Layout Managers were an huge benefit for Java Swing. They enabled software developers to program layout rather than to “drag and drop” it with some proprietary GUI builder. That’s nothing against a good GUI builder, but against the “source code” that gets generated as a result of using it. But after some time of playing and working with the layout managers given by Swing itself, we concluded that they weren’t up to the task. Since then, we were constantly on the lookout for new and better ways to tackle the layouting task.
A history of layout managers
Let’s reiterate our major path with different layout managers:
- GridBagLayout – the most versatile layout manager included in the Java Swing core classes. It’s capable to handle virtually every layouting task, but the price is huge constraint setup code. Since the code bloats with even facile complexity in the dialog, it’s not maintainable once written. The advantages over GUI builders aren’t really present.
- StringGridBagLayout – has the same power as GridBagLayout, but with much more concise constraint definitions. It uses a string based domain specific language that you have to learn. After a while, you begin to feel a clumsiness when inserting variables into the constraints.
- TableLayout – was a new approach to layouting by applying a global grid to your panel. You define the grid by specifying row and column constraints. If you need special cell constraints afterwards, you can alter them, but it’s getting bloated again.
- StringTableLayout – provided a string based domain specific language over the TableLayout. It had some nice additional features, but lacked versatility with dynamic GUIs.
- FormLayout – was a great relief and a good companion for many full sized layouting tasks. By concentrating on a problem domain (form based layouts), it played out some advantages over general purpose layout managers. This layout is still in use here.
- MigLayout – the bigger brother of all these layouts. MigLayout comes with several pages of cheat sheets and you’re soon lost without it. It combines the approaches of all layout managers listed (and many more) and blends them into a massively powerful and versatile product. If you learn this layout manager thoroughly, you’ll never have to look elsewhere. But the learning curve is steep and the complexity of your code scales with the complexity of the GUI (which isn’t a drawback).
All these layout managers added value to our GUIs and are in use until today, albeit seldom.
Keep it simple
Most of the time, your dialogs aren’t these super-fancy, highly dynamic full-page layouts every UI designer dreams about. If they are, pick one of the layout managers from the list and wade through the constraint setup. But let’s say you want to layout a rather plain dialog with some widgets, but you want to do it quick without sacrificing the looks. Here is a developer-friendly solution for this task: Use the DesignGridLayout manager.
Slick and easy layouts
The one thing that differentiates the DesignGridLayout from almost every other layout manager is that you use the layout manager instance itself (in a fluent interface style) to arrange the constraints of your grid. You do not add your widgets to the panel and hope for the layout manager to catch up with the layout, you add them to the layout manager (and hope for it to fill it into your panel, which it does nicely). Here is a little example of the API usage:
JPanel content = new JPanel(); DesignGridLayout layout = new DesignGridLayout(content); JTextArea history = new JTextArea(); history.setRows(5); JTextField message = new JTextField(); JButton sendNow = new JButton("Send"); layout.row().grid(new JLabel("History:")).add(new JScrollPane(history)); layout.row().grid(new JLabel("Message:")).add(message, 2).add(sendNow); content.setLayout(layout);
If you are interested in the possibilities of the layout manager, you should read the usage introduction page of DesignGridLayout.
One big advantage of the fluent API when compared with the string based constraint definitions is the compiler and type system support. You can’t spell anything wrong and the code completion feature of your IDE guides you to the right method and parameter order. The other advantage is that you don’t need to mess with pixel sizes for spacing and such. It’s handled by the layout manager in the most comfortable manner.
And because an article about a layout manager isn’t of any worth without a picture, here’s one: