org.eclipse.swt.widgets
Class Composite

java.lang.Object
  extended by org.eclipse.swt.widgets.Widget
      extended by org.eclipse.swt.widgets.Control
          extended by org.eclipse.swt.widgets.Scrollable
              extended by org.eclipse.swt.widgets.Composite
All Implemented Interfaces:
Drawable
Direct Known Subclasses:
Browser, Canvas, CaptionedControl, Combo, ScrolledText, Table, Tree, WrappedLabel

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
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
enableTraverse, internal_parent
 
Fields inherited from class org.eclipse.swt.widgets.Widget
internal_handle, internal_style
 
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
 boolean allowTraverseByArrowKey(Event event)
           
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 a (possibly empty) 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 (possibly empty) tabbing order for the control.
protected  void internal_createHandle(int index)
           
protected  int internal_getNativeStyle()
           
 void internal_removeChild(Control child)
           
 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.
 void setBounds(int x, int y, int width, int height)
          Sets the receiver's size and location to the rectangular area specified by the arguments.
 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 setSize(int width, int height)
          Sets the receiver's size to the point specified by the arguments.
 void setTabList(Control[] tabList)
          Sets the tabbing order for the specified controls to match the order that they occur in the argument list.
protected  boolean traverse(Event event)
           
 
Methods inherited from class org.eclipse.swt.widgets.Scrollable
computeTrim, getClientArea, getHorizontalBar, getVerticalBar
 
Methods inherited from class org.eclipse.swt.widgets.Control
addControlListener, addFocusListener, addKeyListener, addMouseListener, addMouseMoveListener, addPaintListener, addTraverseListener, computeSize, dispose, forceFocus, getBackground, getBorderWidth, getBounds, getEnabled, getFont, getForeground, getLayoutData, getLocation, getMenu, getParent, getShell, getSize, getToolTipText, getVisible, internal_copyArea, internal_dispose_GC, internal_getBounds, internal_getDefaultClipping, internal_new_GC, isEnabled, isEnableTraverse, isFocusControl, isReparentable, isVisible, moveAbove, moveBelow, pack, pack, redraw, redraw, removeControlListener, removeFocusListener, removeKeyListener, removeMouseListener, removeMouseMoveListener, removePaintListener, removeTraverseListener, setBackground, setBounds, setCapture, setEnabled, setFont, setForeground, setLayoutData, setLocation, setLocation, setMenu, setParent, setRedraw, setSize, setToolTipText, setVisible, toControl, toControl, toDisplay, toDisplay, traverse, traverseByArrowKey, traverseGroup, update
 
Methods inherited from class org.eclipse.swt.widgets.Widget
addDisposeListener, addListener, checkWidget, getData, getData, getDisplay, getStyle, internal_sendEvent, isDisposed, isListening, notifyListeners, removeDisposeListener, removeInternalFilter, removeListener, removeListener, sendEvent, 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:
java.lang.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

internal_removeChild

public void internal_removeChild(Control child)

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 Scrollable
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(boolean), "computeTrim, getClientArea for controls that implement them"

internal_createHandle

protected void internal_createHandle(int index)
Overrides:
internal_createHandle in class Widget

internal_getNativeStyle

protected int internal_getNativeStyle()
Overrides:
internal_getNativeStyle in class Scrollable

getChildren

public Control[] getChildren()
Returns a (possibly empty) array containing the receiver's children. Children are returned in the order that they are drawn.

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
See Also:
Control.moveAbove(org.eclipse.swt.widgets.Control), Control.moveBelow(org.eclipse.swt.widgets.Control)

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 (possibly empty) 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 argument is true the layout must not rely on any information it has cached about the immediate children. If it is false the layout may (potentially) optimize the work it is doing by assuming that none of the receiver's children has changed state since the last layout. If the receiver does not have a layout, do nothing.

If a child is resized as a result of a call to layout, the resize event will invoke the layout of the child. The layout will cascade down through all child widgets in the receiver's widget tree until a child is encountered that does not resize. Note that a layout due to a resize will not flush any cached information (same as layout(false)).

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

setBounds

public void setBounds(int x,
                      int y,
                      int width,
                      int height)
Description copied from class: Control
Sets the receiver's size and location to the rectangular area specified by the arguments. The x and y arguments are relative to the receiver's parent (or its display if its parent is null), unless the receiver is a shell. In this case, the x and y arguments are relative to the display.

Note: Attempting to set the width or height of the receiver to a negative number will cause that value to be set to zero instead.

Overrides:
setBounds in class Control
Parameters:
x - the new x coordinate for the receiver
y - the new y coordinate for the receiver
width - the new width for the receiver
height - the new height for the receiver

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

setSize

public void setSize(int width,
                    int height)
Description copied from class: Control
Sets the receiver's size to the point specified by the arguments.

Note: Attempting to set the width or height of the receiver to a negative number will cause that value to be set to zero instead.

Overrides:
setSize in class Control
Parameters:
width - the new width for the receiver
height - the new height for 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:
java.lang.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

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()

allowTraverseByArrowKey

public boolean allowTraverseByArrowKey(Event event)
Overrides:
allowTraverseByArrowKey in class Control

traverse

protected boolean traverse(Event event)
Overrides:
traverse in class Control