Name
Key.isDown( ) Method — check whether a specific key is currently depressed
Availability
Flash 5
Synopsis
Key.isDown(keycode)
Arguments
- keycode
A number representing the keycode of the key to check. May also be one of the
Key
constants (e.g.,Key.UP
,Key.BACKSPACE
).
Returns
A Boolean indicating whether the key specified by
keycode
is pressed
(true
) or not pressed (false
).
Description
The isDown( )
method tells us whether the key
specified by keycode
is currently being
pressed. It offers arbitrary, immediate access to the state of the
keyboard and is best used with systems that require constant
key-based input or that detect the pressing of simultaneous keys.
One important advantage of isDown( )
over
getCode( )
and getAscii( )
is its ability to detect the simultaneous pressing of multiple keys.
By checking for both Key.UP
and
Key.RIGHT
, for example, we may determine that a
spaceship in a game should be moved diagonally. Depending on the
placement of the specific keys being tested, the maximum number of
keys that can be simultaneously detected may be as low as three.
Example
The isDown( )
method is normally used to create
systems that undergo a constant update with each passing frame. In
the following code, we rotate and thrust a spaceship on any frame
where the appropriate arrow keys are being pressed. Note that if you
need to detect two keys simultaneously, you should use separate
if
statements. In this example, the state of the right arrow key is ignored if the left arrow key is also being ...
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