Develop Reference

Android wifiManager getScanResults always return null

According to a lot of official documents also stackoverflow documents, I am trying to use wifimanager to get list of access points near me but that is not working. I want to tell you I tried to use below code in android 4.4 but right now not working in android 9. Have you any solution?
final WifiManager wifiManager = (WifiManager) mContext.getSystemService(Context.WIFI_SERVICE);
//****************** Enable Wifi And Connect To Hidden Access Point
if(wifiManager.getWifiState() != WifiManager.WIFI_STATE_ENABLING){
wifiManager.setWifiEnabled(true);
wifistate = true;
}
// Start lengthy operation in a background thread
new Thread(new Runnable() {
int count = 0;
public void run() {
while (wifiManager.isWifiEnabled() == false && count < 5) {
try {
// Here I'm making thread sleep to show progress
Thread.sleep(1000L);
count++;
} catch (Exception e) {
}
}
if (wifiManager.isWifiEnabled() == true) {
//
wifiManager.startScan();
List<ScanResult> wifiScanList =wifiManager.getScanResults();

Connect to WiFi Which Doesn't Have Internet

I'm trying to connect to a WiFi hotspot (open network) which doesn't have Internet access when the app starts.
However, there's another saved Wifi which has Internet. When I turn on Wifi, it always connects automatically to the one with Internet access.
I have been trying to fix this issue for like a week now! But nothing is working. In fact, my code disconnects from the network with internet but doesn't connect to the network I want. It doesn't make sense.
On the WiFi settings activity, it says "No Internet detected. Won't reconnect automatically."
private boolean tryConnect(WifiManager wifiManager, List<ScanResult> scanResults) {
for (ScanResult scanResult : scanResults) {
Log.d(TAG, "SCAN-RESULT: " + scanResult);
if (scanResult.SSID.toLowerCase().contains(MainActivity.ARDRONE2_HOTSPOT_NAME) && WifiUtilities.getScanResultSecurity(scanResult) == WifiUtilities.NetworkSecurity.OPEN) {
Log.d(TAG, "Trying Connecting to ARDrone2");
WifiConfiguration wifiConfiguration = new WifiConfiguration();
wifiConfiguration.SSID = String.format("\"%s\"", scanResult.SSID);
wifiConfiguration.allowedKeyManagement.set(WifiConfiguration.KeyMgmt.NONE);
wifiConfiguration.priority = Integer.MAX_VALUE - 1;
List<WifiConfiguration> wifiConfigList = wifiManager.getConfiguredNetworks();
int networkId = -1;
for (WifiConfiguration wifiConfig : wifiConfigList) {
if (wifiConfig != null) {
if (wifiConfig.SSID.equals("\"" + scanResult.SSID + "\"")) {
networkId = wifiConfig.networkId;
} else {
wifiManager.disableNetwork(wifiConfig.networkId);
}
}
}
if (networkId == -1) {
networkId = wifiManager.addNetwork(wifiConfiguration);
} else {
networkId = wifiManager.updateNetwork(wifiConfiguration);;
}
wifiManager.saveConfiguration();
wifiManager.disconnect();
wifiManager.enableNetwork(networkId, true);
wifiManager.reconnect();
return true;
}
}
return false;
}
The debug log: "Trying Connecting to ARDrone2" appears and yet it doesn not connect!!!
A similar question has been asked here Android, automatically connecting to wifi networks that have no internet access but no comments or answers were provided.

