14 - Tile Cursor
Challenge: Create a Tile Cursor Prefab
During game play, it will be helpful to your player to be able to tell more easily which tile they are hovering / selecting. To do this, you can use the selection-a or selection-b model which fit nicely around a tile.
- Create a new Prefab to represent your Tile Cursor
- Add a
modelchild of the Prefab (I will be usingselection-a) - To appear above a tile, set the Y-position to at least 0.201 (tiles are 0.2 units thick)
- Add a Tile Cursor prefab to your scene
Challenge: TileController MonoBehaviour
Currently, your Tile Prefab has no components attached to it. When placing a turret, it will be useful to track if the Tile is occupied. To do this, create a TileController MonoBehaviour Script that has a property bool IsOccupied. By default, this will be false.
- Create a
TileControllerMonoBehaviour Script - Add a property
bool IsOccupiedthat is false by default - Add a
TileControllercomponent to your Tile Prefab
TileController OnCursorEnter Event
The TileCursor will need to listen to your TileControllers to know if the mouse has entered them. To do this, you will add an event to your TileController that will notify listeners when the mouse has entered.
- Add a
UnityEvent<TileController> OnCursorEnter
- Open your Tile Prefab
- If necessary, remove any events you've added to the
model'sMouseEvents
NotifyCursorEnter
You may have noticed that you cannot call TileController.OnCursorEnter.Invoke from the MouseEvents.OnEnter listener in the Inspector. This is because you must provide a TileController to call OnCursorEnter.Invoke. However, you can create a method that invokes it that takes no arguments.
-
Add a method
NotifyCursorEnter() -
In
NotifyCursorEnter()invokeOnCursorEnterwiththis
-
In the Inspector, add a listener to
MouseEvents.OnEnterthat will invokeTileController.NotifyCursorEnter()
TileCursor.HandleTileEntered
With your TileController propagating itself to listeners, you can now register your TileCursor on them and update its position to match.
- Create a
TileCursorMonoBehaviour Script - Add an
HandleTileEntered(TileController)method - In
HandleTileEntered, set thetransform.positionof the cursor to match thetransform.positionof theTileController.
- In your Scene Hierarchy, select one of your Tiles
- In the Inspector, locate the
Tile Controllercomponent - Add a listener to the
OnCursorEnterevent - Add your Tile Cursor to the event
By using a Unity Event that sends a TileController, you gain access to Dynamic TileController functions in the Function Drop Down. When you use this function, it will send the TileController as an argument to the specified method.
- Select the Function Drop Down
- Select TileCursor > HandleTileEntered (the first option under Dynamic TileController)
- Enter Play Mode and test that your Tile Cursor moves when the mouse moves over the Tile that you registered the event on.
GetComponentsInChildren
To move the Tile Cursor to the most recently entered Tile, you need to register the Tile Cursor on all of your Tile Controllers. Doing this through the Hierarchy and Inspector is challenging and error prone. To make things worse, if you decide to change your map, you have to do it again! Remember, as a programmer, any time you find yourself performing a repetitive task, you should ask yourself if there exists a way to automate it. If not, you should consider how difficult it would be to create your own automation.
Because all of your TileControllers are children of your Grid, you can retrieve them all using the GetComponentInChildren method which retrieves all of the components of a specified type from the specified GameObject and all of its children.
- Read the Friendly Manual: Unity - Scripting API: GameObject.GetComponentsInChildren
- Add a
GameObject TargetGridto yourTileCursor - Add a
ListenToTilesIn(GameObject)method to yourTileCursor - In
ListenToTileIn, iterate through all of theTileControllercomponents and add a listener to callHandleTileEntered
- Add a
OnEnable()method toTileCursor - In
OnEnable, callListenToTilesIn(TargetGrid)
- In the Inspector add your Grid as the
TargetGridfor your TileCursor
- Enter Play Mode and test that your cursor changes between tiles as it moves between Tiles
Challenge: On Disable
Recall that it is good practice to remove a listener if the listening object becomes inactive (e.g. OnDisable).
- Write a
StopListeningToTilesIn(GameObject grid)method - In
StopListeningToTilesyou should iterate through the specified grid searching forTileControllers and callOnCursorEnter.RemoveListeneron each one found. - Add an
OnDisablemethod - In
OnDisable, callStopListeningToTileson theTargetGrid
Challenge: OnCursorExit
Currently, when the player moves the mouse off of map into a space on the screen that does not contain a tile, the TileCursor remains on the most recently entered Tile. Instead, you should hide the Tile Cursors model.
- Add an
UnityEvent<TileController> OnCursorExitproperty to yourTileController - Add a
NotifyCursorExit()method that invokesOnCursorExit - Add a
GameObject Modelproperty to yourTileCursor - Add a
HandleTileExited(TileController)method toTileCursor - In
HandleTileExited, callModel.SetActive(false)to hide theTileCursor's model - In
HandleTileEntered, callModel.SetActive(true)to show theTileCursor's model - Connect all necessary events in the Inspector,
OnEnable, andOnDisable
When you have successfully completed this challenge, your test scene should look similar to this:
What's Next
With the ability to easily see which tile the player is interacting with, it is time to implement an OnCursorClicked event and an OnTileSelected method that will allow your player to spawn a turret. 15 - Turret Spawner