A
JScrollBar
is the interface to the Java Swing JScrollBar Component.
Yoix programs normally interact with a
JScrollBar
using event handlers and by reading or writing the following fields:
| background |
The
Color
that is used to paint the background of the scrollbar.
Reading returns a snapshot of the current color.
Writing immediately changes the background to the new color.
Storing
NULL
in
background
is special and means use the background of the nearest component
that contains the scrollbar and was assigned a background color other than
NULL;
if no component qualifies the scrollbar uses
VM.screen.background.
| | blockincrement |
An
int
that if positive is the amount the scrollbar's value increases or decreases
when either of the scrollbar's block increment areas are activated.
If the value is not positive
1
is used unless the scrollbar is explicitly attached to a
JScrollPane
by being mentioned in its
layout
array, in which case the dimensions of the scrollpane are used to automatically
select an appropriate value.
Reading returns the current blockincrement.
Writing immediately sets the blockincrement to the new value.
| | border |
An
Object
that should be a
Border,
Insets,
Number,
or
String
that describes the border that is drawn around this scrollbar.
A
NULL
value, which is the default, means no border.
A
border
that is an
Insets
or
Number
is an easy way to describe margins
(i.e., an
EmptyBorder),
in units of 72 dots per inch, that are left around the sides of this scrollbar.
A
border
that is a
String
is a quick way to surround this scrollbar with a border that uses the
String
as its title.
Reading returns a snapshot of the current border.
Writing immediately sets the scrollbar's border to the new value.
| | compressevents |
An
Object
that must be a
String
or an
Array
of strings that names the events that are automatically ignored
by the Yoix interpreter when there is another event just like it
(i.e., same type and targeted at the same component) in the
event queue.
| | cursor |
An
Object
that should be an
int,
Image,
or
String
that selects the cursor shown when the pointer is over the scrollbar.
A
cursor
that is an
int
should be one of the cursors defined in the
yoix.awt.Cursor
dictionary.
A
cursor
that is an
Image
can describe the cursor using its
size
and
hotspot
fields and often draws it using its
paint
function.
A
cursor
that is a
String
should be the name of a cursor that is already defined in
yoix.awt.Cursor
or the name a local a file or URL that contains a GIF or JPEG image
that will be used as the cursor.
Reading returns the current cursor.
Writing immediately changes the scrollbar's cursor to the new value.
Storing
STANDARD_CURSOR
(the default) or
NULL
in
cursor
is special and means use the cursor assigned to the nearest component
that contains the scrollbar and was assigned a cursor other than
STANDARD_CURSOR;
if no component qualifies the scrollbar uses
DEFAULT_CURSOR.
| | doublebuffered |
An
int
that is
1
when the scrollbar uses double-buffering to draw itself,
0
when it does not, and starts with a default value that is
selected by Java for the scrollbar.
Reading returns the current double-buffering behavior.
Writing immediately sets the scrollbar's double-buffering behavior to the new value.
Note that double-buffering may be required when transparent components are used.
| | dragenabled |
An
int
that should be set to
1
when this scrollbar wants to use the automatic drag handling that Swing provides
for some components, and
0
(the default)
when it does not.
Components that do not provide automatic drag handling always return
0
when their
dragenabled
field is read, so storing
1
in
dragenabled
should only be viewed as a request for a service that may not be available.
Swing components can always take complete control of their drag and drop
handling using their
transferhandler
field or special drag and drop event handlers.
| | enabled |
An
Object
that is
1
when the scrollbar can respond to user input,
0
when it can not respond, and
NULL
(the default)
when the scrollbar inherits the value from the nearest lightweight container,
like a
JPanel,
that contains the scrollbar and has its
enabled
field set to something other than
NULL.
The top-level application window that contains the scrollbar always gets the
final say, so disabling that window always disables the scrollbar.
Reading returns the current state.
Writing immediately sets the scrollbar's state to the new value.
| | focusable |
An
int
that is non-zero (the default)
when the scrollbar can accept the keyboard focus and zero
when it can not.
Reading returns the scrollbar's current focusable state.
Writing immediately changes the scrollbar's focusable state to the new value,
which means the focus is automatically transferred if the new value is zero
and the scrollbar is the current focus owner.
| | focusowner |
A read-only
int
that is non-zero when the scrollbar has the focus.
| | layer |
An
int,
often a small number between 0 and 99,
that identifies the depth of this scrollbar when it is added to a
JLayeredPane
or
JDesktopPane.
Components assigned to lower numbered layers are drawn before
the components in higher numbered layers.
