Trying to open GUI causes game to crash

[jamiemac262]

Hi,

I'm having a problem with displaying a GUI Screen when I right click a block.

 

Whenever I right click the block the game crashes and I get a null pointer exception:

 

Quote

Description: Unexpected error

java.lang.NullPointerException: Unexpected error
 at net.minecraftforge.fml.common.network.NetworkRegistry.getLocalGuiContainer(NetworkRegistry.java:273)
 at net.minecraftforge.fml.common.network.internal.FMLNetworkHandler.openGui(FMLNetworkHandler.java:110)
 at net.minecraft.entity.player.EntityPlayer.openGui(EntityPlayer.java:2729)
 at net.tekkcraft.factions.blocks.BlockCore.onBlockActivated(BlockCore.java:64)
 at net.minecraft.client.multiplayer.PlayerControllerMP.processRightClickBlock(PlayerControllerMP.java:442)
 at net.minecraft.client.Minecraft.rightClickMouse(Minecraft.java:1603)
 at net.minecraft.client.Minecraft.processKeyBinds(Minecraft.java:2281)
 at net.minecraft.client.Minecraft.runTickKeyboard(Minecraft.java:2058)
 at net.minecraft.client.Minecraft.runTick(Minecraft.java:1846)
 at net.minecraft.client.Minecraft.runGameLoop(Minecraft.java:1118)
 at net.minecraft.client.Minecraft.run(Minecraft.java:406)
 at net.minecraft.client.main.Main.main(Main.java:118)
 at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
 at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
 at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
 at java.lang.reflect.Method.invoke(Method.java:498)
 at net.minecraft.launchwrapper.Launch.launch(Launch.java:135)
 at net.minecraft.launchwrapper.Launch.main(Launch.java:28)
 at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
 at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
 at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
 at java.lang.reflect.Method.invoke(Method.java:498)
 at net.minecraftforge.gradle.GradleStartCommon.launch(GradleStartCommon.java:97)
 at GradleStart.main(GradleStart.java:26)

 

I've had a good look at my code and I can't see what's wrong.

 

Can anyone help?

 

The event in the BlockCore.java:

 @Override
    public boolean onBlockActivated(World worldIn, BlockPos pos, IBlockState state, EntityPlayer playerIn, EnumHand hand, @Nullable ItemStack heldItem, EnumFacing side, float hitX, float hitY, float hitZ) {
            System.out.println("Block Right Clicked");
            playerIn.openGui(Factions.instance, GuiHandler.MOD_TILE_ENTITY_GUI, worldIn, pos.getX(), pos.getY(), pos.getZ());
        return true;
    }

 

The GUI Handler:

public class GuiHandler implements IGuiHandler {

    public static final int MOD_TILE_ENTITY_GUI = 0;

    @Override
    public Object getServerGuiElement(int ID, EntityPlayer player, World world, int x, int y, int z) {
        if (ID == MOD_TILE_ENTITY_GUI)
            return new FactionCoreGuiScreen();

        return null;
    }

    @Override
    public Object getClientGuiElement(int ID, EntityPlayer player, World world, int x, int y, int z) {
        if (ID == MOD_TILE_ENTITY_GUI)
            return new FactionCoreGuiScreen();

        return null;
    }

}

 

 

FactionCoreGuiScreen:

 

public class FactionCoreGuiScreen extends GuiScreen {
    @Override
    public void drawScreen(int mouseX, int mouseY, float partialTicks) {
        this.drawDefaultBackground();
        super.drawScreen(mouseX, mouseY, partialTicks);
    }

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

    @Override
    public void initGui() {
    }

    @Override
    protected void actionPerformed(GuiButton button) throws IOException {
    }

 

[larsgerrits]

9 minutes ago, jamiemac262 said:

@Override
public Object getServerGuiElement(int ID, EntityPlayer player, World world, int x, int y, int z) {
    if (ID == MOD_TILE_ENTITY_GUI)
        return new FactionCoreGuiScreen();

    return null;
}

 

 

 

You can only return a Container fromIGuiHandler#getServerGuiElement, and you are returning a GuiScreen.

 

A few other things to check: did you register your IGuiHandler? Is your @Mod.Instance set up correctly?

Edited March 7, 2017 by larsgerrits

[Jay Avery]

A NullPointerException means that something is null where it shouldn't be. Use printlns or the debugger to check the values of all the variables you pass to EntityPlayer#openGui, and see which is null.

 

Edit: scratch that, I read wrong. The null value happens further on, probably as a result of the problem larsgerrits pointed out.

Edited March 7, 2017 by Jay Avery

[jamiemac262]

43 minutes ago, larsgerrits said:

You can only return a Container fromIGuiHandler#getServerGuiElement, and you are returning a GuiScreen.

