Java learn using SWT gridlayout and griddata

Question

I understand and can use FormLayout, FormData, FormAttachment but I can't understand how GridLayout, GridData is working. I want to learn using GridLayout and GridData because it's more like a table, it has a structure and doesn't depend on other widgets.

I was working as a web developer (front-end, back-end) and I got lost in Java "Grid" structure. How am I supposed to align, move widgets within a cell (horizontal/vertical Aling, hor./vert. Indent)? Like in HTML/CSS: margin, padding, etc. Ex: move a block from left by 100px. (margin-left: 100px), but in Java?

When I was working as a web developer, I created a page (here in Java it's view), I know how to organize parents and blocks. Can I compare a Composite to a div, like a block element like in HTML/CSS ?

I need to create the following app:

Am I need to use 4 composites?

Solution

The following article should shed some light on GridLayout for you:

Understanding Layouts in SWT

To achieve something like the form you have there, you would need something like this:

shell.setLayout(new GridLayout(3, false));

Label title = new Label(shell, SWT.NONE);
title.setText("My first text editor");
GridData data = new GridData(SWT.FILL, SWT.BEGINNING, true, false);
data.horizontalSpan = 3;
title.setLayoutData(data);

Label select = new Label(shell, SWT.NONE);
select.setText("Select a file:");
data = new GridData(SWT.FILL, SWT.BEGINNING, true, false);
select.setLayoutData(data);

Text text = new Text(shell, SWT.BORDER);
data = new GridData(SWT.FILL, SWT.BEGINNING, true, false);
text.setLayoutData(data);

Button button = new Button(shell, SWT.PUSH);
button.setText("Browse...");
data = new GridData(SWT.FILL, SWT.BEGINNING, true, false);
button.setLayoutData(data);

List result = new List(shell, SWT.BORDER);
data = new GridData(SWT.FILL, SWT.FILL, true, true);
data.horizontalSpan = 3;
result.setLayoutData(data);    

The GridData us used to define the behavior of the component within the layout. You can define vertical/horizontal alignment, margins and so on. horizontalSpan is used to tell the layout how many columns the widget will cover.