Swing Hacks

Code Models That Don’t Block #93

Chapter 12, Miscellany

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469

HACK

In this case, all the loading is done in a

run( )

method, so the constructor

simply creates a

Thread

called

readThread

to wrap the

run( )

, starts the thread,

and then returns, freeing up the event-dispatch thread almost immediately.

So, now it’s up to

readThread to read the stream and load its contents into

the

Document. As in the blocking version (Example 12-9), it reads bytes into a

buffer, but instead of building a big

StringBuffer with which to do a mass-

insert, it uses

Document’s insertString( ) method to put each bufferful into

the document. Since

insertString( ) will cause the model to fire off events,

this will provide for a constant updating of the view; that’s why this version

calls

insertString( ) each time through the loop instead of once at the bot-

tom, as the blocking version did. However,

insertString( ) is a Swing

method, meaning it’s thread-unsafe, so you can’t call it directly from the

readThread. Instead, you set up a worker and use SwingUtilities.

invokeLater( )

to put the insertString( ) call, and only that call, back onto

the event-dispatch thread.

Running the Code

If you have a fast Internet connection, it is possible that you’ll load the data

so fast that you don’t mind the blocking or you can’t see the incremental

updating of the non-blocking version. To make this more dramatic, increase

the time that each model

sleep( )s, ...