Adding Controls

Let's add three controls to the dialog: a label, a text-box and a button that will display a File Open Dialog when it is clicked. SWT controls are placed on the screen using one of the four layouts:

• FillLayout – lays out equal-sized controls in a single row or column
• RowLayout – lays out controls in a row or rows, with fill, wrap, and spacing options
• GridLayout – lays out controls in a grid
• FormLayout – lays out comtrols by creating attachments for each of their sides

We are going to use the GridLayout for our controls.

 GridLayout gridLayout = new GridLayout ();
 gridLayout.numColumns = 3;
 gridLayout.marginWidth=10;
 shell.setLayout (gridLayout);

Basically, the code says that we want three controls on each row with a margin of 10 pixels on each side of the row.

 final Label label1 = new Label(shell, SWT.NULL);
 label1.setText("File");
 final Text text1 = new Text(shell, SWT.BORDER);
 text1.setText("");
 Button button1 = new Button(shell,SWT.PUSH);
 button1.setText("Browse...");
 button1.setToolTipText("Locate file");

Now, the screen should look like this:

This a big step forward. We displayed controls on the dialog, and they have been given their default size.

However, we'd like the text box to be wider:

 GridData data = new GridData ();
 data.widthHint = 400;
 data.grabExcessHorizontalSpace = true;
 text1.setLayoutData (data);

A layout class in SWT may have a corresponding layout data class that contains layout data for a specific control. In this case, we created an instance of GridData class that specified the width of 400 pixels, and that a control should shrink if there is not enough space for it.

The screen looks like this now:

Right now, the Browse... button does not do anything useful when you click on it. Let's write code that will open a File Dialog and put the selected file name to the text box.

 button1.addSelectionListener(new SelectionAdapter() {
	public void widgetSelected(SelectionEvent e) {
		int style = SWT.NONE;
		FileDialog dialog = new FileDialog (shell, style);
		dialog.setText ("Find a File");
		String result = dialog.open();
		if(result!=null){
			text1.setText(result);
		}
	}
});

Check back for more later.

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