Checking Wi-Fi enabled or not on Android

public static boolean wifiState() {
    WifiManager wifiManager = (WifiManager) getSystemService(Context.WIFI_SERVICE);
    return wifiManager.isWifiEnabled();
}

The top answer is correct, but not up to date because this code may leak memory on certain devices.

Therefore the better answer would be:

WifiManager wifiManager = (WifiManager) getApplicationContext().getSystemService(Context.WIFI_SERVICE);
if (wifiManager.isWifiEnabled()) {
  // wifi is enabled
}

Permissions in app=>mainfests=>AndroidManifest.xml:

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

Reference: https://www.mysysadmintips.com/other/programming/759-the-wifi-service-must-be-looked-up-on-the-application-context

WifiManager wifiManager = (WifiManager) getSystemService(Context.WIFI_SERVICE);
if (wifiManager.isWifiEnabled()) {
  // wifi is enabled
}

For details check here

The above answers work fine. But don't forget to add the right permissions in the Manifest:

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

Hope it helps ..