Writing immediately changes the scrollbar's layer, which usually means the
JLayeredPane
or
JDesktopPane
that contains the scrollbar will be repainted.
| | location |
A
Point
that determines the location of the scrollbar
in a coordinate system that has its origin at the upper left corner
of the container closest to the scrollbar (in the component hierarchy)
that actually contains it, positive x to the right, positive y down,
and a resolution of 72 dots per inch.
Reading returns a snapshot of the current location.
Writing is allowed, but layout managers usually get the final say, so setting
location
should be viewed as a request that may not be honored.
| | maximum |
An
int
that is the largest value represented by the scrollbar.
Reading returns the current maximum.
Writing immediately sets the scrollbar's maximum to the new value.
| | minimum |
An
int
that is the smallest value represented by the scrollbar.
Reading returns the current minimum.
Writing immediately sets the scrollbar's minimum to the new value.
| | nextfocus |
An
Object
that identifies the component that receives the focus after this scrollbar
when the focus traverses from one component to the next
(usually by means of the keyboard
TAB
character).
When
nextfocus
is a
String
it is assumed to be the tag associated with the target component,
which must belong to the same top-level container (e.g., the same
JFrame)
as this scrollbar.
A
NULL
value means the component that gets the focus after this scrollbar will be
selected by Java's default focus traversal policy.
Reading returns the value last stored or
NULL
if the value was a
String
that did not reference a component.
Writing immediately changes the component that gets the focus after this scrollbar.
| | opaque |
An
Object
that is
1
when the scrollbar is opaque,
0
when it is transparent, and
NULL
(the default)
when the scrollbar inherits the value from the nearest component that
contains the scrollbar and has its
opaque
field set to something other than
NULL.
| | orientation |
An
int
that determines the direction that the scrollbar's slider can move.
The value should be
HORIZONTAL
or
VERTICAL,
which are defined in
yoix.swing.
Reading returns the current orientation.
Writing immediately sets the scrollbar's orientation to the new value.
| | popup |
A
JPopupMenu
that is associated with the scrollbar.
Reading returns the current popup menu.
Writing immediately shows the popup menu at the point in the scrollbar's coordinate
system specified by the popup menu's
location
field, assuming of course that the scrollbar is showing on the screen.
Storing
TRUE
in the popup menu's
visible
field, which was added in release 1.2.0, is an easy way to show the
popup menu that currently belongs to the scrollbar.
| | preferredsize |
A
Dimension
that is used by layout managers when they need to know the scrollbar's
preferred size in units of 72 dots per inch.
A
NULL
value means the scrollbar has no preference.
A non-positive height or width is allowed and simply means the scrollbar
has no preference for that dimension.
Reading returns the current preferred size.
Writing changes the preferred size and immediately notifies
root.layoutmanager,
which means the components contained in
root
may be repositioned and resized.
| | requestfocus |
An
int
that can be used to request or transfer the keyboard focus.
Storing a non-zero value in
requestfocus
tries to get the focus.
Storing
0
tries to transfer the focus.
Reading
requestfocus
does not currently return any useful information.
| | requestfocusenabled |
An
int
that is
1
(the default)
when actions, like mouse clicks or changes to the
requestfocus
field, can steal the keyboard focus and
0
when they can not.
Note that this field does not affect acceptance of the keyboard focus
during normal focus traversal.
Reading returns the current state.
Writing immediately sets the scrollbar's state to the new value.
| | root |
An
Object
that is automatically updated by the interpreter's layout machinery
so it is always the top-level object that contains the scrollbar.
For example, put a scrollbar in a panel and
root
will be set to that panel;
add the panel to a frame and the scrollbar's
root
field will be set to that frame.
A scrollbar's event handlers can use
root
when they need to interact with the other components in the container.
| | setValues(int value, int extent, int minimum, int maximum) |
A
Builtin
that accepts 4
int
arguments specifying the
value, extent, minimum, and maximum values for the scrollbar.
setValues
provides an easy way to set all four values at once without generating
multiple state change events and without having to worry too much about
adjustments that Java sometimes quietly makes to guarantee a consistent
set of values.
| | showing |
A read-only
int
that is non-zero when the scrollbar is showing on the screen.
| | size |
A
Dimension
that determines the size of the scrollbar
in units of 72 dots per inch.
Reading returns a snapshot of the current size.
Writing is allowed, but layout managers usually get the final say, so setting
size
should be viewed as a request that may not be honored.
| | tag |
A
String
used to identify the scrollbar that is either supplied when
the scrollbar is declared, or automatically generated otherwise.
