat I get ERROR/wpa_supplicant(5837): Ongoing Scan action.... Seems like 2s is the lowest scanning interval though. Please correct me if my assumptions are wrong.

推荐答案

当你调用 startScan（）你不知道实际的扫描需要多长时间（一般来说也可以是1毫秒或5小时）。所以，你不能可靠地调用 getScanResults（）为完成时，扫描的时候，你不知道。

When you call startScan() you don't know how long the actual scan will take (generally speaking it can be 1 ms or 5 hours). So you cannot reliably call getScanResults() as you don't know when the scan is completed.

要跟踪时，当 getScanResults（）将返回更新扫描的事件结果，你需要订阅 SCAN_RESULTS_AVAILABLE_ACTION 。

To track the event when when getScanResults() will return update scan results you need to subscribe to SCAN_RESULTS_AVAILABLE_ACTION.

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