Button (leJOS EV3 API documentation)

java.lang.Object
- lejos.hardware.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.

Field Summary

Fields
Modifier and Type	Field and Description
`static Key`	`DOWN` The Down button.
`static Key`	`ENTER` The Enter button.
`static Key`	`ESCAPE` The Escape button.
`static java.lang.String`	`FREQ_SETTING`
`static int`	`ID_ALL`
`static int`	`ID_DOWN`
`static int`	`ID_ENTER`
`static int`	`ID_ESCAPE`
`static int`	`ID_LEFT`
`static int`	`ID_RIGHT`
`static int`	`ID_UP`
`static Keys`	`keys`
`static Key`	`LEFT` The Left button.
`static java.lang.String`	`LEN_SETTING`
`static Key`	`RIGHT` The Right button.
`static Key`	`UP` The Up button.
`static java.lang.String`	`VOL_SETTING`

Method Summary

All Methods Static Methods Concrete Methods
Modifier and Type	Method and Description
`static void`	`discardEvents()` This method discards any events.
`static int`	`getButtons()` Low-level API that reads status of buttons.
`static int`	`getKeyClickLength()` Return the current key click length.
`static int`	`getKeyClickTone(int key)` Return the click freq for a particular key.
`static int`	`getKeyClickVolume()` Return the current key click volume.
`static void`	`LEDPattern(int pattern)`
`static int`	`readButtons()` Low-level API that reads status of buttons.
`static void`	`setKeyClickLength(int len)` Set the len used for key clicks
`static void`	`setKeyClickTone(int key, int freq)` Set the frequency used for a particular key.
`static void`	`setKeyClickVolume(int vol)` Set the volume used for key clicks
`static int`	`waitForAnyEvent()` Waits for some button to be pressed or released.
`static int`	`waitForAnyEvent(int timeout)` Waits for some button to be pressed or released.
`static int`	`waitForAnyPress()` Waits for some button to be pressed.
`static int`	`waitForAnyPress(int timeout)` Waits for some button to be pressed.

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- Field Detail
  - ID_UP
```
public static final int ID_UP
```
    See Also:
    
    Constant Field Values
  - ID_ENTER
```
public static final int ID_ENTER
```
    See Also:
    
    Constant Field Values
  - ID_DOWN
```
public static final int ID_DOWN
```
    See Also:
    
    Constant Field Values
  - ID_RIGHT
```
public static final int ID_RIGHT
```
    See Also:
    
    Constant Field Values
  - ID_LEFT
```
public static final int ID_LEFT
```
    See Also:
    
    Constant Field Values
  - ID_ESCAPE
```
public static final int ID_ESCAPE
```
    See Also:
    
    Constant Field Values
  - ID_ALL
```
public static final int ID_ALL
```
    See Also:
    
    Constant Field Values
  - VOL_SETTING
```
public static final java.lang.String VOL_SETTING
```
    See Also:
    
    Constant Field Values
  - LEN_SETTING
```
public static final java.lang.String LEN_SETTING
```
    See Also:
    
    Constant Field Values
  - FREQ_SETTING
```
public static final java.lang.String FREQ_SETTING
```
    See Also:
    
    Constant Field Values
  - ENTER
```
public static final Key ENTER
```
    The Enter button.
  - LEFT
```
public static final Key LEFT
```
    The Left button.
  - RIGHT
```
public static final Key RIGHT
```
    The Right button.
  - ESCAPE
```
public static final Key ESCAPE
```
    The Escape button.
  - UP
```
public static final Key UP
```
    The Up button.
  - DOWN
```
public static final Key DOWN
```
    The Down button.
  - keys
```
public static final Keys keys
```
- 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)
```

Class Button

Field Summary

Method Summary

Methods inherited from class java.lang.Object

Field Detail

ID_UP

ID_ENTER

ID_DOWN

ID_RIGHT

ID_LEFT

ID_ESCAPE

ID_ALL

VOL_SETTING

LEN_SETTING

FREQ_SETTING

ENTER

LEFT

RIGHT

ESCAPE

UP

DOWN

keys

Method Detail

discardEvents

waitForAnyEvent

waitForAnyEvent

waitForAnyPress

waitForAnyPress

getButtons

readButtons

setKeyClickVolume

getKeyClickVolume

setKeyClickLength

getKeyClickLength

setKeyClickTone

getKeyClickTone

LEDPattern