 

A few other things to check: did you register your IGuiHandler? Is your @Mod.Instance set up correctly?

 

I changed getServerGuiElement to just return null..... tested the mod and got the same problem.

 

I have no idea what I'm meant to do here  

 

IGuiHandler is registered in the common proxy:

 

 public void init(FMLInitializationEvent e){
        NetworkRegistry.INSTANCE.registerGuiHandler(Factions.instance, new GuiHandler());

    }

 

is that correct?

 

also my @Mod.Instance should be find as I've used it in other parts of the mod

 

@Mod.Instance(MODID)
    public static Factions instance;

 

It looks like the problem might be what you suggested, I just don't know how to fix it  

 

thanks

Jamie

 

[Leomelonseeds]

No in your gui handler serverside you need to return your mod CONTAINER.

[jamiemac262]

55 minutes ago, Jay Avery said:

A NullPointerException means that something is null where it shouldn't be. Use printlns or the debugger to check the values of all the variables you pass to EntityPlayer#openGui, and see which is null.

 

Edit: scratch that, I read wrong. The null value happens further on, probably as a result of the problem larsgerrits pointed out.

I added println's to the 2 GuiHandler functions and it turns out the game is crashing before it calls either of the functions

 

so it's not the getServerGUIElement  

[jamiemac262]

Quote

No in your gui handler serverside you need to return your mod CONTAINER.

wait... do I NEED a container to open a GUI?

 

It's just going to be text and buttons, not storing any items...... (or have I misunderstood "container")?

Edited March 7, 2017 by jamiemac262
wrong quote

[Leomelonseeds]

Yes you do need a container. Go look at tutorial for that.

[larsgerrits]

If you only want to have a gui, only call EntityPlayer#openGui on the client side (world.isRemote).

[jamiemac262]

3 minutes ago, larsgerrits said:

If you only want to have a gui, only call EntityPlayer#openGui on the client side (world.isRemote).

my god

 

it was actually in the damn tutorial! I must have overlooked that at least a dozen times!  

 

https://bedrockminer.jimdo.com/modding-tutorials/advanced-modding/gui-screen/

[jamiemac262]

nope, ignore me, that didn't fix it  

[Leomelonseeds]

Just now, jamiemac262 said:

 

https://bedrockminer.jimdo.com/modding-tutorials/advanced-modding/gui-screen/

 

Eyy! I use those too! Even tho their outdated, they are a great help. Wish he could continue them though

[jamiemac262]

Just now, Leomelonseeds said:

Eyy! I use those too! Even tho their outdated, they are a great help. Wish he could continue them though

indeed.... I'll bet my problem is something that's changed since this was written  

[Leomelonseeds]

Just now, jamiemac262 said:

nope, ignore me, that didn't fix it

Post your code -.-

[jamiemac262]

2 minutes ago, Leomelonseeds said:

Post your code -.-

 

here's what I've changed so far

 

I can only see "Block Right Clicked" in the logs, that's where it crashes

 

The right click event:

public boolean onBlockActivated(World worldIn, BlockPos pos, IBlockState state, EntityPlayer playerIn, EnumHand hand, @Nullable ItemStack heldItem, EnumFacing side, float hitX, float hitY, float hitZ) {
            System.out.println("Block Right Clicked");
           if(worldIn.isRemote) {
               playerIn.openGui(Factions.instance, GuiHandler.MOD_TILE_ENTITY_GUI, worldIn, pos.getX(), pos.getY(), pos.getZ());
           }
        return true;
    }

 

The GuiHandler:

 

 @Override
    public Object getServerGuiElement(int ID, EntityPlayer player, World world, int x, int y, int z) {
        System.out.println("GetServerGUI Will return null");
        return null;
    }

    @Override
    public Object getClientGuiElement(int ID, EntityPlayer player, World world, int x, int y, int z) {
        System.out.println("clientGUI");
        if (ID == MOD_TILE_ENTITY_GUI)
            return new FactionCoreGuiScreen();
        else
            System.out.println("clientGUI null");

        return null;
    }

 

[larsgerrits]

Things that could be null down the line: the player variable, which is highly unlikely if you are the one opening the GUI, or the IGuiHandler on the client side. If you override CommonProxy#init in the ClientProxy, be sure to call the super method so it actually registers on the client side.

[jamiemac262]

hold up... I think the tutorial I followed when setting up proxies missed a step 0.o

 

override commonProxy.init? CommonProxy doesn't extend anything lol

 

(I looked at bedrockminer's tutorial and noticed he has a "serverProxy" that extends Common proxy... I'll follow his proxy tutorial now and make changes)

[jamiemac262]

I fixed it!

 

thanks guys, The problem was the way I had set up my proxies

 

Not only did I not have all the classes and methods I needed, but I also wasn't calling them in the main class -.-

 

The client no longer crashes!