It seems like the problem was with my own phone. I have CM13.0 and apparently they don't allow connecting to networks that don't have Internet access. Even manual connecting to a network without Internet is a lot of trouble.
I tried it on other phones with non-custom ROMs and they all worked as expected according to the code above:
Disable all saved networks (this could be improved)
Disconnect from currently connected network
Connect to the ARDrone2

Android fast switch to known wifi network

I am trying to write some code that will disconnect current wifi network (if any) and reconnect to a specific wifi network with known SSID.
I have been following the code used here; How do I connect to a specific Wi-Fi network in Android programmatically?
which works but the connection takes several seconds, upto about 10 seconds.
Specifically, I use the code as follows;
WifiManager wifiManager = (WifiManager)context.getSystemService(Context.WIFI_SERVICE);
WifiConfiguration config;
I obtain the config, whether by creating a new one and setting the SSID and KeyMgmt to NONE and then adding it;
wifiManager.add(config);
or by getting a config that already exists;
List<WifiConfiguration> list = wifiManager.getConfiguredNetworks();
for( WifiConfiguration i : list ) {
if(i.SSID != null && i.SSID.equals("\"" + networkSSID + "\"")) {
config = i;
break;
}
}
Then I call;
wifiManager.disconnect();
wifiManager.enableNetwork(i.networkId, true);
wifiManager.reconnect();
I have a broadcast received checking the wifi state and when i get a connected for my correct SSID i can continue, however, this process takes upto 10 seconds, how can i set up the config or wifimanager to connect to this much quicker?
Thanks

I think this code is help to you..
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.network_test);
context = this;
mUpdate = new UpdateTimeTask();
mHandler = new Handler();
mHandler.post(mUpdate);
}
public Boolean isNetAvailable(Context con) {
try{
connectivityManager = (ConnectivityManager) con.getSystemService(Context.CONNECTIVITY_SERVICE);
wifiInfo = connectivityManager.getNetworkInfo(ConnectivityManager.TYPE_WIFI);
mobileInfo = connectivityManager.getNetworkInfo(ConnectivityManager.TYPE_MOBILE);
if(wifiInfo.isConnected() || mobileInfo.isConnected()) {
return true;
}
}catch(Exception e){
e.printStackTrace();
}
return false;
}
private class UpdateTimeTask implements Runnable{
public void run() {
boolean net = isNetAvailable(context);
if(net != false) {
Toast.makeText(getBaseContext(), "network Available", Toast.LENGTH_SHORT).show();
}
else
{
Toast.makeText(getBaseContext(), "network Not Available", Toast.LENGTH_SHORT).show();
}
mHandler.postDelayed(mUpdate, 30000);
}
}
}

Have you tried adding startScan() to your routine to force an immediate rescan for available networks at the time you wish to connect? I imagine forcing that command repeatedly with an alarmManager or something similar is possible, but I would think that has the potential to have an expensive performance/battery impact. If you have a specific trigger, it could be a solution.
See here: http://developer.android.com/reference/android/net/wifi/WifiManager.html#startScan()

How to detect WiFi tethering state

I want to know how to detect state of WiFi tethering. I've seen an article: Android 2.3 wifi hotspot API But it doesn't work! It returns always WIFI_AP_STATE_DISABLED = 1. It doesn't depend on real state of WiFi tethering.

Using reflection:
WifiManager wifi = (WifiManager) getSystemService(Context.WIFI_SERVICE);
Method[] wmMethods = wifi.getClass().getDeclaredMethods();
for (Method method: wmMethods) {
if (method.getName().equals("isWifiApEnabled")) {
try {
boolean isWifiAPenabled = method.invoke(wifi);
} catch (IllegalArgumentException e) {
e.printStackTrace();
} catch (IllegalAccessException e) {
e.printStackTrace();
} catch (InvocationTargetException e) {
e.printStackTrace();
}
}
As you can see here

In addition to the reflexion, to get the Wifi tethering status update, you can listen to this broadcast Action :
IntentFilter filter = new IntentFilter("android.net.wifi.WIFI_AP_STATE_CHANGED");
To get all tethering option update :
IntentFilter filter = new IntentFilter("android.net.conn.TETHER_STATE_CHANGED");
Those actions are hidden inside the Android source code

