could someone tell me why the buttons are not working

 

package com.mcpixelplex.Gui;

import org.lwjgl.opengl.GL11;

import com.mcpixelplex.lib.RefStrings;

import net.minecraft.client.Minecraft;
import net.minecraft.client.gui.GuiButton;
import net.minecraft.client.gui.GuiScreen;
import net.minecraft.entity.item.EntityXPOrb;
import net.minecraft.entity.player.EntityPlayer;
import net.minecraft.util.ResourceLocation;
import net.minecraft.world.World;


public class TestGui extends GuiScreen {

Minecraft mc = Minecraft.getMinecraft();

GuiButton testButton;

public String[] levelDisplay = new String[]{"1","2","3","4","5","6","7","8","9","10"};
public int level = 0;

public int currentPower = 0;
public int maxPower = 1000;

public final int xSizeOfTexture = 256;
public final int ySizeOfTexture = 156;

public TestGui(EntityPlayer player){

}

@Override
public void drawScreen(int x, int y, float f){

	int xPos = (this.width - xSizeOfTexture) / 2;
	int yPos = (this.height - ySizeOfTexture) / 2;

	int levelPosX = (xSizeOfTexture) / 2;
	int levelPosY = (ySizeOfTexture) / 2;

	GL11.glColor4f(1F, 1F, 1F, 1F);
	mc.renderEngine.bindTexture(new ResourceLocation(RefStrings.MODID, "/textures/gui/background.png"));

	drawDefaultBackground();
	drawTexturedModalRect(xPos, yPos, 0, 0, xSizeOfTexture, ySizeOfTexture);

	fontRendererObj.drawString("XP Block", xPos + 20, yPos + 5, 0x000000);		
	fontRendererObj.drawString(String.valueOf(level), levelPosX + 85 , levelPosY + 45, 0x000000);	
	super.drawScreen(xPos, y, f);

}

public void initGui(){

	int xSize = 100;
	int ySize = 20;

	int xPos = (xSizeOfTexture) / 2;
	int yPos = (ySizeOfTexture) / 2;

	int bottomButton = (ySizeOfTexture - ySize - 2);

	buttonList.clear();
	buttonList.add(new GuiButton(0, xPos + 40, bottomButton + 40, 100, 20, "Give XP"));
	buttonList.add(new GuiButton(1, xPos + 40, yPos + 40, 20, 20, "+"));
	buttonList.add(new GuiButton(2, xPos + 120, yPos + 40, 20, 20, "-"));

	super.initGui();
}

public void spawnXP(World world, EntityPlayer player){
	double pX = player.posX;
	double pY = player.posY;
	double pZ = player.posZ;
	int xp = 1000;

	world.spawnEntityInWorld(new EntityXPOrb(world, pX, pY, pZ, xp));

}

public void actionPerformed(GuiButton button, World world, EntityPlayer player){
	switch(button.id){
	case 0:
		//this.spawnXP(world, player);
		break;
	case 1:
		level++;
		break;
	case 2:
		if(level == 0){

		}else{
			level--;
		}
		break;
	}
}

@Override
public boolean doesGuiPauseGame(){
	return false;
}

}

Ok how can I get the params for world and player