Eclipse Platform
Release 3.6

org.eclipse.swt.layout
Class GridLayout

java.lang.Object
  extended by org.eclipse.swt.widgets.Layout
      extended by org.eclipse.swt.layout.GridLayout

public final class GridLayout
extends Layout

Instances of this class lay out the control children of a Composite in a grid.

GridLayout has a number of configuration fields, and the controls it lays out can have an associated layout data object, called GridData. The power of GridLayout lies in the ability to configure GridData for each control in the layout.

The following code creates a shell managed by a GridLayout with 3 columns:

                Display display = new Display();
                Shell shell = new Shell(display);
                GridLayout gridLayout = new GridLayout();
                gridLayout.numColumns = 3;
                shell.setLayout(gridLayout);
 
The numColumns field is the most important field in a GridLayout. Widgets are laid out in columns from left to right, and a new row is created when numColumns + 1 controls are added to the Composite.

See Also:
GridData, GridLayout snippets, SWT Example: LayoutExample, Sample code and further information

Field Summary
 int horizontalSpacing
          horizontalSpacing specifies the number of pixels between the right edge of one cell and the left edge of its neighbouring cell to the right.
 boolean makeColumnsEqualWidth
          makeColumnsEqualWidth specifies whether all columns in the layout will be forced to have the same width.
 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 numColumns
          numColumns specifies the number of cell columns in the layout.
 int verticalSpacing
          verticalSpacing specifies the number of pixels between the bottom edge of one cell and the top edge of its neighbouring cell underneath.
 
Constructor Summary
GridLayout()
          Constructs a new instance of this class.
GridLayout(int numColumns, boolean makeColumnsEqualWidth)
          Constructs a new instance of this class given the number of columns, and whether or not the columns should be forced to have the same width.
 
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.
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait
 

Field Detail

numColumns

public int numColumns
numColumns specifies the number of cell columns in the layout. If numColumns has a value less than 1, the layout will not set the size and position of any controls. The default value is 1.


makeColumnsEqualWidth

public boolean makeColumnsEqualWidth
makeColumnsEqualWidth specifies whether all columns in the layout will be forced to have the same width. The default value is false.


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 5.


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 5.


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.

Since:
3.1

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.

Since:
3.1

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.

Since:
3.1

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.

Since:
3.1

horizontalSpacing

public int horizontalSpacing
horizontalSpacing specifies the number of pixels between the right edge of one cell and the left edge of its neighbouring cell to the right. The default value is 5.


verticalSpacing

public int verticalSpacing
verticalSpacing specifies the number of pixels between the bottom edge of one cell and the top edge of its neighbouring cell underneath. The default value is 5.

Constructor Detail

GridLayout

public GridLayout()
Constructs a new instance of this class.


GridLayout

public GridLayout(int numColumns,
                  boolean makeColumnsEqualWidth)
Constructs a new instance of this class given the number of columns, and whether or not the columns should be forced to have the same width. If numColumns has a value less than 1, the layout will not set the size and position of any controls.

Parameters:
numColumns - the number of columns in the grid
makeColumnsEqualWidth - whether or not the columns will have equal width
Since:
2.0
Method Detail

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.

Overrides:
toString in class Object
Returns:
a string representation of the layout

Eclipse Platform
Release 3.6

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