Hello, my minecraft crashes when I try it in the real launcher, crash:

[17:33:41] [Client thread/ERROR] [FML]: Exception caught during firing event net.minecraftforge.client.event.GuiScreenEvent$InitGuiEvent$Post@df6cc57:
java.lang.NullPointerException
at com.Egietje.degeweldigemod.handler.CheeseClientHandler.onGuiPostInit(CheeseClientHandler.java:101) ~[CheeseClientHandler.class:?]
at net.minecraftforge.fml.common.eventhandler.ASMEventHandler_11_CheeseClientHandler_onGuiPostInit_Post.invoke(.dynamic) ~[?:?]
at net.minecraftforge.fml.common.eventhandler.ASMEventHandler.invoke(ASMEventHandler.java:90) ~[ASMEventHandler.class:?]
at net.minecraftforge.fml.common.eventhandler.EventBus.post(EventBus.java:185) [EventBus.class:?]
at net.minecraft.client.gui.GuiScreen.func_146280_a(GuiScreen.java:489) [bho.class:?]
at net.minecraft.client.Minecraft.func_147108_a(Minecraft.java:966) [bes.class:?]
at net.minecraft.client.gui.GuiWorldSelection.func_146284_a(SourceFile:85) [bka.class:?]
at net.minecraft.client.gui.GuiScreen.func_73864_a(GuiScreen.java:452) [bho.class:?]
at net.minecraft.client.gui.GuiWorldSelection.func_73864_a(SourceFile:116) [bka.class:?]
at net.minecraft.client.gui.GuiScreen.func_146274_d(GuiScreen.java:542) [bho.class:?]
at net.minecraft.client.gui.GuiWorldSelection.func_146274_d(SourceFile:49) [bka.class:?]
at net.minecraft.client.gui.GuiScreen.func_146269_k(GuiScreen.java:510) [bho.class:?]
at net.minecraft.client.Minecraft.func_71407_l(Minecraft.java:1695) [bes.class:?]
at net.minecraft.client.Minecraft.func_71411_J(Minecraft.java:1056) [bes.class:?]
at net.minecraft.client.Minecraft.func_99999_d(Minecraft.java:372) [bes.class:?]
at net.minecraft.client.main.Main.main(SourceFile:124) [Main.class:?]
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[?:1.8.0_25]
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[?:1.8.0_25]
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[?:1.8.0_25]
at java.lang.reflect.Method.invoke(Method.java:483) ~[?:1.8.0_25]
at net.minecraft.launchwrapper.Launch.launch(Launch.java:135) [launchwrapper-1.12.jar:?]
at net.minecraft.launchwrapper.Launch.main(Launch.java:28) [launchwrapper-1.12.jar:?]

Client handler:

	@SubscribeEvent
public void onGuiPostInit(GuiScreenEvent.InitGuiEvent.Post event) {
	GuiScreen gui = event.getGui();
	if (gui instanceof GuiCreateWorld) {
		List<GuiButton> buttonList = event.getButtonList();
		GuiButton giveItem;
		giveItem = addButton(new GuiButton(11, gui.width / 2 + 5, 187, 150, 20, "Give Items: OFF"), buttonList); LINE 101
		giveItem.visible = (Boolean) CheeseUtils.getField(GuiCreateWorld.class, gui, "inMoreWorldOptionsDisplay");
		for (int i = 0; i < buttonList.size(); i++) {
			GuiButton button = event.getButtonList().get(i);
			if (button.id == 3) {
				if ((Boolean) CheeseUtils.getField(GuiCreateWorld.class, gui, "inMoreWorldOptionsDisplay")) {
					button.xPosition = gui.width / 2 - 155;
				} else {
					button.xPosition = gui.width / 2 - 75;
				}
			}
		}
	}
}

protected <T extends GuiButton> T addButton(T button, List<GuiButton> list) {
	list.add(button);
	return button;
}

	@SubscribeEvent
public void onGuiPostInit(GuiScreenEvent.InitGuiEvent.Post event) {
	GuiScreen gui = event.getGui();
	if (gui instanceof GuiCreateWorld) {
	List<GuiButton> buttonList = event.getButtonList();
		GuiButton giveItem;
		giveItem = addButton(new GuiButton(11, gui.width / 2 + 5, 187, 150, 20, "Give Items: OFF"), buttonList); LINE 101
		giveItem.visible = (Boolean) CheeseUtils.getField(GuiCreateWorld.class, gui, "inMoreWorldOptionsDisplay");
		for (int i = 0; i < buttonList.size(); i++) {
			GuiButton button = event.getButtonList().get(i);
			if (button.id == 3) {
				if ((Boolean) CheeseUtils.getField(GuiCreateWorld.class, gui, "inMoreWorldOptionsDisplay")) {
					button.xPosition = gui.width / 2 - 155;
				} else {
					button.xPosition = gui.width / 2 - 75;
				}
			}
		}
	}
}

protected <T extends GuiButton> T addButton(T button, List<GuiButton> list) {
	list.add(button);
	return button;
}

If you would just take a look....

What is line 101?

 

He'd marked it in his OP.

giveItem = addButton(new GuiButton(11, gui.width / 2 + 5, 187, 150, 20, "Give Items: OFF"), buttonList); LINE 101

But I don't see what could be null on that line.

And it works in eclipse, and I have the same forge version

It is the right line, I triple checked, update my github, see for yourself

Done

Where can I find the srg name? Also, how can I use the srg name in real minecraft, and use the other name in eclipse

You need to use the SRG name (see MCPBot).

Yes, how can I see them?

http://mcpbot.bspk.rs/help

I still don't know how... Sorry if I miss something

Ah, got it, but how can I use the srg name in real minecraft, and use the other name in eclipse?

Type mismatch: cannot convert from Field to boolean

What should I do?

I'm trying to get the booleans from the class, but I get a Field, which you can't convert to a boolean

I now have this:

final boolean inMoreWorldOptionsDisplay = (Boolean) ReflectionHelper.findField(GuiCreateWorld.class, "field_146344_y", "inMoreWorldOptionsDisplay").get(gui);

Shouldn't that work

	private static final Field inMoreWorldOptionsDisplay = ReflectionHelper.findField(GuiCreateWorld.class, "field_146344_y", "inMoreWorldOptionsDisplay");

@SubscribeEvent
public void onGuiPostInit(GuiScreenEvent.InitGuiEvent.Post event) {
	GuiScreen gui = event.getGui();
	if (gui instanceof GuiCreateWorld) {
		List<GuiButton> buttonList = event.getButtonList();
		GuiButton giveItem;
		giveItem = addButton(new GuiButton(11, gui.width / 2 + 5, 187, 150, 20, "Give Items: OFF"), buttonList);
		giveItem.visible = inMoreWorldOptionsDisplay.getBoolean(gui);
		ShouldGiveItems.worldCreateGive = false;
		for (int i = 0; i < buttonList.size(); i++) {
			GuiButton button = event.getButtonList().get(i);
			if (button.id == 3) {
				if (inMoreWorldOptionsDisplay.getBoolean(gui)) {
					button.xPosition = gui.width / 2 - 155;
				} else {
					button.xPosition = gui.width / 2 - 75;
				}
			}
		}
	}
}

What should I do exceptions?

How do I use Throwables.propagate?