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The variations of <code>BlockEvent</code> let modders intercept interactions between the player and blocks in the world. All of these events have in common the following: the <code>World</code> the action was taken in, and the <code>BlockPos</code> and <code>BlockState</code> that's being modified. == BreakEvent == This event is fired before a block is broken by a player. Predictably, cancelling this event prevents the block from getting broken. Modders have two extra variables to play with: <code>getExpToDrop()</code>: Returns how much experience ought to drop when the block is broken. Will be zero if the event is currently canceled. <code>setExpToDrop()</code>: Sets the experience that's going to drop manually. <code>getPlayer()</code>: Gets the player that's doing the action. Example usage: <syntaxhighlight lang="java"> public void onBlockBreak(final BlockEvent.BreakEvent event) { if (event.getState().is(Tags.Blocks.SAND)) // use the base event to get the state and see what it is { event.setExpToDrop(10); // change the amount of experience we'll be dropping PlayerEntity player = event.getPlayer(); if (player.getUseItem().getItem().is(Tags.Items.SHEARS)) // check if the player is holding shears { ItemHandlerHelper.giveItemToPlayer(player, new ItemStack(Items.BONE)); // give a bone to the player! } } } </syntaxhighlight> Some ideas for using this event: * Stopping players from breaking a block * Changing the XP drop of a vanilla block * Modify the behavior of a tool == EntityPlaceEvent == This event is called when a block is placed. <code>getEntity()</code>: This is the entity placing the block. Note that this might not be a player! It can be null. This means you should null check the entity. By default, Forge adds this in three places: players placing blocks, endermen placing their held block, as well as ice placed by the Frost Walker enchantment. <code>getBlockSnapshot()</code>: Gets the snapshot of what's about to be placed. A <code>BlockSnapshot</code> is just an object containing the dimension, position, NBT, and state of a block, along with some other info. Typically, this isn't necessary. <code>getPlacedBlock()</code> The <code>BlockState</code> to be placed. <code>getPlacedAgainst()</code> The <code>BlockState</code> that was clicked in order to place the block. Imagine planting a flower on some dirt. The dirt would be the state here. Example usage: <syntaxhighlight lang="java"> public void onEntityPlace(final BlockEvent.BreakEvent event) { Entity entity = event.getEntity(); if (entity != null) // check if the entity is null { Block block = event.getState().getBlock(); // get the block that was placed if (entity instanceof PlayerEntity && block.is(Blocks.FROSTED_ICE)) { event.setCanceled(true); // cancel the placing event.getWorld().setBlock(event.getPos(), Blocks.COBBLESTONE.defaultBlockState(), 3); // set cobble instead } } } </syntaxhighlight> Some ideas for using this event: * (See above) Changing how frost walker works based on certain conditions * Preventing a block from being placed * Changing the player's inventory when a block is placed * Cause another block to be placed instead of another == EntityMultiPlaceEvent == This is the same as above except it's fired when a block causes another block to be replaced. A great example is beds, where placing one half of the bed causes another half to be placed. <code>getReplacedBlockSnapshots()</code>: Everything is the same as before, except we now have a list of snapshots. How sweet. == NeighborNotifyEvent == This event is fired when a block tells its neighbors to update themselves. This happens all the time, typically with redstone blocks like tripwires or repeaters. <code>getNotifiedSides()</code>: A set of <code>Direction</code> values that were updated during the event. Sometimes, blocks will choose to exclude a side from being updated, but most often this will be all six directions. <code>getForceRedstoneUpdate()</code> This is a little funky. There's an option when blocks are set to force a redstone update. If that happened, this will be true. You typically won't need this. Example usage: <syntaxhighlight lang="java"> public void onNeighborNotify(final BlockEvent.BreakEvent event) { BlockPos eventPos = event.getPos(); for (Direction direction : event.getNotifiedSides()) // cycle through notified directions { BlockPos pos = eventPos.relative(direction); // move to the direction given double x = pos.getX() + 0.5D; // move to center of the block double y = pos.getY() + 0.5D; double z = pos.getZ() + 0.5D; // add particle event.getWorld().addParticle(ParticleTypes.CLOUD, x, y, z, 0.0D, 0.0D, 0.0D); } } </syntaxhighlight> Some ideas for