Java Tutorial/SWT/Layout Basics

A few terms that are used frequently when discussing layouts

1. Client area: the size of the composite"s bounds minus its trim.
2. Margins: the number of pixels placed on an edge of the layout.
3. Spacing: the number of pixels between the edges of children of a composite.
4. Preferred size: best-display size.

Laying Out Children of a Composite

   <source lang="java">

public void layout(boolean changed)</source>

Layouts

A layout can be used to control the position and size of children of a composite. Four standard layouts and one custom layout provided in SWT:

1. FillLayout
2. RowLayout
3. GridLayout
4. FormLayout
5. StackLayout

Layout term: bounds, client area

   <source lang="java">

import org.eclipse.swt.SWT; import org.eclipse.swt.layout.RowLayout; import org.eclipse.swt.widgets.Button; import org.eclipse.swt.widgets.Display; import org.eclipse.swt.widgets.Shell; public class LayoutTerm {

 public static void main(String[] args) {
   Display display = new Display();
   Shell shell = new Shell(display);
   System.out.println("Bounds: " + shell.getBounds());
   System.out.println("Client area: " + shell.getClientArea());
   shell.setBackground(display.getSystemColor(SWT.COLOR_WHITE));
   RowLayout rowLayout = new RowLayout();
   shell.setLayout(rowLayout);
   Button button1 = new Button(shell, SWT.PUSH);
   button1.setText("button1");
   Button button2 = new Button(shell, SWT.PUSH);
   button2.setText("button2");
   Button button3 = new Button(shell, SWT.PUSH);
   button3.setText("button33333333333333333333333333333333333333");
   shell.pack();
   shell.open();
   System.out.println("button1: " + button1.getBounds());
   System.out.println("button2: " + button2.getBounds());
   while (!shell.isDisposed()) {
     if (!display.readAndDispatch()) {
       display.sleep();
     }
   }
   display.dispose();
 }

}</source>

Setting Layouts

   <source lang="java">

public Layout getLayout()

   public void setLayout(Layout layout)</source>
   
  
 
  

By default, a composite does not have any layout.

Using Layout Data Objects to control layout

   <source lang="java">

import org.eclipse.swt.SWT; import org.eclipse.swt.layout.GridData; import org.eclipse.swt.layout.GridLayout; import org.eclipse.swt.widgets.Display; import org.eclipse.swt.widgets.Shell; import org.eclipse.swt.widgets.Text; public class LayoutDataControlLayout {

 public static void main(String[] args) {
   Display display = new Display();
   final Shell shell = new Shell(display);
   shell.setLayout(new GridLayout()); // Only with GridLayout you can use GridData
   Text text = new Text(shell, SWT.SINGLE|SWT.BORDER);
   text.setLayoutData(new GridData(GridData.GRAB_HORIZONTAL));
   
   shell.setSize(450, 100);
   shell.open();
   while (!shell.isDisposed()) {
     if (!display.readAndDispatch()) {
       display.sleep();
     }
   }
   display.dispose();
 }

}</source>