org.eclipse.swt.layout
Class FormLayout
java.lang.Object
org.eclipse.swt.widgets.Layout
org.eclipse.swt.layout.FormLayout
- public final class FormLayout
- extends
Layout
Instances of this class control the position and size of the
children of a composite control by using FormAttachments
to optionally configure the left, top, right and bottom edges of
each child.
The following example code creates a FormLayout and then sets
it into a Shell:
Display display = new Display ();
Shell shell = new Shell(display);
FormLayout layout = new FormLayout();
layout.marginWidth = 3;
layout.marginHeight = 3;
shell.setLayout(layout);
To use a FormLayout, create a FormData with
FormAttachment for each child of Composite.
The following example code attaches button1 to the top
and left edge of the composite and button2 to the right
edge of button1 and the top and right edges of the
composite:
FormData data1 = new FormData();
data1.left = new FormAttachment(0, 0);
data1.top = new FormAttachment(0, 0);
button1.setLayoutData(data1);
FormData data2 = new FormData();
data2.left = new FormAttachment(button1);
data2.top = new FormAttachment(0, 0);
data2.right = new FormAttachment(100, 0);
button2.setLayoutData(data2);
Each side of a child control can be attached to a position in the parent
composite, or to other controls within the Composite by
creating instances of FormAttachment and setting them into
the top, bottom, left, and right fields of the child's FormData.
If a side is not given an attachment, it is defined as not being attached
to anything, causing the child to remain at its preferred size. If a child
is given no attachment on either the left or the right or top or bottom, it is
automatically attached to the left and top of the composite respectively.
The following code positions button1 and button2
but relies on default attachments:
FormData data2 = new FormData();
data2.left = new FormAttachment(button1);
data2.right = new FormAttachment(100, 0);
button2.setLayoutData(data2);
IMPORTANT: Do not define circular attachments. For example, do not attach
the right edge of button1 to the left edge of button2
and then attach the left edge of button2 to the right edge of
button1. This will over constrain the layout, causing undefined
behavior. The algorithm will terminate, but the results are undefined.
-
Since:
- 1.0
-
See Also:
-
FormData,
FormAttachment,
FormLayout snippets,
SWT Example: LayoutExample,
Sample code and further information
|
Field Summary
|
int
|
marginBottom
marginBottom specifies the number of pixels of vertical margin
that will be placed along the bottom edge of the layout. |
int
|
marginHeight
marginHeight specifies the number of pixels of vertical margin
that will be placed along the top and bottom edges of the layout. |
int
|
marginLeft
marginLeft specifies the number of pixels of horizontal margin
that will be placed along the left edge of the layout. |
int
|
marginRight
marginRight specifies the number of pixels of horizontal margin
that will be placed along the right edge of the layout. |
int
|
marginTop
marginTop specifies the number of pixels of vertical margin
that will be placed along the top edge of the layout. |
int
|
marginWidth
marginWidth specifies the number of pixels of horizontal margin
that will be placed along the left and right edges of the layout. |
int
|
spacing
spacing specifies the number of pixels between the edge of one control
and the edge of its neighbouring control. |
|
Constructor Summary
|
FormLayout
()
Constructs a new instance of this class. |
|
Method Summary
|
protected
Point
|
computeSize
(
Composite composite,
int wHint,
int hHint,
boolean flushCache)
Computes and returns the size of the specified composite's client area
according to this layout. |
protected boolean
|
flushCache
(
Control control)
Instruct the layout to flush any cached values
associated with the control specified in the argument
control. |
protected void
|
layout
(
Composite composite,
boolean flushCache)
Lays out the children of the specified composite according to this
layout. |
String
|
toString
()
Returns a string containing a concise, human-readable
description of the receiver. |
marginWidth
public int marginWidth
- marginWidth specifies the number of pixels of horizontal margin
that will be placed along the left and right edges of the layout.
The default value is 0.
marginHeight
public int marginHeight
- marginHeight specifies the number of pixels of vertical margin
that will be placed along the top and bottom edges of the layout.
The default value is 0.
marginLeft
public int marginLeft
- marginLeft specifies the number of pixels of horizontal margin
that will be placed along the left edge of the layout.
The default value is 0.
marginTop
public int marginTop
- marginTop specifies the number of pixels of vertical margin
that will be placed along the top edge of the layout.
The default value is 0.
marginRight
public int marginRight
- marginRight specifies the number of pixels of horizontal margin
that will be placed along the right edge of the layout.
The default value is 0.
marginBottom
public int marginBottom
- marginBottom specifies the number of pixels of vertical margin
that will be placed along the bottom edge of the layout.
The default value is 0.
spacing
public int spacing
- spacing specifies the number of pixels between the edge of one control
and the edge of its neighbouring control.
The default value is 0.
FormLayout
public FormLayout()
- Constructs a new instance of this class.
computeSize
protected
Point computeSize(
Composite composite,
int wHint,
int hHint,
boolean flushCache)
-
Description copied from class:
Layout
- Computes and returns the size of the specified composite's client area
according to this layout.
This method computes the size that the client area of the composite must
be in order to position all children at their preferred size inside the
composite according to the layout algorithm encoded by this layout.
When a width or height hint is supplied, it is used to constrain the
result. For example, if a width hint is provided that is less than the
width of the client area, the layout may choose to wrap and increase
height, clip, overlap, or otherwise constrain the children.
-
-
Specified by:
-
computeSize
in class
Layout
-
-
Parameters:
-
composite - a composite widget using this layout -
wHint - width (SWT.DEFAULT for preferred size) -
hHint - height (SWT.DEFAULT for preferred size) -
flushCache - true means flush cached layout values
-
Returns:
- a point containing the computed size (width, height)
-
See Also:
-
Layout.layout(org.eclipse.swt.widgets.Composite, boolean),
Control.getBorderWidth(),
Control.getBounds(),
Control.getSize(),
Control.pack(boolean),
"computeTrim, getClientArea for controls that implement them"
flushCache
protected boolean flushCache(
Control control)
-
Description copied from class:
Layout
- Instruct the layout to flush any cached values
associated with the control specified in the argument
control.
-
-
Overrides:
-
flushCache
in class
Layout
-
-
Parameters:
-
control - a control managed by this layout
-
Returns:
- true if the Layout has flushed all cached information associated with control
layout
protected void layout(
Composite composite,
boolean flushCache)
-
Description copied from class:
Layout
- Lays out the children of the specified composite according to this
layout.
This method positions and sizes the children of a composite using the
layout algorithm encoded by this layout. Children of the composite are
positioned in the client area of the composite. The position of the
composite is not altered by this method.
When the flush cache hint is true, the layout is instructed to flush any
cached values associated with the children. Typically, a layout will
cache the preferred sizes of the children to avoid the expense of
computing these values each time the widget is laid out.
When layout is triggered explicitly by the programmer the flush cache
hint is true. When layout is triggered by a resize, either caused by the
programmer or by the user, the hint is false.
-
-
Specified by:
-
layout
in class
Layout
-
-
Parameters:
-
composite - a composite widget using this layout -
flushCache - true means flush cached layout values
toString
public
String toString()
- Returns a string containing a concise, human-readable
description of the receiver.
-
-
Returns:
- a string representation of the layout
Copyright (c) Innoopract Informationssysteme GmbH and others 2002, 2008. All rights reserved.
