Question

i am creating own framework api (telephone services related api) i am creating one library app this library app to create myjar.jar i am developing another application just i am adding asset folder this myjar.jar and configure this jar adding buildpath
in coding importing the package

this application run into real device:

MacTesting mp = new MacTesting();
mp.getMacAddress();
Log.v("1111","this is mac add"+ mp.getMacAddress());

result is null

public class MacIdTesting extends Activity implements Parcelable
{
    public static final String KEY_WIFI_MAC_ADDRESS = null;

    public  static final String READ_PHONE_STATE = null;

    /** Called when the activity is first created. */
       public String mMacAddress;
       public String phonenumber;
       void setMacAddress(String macAddress) {
           this.mMacAddress = macAddress;
       }

       public String getMacAddress() {
           return mMacAddress;
       }
       public String getLine1Number() 
       {
       ContextWrapper mContext = null;
       mContext.enforceCallingOrSelfPermission(READ_PHONE_STATE, "Requires READ_PHONE_STATE");
           MacIdTesting mPhone = null;
        return mPhone.getLine1Number();
       }

      public void onCreate(Bundle savedInstanceState) 
      {
        super.onCreate(savedInstanceState);

        WifiManager manager = (WifiManager) getSystemService(Context.WIFI_SERVICE);
        WifiInfo wifiInfo = manager.getConnectionInfo();
        String MACAddress = wifiInfo.getMacAddress(); 
        System.out.println("macsddress "+MACAddress);
       }

    @Override
    public int describeContents()
    {
        // TODO Auto-generated method stub
        return 0;


    }
    @Override
    public void writeToParcel(Parcel dest, int flags)
    {
        // TODO Auto-generated method stub
        dest.writeString(mMacAddress);  
    }
}

see this screenshot

how can solve this problem

Answer 1

Your class is an activity and has onCreate method, but not a constructor.

I change the onCreate method to be a constructor like that (and remove the extends activity):

 public MacIdTesting(Context ctx) 
      {
        WifiManager manager = (WifiManager) ctx.getSystemService(Context.WIFI_SERVICE);
        WifiInfo wifiInfo = manager.getConnectionInfo();
        mMacAddress = wifiInfo.getMacAddress();
       }

And call it from the activity like that:

MacTesting mp = new MacTesting(this);

Also, I would keep private members instead of public (private String mMacAddress).