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How to write Java Swing GUI in XML

1: How to write Java Swing GUI in XML

The remarkable points of Java Swing GUI are:

• Java Swing GUI has the tree structure, i.e. the higher level component has the lower level components as its child components. For example, JFrame has JPanel as its child component. And JButton can be placed on this JPanel.
• Each component has a set of the attributes, such as the size, the alignment, the font, the background color and so on.

• [xml_panel_1_3.dtd]

1.1: How to represent the tree-structure

1.1.1: The root element of the tree-structure

To represent the tree-structure of Java Swing GUI, the root element must always be the same kind of Java component.
Because JPanel can be placed on JFrame or JDialog, JPanel is always the root element of XML.

1.1.2: Intermediate-level container classes

As a child component, any Java components can be placed on the root element (JPanel). JButton, JLable or JTextField is the typical child component. But, 'intermediate-level' container (such as JTabbedPane or JScrollPane) is also the child component in the XML. Moreover, another JPanel can be the child component of the root JPanel. In this case, we can think of the child JPanel as 'intermediate-level' container class.
Each 'intermediate-level' container class has the rule about its child component. The tables below show them:

1.1.3: JToolBar and its children

JToolBar is the special kind of 'intermediate-level' container class, because its child component is 'Action' object. 'Action' object appears as JButton on JToolBar, but it can also be JMenuItem on JMenu. Because the pair of JButton and JMenuItem comes from the same 'Action' object, they can be activated/disabled at the same time. This is very useful in many cases. In the subsequent section, I'll describe how to play with 'Action' object.

1.2: What attributes can be set on each components

1.2.1: Layout, Size, Border, Insets and Dimension

Let's look at the quote from the DTD:

   <!ENTITY % panel.mdl
      "layout?,size?,border?,toolbar?,panel.child*">

   <!ENTITY % tab.pane.mdl
      "size?,border?,tab.pane.child+">

   <!ENTITY % component.mdl
      "size?,border?">

The following subsections describes about each attributes.

1.2.1.1: Layout

Layout must be one of:

• FlowLayout
• BoxLayout
• GridLayout
• BorderLayout

FlowLayout

We must specify how components are aligned by one of the following constants:
CENTER LEADING LEFT RIGHT TRAILING

BoxLayout

We must specify the direction of placing the components. It is assigned by:
X_AXIS Y_AXIS

GridLayout

We must specify the number of columns and the number of rows. We can also specify the gap between each component by the horizontal gap and the vertical gap.

BorderLayout

We can specify the gap between each component by the horizontal gap and the vertical gap.

1.2.1.2: Size

Any of three kind of sizes can be set as the Size. They are:

• Preferred size
• Maximum size
• Minimum size

1.2.1.3: Border

Border must be one of:

• RAISED
• LOWERED
• ETCHED
• TITLED

1.2.1.4: Insets

Insets attribute specifies how far form the edge lines of the component. This means the 4 integer must be specified for this attribute: they are TOP, BOTTOM, LEFT and RIGHT.

1.2.1.5: Dimension

Dimension attribute consists of the width and the height. We must specify the integers for both of them.

1.2.2: Other attributes

The attributes other than Layout, Size, Border, Insets and Dimension are well-known, because they are the 'Java-Beans properties'. You can easily guess what they mean.
The table below lists the available attributes for each component:

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