First, you need to get WifiManager:
Context context = ...
final WifiManager wifi = (WifiManager) context.getSystemService(Context.WIFI_SERVICE);
Then:
public static boolean isSharingWiFi(final WifiManager manager)
{
try
{
final Method method = manager.getClass().getDeclaredMethod("isWifiApEnabled");
method.setAccessible(true); //in the case of visibility change in future APIs
return (Boolean) method.invoke(manager);
}
catch (final Throwable ignored)
{
}
return false;
}
Also you need to request a permission in AndroidManifest.xml:
<uses-permission android:name="android.permission.ACCESS_WIFI_STATE"/>

Here is the Xamarin C# version if anyone is looking:
static Method isWifiApEnabledMethod;
public static bool IsWifiApEnabled ()
{
var wifiManager = WifiManager.FromContext (Application.Context);
if (isWifiApEnabledMethod == null)
{
try
{
isWifiApEnabledMethod = wifiManager.Class.GetDeclaredMethod ("isWifiApEnabled");
isWifiApEnabledMethod.Accessible = true; //in the case of visibility change in future APIs
}
catch (NoSuchMethodException e)
{
Debug.WriteLine ("Can't get method by reflection" + e);
}
catch (System.Exception ex)
{
Debug.WriteLine ("Can't get method by reflection" + ex);
}
}
if (isWifiApEnabledMethod != null)
{
try
{
return (bool)isWifiApEnabledMethod.Invoke (wifiManager);
}
catch (System.Exception ex)
{
Debug.WriteLine ("Can't invoke by reflection" + ex);
}
}
return false;
}

(without using reflection since they say google is restricting it)
I'm writting this answer 10 years later. also I don't know if this can be considered a good aproach or not but I first get the Wlan network interface IPs
and if there is no address I assume that it tethering isn't enabled. if there is an address, I check using the connectivity manger whether WI-FI is connected to a network or not. if there is an IP for the Wlan network interface but it isn't connected to a network, I assume tethering is enabled.
you probably would need to add this line to your manifest file
<uses-permission android:name="android.permission.ACCESS_WIFI_STATE" />
code to get the ip of an inteface (this only gets the IPv4, you can modify it to get the IPv6 or both if you want)
// method used to retrieve Wlan ip addresses IPv4 of the device.
public static String IpAddresses() throws NoAddressFoundException, SocketException {
Enumeration<NetworkInterface> Nics = NetworkInterface.getNetworkInterfaces();
while (Nics.hasMoreElements()) {
NetworkInterface NIC = Nics.nextElement();
if (NIC.isUp() && !NIC.isLoopback() && NIC.getName().contains("wlan")) {
Enumeration<InetAddress> Addresses = NIC.getInetAddresses();
while (Addresses.hasMoreElements()) {
InetAddress WlanAddress = Addresses.nextElement();
if (WlanAddress instanceof Inet4Address)
return WlanAddress.getHostAddress();
}
}
}
throw new NoAddressFoundException("No suitable wifi address found");
}
then if there is an address i check if wifi is connected by this method:
//method to check if the device is connected to a Wi-Fi network; it doesn't matter if network has access to internet
public static boolean isWifiConnected(Context context) {
ConnectivityManager ConMan = (ConnectivityManager) context.getSystemService(Context.CONNECTIVITY_SERVICE);
NetworkInfo WifiInfo = ConMan.getNetworkInfo(ConnectivityManager.TYPE_WIFI);
return WifiInfo.isConnected();
}
NOTE: the "NoAddressFoundException" is a custom exception in my app if anyone is wondering. it won't exist in your case.

