[Android] Making static reference to the non-static method

To get the MAC address of the user's device (in my case I also removed the colleen for manipulation), we can use:

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WifiManager manager = (WifiManager) getSystemService(Context.WIFI_SERVICE); WifiInfo info = manager.getConnectionInfo(); String MAC = info.getMacAddress().replace(":", "");

If multiple Activities are to use this information, we can copy paste these three lines for every Activity, or we can create a global function with these three lines and reuse the code. To do this we must not simply:

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public class GlobalVariable extends Application{ public String getMAC(){ WifiManager manager = (WifiManager) getSystemService(Context.WIFI_SERVICE); WifiInfo info = manager.getConnectionInfo(); return info.getMacAddress().replace(":", ""); } } //Usage: GlobalVariable global = new GlobalVariable(); global.getMAC();

This will result in error

If you simply set getMAC() to static, you will get a compile error:
Cannot make a static reference to the non-static method getSystemService(String)

To solve this, simply pass a context into the static method like this:

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public class GlobalVariable extends Application{ public static String getMAC(Context ctx){ WifiManager manager = (WifiManager) ctx.getSystemService(Context.WIFI_SERVICE); WifiInfo info = manager.getConnectionInfo(); return info.getMacAddress().replace(":", ""); } } //Usage: GlobalVariable.getMAC(this);