Package lejos.hardware

Class Button

  • public class Button
extends java.lang.Object
    Abstraction for an NXT button. Example: 
     Button.ENTER.waitForPressAndRelease();
 Sound.playTone(1000, 1);
    Notions: The API is designed around two notions: states (up / down) and events (press / release). It is said that a button is pressed (press event), if its state changes from up to down. Similarly, it is said that a button is released (release event), if its states changed from down to up. Thread Safety: All methods that return buttons states can be used safely from multiple threads, even while a call to one of the waitFor* methods active. However, it is not safe to invoke waitFor* methods in parallel from different threads. This includes the waitFor* methods of different buttons. For example Button.ENTER.waitForPress() must not be invoked in parallel to Button.ESCAPE.waitForPress() or the static Button.waitForAnyEvent(). In case this is needed, it is strongly recommended that you write your own Thread, which waits for button events and dispatches the events to anyone who's interested.

    • Method Detail

      • discardEvents

        public static void discardEvents()
        This method discards any events. In contrast to readButtons(), this method doesn't beep if a button is pressed.

      • waitForAnyEvent

        public static int waitForAnyEvent()
        Waits for some button to be pressed or released. Which buttons have been released or pressed is returned as a bitmask. The lower eight bits (bits 0 to 7) indicate, which buttons have been pressed. Bits 8 to 15 indicate which buttons have been released.
        Returns:
        the bitmask
        See Also:
        ID_ENTER, ID_LEFT, ID_RIGHT, ID_ESCAPE

      • waitForAnyEvent

        public static int waitForAnyEvent​(int timeout)
        Waits for some button to be pressed or released. Which buttons have been released or pressed is returned as a bitmask. The lower eight bits (bits 0 to 7) indicate, which buttons have been pressed. Bits 8 to 15 indicate which buttons have been released.
        Parameters:
        timeout - The maximum number of milliseconds to wait
        Returns:
        the bitmask
        See Also:
        ID_ENTER, ID_LEFT, ID_RIGHT, ID_ESCAPE

      • waitForAnyPress

        public static int waitForAnyPress​(int timeout)
        Waits for some button to be pressed. If a button is already pressed, it must be released and pressed again.
        Parameters:
        timeout - The maximum number of milliseconds to wait
        Returns:
        the ID of the button that has been pressed or in rare cases a bitmask of button IDs, 0 if the given timeout is reached

      • waitForAnyPress

        public static int waitForAnyPress()
        Waits for some button to be pressed. If a button is already pressed, it must be released and pressed again.
        Returns:
        the ID of the button that has been pressed or in rare cases a bitmask of button IDs

      • getButtons

        public static int getButtons()
        Low-level API that reads status of buttons.
        Returns:
        An integer with possibly some bits set: ID_ENTER (ENTER button pressed) ID_LEFT (LEFT button pressed), ID_RIGHT (RIGHT button pressed), ID_ESCAPE (ESCAPE button pressed). If all buttons are released, this method returns 0.

      • readButtons

        public static int readButtons()
        Low-level API that reads status of buttons.
        Returns:
        An integer with possibly some bits set: ID_ENTER (ENTER button pressed) ID_LEFT (LEFT button pressed), ID_RIGHT (RIGHT button pressed), ID_ESCAPE (ESCAPE button pressed). If all buttons are released, this method returns 0.

      • setKeyClickVolume

        public static void setKeyClickVolume​(int vol)
        Set the volume used for key clicks
        Parameters:
        vol -

      • getKeyClickVolume

        public static int getKeyClickVolume()
        Return the current key click volume.
        Returns:
        current click volume

      • setKeyClickLength

        public static void setKeyClickLength​(int len)
        Set the len used for key clicks
        Parameters:
        len - the click duration

      • getKeyClickLength

        public static int getKeyClickLength()
        Return the current key click length.
        Returns:
        key click duration

      • setKeyClickTone

        public static void setKeyClickTone​(int key,
                                   int freq)
        Set the frequency used for a particular key. Setting this to 0 disables the click. Note that key may also be a corded set of keys.
        Parameters:
        key - the NXT key
        freq - the frequency

      • getKeyClickTone

        public static int getKeyClickTone​(int key)
        Return the click freq for a particular key.
        Parameters:
        key - The key to obtain the tone for
        Returns:
        key click duration

      • LEDPattern

        public static void LEDPattern​(int pattern)