Reflection is a poor way to achieve this.
We can inspect the DhcpInfo to determine if the device is allocating addresses (mobile hotspot) or is being allocated by another DHCP server.
Here is a kotlin function that will determine if a device is a mobile hotspot, it has not been widely tested so YMMV.
fun isMobileHotspot(manager: WifiManager): Boolean {
val info = manager.dhcpInfo
return (
info.ipAddress == 0
&& info.netmask == 0
&& info.gateway == 0
&& info.serverAddress == 16885952) // 192.168.1.1
}

Force Android to use 3G when on local area wifi without net access

I have a wifi LAN setup which does not have internet access. Just various other local wifi devices connected to it. The DHCP is configured to not return a gateway or dns server. Only an IP and netmask.
When I connect my android to this wifi AP it connects fine, but all internet connectivity on the phone stops working.
I would expect that since the wifi has no gateway setting that android should realize the internet can't go through that connection and should instead be routed through the 3G connection which is at 5 bars.
I've tried setting a static IP on the android phone as well, but this did not help.
The main reason for this setup is so that the android device can transfer data on this remote network to an internet based server since it can connect to the local devices without issue. However the 3G side is broken once the wifi is setup.
Any thoughts on how to work around this issue?

After a bit of coding and testing I have merged Squonk and this solution. This is the class I have created:
package it.helian.exampleprj.network;
import java.net.InetAddress;
import java.net.UnknownHostException;
import android.content.Context;
import android.net.ConnectivityManager;
import android.net.NetworkInfo.State;
import android.net.wifi.WifiManager;
import android.text.TextUtils;
import android.util.Log;
public class NetworkUtils {
private static final String TAG_LOG = "ExamplePrj";
Context context;
WifiManager wifiMan = null;
WifiManager.WifiLock wifiLock = null;
public NetworkUtils(Context context) {
super();
this.context = context;
}
/**
* Enable mobile connection for a specific address
* #param context a Context (application or activity)
* #param address the address to enable
* #return true for success, else false
*/
public boolean forceMobileConnectionForAddress(Context context, String address) {
ConnectivityManager connectivityManager = (ConnectivityManager) context.getSystemService(Context.CONNECTIVITY_SERVICE);
if (null == connectivityManager) {
Log.d(TAG_LOG, "ConnectivityManager is null, cannot try to force a mobile connection");
return false;
}
//check if mobile connection is available and connected
State state = connectivityManager.getNetworkInfo(ConnectivityManager.TYPE_MOBILE_HIPRI).getState();
Log.d(TAG_LOG, "TYPE_MOBILE_HIPRI network state: " + state);
if (0 == state.compareTo(State.CONNECTED) || 0 == state.compareTo(State.CONNECTING)) {
return true;
}
//activate mobile connection in addition to other connection already activated
int resultInt = connectivityManager.startUsingNetworkFeature(ConnectivityManager.TYPE_MOBILE, "enableHIPRI");
Log.d(TAG_LOG, "startUsingNetworkFeature for enableHIPRI result: " + resultInt);
//-1 means errors
// 0 means already enabled
// 1 means enabled
// other values can be returned, because this method is vendor specific
if (-1 == resultInt) {
Log.e(TAG_LOG, "Wrong result of startUsingNetworkFeature, maybe problems");
return false;
}
if (0 == resultInt) {
Log.d(TAG_LOG, "No need to perform additional network settings");
return true;
}
//find the host name to route
String hostName = extractAddressFromUrl(address);
Log.d(TAG_LOG, "Source address: " + address);
Log.d(TAG_LOG, "Destination host address to route: " + hostName);
if (TextUtils.isEmpty(hostName)) hostName = address;
//create a route for the specified address
int hostAddress = lookupHost(hostName);
if (-1 == hostAddress) {
Log.e(TAG_LOG, "Wrong host address transformation, result was -1");
return false;
}
//wait some time needed to connection manager for waking up
try {
for (int counter=0; counter<30; counter++) {
State checkState = connectivityManager.getNetworkInfo(ConnectivityManager.TYPE_MOBILE_HIPRI).getState();
if (0 == checkState.compareTo(State.CONNECTED))
break;
Thread.sleep(1000);
}
} catch (InterruptedException e) {
//nothing to do
}
