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[1.7.10] onBlockAdded vs onBlockPlacedBy


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I have searched the death out of this for a few hours now and come up empty.  Basic principle of what I'm doing is that if a player places a block, that block will place a number of other blocks relative to it's position.


I can get onBlockAdded to work no problem, except that's called every time the block is added in game even if it's not by the player, as you can imagine this doesn't end well with each block replicating into more and more.


So I found onBlockPlaced but I simply cannot get it to work no matter what I do.  does anyone have an example usage of onBlockPlaced? or even onBlockPlacedBy if that would be the more correct approach?


Many thanks in advance kind people :)

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Ok, I broke it down to absolute basic level to debug and these are the two I have:


public void onBlockAdded(World world, int x, int y, int z) 

System.out.println("I Added");

world.setBlock(x, y+1, z, this);



public void onBlockPlaced(World world, int x, int y, int z) 

System.out.println("I Placed");

world.setBlock(x, y+1, z, this);



Now, the onBlockAdded works no problem (except making a never ending pillar into the sky of course), but the onBlockPlaced doesn't even run it's debug print.  I'm clearly using it incorrectly but I can't figure out how it would be used. 


Moreover, I can't say for sure that I know that onBlockPlaced only runs on player placement (I'm kinda just going off the name), which lead me to believe I may need onBlockPlacedBy, for which the syntax becomes less clear.

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Ok, after a bit of headscratching I can think of a workaround...  If I have two blocks, same texture, however one is placed by the player and one is the spawned one.  Call them block1 and block2 with position x y z being the initial placement position of block1.


on placement of block1

place block2 at (x, y, z)

for counter = 1 to countercap

	if (x,y+counter,z) = air then

		place block2 at (x, y+counter, z)




Where countercap is the max distance for the blocks to go.


It's pretty messy, but until i figure out how to differentiate between the player placing a block and it just being added it'll have to do...




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Your onBlockPlaced doesn't work, because you're not overriding it, you created your own function. The signature for it is not the same as in the Block class. Always use @Override annotations to check if you overrode it correctly. Here are the signatures for these methods in Block.java:

public void onBlockAdded(World, int, int, int)
public int onBlockPlaced(World, int, int, int, int, float, float, float, int)
public void onBlockPlacedBy(World, int, int, int, EntityLivingBase, ItemStack)

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Haha perfect timing! I'd just finished fudging it with multiple blocks, it worked but it made me feel dirty. 


Thankyou, however I'm still not quite there.  After popping @Override above the Public int onBlockPlaced, i receive the error:

The method onBlockPlaced(World, int, int, int) of type BlockNumenorStone must override or implement a supertype method


I think that this is likely just me being very noobish with the Java language, so I understand if I don't get a reply to how to resolve that.

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@Override only checks if you've overriden a supertype method, so you get an error when you didn't, and because of that you know where you've made a mistake.

This annotation, however, doesn't actually make the method override anything.

For it to override a supertype method, it has to have the same signature and the modifiers as the one in the superclass.

A signature of a method is what follows:

  • its name: onBlockPlaced
  • its parameter types: World, int, int, int, int, float, float, float, int

While the method name is important, the parameter names are only for your convenience.

Now look at the error you got. It says that the method onBlockPlaced(World, int, int, int) must override or implement a supertype method.

The supertype method signature for onBlockPlaced is:

onBlockPlaced(World, int, int, int, int, float, float, float, int)

And the modifiers are:

public int

As you can see, it is not the same as your method.

You have to change the parameters of your method to be the same as in the supertype, and then it is going to override it.

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