With the setup I have, it practically transforms the method you tell it into what you define in a certain class. Pretty standard, huh? Well, it seems to transform it correctly, but then MC cannot find the class that was transformed for some reason and it just crashes.

 

Here is the error:

java.lang.reflect.InvocationTargetException
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at net.minecraft.launchwrapper.Launch.launch(Launch.java:131)
at net.minecraft.launchwrapper.Launch.main(Launch.java:27)
Caused by: java.lang.NoClassDefFoundError: net/minecraft/client/gui/GuiMainMenu
at net.minecraft.client.main.Main.main(Main.java:37)
... 6 more
Caused by: java.lang.ClassNotFoundException: net.minecraft.client.gui.GuiMainMenu
at net.minecraft.launchwrapper.LaunchClassLoader.findClass(LaunchClassLoader.java:186)
at java.lang.ClassLoader.loadClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
... 7 more
Caused by: java.lang.NullPointerException
at org.objectweb.asm.tree.ClassNode.accept(ClassNode.java:340)
at net.winneonsword.WCClient.asm.WCClassTransformer.transform(WCClassTransformer.java:92)
at net.winneonsword.WCClient.asm.WCClassTransformer.transform(WCClassTransformer.java:38)
at net.minecraft.launchwrapper.LaunchClassLoader.runTransformers(LaunchClassLoader.java:274)
at net.minecraft.launchwrapper.LaunchClassLoader.findClass(LaunchClassLoader.java:172)
... 9 more

 

ClassTransformer:

package net.winneonsword.WCClient.asm;

import java.io.IOException;
import java.util.ArrayList;
import java.util.HashMap;

import org.objectweb.asm.ClassReader;
import org.objectweb.asm.ClassWriter;
import org.objectweb.asm.tree.ClassNode;
import org.objectweb.asm.tree.MethodNode;

import net.minecraft.launchwrapper.IClassTransformer;
import net.minecraft.launchwrapper.LaunchClassLoader;

public class WCClassTransformer implements IClassTransformer {

private static ArrayList<PatchInfo> list = new ArrayList<PatchInfo>();


static {

	PatchInfo temp;
	temp = new PatchInfo("net.minecraft.client.gui.GuiMainMenu");

	temp.methods.add(new MethodInfo("addSingleplayerMultiplayerButtons", "b", "(II)V", "(II)V"));
	list.add(temp);

}

@Override
public byte[] transform(String x, String y, byte[] z){

	byte[] bytes = z;
	PatchInfo patch = this.getPatchInfo(y);

	if (patch != null){

		bytes = this.transform(patch, bytes);

	}

	return bytes;

}

private byte[] transform(PatchInfo patch, byte[] z){

	boolean patched = false;
	byte[] bytes = z;

	ClassNode node = new ClassNode();
	ClassReader reader = new ClassReader(bytes);

	reader.accept(node, 0);

	System.out.println(String.format("Patching Class: %s", patch.target));

	HashMap<MethodNode, MethodNode> replace = new HashMap();

	for (MethodNode target : node.methods){

		for (MethodInfo method : patch.methods){

			if ((method.name.equals(method.name) || method.name.equals(method.mappedName))
					&& (method.desc.equals(method.desc) || method.desc.equals(method.mappedDesc))){

				MethodNode replacement = this.getReplacementMethod(patch, method);

				replace.put(target, replacement);

				patched = true;

			}

		}

	}

	if (patched){

		for (MethodNode method : replace.keySet()){

			MethodNode replacement = replace.get(method);

			node.methods.remove(method);
			node.methods.add(replacement);

		}

		ClassWriter writer = new ClassWriter(ClassWriter.COMPUTE_MAXS | ClassWriter.COMPUTE_FRAMES);

		node.accept(writer);

		bytes = writer.toByteArray();

	}

	return bytes;

}

private PatchInfo getPatchInfo(String name){

	for (PatchInfo patch : list){

		if (patch.target.equals(name)){

			return patch;

		}

	}

	return null;

}

private MethodNode getReplacementMethod(PatchInfo patch, MethodInfo method){

	try {

		LaunchClassLoader loader = (LaunchClassLoader) this.getClass().getClassLoader();
		ClassNode node = new ClassNode();
		ClassReader reader = new ClassReader(loader.getClassBytes(patch.getReplacementClass()));

		reader.accept(node, 0);

		for (MethodNode m : node.methods){

			if ((m.name.equals(method.name) || m.name.equals(method.mappedName))
					&& (m.desc.equals(method.desc) || m.desc.equals(method.mappedDesc))){

				return m;

			}

		}

	} catch (IOException e){

		e.printStackTrace();

	}

	return null;

}

}

 

PatchInfo:

package net.winneonsword.WCClient.asm;

import java.util.ArrayList;

public class PatchInfo {

public String target;
public ArrayList<MethodInfo> methods = new ArrayList<MethodInfo>();

private static String path = "net.winneonsword.WCClient.asm.containers.";

public PatchInfo(String target){

	this.target = target;

}

public String getReplacementClass(){

	String[] part = this.target.split("[.]");
	String newPath = path + "ASM" + part[part.length - 1];

	return newPath;

}

}

 

MethodInfo:

package net.winneonsword.WCClient.asm;

public class MethodInfo {

public String name;
public String mappedName;

public String desc;
public String mappedDesc;

public MethodInfo(String name, String mappedName, String desc, String mappedDesc){

	this.name = name;
	this.mappedName = mappedName;
	this.desc = desc;
	this.mappedDesc = mappedDesc;

}

}

 

The replacement method / class:

package net.winneonsword.WCClient.asm.containers;

import net.minecraft.client.gui.GuiButton;
import net.minecraft.client.gui.GuiMainMenu;
import net.minecraft.client.resources.I18n;

public class ASMGuiMainMenu extends GuiMainMenu {

public void addSingleplayerMultiplayerButtons(int par1, int par2){

	this.buttonList.add(new GuiButton(1, this.width / 2 - 100, par1, I18n.getString("menu.singleplayer")));
	this.buttonList.add(new GuiButton(2, this.width / 2 - 100, par1 + par2 * 1, I18n.getString("menu.multiplayer")));

	GuiButton fmlModButton = new GuiButton(6, this.width / 2 - 100, par1 + par2 * 2, "Mods");

	this.buttonList.add(fmlModButton);

	GuiButton minecraftRealmsButton = new GuiButton(14, this.width / 2 - 100, par1 + par2 * 2, I18n.getString("menu.online"));
	minecraftRealmsButton.width = 98;
	minecraftRealmsButton.xPosition = this.width / 2 - 100;

	this.buttonList.add(minecraftRealmsButton);
	minecraftRealmsButton.drawButton = false;

}

}

Hi

 

My advice would be

"don't use ASM unless you really really have to" :-)

 

Are you certain that you can't do what you want in a less-error-prone way?

 

-TGG

Hi

 

My advice would be

"don't use ASM unless you really really have to" :-)

 

Are you certain that you can't do what you want in a less-error-prone way?

 

-TGG

Yes, I'm using ASM because I am editing main classes such as the vanilla gui's and a few other things. This is just the first one, and I don't want to go down the crude TickHandler route of overriding gui's when this is more mod - compatible.

Your thing isn't mod compatible at all.

You are replacing the entire class simply to add a method.

Use ASM to add the method into the vanilla class.