How to make a block emit a weak redstone signal only when there is air below it?

[FlowGD]

Hi, I'm pretty new to modding (just started yesterday). I've learned how to make blocks, items, tools, food, recipes etc. and I was thinking I want to learn some slightly more advanced things such as redstone signals. I know how to make a block output a signal, but I have no clue how to check for surrounding blocks, how to check for updates, or how to modify the signal after the block has been placed. How can I make a block output a weak redstone signal only when the block below is air?

[unassigned]

7 hours ago, FlowGD said:

Hi, I'm pretty new to modding (just started yesterday). I've learned how to make blocks, items, tools, food, recipes etc. and I was thinking I want to learn some slightly more advanced things such as redstone signals. I know how to make a block output a signal, but I have no clue how to check for surrounding blocks, how to check for updates, or how to modify the signal after the block has been placed. How can I make a block output a weak redstone signal only when the block below is air?

2

You probably are going to want a TileEntity (that extends ITickable - to allow your tile to update every tick) for this block. 

To check for air below a block, you are going to want to use World#getBlockState and check the position below the block (invoke BlockPos#down to offset the tile's pos down one).

Something like:

    @Override
    public void update() {
        if(!this.world.isRemote) {
            BlockPos downPos = this.getPos().down();
            if(world.getBlockState(downPos) == Blocks.AIR.getDefaultState()) {
                //set a bool to output redstone.
            }
        }
    }

Then, in your block class, when you go to set your weak power, you grab the TE from World#getTileEntity and check whether it should be outputting power or not.

[Cadiboo]

Neither a tile entity nor ITickable is needed here, you can just override onNeighbourChanged.

Edit: you may need to override hasTileEntity and return true, but still return null from createTileEntity (this is perfectly fine and doesn’t break anything) for onNeighbourChanged to fire for your block. Check without doing this first though

Edited January 30, 2019 by Cadiboo

[FlowGD]

Thanks very much for the answers! I'll try these options today.

[FlowGD]

7 hours ago, unassigned said:

You probably are going to want a TileEntity (that extends ITickable - to allow your tile to update every tick) for this block. 

To check for air below a block, you are going to want to use World#getBlockState and check the position below the block (invoke BlockPos#down to offset the tile's pos down one).

Something like:

    @Override
    public void update() {
        if(!this.world.isRemote) {
            BlockPos downPos = this.getPos().down();
            if(world.getBlockState(downPos) == Blocks.AIR.getDefaultState()) {
                //set a bool to output redstone.
            }
        }
    }

Then, in your block class, when you go to set your weak power, you grab the TE from World#getTileEntity and check whether it should be outputting power or not.

I've made the tile entity and it works great, however I can't access the boolean from the tile entity

 

This is the code I'm using to set the weak power:

public int getWeakPower(World worldIn, IBlockState blockState, IBlockAccess blockAccess, BlockPos pos, EnumFacing side)
    {
		TileEntity tileentity = worldIn.getTileEntity(pos);
		
        if(tileentity.power) {
        	return 15;
        }else {
        	return 0;
        }
    }

I can't access the power variable, however I don't know how I would do it otherwise.

 

 

EDIT: I have fixed the problem, however I cannot see any changes in the redstone power when playing the game.

Edited January 30, 2019 by FlowGD

[Cadiboo]

Don’t use a tickable tile entity, you don’t need one, and using one in this case is horrible for performance.

19 hours ago, FlowGD said:

I can't access the power variable, however I don't know how I would do it otherwise.

 

 

EDIT: I have fixed the problem, however I cannot see any changes in the redstone power when playing the game.

Are you syncing and serialising your data?

Edited January 31, 2019 by Cadiboo