error on setOnClickListener

view story

http://stackoverflow.com – i keep getting this error on btn.setOnClickListener(this). I have the same code as before however i never got this error until i opened up my eclipse a few minutes ago. Help soon would be great thank you. package com.example.bmisummative; import android.app.Activity; import android.content.DialogInterface; import android.view.View.OnClickListener; import android.content.Intent; import android.os.Bundle; import android.view.View; import android.widget.Button; import android.widget.EditText; import android.widget.TextView; public class weightloss extends Activity { Button btn; @Ove (HowTos)