| ActionEvent |
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typedict |
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An
ActionEvent
is an event that represents a high level action that is usually
a combination of several low level events.
For example, an
ActionEvent
from a
Button
or
JButton
means it was pressed and released while the pointer was inside the button.
Components that display popup menus or menubars can also get
ActionEvents
from their menus.
The fields in an
ActionEvent
are:
| command |
A
String
that lets the
actionPerformed
event handler figure out where the event came from.
command
is normally only used to identify the menu item that was selected
from a menubar or popup menu.
| | id |
An
Object
that must be an
int
or
String,
that identifies the type of this event.
A value that is a
String
must be the name of an event handler that can process this event.
A value that is an
int
must be a number that the
yoix.event.HandlerID
dictionary associates with an event handler that can process this event.
In practice,
id
is only used when you build an event that gets handed to
postEvent,
and in that case the value assigned to
id
is almost always a
String.
| | modifiers |
An
int
that is a bitmask that always records the state of the keyboard modifiers
when the event occurred.
modifiers
also tries to record the state of the mouse buttons at the time of the event.
Unfortunately, mouse button and keyboard modifier flags overlap
(e.g.,
BUTTON2_MASK
and
ALT_MASK
match), so in practice
modifiers
only records the state of mouse button 1, which will always appear to be pressed.
modifiers
should be tested using some combination of
BUTTON1_MASK,
BUTTON2_MASK,
BUTTON3_MASK,
SHIFT_MASK,
CTRL_MASK,
ALT_MASK,
META_MASK,
and
ALT_GRAPH_MASK,
which are defined in
yoix.awt
and
yoix.swing.
Also available are
BUTTON_MASK
and
KEY_MASK,
which are convenient combinations that can be used to test for
any mouse button or any keyboard modifier.
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Components like
JButton,
JComboBox,
JTextField,
Button,
List,
and
TextField
can receive
ActionEvents,
but they only arrive if the component has defined an
actionPerformed
event handler.
In addition, any component that displays a popup menu or menubar can get
ActionEvents
from those menus if they have an
actionPerformed
event handler.
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| Event Handlers: |
actionPerformed
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| Example: |
The program,
import yoix.*.*;
VM.exitmodel = 0; // so main thread does not exit
JButton button = {
actionPerformed(Event e) {
printf("Received: %O\n", e);
exit(0);
}
};
ActionEvent event = {
String command = "Fake Event";
String id = "actionPerformed";
int modifiers = BUTTON2_MASK | SHIFT_MASK;
};
printf("Posting: %O\n", event);
postEvent(event, button);
prints something like
Posting: Event[3:0]
>command=^"Fake Event"
id=^"actionPerformed"
modifiers=9
Received: Event[3:0]
>command=^"Fake Event"
id=1001
modifiers=9
on standard output.
Notice how the
id
field changed from a string to the corresponding
integer by the time
actionPerformed
got the event.
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| See Also: |
AdjustmentEvent,
CaretEvent,
ChangeEvent,
ComponentEvent,
DragGestureEvent,
DragSourceEvent,
DropTargetEvent,
Event,
FocusEvent,
HyperlinkEvent,
InvocationEvent,
invokeLater,
isDispatchThread,
ItemEvent,
KeyEvent,
ListSelectionEvent,
MouseEvent,
MouseWheelEvent,
PaintEvent,
postEvent,
TextEvent,
TreeSelectionEvent,
WindowEvent
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Yoix is a registered trademark of AT&T Inc.
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