Swing Hacks

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Chapter 12, Miscellany

#93 Code Models That Don’t Block

HACK

Models Aren’t Always Dumb

Adapt Example 12-8 to create AWTBlockModels.java. To illustrate the load-

ing, this hack has a

JProgressBar that you need to declare before the con-

structor, and which you add at the bottom of

initMainLayout( )

:

progressBar = new JProgressBar (0, 100);

getContentPane( ).add (progressBar, BorderLayout.SOUTH);

The strategy in this hack is to make the JTextArea’s model responsible for its

own threaded loading, so get rid of the

loadURL( ) method. That code will

move to the models, which subclass

javax.swing.text.PlainDocument. First,

change the actions to use these documents:

class BlockingLoadAction extends AbstractAction {

public void actionPerformed (ActionEvent e) {

BlockingURLDocument bud =

new BlockingURLDocument (urlField.getText( ));

progressBar.setEnabled (true);

progressBar.setValue (0);

contentArea.setDocument (bud);

progressBar.setValue (100);

}

}

class NonBlockingLoadAction extends AbstractAction {

public void actionPerformed (ActionEvent e) {

NonBlockingURLDocument nbud =

new NonBlockingURLDocument (urlField.getText( ));

contentArea.setDocument (nbud);

// makeProgressBarUpdaterFor (nbud);

}

}

The actions are pretty much the same, except for the fact that the blocking

version sets the

JProgressBar before and after setting the JTextArea’s docu-

ment. Why doesn’t the non-blocking action touch the progress ...