Add a scrollbar to a container, like a
JFrame
or
JPanel,
and the interpreter's layout machinery updates the
root
field so it points at the top-level container and then adds the scrollbar, as
tag,
to the
root.components
dictionary.
| | tooltiptext |
A
String
of characters that is displayed in a tightly sized pop-up window that
appears near the cursor whenever the cursor lingers over the scrollbar.
Setting this value to
NULL
(the default)
disables the tooltip mechanism.
Reading returns the current tooltip text.
Writing immediately sets the new tooltip text.
| | transferhandler |
An
Object
that should be a
TransferHandler
or
String
that determines how the scrollbar handles data transfer operations
like drag and drop.
A value that is a
String
but not
""
means the field named by the
String
should be used as the source and sink of the data that is transferred by
the scrollbar.
The result is the same as assigning the
String
to the
property
field in a
TransferHandler
and then assigning that
TransferHandler
to
transferhandler.
The empty
String
""
is special and refers to the
TransferHandler
that Swing uses for automatic drag handling, if there is one.
Swing components that provide automatic drag handling start out with a
transferhandler
field that is not
NULL,
but the automatic drag handling is not enabled until
1
is stored in
dragenabled.
Swing components that provide their own drag and drop event handlers
currently must store
NULL
in
transferhandler
before those event handlers will start working.
| | unitincrement |
An
int
that if positive is the amount the scrollbar's value increases or decreases
when either of the scrollbar's unit increment areas are activated.
If the value is not positive
1
is used unless the scrollbar is explicitly attached to a
JScrollPane
by being mentioned in its
layout
array, in which case the dimensions of the scrollpane are used to automatically
select an appropriate value.
Reading returns the current unitincrement.
Writing immediately sets the unitincrement to the new value.
| | value |
An
int
that is the current value of the scrollbar, as determined by the
position of the slider, in the range:
minimum <= value <= maximum - visibleamount
Reading returns the current value.
Writing immediately sets the new value and moves the slider to the
appropriate position.
| | visible |
An
int
that is
1
when the scrollbar is visible, and
0
otherwise.
Reading returns the current visibility.
Writing immediately sets the scrollbar's visibility to the new state.
| | visibleamount |
An
int
that is the range of values represented by the slider.
Reading returns the current visibleamount.
Writing immediately sets the new visibleamount and adjusts the slider's
size so it represents the new value.
|
Several permanent fields have not been documented and should not be
used in Yoix applications.
Event handlers are functions that must be added to a scrollbar when it is
declared.
The handlers that work with scrollbars are listed below;
the names should be familiar if you have done some Java programming.
| |
| Event Handlers: |
actionPerformed,
adjustmentValueChanged,
componentHidden,
componentMoved,
componentResized,
componentShown,
dragDropEnd,
dragEnter,
dragExit,
dragGestureRecognized,
dragMouseMoved,
dragOver,
drop,
dropActionChanged,
focusGained,
focusLost,
invocationRun,
itemStateChanged,
keyPressed,
keyReleased,
keyTyped,
mouseClicked,
mouseDragged,
mouseEntered,
mouseExited,
mouseMoved,
mousePressed,
mouseReleased,
mouseWheelMoved
| | |
| Example: |
The program,
import yoix.*.*;
JFrame f = {
Array layout = {
new JCanvas {
String tag = "canvas";
Color background = Color.black;
}, CENTER,
new JScrollBar {
int orientation = HORIZONTAL;
int visibleamount = 5;
adjustmentValueChanged(e) {
root.components.canvas.background = new Color {
double red =
(value + 0.0)/(maximum - visibleamount);
};
}
}, SOUTH,
};
};
f.visible = TRUE;
uses a horizontal scrollbar to set the background color of a canvas.
| | |
| See Also: |
BevelBorder,
Border,
EmptyBorder,
EtchedBorder,
invokeLater,
JButton,
JCanvas,
JCheckBox,
JCheckBoxMenuItem,
JChoice,
JColorChooser,
JComboBox,
JDesktopPane,
JDialog,
JFileChooser,
JFileDialog,
JFrame,
JInternalFrame,
JLabel,
JLayeredPane,
JList,
JMenu,
JMenuBar,
JMenuItem,
JPanel,
JPasswordField,
JPopupMenu,
JProgressBar,
JRadioButton,
JRadioButtonMenuItem,
JScrollPane,
JSeparator,
JSlider,
JSplitPane,
JTabbedPane,
JTable,
JTextArea,
JTextCanvas,
JTextField,
JTextPane,
JTextTerm,
JToggleButton,
JToolBar,
JTree,
JWindow,
LineBorder,
MatteBorder,
postEvent,
SoftBevelBorder,
TransferHandler
|
|