using this event: * Adding blocks that interact with redstone * Making a block update detector block == CreateFluidSourceEvent == This event controls creation of fluid sources. This is different than cancellable events, because it has a <code>Result</code>. Setting it to <code>ALLOW</code> causes a source block to created, even if that's not normally what would happen. Setting it to <code>DENY</code> always prevents source creation. Example usage: <syntaxhighlight lang="java"> public void onNeighborNotify(final BlockEvent.BreakEvent event) { if (event.getPos().getY() > 100) { event.setResult(Event.Result.DENY); // prevent source creation above y = 100 } } </syntaxhighlight> == FluidPlaceBlockEvent == This event fires when fluids place blocks. Examples of this happening are: basalt, stone, cobblestone, obsidian, and fire (think lava pools). You can cancel this event to prevent placement. <code>getLiquidPos()</code> This is the liquid's position. For cases like cobble generation, this is the same as the original <code>getPos()</code>. But for placing fire, this won't be the same. <code>getNewState()</code> Gets the state to be placed. <code>setNewState()</code> Sets the state to be placed. <code>getOriginalState()</code> What the block was before this event. Example usage: <syntaxhighlight lang="java"> public void onBreak(final BlockEvent.BreakEvent event) { BlockState newState = event.getNewState(); if (newState.is(Blocks.FIRE)) { event.setCanceled(true); // prevent fire placing from lava } else if (newState.is(Blocks.COBBLESTONE) && event.getWorld().dayTime() > 14000L) { event.setNewState(Blocks.ANDESITE.defaultBlockState()); // change the block if done during nighttime. } } </syntaxhighlight> Some ideas for using this event: * Changing behavior of cobble generators * Preventing cobble generators * Adding more aggressive effects during fire spreading from lava == CropGrowEvent == These events are fired during crop growth. The <code>Pre</code> event is fired before. It's fired when vanilla blocks try to 'grow' during random ticks (think cacti getting taller). Setting <code>DEFAULT</code> as the result will cause no change. Setting <code>ALLOW</code> forces growth. Setting <code>DENY</code> prevents growth. The <code>Post</code> event is fired after growth. <code>getOriginalState</code> Get the state before growth happened. Example usage: <syntaxhighlight lang="java"> public void onCropGrowPre(final BlockEvent.CropGrowEvent.Pre event) { BlockState state = event.getState(); if (state.is(Blocks.WHEAT)) { event.setResult(Event.Result.DENY); // prevent wheat from growing } else if (state.is(Blocks.BAMBOO)) { if (event.getWorld().getRandom().nextFloat() > 0.2F) // take a 4/5 chance { event.setResult(Event.Result.DENY); // make bamboo grow less often } } } </syntaxhighlight> Some ideas for using this event: * Changing growth rate of crops * Preventing crop growth under certain conditions * Spawning an entity when something grows == FarmlandTrampleEvent == This event is fired when farmland gets trampled. You can cancel it to prevent trampling. <code>getEntity()</code> The entity that trampled <code>getFallDistance()</code> How far that entity fell Example usage: <syntaxhighlight lang="java"> public void onTrample(final BlockEvent.FarmlandTrampleEvent event) { if (event.getFallDistance() < 10.0F) { event.setCanceled(true); // change conditions for trampling } } </syntaxhighlight> == PortalSpawnEvent == This event is fired when a nether portal is created. <code>getPortalSize()</code> returns a <code>PortalSize</code> object, basically only useful for determining if the portal is going to be valid or not. This is mostly used for preventing portal spawning in certain dimensions (even the overworld). == BlockToolInteractEvent == This event is fired on right click tool events, such as path creation, wood stripping, and farmland tilling. You have access to the player, the <code>ItemStack</code> they're holding, and the <code>ToolType</code> they have. <code>setFinalState()</code>: Set what you want the result to be. <code>getFinalState()</code>: Returns what it will be changed to. Example usage: <syntaxhighlight lang="java"> public void event(final BlockEvent.BlockToolInteractEvent event) { if (event.getFinalState().is(Blocks.FARMLAND) && event.getHeldItemStack().getItem() == Items.NETHERITE_HOE) { event.setFinalState(Blocks.NETHERRACK.defaultBlockState()); // change the final state under certain conditions } } </syntaxhighlight> Some ideas for using this: * Setting your custom farmland block during tilling * Adding stripped wood behavior for other blocks * Disable path creation

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Revision as of 01:09, 20 April 2021