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Eclipse Platform
Release 3.0

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org.eclipse.swt.widgets
Class Composite

java.lang.Object
  org.eclipse.swt.widgets.Widget
      org.eclipse.swt.widgets.Control
          org.eclipse.swt.widgets.Scrollable
              org.eclipse.swt.widgets.Composite

All Implemented Interfaces:

Drawable

Direct Known Subclasses:

Browser, Canvas, CBanner, CCombo, Combo, CoolBar, CTabFolder, DrillDownComposite, ExpandableComposite, FilteredList, Form, Group, OleClientSite, OleFrame, PageBook, ProgressIndicator, ProgressMonitorPart, SashForm, ScrolledComposite, TabFolder, Table, TableTree, ToolBar, Tree, ViewForm

public class Composite

extends Scrollable

Instances of this class are controls which are capable of containing other controls.

Styles:

NO_BACKGROUND, NO_FOCUS, NO_MERGE_PAINTS, NO_REDRAW_RESIZE, NO_RADIO_GROUP, EMBEDDED

Events:

(none)

Note: The NO_BACKGROUND, NO_FOCUS, NO_MERGE_PAINTS, and NO_REDRAW_RESIZE styles are intended for use with Canvas. They can be used with Composite if you are drawing your own, but their behavior is undefined if they are used with subclasses of Composite other than Canvas.

This class may be subclassed by custom control implementors who are building controls that are constructed from aggregates of other controls.

See Also:

Canvas

Field Summary

Fields inherited from class org.eclipse.swt.widgets.Control

handle

Constructor Summary

Composite(Composite parent, int style)
Constructs a new instance of this class given its parent and a style value describing its behavior and appearance.

Method Summary

protected void	checkSubclass() Checks that this class can be subclassed.
Point	computeSize(int wHint, int hHint, boolean changed) Returns the preferred size of the receiver.
Control[]	getChildren() Returns an array containing the receiver's children.
Layout	getLayout() Returns layout which is associated with the receiver, or null if one has not been set.
Control[]	getTabList() Gets the last specified tabbing order for the control.
void	layout() If the receiver has a layout, asks the layout to lay out (that is, set the size and location of) the receiver's children.
void	layout(boolean changed) If the receiver has a layout, asks the layout to lay out (that is, set the size and location of) the receiver's children.
boolean	setFocus() Causes the receiver to have the keyboard focus, such that all keyboard events will be delivered to it.
void	setLayout(Layout layout) Sets the layout which is associated with the receiver to be the argument which may be null.
void	setTabList(Control[] tabList) Sets the tabbing order for the specified controls to match the order that they occur in the argument list.

Methods inherited from class org.eclipse.swt.widgets.Scrollable

computeTrim, getClientArea, getHorizontalBar, getVerticalBar

Methods inherited from class org.eclipse.swt.widgets.Control

addControlListener, addFocusListener, addHelpListener, addKeyListener, addMouseListener, addMouseMoveListener, addMouseTrackListener, addPaintListener, addTraverseListener, computeSize, forceFocus, getAccessible, getBackground, getBorderWidth, getBounds, getEnabled, getFont, getForeground, getLayoutData, getLocation, getMenu, getMonitor, getParent, getShell, getSize, getToolTipText, getVisible, internal_dispose_GC, internal_new_GC, isEnabled, isFocusControl, isReparentable, isVisible, moveAbove, moveBelow, pack, pack, redraw, redraw, removeControlListener, removeFocusListener, removeHelpListener, removeKeyListener, removeMouseListener, removeMouseMoveListener, removeMouseTrackListener, removePaintListener, removeTraverseListener, setBackground, setBounds, setBounds, setCapture, setCursor, setEnabled, setFont, setForeground, setLayoutData, setLocation, setLocation, setMenu, setParent, setRedraw, setSize, setSize, setToolTipText, setVisible, toControl, toControl, toDisplay, toDisplay, traverse, update

Methods inherited from class org.eclipse.swt.widgets.Widget

addDisposeListener, addListener, checkWidget, dispose, getData, getData, getDisplay, getStyle, isDisposed, isListening, notifyListeners, removeDisposeListener, removeListener, removeListener, setData, setData, toString

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Constructor Detail

Composite

public Composite(Composite parent,
                 int style)

Constructs a new instance of this class given its parent and a style value describing its behavior and appearance.

The style value is either one of the style constants defined in class SWT which is applicable to instances of this class, or must be built by bitwise OR'ing together (that is, using the int "|" operator) two or more of those SWT style constants. The class description lists the style constants that are applicable to the class. Style bits are also inherited from superclasses.

Parameters:

parent - a widget which will be the parent of the new instance (cannot be null)

style - the style of widget to construct

Throws:

IllegalArgumentException -

• ERROR_NULL_ARGUMENT - if the parent is null

SWTException -

• ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the parent

See Also:

SWT.NO_BACKGROUND, SWT.NO_FOCUS, SWT.NO_MERGE_PAINTS, SWT.NO_REDRAW_RESIZE, SWT.NO_RADIO_GROUP, Widget.getStyle()

Method Detail

checkSubclass

protected void checkSubclass()

Description copied from class: Widget

Checks that this class can be subclassed.

