Button#

Introduction#

The button class is a derived class of the controller class. It provides access to controller button states and button event callbacks.

A button object is accessed through a controller object. It is not constructed directly.

Access#

The controller class provides the following button objects. Each object is an instance of the button class.

Object	Example Usage	Description
`ButtonEDown`	`Controller.ButtonEDown.pressing()`	The E ▼ button.
`ButtonEUp`	`Controller.ButtonEUp.pressing()`	The E ▲ button.
`ButtonFDown`	`Controller.ButtonFDown.pressing()`	The F ▼ button.
`ButtonFUp`	`Controller.ButtonFUp.pressing()`	The F ▲ button.
`ButtonL3`	`Controller.ButtonL3.pressing()`	The Left Joystick button. IQ (2nd gen) Controller only.
`ButtonLDown`	`Controller.ButtonLDown.pressing()`	The L ▼ button.
`ButtonLUp`	`Controller.ButtonLUp.pressing()`	The L ▲ button.
`ButtonR3`	`Controller.ButtonR3.pressing()`	The Right Joystick button. IQ (2nd gen) Controller only.
`ButtonRDown`	`Controller.ButtonRDown.pressing()`	The R ▼ button.
`ButtonRUp`	`Controller.ButtonRUp.pressing()`	The R ▲ button.

Notes#

Before using a button member function, create a controller object.
ButtonL3 and ButtonR3 are only available on the IQ (2nd gen) Controller.

// Create a controller object
controller Controller = controller();

Member Functions#

The button class includes the following member functions:

Getter — Read button state.

pressing — Returns whether the button is being pressed.

Callbacks — Run functions when button events occur.

pressed — Registers a function to run when the button is pressed.
released — Registers a function to run when the button is released.

Getter#

pressing#

pressing returns whether the button is currently being pressed.

Available Function

bool pressing() const;

Parameters

This function does not have parameters.

Return Value

Returns a Boolean value.

true — The button is being pressed.
false — The button is not being pressed.

Example

// Turn right while R Up is pressed
while (true) {
  if (Controller.ButtonRUp.pressing()) {
    Drivetrain.turn(right);
  }
  else {
    Drivetrain.stop();
  }

  wait(20, msec);
}

Callbacks#

pressed#

pressed registers a function that runs when the button is pressed.

Available Function

void pressed(void (* callback)(void)) const;

Parameter	Type	Description
`callback`	`void (*)(void)`	A function that runs when the button is pressed.

Return Value

This function does not return a value.

Example

Define the callback function outside of main.

// Drive forward when F Up is pressed
void driveForward() {
  Drivetrain.driveFor(forward, 100, mm);
}

int main() {
  vexcodeInit();

  // Run driveForward when F Up is pressed
  Controller.ButtonFUp.pressed(driveForward);
}

released#

released registers a function that runs when the button is released.

Available Function

void released(void (* callback)(void)) const;

Parameter	Type	Description
`callback`	`void (*)(void)`	A function that runs when the button is released.

Return Value

This function does not return a value.

Example

Define the callback function outside of main.

// Stop the drivetrain when F Up is released
void stopDriving() {
  Drivetrain.stop();
}

int main() {
  vexcodeInit();

  // Run stopDriving when F Up is released
  Controller.ButtonFUp.released(stopDriving);
}