Polling refers to checking the state of an input device. It is an easy way to check and process user input and will most likely suffice for most simple games.
Polling anything
The Context object provides an Input that can be used to poll the current state of mouse, keyboards, and gamepads. The input can be accessed by the context.input property. To shorten it even more, a ContextListener delegates to the Context by default and allows us to access it just by the input property.
Polling mouse/touch
There are a number of methods that are provided by polling the input.
To get the coordinates of the mouse we can do the following:
val x = input.x
val y = input.y
Once touch input is provided, we can grab coordinates of a specific pointer / finger:
val x = input.getX(Pointer.POINTER2)
val y = input.getY(Pointer.POINTER2)
Pressure
We can find the amount of pressure applied one a pointer which returns a value between 0 and 1:
val pressure = input.getPressure(Pointer.POINTER1)
To determine which mouse buttons are pressed on desktop:
val leftPressed = input.isTouching(Pointer.MOUSE_LEFT)
val rightPressed = input.isTouching(Pointer.MOUSE_RIGHT)
Determing if a pointer is just touched with the past frame or just released within the last frame:
val justTouched = input.isJustTouched(Pointer.POINTER1)
val justReleased = input.isTouchJustReleased(Pointer.POINTER1)
Polling Keyboard
Polling the keyboard is very simple and the Input class provides a bunch of util methods to make it easy.
Determine if a key is currently being pressed:
val down = input.isKeyPressed(Key.S)
Determine if a key was just pressed within the past frame:
val down = input.isKeyJustPressed(Key.S)
Determine if a key was just released with the past frame:
val justReleased = input.isKeyJustReleased(Key.S)
Input provides a bunch more of similar methods as the ones above for determining if multiple keys are pressed, not pressed, or any of them are pressed.
/**
* Determines if any of the specified [keys] are currently pressed.
* @return `true` if any of the keys are pressed; `false` otherwise.
*/
fun areAnyKeysPressed(vararg keys: Key): Boolean = keys.any { isKeyPressed(it) }
/**
* Determines if all of the specified [keys] are currently pressed.
* @return `true` if all of the keys are pressed; `false` otherwise.
*/
fun areAllKeysPressed(vararg keys: Key): Boolean = keys.all { isKeyPressed(it) }
/**
* Determines if all of the specified [keys] are **NOT** currently pressed.
* @return `true` if no keys are pressed; `false` otherwise.
*/
fun areNoKeysPressed(vararg keys: Key): Boolean = keys.none { isKeyPressed(it) }
Polling Gamepads
Just like the mouse and keyboard we can also poll the state of gamepads. By default, it checks for the first gamepad connected but allows for checking for any additional by passing in the gamepad id.
Determining a the axis of either left or right joystick of the initial gamepad:
val xLeft = input.axisLeftX
val yLeft = input.axisLeftY
val xRight = input.axisRightX
val yRight = input.axisRightY
We can also determine the these values by using the getGamepadJoystickDistanceXY methods:
Joysticks
val leftAxis = input.getGamepadJoystickDistance(GameStick.LEFT)
val rightAxis = input.getGamepadJoystickDistance(GameStick.RIGHT)
val leftAxis2 = input.getGamepadJoystickDistance(GameStick.LEFT, gamepad = 1) // grabbing the axis from a different gamepad
val rightAxis2 = input.getGamepadJoystickDistance(GameStick.RIGHT, gamepad = 1)
val x = input.getGamepadJoystickXDistance(GameStick.LEFT)
val y = input.getGamepadJoystickYDistance(GameStick.LEFT)
Buttons
Very similar to how the keyboard polling works, Input provides the same pressed and released methods:
val justPressed = input.isGamepadButtonJustPressed(GameButton.XBOX_A)
val pressed = input.isGamepadButtonPressed(GameButton.XBOX_A)
val justReleased = input.isGamepadButtonJustReleased(GameButton.XBOX_X)
Pressure
The pressure of each button can be determines. For most buttons it will return either a -1 or 1. But for trigger buttons such as the LT or RT triggers on an Xbox controller they will return any value between -1 to 1.
val pressure = input.getGamepadButtonPressure(GameButton.LEFT_TRIGGER)
Iterating through multiple connected gamepads
The Input interface provides a list of connected gamepads that can be used for polling each individual gamepad.
input.connectedGamepads.forEach { gamepad ->
val pressed = input.isGamepadButtonPressed(GameButton.PS_CROSS, gamepad = gamepad.index)
}