The SWT class library is intended to be subclassed only at specific, controlled points (most notably, Composite and Canvas when implementing new widgets). This method enforces this rule unless it is overridden.

IMPORTANT: By providing an implementation of this method that allows a subclass of a class which does not normally allow subclassing to be created, the implementer agrees to be fully responsible for the fact that any such subclass will likely fail between SWT releases and will be strongly platform specific. No support is provided for user-written classes which are implemented in this fashion.

The ability to subclass outside of the allowed SWT classes is intended purely to enable those not on the SWT development team to implement patches in order to get around specific limitations in advance of when those limitations can be addressed by the team. Subclassing should not be attempted without an intimate and detailed understanding of the hierarchy.

Overrides:

checkSubclass in class Widget

computeSize

public Point computeSize(int wHint,
                         int hHint,
                         boolean changed)

Description copied from class: Control

Returns the preferred size of the receiver.

The preferred size of a control is the size that it would best be displayed at. The width hint and height hint arguments allow the caller to ask a control questions such as "Given a particular width, how high does the control need to be to show all of the contents?" To indicate that the caller does not wish to constrain a particular dimension, the constant SWT.DEFAULT is passed for the hint.

If the changed flag is true, it indicates that the receiver's contents have changed, therefore any caches that a layout manager containing the control may have been keeping need to be flushed. When the control is resized, the changed flag will be false, so layout manager caches can be retained.

Overrides:

computeSize in class Control

Parameters:

wHint - the width hint (can be SWT.DEFAULT)

hHint - the height hint (can be SWT.DEFAULT)

changed - true if the control's contents have changed, and false otherwise

Returns:

the preferred size of the control.

See Also:

Layout, Control.getBorderWidth(), Control.getBounds(), Control.getSize(), Control.pack(), "computeTrim, getClientArea for controls that implement them"

getChildren

public Control[] getChildren()

Returns an array containing the receiver's children.

Note: This is not the actual structure used by the receiver to maintain its list of children, so modifying the array will not affect the receiver.

Returns:

an array of children

Throws:

SWTException -

• ERROR_WIDGET_DISPOSED - if the receiver has been disposed
• ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver

getLayout

public Layout getLayout()

Returns layout which is associated with the receiver, or null if one has not been set.

Returns:

the receiver's layout or null

Throws:

SWTException -

• ERROR_WIDGET_DISPOSED - if the receiver has been disposed
• ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver

getTabList

public Control[] getTabList()

Gets the last specified tabbing order for the control.

Returns:

tabList the ordered list of controls representing the tab order

Throws:

SWTException -

• ERROR_WIDGET_DISPOSED - if the receiver has been disposed
• ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver

See Also:

setTabList(org.eclipse.swt.widgets.Control[])

layout

public void layout()

If the receiver has a layout, asks the layout to lay out (that is, set the size and location of) the receiver's children. If the receiver does not have a layout, do nothing.

This is equivalent to calling layout(true).

Throws:

SWTException -

• ERROR_WIDGET_DISPOSED - if the receiver has been disposed
• ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver

layout

public void layout(boolean changed)

If the receiver has a layout, asks the layout to lay out (that is, set the size and location of) the receiver's children. If the the argument is true the layout must not rely on any cached information it is keeping about the children. If it is false the layout may (potentially) simplify the work it is doing by assuming that the state of the none of the receiver's children has changed since the last layout. If the receiver does not have a layout, do nothing.

Parameters:

changed - true if the layout must flush its caches, and false otherwise

Throws:

SWTException -

• ERROR_WIDGET_DISPOSED - if the receiver has been disposed
• ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver

setFocus

public boolean setFocus()

Description copied from class: Control

Causes the receiver to have the keyboard focus, such that all keyboard events will be delivered to it. Focus reassignment will respect applicable platform constraints.

Overrides:

setFocus in class Control

Returns:

true if the control got focus, and false if it was unable to.

See Also:

Control.forceFocus()

setLayout

public void setLayout(Layout layout)

Sets the layout which is associated with the receiver to be the argument which may be null.

Parameters:

layout - the receiver's new layout or null

Throws:

SWTException -

• ERROR_WIDGET_DISPOSED - if the receiver has been disposed
• ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver

setTabList

public void setTabList(Control[] tabList)

Sets the tabbing order for the specified controls to match the order that they occur in the argument list.

Parameters:

tabList - the ordered list of controls representing the tab order or null

Throws:

IllegalArgumentException -

• ERROR_INVALID_ARGUMENT - if a widget in the tabList is null or has been disposed
• ERROR_INVALID_PARENT - if widget in the tabList is not in the same widget tree

SWTException -

• ERROR_WIDGET_DISPOSED - if the receiver has been disposed
• ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver