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
`ButtonA`	`Controller.ButtonA.pressing()`	The A button.
`ButtonB`	`Controller.ButtonB.pressing()`	The B button.
`ButtonDown`	`Controller.ButtonDown.pressing()`	The Down button.
`ButtonUp`	`Controller.ButtonUp.pressing()`	The Up button.
`ButtonL1`	`Controller.ButtonL1.pressing()`	The L1 button.
`ButtonL2`	`Controller.ButtonL2.pressing()`	The L2 button.
`ButtonL3`	`Controller.ButtonL3.pressing()`	The L3 button.
`ButtonR1`	`Controller.ButtonR1.pressing()`	The R1 button.
`ButtonR2`	`Controller.ButtonR2.pressing()`	The R2 button.
`ButtonR3`	`Controller.ButtonR3.pressing()`	The R3 button.

Notes #

Before using a button member function, create a controller object.

// 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 L1 is pressed
while (true) {
  if (Controller.ButtonL1.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 R1 is pressed
void driveForward() {
  Drivetrain.driveFor(forward, 200, mm);
}

int main() {
  vexcodeInit();

  // Run driveForward when R1 is pressed
  Controller.ButtonR1.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 R1 is released
void stopDriving() {
  Drivetrain.stop();
}

int main() {
  vexcodeInit();

  // Run stopDriving when R1 is released
  Controller.ButtonR1.released(stopDriving);
}