So far all the tutorials i've found are for 1.7.10, and i can get the keybind to show up in the controls area of settings. But when i press the associated key nothing happens, until i quit the game, then a flood of msgs show up. Also the drawString doesn't seem to happen at all.

import net.minecraft.client.Minecraft;
import net.minecraftforge.fml.common.eventhandler.SubscribeEvent;
import net.minecraftforge.fml.common.gameevent.InputEvent;
public class KeyInputHandler {
@SubscribeEvent
public void onKeyInput(InputEvent.KeyInputEvent event) {
  if(KeyBindings.openGUI.isPressed()){
  mc.fontRendererObj.drawString("Z Pressed", 2, 20, 0xffffff);
  System.out.println("KEY Z");
  
  //OPEN GUI
   
  }
}
protected static Minecraft mc = Minecraft.getMinecraft();
}

 

I must be missing something. Also how do i enable/disable a class when the key is pressed?

Well, obviously. DrawString is drawing method, you can't just call it anywhere.

If you want to have message in Chat then you do: Minecraft.getMinecraft().thePlayer.addChatMessage(message); for client.