CODEWITHSUNDEEP
javaswing
user2256790
user2256790

Reputation: 111

How do I get an incremental display in java GUI program

I have a problem in moving from a java console to a GUI program.

My console program loads all the words from a dictionary. It then uses each word in turn to decrypt a cipher, displaying the deciphered text on the screen for the first word, then for the second word and so on.

When I write the GUI program, I have the command 

jTextArea.append(decipherment);

but nothing is displayed until the program has deciphered with every word and then all the decipherments are displayed together, rather than one by one as I want.

The structure of my GUI program includes a button with the code:

private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) {                                         
    decrypt();
}

and then there is a section:

public void decrypt(){
    ...
}

that contains the code to load the dictionary words, do the deciphering with each word and display each decipherment with the method call: jTextArea.append(decipherment);

But, as mentioned, the individual decipherments are not displayed. Rather the program runs to the end and then displays all the decipherments together.

After reading other threads I have the feeling that I am not writing the GUI program correctly but I haven’t found what my mistake is. Help would be appreciated.

Upvotes: 1

Views: 133

Answers (2)

camickr
camickr

Reputation: 324118

Read the section from the Swing tutorial on Concurrency to understand why the GUI is being blocked.

You can use a SwingWorker for your background Thread and then publish the results as you go so the GUI can be updated.

Upvotes: 4

martinez314
martinez314

Reputation: 12332

Your decrypting is most likely running in the same thread as your GUI and is locking it up. Try spawning a new thread to run your decryption, then update your GUI in the Swing thread.

Try something like this:

Thread workThread = new Thread(new Runnable() {  // run process in new thread
  public void run() {
    decrypt();
  }
});

workThread.start();

How to update your Swing thread:

EventQueue.invokeLater(new Runnable() {  // update Swing thread here
  public void run() {
    jTextArea.append(decipherment);
  }
});

Upvotes: 4

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