我正在搜索以掃描可用的 wifi 網(wǎng)絡(luò)，但方法 getScanResults() 返回空列表。我包含了所有需要的權(quán)限：android.permission.ACCESS_COARSE_LOCATIONandroid.permission.CHANGE_WIFI_STATEandroid.permission.ACCESS_FINE_LOCATIONandroid.permission.ACCESS_WIFI_STATE主要活動(dòng)類(lèi)是：public class Home extends Activity {`    Context context;    WifiManager wifiManager = null;    WiFiReceiver wifiReceiver = null;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.home);        context = this;        wifiManager = (WifiManager)         context.getSystemService(Context.WIFI_SERVICE);        wifiReceiver = new WiFiReceiver(wifiManager);        IntentFilter intentFilter = new IntentFilter();        intentFilter.addAction(WifiManager.SCAN_RESULTS_AVAILABLE_ACTION);        registerReceiver(wifiReceiver, intentFilter);        wifiManager.startScan();        List<ScanResult> results = wifiReceiver.results;    }    @Override    protected void onDestroy() {        super.onDestroy();        unregisterReceiver(wifiReceiver);    }}廣播接收器是：public class WiFiReceiver extends BroadcastReceiver {`    public List<ScanResult> results;    private WifiManager wifiManager;    public WiFiReceiver(WifiManager wifiManager) {        this.wifiManager = wifiManager;    }    @Override    public void onReceive(Context context, Intent intent) {        boolean success = intent.getBooleanExtra(WifiManager.EXTRA_RESULTS_UPDATED, false);        if (success) {            results = wifiManager.getScanResults();            Log.e("wiFi Manager", "Done");        } else {            Log.e("wiFi Manager", "Scan failure");        }    }}