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WifiManager::getScanResults() always returns empty list

P

Paul Dirac

Lurker
Hi,
As a newbie to Android programming, I am trying to get the SSID list using WifiManager's getScanResults() method, but it remains empty, even though I have granted it the
ACCESS_COARSE_LOCATION permission as well as the CHANGE_WIFI_STATE (for the startScan() method), both in the manifest and by checking/requesting it at runtime.

In the broadcast receiver for the SCAN_RESULTS_AVAILABLE_ACTION, I even check the extra field of the intent with key EXTRA_RESULTS_UPDATED and the result returns true.

Yet, the list.size() always returns 0.

What am I missing here? I am testing on a Android 7.0 API 24 device.

Thank you!

Edit: I added the code:

MainActivity.java:

Code: 
package com.wifi2ir.umagi.wifitest2;

import java.util.List;

import android.Manifest;
import android.content.Intent;
import android.content.pm.PackageManager;
import android.net.wifi.ScanResult;
import android.net.wifi.WifiInfo;
import android.net.wifi.WifiManager;
import android.os.Bundle;
import android.app.Activity;
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.IntentFilter;
import android.support.v4.app.ActivityCompat;
import android.support.v4.content.ContextCompat;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;
import android.widget.Toast;

public class MainActivity extends Activity implements View.OnClickListener
{
   private static final String TAG="WiFiDemo";

   WifiManager wifiManager;
   WifiBroadcastReceiver wifiReceiver;

   TextView textView;
   Button btn;

   [USER=1021285]@override[/USER]
   protected void onCreate(Bundle savedInstanceState)
   {
       Log.d(TAG, "onCreate()");
       super.onCreate(savedInstanceState);
       setContentView(R.layout.activity_main);

       //Check for permissions
       if ((ContextCompat.checkSelfPermission(this, Manifest.permission.ACCESS_COARSE_LOCATION)
               != PackageManager.PERMISSION_GRANTED)
           || (ContextCompat.checkSelfPermission(this, Manifest.permission.CHANGE_WIFI_STATE)
                   != PackageManager.PERMISSION_GRANTED))
       {
           Log.d(TAG, "Requesting permissions");

           //Request permission
           ActivityCompat.requestPermissions(this,
                   new String[]{Manifest.permission.ACCESS_COARSE_LOCATION,
                                Manifest.permission.ACCESS_FINE_LOCATION,
                                Manifest.permission.ACCESS_WIFI_STATE,
                                Manifest.permission.CHANGE_WIFI_STATE,
                                Manifest.permission.ACCESS_NETWORK_STATE},
                   123);
       }
       else
           Log.d(TAG, "Permissions already granted");

       wifiManager = (WifiManager) getSystemService(Context.WIFI_SERVICE);

       textView = findViewById(R.id.text);
       textView.setTextAlignment(View.TEXT_ALIGNMENT_TEXT_START);

       btn = findViewById(R.id.btn);
       btn.setOnClickListener(this);

       //Instantiate broadcast receiver
       wifiReceiver = new WifiBroadcastReceiver();

       //Register the receiver
       registerReceiver(wifiReceiver, new IntentFilter(WifiManager.SCAN_RESULTS_AVAILABLE_ACTION));
   }

   [USER=1021285]@override[/USER]
   public void onRequestPermissionsResult(int requestCode, String permissions[], int[] grantResults)
   {
       Log.d(TAG, "onRequestPermissionsResult");

       switch (requestCode)
       {
           case 123:
           {
               // If request is cancelled, the result arrays are empty.
               if (grantResults.length > 0 && grantResults[0] == PackageManager.PERMISSION_GRANTED)
               {
                   // permission was granted
                   Log.d(TAG, "permission granted: " + permissions[0]);
               }
               else
               {
                   // permission denied, boo! Disable the
                   // functionality that depends on this permission.
                   Log.d(TAG, "permission denied: " + permissions[0]);
               }

               return;
           }

           // other 'case' lines to check for other
           // permissions this app might request.
       }
   }

   //Define class to listen to broadcasts
   class WifiBroadcastReceiver extends BroadcastReceiver
   {
       [USER=1021285]@override[/USER]
       public void onReceive(Context context, Intent intent)
       {
           Log.d(TAG, "onReceive()");
           Toast.makeText(getApplicationContext(), "Scan complete!", Toast.LENGTH_SHORT).show();

           boolean ok = intent.getBooleanExtra(WifiManager.EXTRA_RESULTS_UPDATED, false);

           if (ok)
           {
               Log.d(TAG, "scan OK");

               //StringBuffer buffer = new StringBuffer();
               List<ScanResult> list = wifiManager.getScanResults();

               Toast.makeText(getApplicationContext(), Integer.toString(list.size()), Toast.LENGTH_SHORT).show();

               for (ScanResult scanResult : list)
               {
                   //buffer.append(scanResult);
                   textView.append(scanResult.toString());
               }
           }
           else
               Log.d(TAG, "scan not OK");
       }
   }

   [USER=1021285]@override[/USER]
   protected void onStop()
   {
       // TODO Auto-generated method stub
       unregisterReceiver(wifiReceiver);
       super.onStop();
   }

   [USER=1021285]@override[/USER]
   public void onClick(View view)
   {
       // TODO Auto-generated method stub
       //Toast.makeText(getApplicationContext(), "All Network seached !!",0).show();
       if(view.getId()==R.id.btn)
       {
           Log.d(TAG, "onCreate() wifi.startScan()");

           //if (!wifiManager.isWifiEnabled())
           //    wifiManager.setWifiEnabled(true);

           wifiManager.startScan();
       }
   }
}

In the manifest:

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
   package="com.wifi2ir.umagi.wifitest2">

   <application
       android:allowBackup="true"
       android:icon="@mipmap/ic_launcher"
       android:label="@string/app_name"
       android:roundIcon="@mipmap/ic_launcher_round"
       android:supportsRtl="true"
       android:theme="@style/AppTheme">
       <activity android:name=".MainActivity">
           <intent-filter>
               <action android:name="android.intent.action.MAIN" />
               <category android:name="android.intent.category.LAUNCHER" />
           </intent-filter>
       </activity>
   </application>

   <uses-permission android:name="android.permission.ACCESS_WIFI_STATE" />
   <uses-permission android:name="android.permission.CHANGE_WIFI_STATE" />
   <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
   <uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION" />
   <uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" />
</manifest>

Code: 
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
   package="com.wifi2ir.umagi.wifitest2">

   <application
       android:allowBackup="true"
       android:icon="@mipmap/ic_launcher"
       android:label="@string/app_name"
       android:roundIcon="@mipmap/ic_launcher_round"
       android:supportsRtl="true"
       android:theme="@style/AppTheme">
       <activity android:name=".MainActivity">
           <intent-filter>
               <action android:name="android.intent.action.MAIN" />
               <category android:name="android.intent.category.LAUNCHER" />
           </intent-filter>
       </activity>
   </application>

   <uses-permission android:name="android.permission.ACCESS_WIFI_STATE" />
   <uses-permission android:name="android.permission.CHANGE_WIFI_STATE" />
   <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
   <uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION" />
   <uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" />
</manifest>
 
Last edited:
Paul Dirac said:
  • Have you enabled location services? From Android 6, granting permissions only is not enough to get the results.– Sagar 1 hour ago
Click to expand...
Hi, yes, I finally got that... I kept confusing the app's location permissions with the location service itself until it finally dawned upon me that I had to manually enable this service somewere else than in the app's permission settings...
Thanks for your kind reply.

Edlt: wait! you must be the same Sagar who posted the reply on Stack Overflow... thanks again!
 
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