As said in the title, I'm getting a NullPointerException when I edit the guiButton.displayText. I'm doing this while the gui is open and I'm not sure of any other way of doing it. Any help?

 

 protected void actionPerformed(GuiButton guiButton) {
	super.actionPerformed(guiButton);
	switch(guiButton.id) {
	case 1:
		System.out.println("Button clicked");
		if(this.isLinkEnabled == 0){
			System.out.println("Disabled");
			this.isLinkEnabled = 1;
			drawButton(false, isLinkEnabled);
		} else{
			System.out.println("Enabled");
			this.isLinkEnabled = 0;
			drawButton(false, isLinkEnabled);
		}
		break;
	}
	//Packet code here
	//PacketDispatcher.sendPacketToServer(packet); //send packet
}

private void drawButton(boolean firstRun, int enabled){
	if(firstRun){
		this.buttonList.clear();
		//id, x, y, width, height, text
		this.buttonList.add(new GuiButton(neiLinkID, this.textBoxFilter.xPosition, (this.textBoxFilter.yPosition + 10) + 2, neiLinkWidth, neiLinkHeight, "A"));
		this.isLinkEnabled = 0;
	}else{
		try{
			switch(enabled){
			case 0:
				this.neiLink.displayString = "A";
				break;
			case 1:
				this.neiLink.displayString = "B";
				break;
			}
		} catch(NullPointerException e){
			e.printStackTrace();
		}
	}
} 

I'm adding a button to allow the search bar in ProjectE to interface with the NEI search bar. Here's the code:

 

package moze_intel.projecte.gameObjs.gui;

import cpw.mods.fml.common.FMLCommonHandler;
import cpw.mods.fml.common.network.simpleimpl.IMessage;
import moze_intel.projecte.PECore;
import moze_intel.projecte.gameObjs.container.TransmuteContainer;
import moze_intel.projecte.gameObjs.tiles.TransmuteTile;
import moze_intel.projecte.network.PacketHandler;
import moze_intel.projecte.network.packets.ClientSyncTabletLinkPKT;
import moze_intel.projecte.network.packets.SearchUpdatePKT;
import net.minecraft.client.Minecraft;
import net.minecraft.client.gui.inventory.GuiContainer;
import net.minecraft.entity.player.InventoryPlayer;
import net.minecraft.util.ResourceLocation;
import net.minecraft.client.gui.GuiButton;
import net.minecraft.client.gui.GuiTextField;

import org.lwjgl.opengl.GL11;

public class GUITransmute extends GuiContainer
{
private static final ResourceLocation texture = new ResourceLocation(PECore.MODID.toLowerCase(), "textures/gui/transmute.png");
private TransmuteTile tile;
private GuiTextField textBoxFilter;
private GuiButton neiLink;

int xLocation;
int yLocation;

int neiLinkID = 1;
int neiLinkWidth = 15;
int neiLinkHeight = 10;

private static int isLinkEnabled = 0;

public GUITransmute(InventoryPlayer invPlayer, TransmuteTile tile) 
{
	super(new TransmuteContainer(invPlayer, tile));
	this.tile = tile;
	this.xSize = 228;
	this.ySize = 196;
}

@Override
public void initGui() 
{
	tile.setPlayer(Minecraft.getMinecraft().thePlayer);
	super.initGui();

	this.xLocation = (this.width - this.xSize) / 2;
	this.yLocation = (this.height - this.ySize) / 2;

	this.textBoxFilter = new GuiTextField(this.fontRendererObj, this.xLocation + 88, this.yLocation + 8, 45, 10);
	this.textBoxFilter.setText(tile.filter);
	drawButton(true, isLinkEnabled);
}

protected void actionPerformed(GuiButton guiButton) {
	super.actionPerformed(guiButton);
	switch(guiButton.id) {
	case 1:
		System.out.println("Button clicked");
		if(this.isLinkEnabled == 0){
			System.out.println("Disabled");
			PacketHandler.sendToServer(new ClientSyncTabletLinkPKT(1));
			drawButton(false, isLinkEnabled);
		} else{
			System.out.println("Enabled");
			PacketHandler.sendToServer(new ClientSyncTabletLinkPKT(0));
			drawButton(false, isLinkEnabled);
		}
		break;
	}
}