boolean resultBool = connectivityManager.requestRouteToHost(ConnectivityManager.TYPE_MOBILE_HIPRI, hostAddress);
Log.d(TAG_LOG, "requestRouteToHost result: " + resultBool);
if (!resultBool)
Log.e(TAG_LOG, "Wrong requestRouteToHost result: expected true, but was false");
state = connectivityManager.getNetworkInfo(ConnectivityManager.TYPE_MOBILE_HIPRI).getState();
Log.d(TAG_LOG, "TYPE_MOBILE_HIPRI network state after routing: " + state);
return resultBool;
}
/**
* This method extracts from address the hostname
* #param url eg. http://some.where.com:8080/sync
* #return some.where.com
*/
public String extractAddressFromUrl(String url) {
String urlToProcess = null;
//find protocol
int protocolEndIndex = url.indexOf("://");
if(protocolEndIndex>0) {
urlToProcess = url.substring(protocolEndIndex + 3);
} else {
urlToProcess = url;
}
// If we have port number in the address we strip everything
// after the port number
int pos = urlToProcess.indexOf(':');
if (pos >= 0) {
urlToProcess = urlToProcess.substring(0, pos);
}
// If we have resource location in the address then we strip
// everything after the '/'
pos = urlToProcess.indexOf('/');
if (pos >= 0) {
urlToProcess = urlToProcess.substring(0, pos);
}
// If we have ? in the address then we strip
// everything after the '?'
pos = urlToProcess.indexOf('?');
if (pos >= 0) {
urlToProcess = urlToProcess.substring(0, pos);
}
return urlToProcess;
}
/**
* Transform host name in int value used by {#link ConnectivityManager.requestRouteToHost}
* method
*
* #param hostname
* #return -1 if the host doesn't exists, elsewhere its translation
* to an integer
*/
private int lookupHost(String hostname) {
InetAddress inetAddress;
try {
inetAddress = InetAddress.getByName(hostname);
} catch (UnknownHostException e) {
return -1;
}
byte[] addrBytes;
int addr;
addrBytes = inetAddress.getAddress();
addr = ((addrBytes[3] & 0xff) << 24)
| ((addrBytes[2] & 0xff) << 16)
| ((addrBytes[1] & 0xff) << 8 )
| (addrBytes[0] & 0xff);
return addr;
}
#SuppressWarnings("unused")
private int lookupHost2(String hostname) {
InetAddress inetAddress;
try {
inetAddress = InetAddress.getByName(hostname);
} catch (UnknownHostException e) {
return -1;
}
byte[] addrBytes;
int addr;
addrBytes = inetAddress.getAddress();
addr = ((addrBytes[3] & 0xff) << 24)
| ((addrBytes[2] & 0xff) << 16)
| ((addrBytes[1] & 0xff) << 8 )
| (addrBytes[0] & 0xff);
return addr;
}
public Boolean disableWifi() {
wifiMan = (WifiManager) context.getSystemService(Context.WIFI_SERVICE);
if (wifiMan != null) {
wifiLock = wifiMan.createWifiLock(WifiManager.WIFI_MODE_SCAN_ONLY, "HelianRCAWifiLock");
}
return wifiMan.setWifiEnabled(false);
}
public Boolean enableWifi() {
Boolean success = false;
if (wifiLock != null && wifiLock.isHeld())
wifiLock.release();
if (wifiMan != null)
success = wifiMan.setWifiEnabled(true);
return success;
}
}
This is the usage:
USAGE CODE
boolean mobileRoutingEnabled = checkMobileInternetRouting();
if(!mobileRoutingEnabled) {
networkUtils.disableWifi();
try {
Thread.sleep(3000);
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
networkUtils.forceMobileConnectionForAddress(context, RCA_URL);
if(!mobileRoutingEnabled) {
networkUtils.enableWifi();
}
// This second check is for testing purpose
checkMobileInternetRouting();
return callWebService(RCA_COMPLETE_URL, _plate);
where checkMobileInternetRouting is:
private boolean checkMobileInternetRouting() {
ConnectivityManager cm = (ConnectivityManager) context.getSystemService(Context.CONNECTIVITY_SERVICE);
State state = cm.getNetworkInfo(ConnectivityManager.TYPE_MOBILE_HIPRI).getState();
return 0 == state.compareTo(State.CONNECTED) || 0 == state.compareTo(State.CONNECTING);
}
USAGE PROCEDURE
Check if the routing to the host is enabled
If yes go with the communication regardless the wifi is connected or not and execute only points 6 (the point 4 will only check that routing is already enable without executing any rilevant action). Otherwise temporary disables the wifi.
Thread sleep of about 3 seconds for letting the 3g connection comes back
Set the 3g routing to the given url
Enable back the wifi
Now the given url can be called even with a wifi connection without net acces
CONCLUSIONS
This is a bit hacky but works properly. The only problem is that this routing has got a timeout of few seconds (like 20-30) that forces you to execute the entire above procedure once more. Setting this timeout to a higher value would be very good.

