SWT: GridLayout

GridLayout provides much flexibility to design user interfaces. GridLayout provides number of properties to manipulate to get good looking user interface.

How to define GridLayout?

GridLayout gridLayout = new GridLayout();

gridLayout.numColumns = 2;

shell.setLayout(gridLayout);

Following are the different properties associated with GridLayout instance.

Property	Description
horizontalSpacing	Specifies the number of pixels between the right edge of one cell and the left edge of its neighbouring cell to the right.
makeColumnsEqualWidth	makeColumnsEqualWidth specifies whether all columns in the layout will be forced to have the same width. Default value is false.
marginBottom	marginBottom specifies the number of pixels of vertical margin that will be placed along the bottom edge of the layout.
marginLeft	marginLeft specifies the number of pixels of horizontal margin that will be placed along the left edge of the layout.
marginRight	marginRight specifies the number of pixels of horizontal margin that will be placed along the right edge of the layout.
marginTop	marginTop specifies the number of pixels of vertical margin that will be placed along the top edge of the layout.
marginWidth	marginWidth specifies the number of pixels of horizontal margin that will be placed along the left and right edges of the layout.
numColumns	numColumns specifies the number of cell columns in the layout.
verticalSpacing	verticalSpacing specifies the number of pixels between the bottom edge of one cell and the top edge of its neighbouring cell underneath.

What is GridData objects?

GridData object is the layout data object associated with GridLayout, this is used to control the behavior of widgets.

Following statements tells the layout to span the button across two columns.

GridData data3 = new GridData();

data3.horizontalSpan = 2;

button.setLayoutData(data3);

How to define GridData object?

There are two way.

Way1

Define GridData object and set the properties.

Ex:

GridData gridData = new GridData();

gridData.horizontalAlignment = GridData.FILL;

gridData.verticalAlignment = GridData.FILL;

gridData.grabExcessHorizontalSpace = true;

gridData.grabExcessVerticalSpace = true;

gridData.horizontalSpan = 2;

button2.setLayoutData(gridData);

Way 2

Define using parameterized constructors.

Ex:

GridData gridData1 = new GridData (SWT.FILL, SWT.CENTER, true, false)

GridData gridData2 = new GridData (SWT.FILL, SWT.FILL, true, true, 2, 1)

button1.setLayoutData(gridData1);

button1.setLayoutData(gridData2);

Note:

Don't reuse the GridData object, As per JavaSpecification, Every control in a Composite that is managed by a GridLayout must have a unique GridData object. If the layout data for a control in a GridLayout is null at layout time, a unique GridData object is created for it.

Following is the complete working application.

import org.eclipse.swt.SWT;
import org.eclipse.swt.layout.GridData;
import org.eclipse.swt.layout.GridLayout;
import org.eclipse.swt.widgets.Button;
import org.eclipse.swt.widgets.Display;
import org.eclipse.swt.widgets.Label;
import org.eclipse.swt.widgets.Shell;
import org.eclipse.swt.widgets.Text;

public class Test {

 private static void addWidgetsToShell(Display display, Shell shell) {

  GridLayout gridLayout = new GridLayout();
  gridLayout.numColumns = 2;
  shell.setLayout(gridLayout);

  Label label1 = new Label(shell, SWT.NONE);
  label1.setText("Name:");
  Text text1 = new Text(shell, SWT.BORDER);

  Label label2 = new Label(shell, SWT.NONE);
  label2.setText("Age:");
  Text text2 = new Text(shell, SWT.BORDER);

  Label label3 = new Label(shell, SWT.NONE);
  label3.setText("Gender:");
  Text text3 = new Text(shell, SWT.BORDER);

  Button button = new Button(shell, SWT.CHECK);
  button.setText("Have you been employed in the past six months?");

  GridData gridData1 = new GridData();
  GridData gridData2 = new GridData();
  GridData gridData3 = new GridData();

  gridData1.widthHint = 60;
  gridData2.widthHint = 60;
  gridData3.widthHint = 60;

  label1.setLayoutData(gridData1);
  label2.setLayoutData(gridData2);
  label3.setLayoutData(gridData3);

  GridData gridData4 = new GridData(GridData.FILL_HORIZONTAL);
  GridData gridData5 = new GridData(GridData.FILL_HORIZONTAL);
  GridData gridData6 = new GridData(GridData.FILL_HORIZONTAL);

  text1.setLayoutData(gridData4);
  text2.setLayoutData(gridData5);
  text3.setLayoutData(gridData6);

  GridData gridData7 = new GridData();
  gridData7.horizontalSpan = 2;
  button.setLayoutData(gridData7);

  shell.open();

 }

 public static void main(String[] args) {

  /* Instantiate Display object, it represents SWT session */
  Display display = new Display();

  /*
   * Define Shell, it represent a window, You can add more than one shell
   * to Display
   */
  Shell shell = new Shell(display);
  shell.setSize(700, 200);
  shell.setText("GridLayout Demo");
  addWidgetsToShell(display, shell);

  /*
   * Run the event dispatching loop until an exit condition occurs, which
   * is typically when the main shell window is closed by the user.
   */

  while (!shell.isDisposed()) {
   if (!display.readAndDispatch()) {
    display.sleep();
   }
  }

  /* Dispose the display */
  display.dispose();

 }
}

Run above application, you can able to see following screen.

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