public static int getLinkEnabled(){
	return isLinkEnabled;
}

public static void setLinkEnabled(int i){
	isLinkEnabled = i;
}

private void drawButton(boolean firstRun, int enabled){
	if(firstRun){
		this.buttonList.clear();
		//id, x, y, width, height, text
		this.buttonList.add(new GuiButton(neiLinkID, this.textBoxFilter.xPosition, (this.textBoxFilter.yPosition + 10) + 2, neiLinkWidth, neiLinkHeight, "A"));
		this.isLinkEnabled = 0;
	}else{
		try{
			switch(enabled){
			case 0:
				this.neiLink.displayString = "A";
				break;
			case 1:
				this.neiLink.displayString = "B";
				break;
			}
		} catch(NullPointerException e){
			e.printStackTrace();
		}
	}
}

@Override
public void drawScreen(int par1, int par2, float par3)
{
	super.drawScreen(par1, par2, par3);
	this.textBoxFilter.drawTextBox();
}

@Override
protected void drawGuiContainerBackgroundLayer(float var1, int var2, int var3) 
{
	GL11.glColor4f(1F, 1F, 1F, 1F);
	Minecraft.getMinecraft().renderEngine.bindTexture(texture);
	this.drawTexturedModalRect(guiLeft, guiTop, 0, 0, xSize, ySize);
}

@Override
protected void drawGuiContainerForegroundLayer(int var1, int var2) 
{
	this.fontRendererObj.drawString("Transmutation", 6, 8, 4210752);
	String emc = String.format("EMC: %,d", (int) tile.getStoredEmc());
	this.fontRendererObj.drawString(emc, 6, this.ySize - 94, 4210752);

	if (tile.learnFlag > 0)
	{
		this.fontRendererObj.drawString("L", 98, 30, 4210752);
		this.fontRendererObj.drawString("e", 99, 38, 4210752);
		this.fontRendererObj.drawString("a", 100, 46, 4210752);
		this.fontRendererObj.drawString("r", 101, 54, 4210752);
		this.fontRendererObj.drawString("n", 102, 62, 4210752);
		this.fontRendererObj.drawString("e", 103, 70, 4210752);
		this.fontRendererObj.drawString("d", 104, 78, 4210752);
		this.fontRendererObj.drawString("!", 107, 86, 4210752);

		tile.learnFlag--;
	}
}

@Override
public void updateScreen() 
{
	super.updateScreen();
	this.textBoxFilter.updateCursorCounter();
}

@Override
protected void keyTyped(char par1, int par2)
{
	if (this.textBoxFilter.isFocused()) 
	{
		this.textBoxFilter.textboxKeyTyped(par1, par2);

		String srch = this.textBoxFilter.getText().toLowerCase();

		if (!tile.filter.equals(srch)) 
		{
			PacketHandler.sendToServer(new SearchUpdatePKT(srch));
			tile.filter = srch;
			tile.updateOutputs();
		}
	}

	if (par2 == 1 || par2 == this.mc.gameSettings.keyBindInventory.getKeyCode() && !this.textBoxFilter.isFocused())
	{
		this.mc.thePlayer.closeScreen();
	}
}

@Override
protected void mouseClicked(int x, int y, int mouseButton)
{
	super.mouseClicked(x, y, mouseButton);

	int minX = textBoxFilter.xPosition;
	int minY = textBoxFilter.yPosition;
	int maxX = minX + textBoxFilter.width;
	int maxY = minY + textBoxFilter.height;

	if (mouseButton == 1 && x >= minX && x <= maxX && y <= maxY)
	{
		PacketHandler.sendToServer(new SearchUpdatePKT(""));
		tile.filter = "";
		tile.updateOutputs();
		this.textBoxFilter.setText("");
	}

	this.textBoxFilter.mouseClicked(x, y, mouseButton);

}

@Override
public void onGuiClosed()
{
	super.onGuiClosed();
	tile.learnFlag = 0;
}
}