Google added some useful methods in Android SDK 21 for this purpose.
You can create NetworkRequest:
NetworkRequest networkRequest = new NetworkRequest.Builder()
.addCapability(NetworkCapabilities.NET_CAPABILITY_INTERNET)
.build();
And then you can request such network using ConnectivityManager. For example, you want to be sure that all HTTP requests will be passed through the network with internet access. You can build your Retrofit API in this way:
ApiConfig apiConfig;
ConnectivityManager connectivityManager = (ConnectivityManager) context.getSystemService(Context.CONNECTIVITY_SERVICE);
connectivityManager.requestNetwork(networkRequest, new ConnectivityManager.NetworkCallback() {
#Override
public void onAvailable(Network network) {
apiConfig = new Retrofit.Builder()
.baseUrl("https://api.imatrix.io/")
.client(new OkHttpClient.Builder()
.socketFactory(network.getSocketFactory())
.build())
.build()
.create(ApiConfig.class);
}
#Override
public void onLost(Network network) {
apiConfig = null;
}
});
Please, mind the thread-safety when you're using such snippet of code.
In addition, I suggest check ConnectivityManager#bindProcessToNetwork and this blog.
ConnectivityManager.NetworkCallback is an empty class and it has several methods.

From code, when you detect there is no connectivity, you could switch off WiFi...
As for a setting, there is none (no good way to check if there really is connectivity universally and reliably). But some phones do just what you describe automatically, like for example my LG P-970.
(Note: Android disconnects from mobile networks when it connects to a WiFi, so there is no way to still be connected to a WiFi but route internet access through mobile, even though Linux can do it (with the ip route ... suite of tools))

I can't guarantee this will work as it's something I only experimented with some time ago. I had a similar need to use 3G (or other mobile network) when the wifi-connected network had no route to the outside world.
The following code should drop the wifi connection in order to allow the mobile network to come in to play. You'll need to do various tests along the way and re-establish the wifi connection again afterwards...
WifiManager wifiMan = null;
WifiManager.WifiLock wifiLock = null;
private Boolean disableWifi() {
wifiMan = (WifiManager) getSystemService(Context.WIFI_SERVICE);
if (wifiMan != null) {
wifiLock = wifiMan.createWifiLock(WifiManager.WIFI_MODE_SCAN_ONLY, "MyWifiLock");
}
return wifiMan.setWifiEnabled(false);
}
private Boolean enableWifi() {
Boolean success;
if (wifiLock != null)
wifiLock.release();
if (wifiMan != null)
success = wifiMan.setWifiEnabled(true);
return success;
}

you don't need to code anything. i found an app that do exactly this thing. you can configure to disconnect automatically from the wifi if there is no internet from this connection.
https://play.google.com/store/apps/details?id=com.nLabs.internetconnectivity&hl=en