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55 lines
1.9 KiB
Markdown
55 lines
1.9 KiB
Markdown
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The [_BUTTONCHANGE](_BUTTONCHANGE) function returns -1 or 1 when a specified button number on a controller device has been pressed or released.
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## Syntax
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> press% = [_BUTTONCHANGE](_BUTTONCHANGE)(button_number%)
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## Description
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* The **[_DEVICEINPUT](_DEVICEINPUT) function should be read first to specify which device [_BUTTONCHANGE](_BUTTONCHANGE) is intended to check.**
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* Values returned are -1 for a press and 1 when a button is released. No press or release event returns zero.
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* The button_number% must be a number which does not exceed the number of buttons found by the [_LASTBUTTON](_LASTBUTTON) function.
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* **The number of [_DEVICES](_DEVICES) must be read before using [_DEVICE$](_DEVICE$), [_DEVICEINPUT](_DEVICEINPUT) or [_LASTBUTTON](_LASTBUTTON).**
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* **Note:** The center mouse button is button number 2. Center can also be read using [_MOUSEBUTTON](_MOUSEBUTTON)(3).
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## Example(s)
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Reading multiple controller device buttons, axis and wheels.
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```vb
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FOR i = 1 TO _DEVICES
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PRINT STR$(i) + ") " + _DEVICE$(i) + " Buttons:"; _LASTBUTTON(i); ",Axis:"; _LASTAXIS(i); ",Wheel:"; _LASTWHEEL(i)
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NEXT
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DO
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d& = _DEVICEINPUT
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IF d& THEN ' the device number cannot be zero!
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PRINT "Found"; d&;
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FOR b = 1 TO _LASTBUTTON(d&)
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PRINT _BUTTONCHANGE(b); _BUTTON(b);
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NEXT
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FOR a = 1 TO _LASTAXIS(d&)
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PRINT _AXIS(a);
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NEXT
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FOR w = 1 TO _LASTWHEEL(d&)
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PRINT _WHEEL(w);
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NEXT
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PRINT
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END IF
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LOOP UNTIL INKEY$ = CHR$(27) 'escape key exit
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END
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```
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> *Note:* When there is no device control to read, a [FOR...NEXT](FOR...NEXT) n = 1 TO 0 loop will not run thus avoiding a control function read error.
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## See Also
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* [_LASTWHEEL](_LASTWHEEL), [_LASTBUTTON](_LASTBUTTON), [_LASTAXIS](_LASTAXIS)
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* [_AXIS](_AXIS), [_WHEEL](_WHEEL), [_BUTTON](_BUTTON)
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* [_DEVICE$](_DEVICE$), [_DEVICES](_DEVICES)
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* [_MOUSEBUTTON](_MOUSEBUTTON)
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* [Controller Devices](Controller-Devices)
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