Java Tips Weblog

There may be times when you want to capture output from your program and display it for the user. This is generally done by creating a console. Using Swing it is not too difficult to create a simple console using a JTextArea or JTextPane. Our message console will be able to display output written to System.out and System.err.
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There may be times when you want to temporarily disable your frame. The easiest way to do this is to simply use setEnabled(false) on the frame. There are two things I don’t really like using this approach:

• there is no visual indication the frame is disabled
• the frame beeps at you when you click on it

Maybe you also require a different solution?
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A layout manager has two main functions:

• determine the preferred size of the container
• layout the components in the container based on the layout rules

The FlowLayout is a strange animal. It does both of these functions. The preferred size of the container assumes all components will be laid out in a single row. The layout code will wrap components to the next row when the maximum width of the container is encountered. However, the problem is that the functions don’t talk to one another. When the components are wrapped to a new row, the preferred size doesn’t change so you never see the components on the extra row.
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A JTable is usually displayed in a JScrollPane. This allows the table to scroll vertically or horizontally as required. Horizontal scrolling causes all columns in the table to be scrolled. In some cases you may want to prevent the leading column(s) in the table from scrolling.
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The default Tab Action in a JTable causes focus to move to the next cell. When the end of line is reached focus move to the first cell of the next line. When the end of the table is reached focus moves to the top of the table. There may be times when you want to change this default behaviour.
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Swing components use Actions to provide basic functionality for the component. Of course these Actions can never provide all the functionality you desire and there may be times when you need to customize the default behaviour of an Action.
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Layout managers are a great feature of Java. I am not a big fan of layout managers that use multiple constraints to achieve a layout. This entry will propose a simple layout manager that will use a single constraint, yet provide flexibility. It was designed around the notion that you want a container that will use all the space available to it. As a component is added to the container you specify the relative amount of space that component requires. You could divide your container 50/50, or like most cars today you could provide a 60/40 split.
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