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GUI Overlay like GuiIngame - drawString - NullPointerException


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Hello everyone,


I'm trying to create an overlay mod. I'm pretty much at the beginning of it and I'm trying to understand how rendering and gui-classes works.


My goal is a pretty simple overlay that shows a current state of an item i already created. (goal -> somewhat like the energy level of the ultimate lappack from the GraviChestPlate MOD)


I'm trying to render a string onto the screen with the FontRenderer - drawString method. I pretty much copied it together from the GuiIngame class.


GUI class

public class GuiMasterWrench extends Gui {
private final Minecraft mc;

public GuiMasterWrench(Minecraft minecraft) {
	this.mc = minecraft;

public void renderWrenchState() {
	FontRenderer fontRender = this.mc.fontRenderer;
	ScaledResolution sclRes = new ScaledResolution(this.mc.gameSettings, this.mc.displayWidth, this.mc.displayHeight);

	//GL11.glColor4f(1.0F, 1.0F, 1.0F, 1.0F);

	fontRender.drawStringWithShadow("This is the test string!", 1, 1, 0xffffffff);



In the item class I'm trying to call the overlay with the onItemUseFirst method.


public boolean onItemUseFirst(ItemStack stack, EntityPlayer player, World world, int X, int Y, int Z, int side) {
	if (world.isRemote)
		return false;
	if (Keyboard.isKeyDown(Keyboard.KEY_M)) {
		if (wrenchState > 3) wrenchState = 0;
		GuiMasterWrench mwGui = new GuiMasterWrench(Minecraft.getMinecraft());
		player.addChatMessage("You've set the Master Wrench to state "+ wrenchState);
	} else {
		player.addChatMessage("You've used the Master Wrench!");
	return false;


When i try to right-click my item ingame, i get the following error.


Error - Stack Trace

2012-08-31 11:24:54 [sEVERE] [ForgeModLoader] A critical server error occured handling a packet, kicking net.minecraft.src.NetServerHandler@109099d
at org.lwjgl.opengl.GL11.glColor4f(GL11.java:881)
at net.minecraft.src.FontRenderer.renderString(FontRenderer.java:606)
at net.minecraft.src.FontRenderer.drawStringWithShadow(FontRenderer.java:327)
at tay.mods.masterwrench.common.GuiMasterWrench.renderWrenchState(GuiMasterWrench.java:34)
at tay.mods.masterwrench.common.ItemMasterWrench.onItemUseFirst(ItemMasterWrench.java:35)
at net.minecraft.src.Item.onItemUseFirst(Item.java:692)
at net.minecraft.src.ItemInWorldManager.activateBlockOrUseItem(ItemInWorldManager.java:340)
at net.minecraft.src.NetServerHandler.handlePlace(NetServerHandler.java:500)
at net.minecraft.src.Packet15Place.processPacket(Packet15Place.java:78)
at net.minecraft.src.MemoryConnection.processReadPackets(MemoryConnection.java:75)
at net.minecraft.src.NetServerHandler.networkTick(NetServerHandler.java:72)
at net.minecraft.src.NetworkListenThread.networkTick(NetworkListenThread.java:55)
at net.minecraft.src.IntegratedServerListenThread.networkTick(IntegratedServerListenThread.java:132)
at net.minecraft.server.MinecraftServer.updateTimeLightAndEntities(MinecraftServer.java:630)
at net.minecraft.server.MinecraftServer.tick(MinecraftServer.java:547)
at net.minecraft.src.IntegratedServer.tick(IntegratedServer.java:105)
at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:453)
at net.minecraft.src.ThreadServerApplication.run(ThreadServerApplication.java:17)



I would appreciate any kind of help.

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  • 1 month later...

Hi Taylantz,

I don't know if you are interested anymore in the solution but I think, I have a solution.

I suggest that this error is thrown in the Serverthread. In this Thread no LWJGL is used and therefore not initialized. This might cause your exception when rendering.

You should not call the render funtion of your gui in the Item class, rather in the proxy, that you hopefully have, because onItemFirstUse is also called in the server and ends in your exception.

With the proxy, the you can create a stub in the server version and a your render call is in the client one.

Besides, your rendering is only called once (you can see one tick long), unless you right-click your item all the time ;)

Therefore you should add a TickHandler which implements ITickHandler and can be registered in your ClientProxy using

TickRegistry.registerTickHandler(new ClientTickHandler(), Side.CLIENT);

In the TickHandler you have to put several methods, but if you're using eclipse, it should not be such a big problem. One of them is ticks, which return when your tickStart and tickEnd methods are fired. The functions tickStart and tickEnd are self explanatory, I hope. I suggest, you call your render function in the tickEnd, because it is fired after all is drawn and you draw your stuff onto, what is drawn.

public EnumSet<TickType> ticks() {
  return EnumSet.of(TickType.RENDER);

public void tickEnd(EnumSet<TickType> type, Object... tickData) {
  if(type.contains(TickType.RENDER)) {
    // render stuff


Oh my, that was long. I hope, I helped you.


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