每次按下按钮时，如何在Android手机中接收新的扫描结果？

Question

I am creating an app that needs to scan for surrounding access points and according to the results do some calculations. By now I am convinced that the WifiManager.statScan() method although it initiates a new scan, it doesn't automatically return results from a new scan.

This is my code:

public void onClick(View v) {
    switch (v.getId()){
        case R.id.button:
            //do some reseting for the GUI and the values of the problem.
            break;
        case R.id.button2:
            wifiManager = (WifiManager) getSystemService(Context.WIFI_SERVICE);
            wifiManager.startScan();
            List<ScanResult> scanResult = null;
            if(wifiManager.startScan()){
                scanResult = wifiManager.getScanResults();
            }
            // Do the calculations.
            break;

    }
}

My problem is that I am not sure if using this code I actually get the results from the initiated scan or the results coming from previous scans, and if the latter is correct, how can I get the results from the new scan?

Thank you very much.

After searching and reading various posts and tutorias, my code has transformed as follows:

public class MainActivity extends AppCompatActivity implements View.OnClickListener{
BroadcastReceiver receiver;
private List<ScanResult> scanResult;
boolean waiting;
// and other irrelevant variables.

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    //initialization of the elements of the GUI
    reset.setOnClickListener(this);
    locate.setOnClickListener(this);
    wifiManager = (WifiManager) getSystemService(Context.WIFI_SERVICE);
    waiting = true;
    receiver = new WifiScaner(this);
    registerReceiver(receiver, new IntentFilter(WifiManager.SCAN_RESULTS_AVAILABLE_ACTION));

}

@Override
public void onClick(View v) {
    switch (v.getId()){
        case R.id.button:
            // resetting the variables of the application
            break;
        case R.id.button2:
            wifiManager.startScan();
            while (waiting)  {
                try {
                    Thread.sleep(200);
                } catch (InterruptedException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }
                Log.d("PROJECT1","Wifi WAITING");
            }
            //Calculations
            break;

    }
}

public class WifiScaner extends BroadcastReceiver{
    MainActivity main;
    public WifiScaner(MainActivity main){
        super();
        this.main = main;
    }
    public void onReceive(Context c, Intent intent) {
        scanResult = main.wifiManager.getScanResults();
        waiting = false;
        Log.d("PROJECT1","Wifi RECEIVED");
    }
}

} But for some reason it seems that I never get into the onReceive of WifiScaner. Any clues why this is happening?

Answer 1

You are right, a scan takes some time so results are not available immediately. This is confirmed by the doc for startScan() method:

"Request a scan for access points. Returns immediately. The availability of the results is made known later by means of an asynchronous event sent on completion of the scan."

The following link seems to have a good example of how to be notified when the scan completes: http://www.tutorialspoint.com/android/android_wi_fi.htm .