Set text on jlabel on main form from Thread

Question

I have a java application in which I call threads for executing some stuff:

public class ThreadTest implements Runnable {
private final int functionNumber;
public static mainForm main = new mainForm();
private final int time2start;
public static YourClass obj  = new YourClass();
public ThreadTest(int functionNumber, int time2start, YourClass obj){
this.functionNumber = functionNumber;
this.time2start = time2start;

}
 @Override
public void run(){

try{Thread.sleep(time2start);}catch(Exception ex){}//Time Delay before executing methods
switch(functionNumber){
    case 1:
        obj.runFirst();
        break;
    case 2:
        obj.runSecond();
        main.appendText("Something");
        break;
    case 3:

{
    try {
        obj.runThird();
    } catch (IOException ex) {
        Logger.getLogger(ThreadTest.class.getName()).log(Level.SEVERE, null, ex);
    }
}
        break;

And this is method in my main form with swing gui on which i want to append text from thread:

 void appendText(String text){
  generalStatus.setText(text);
 }

How is this achieved? I am guessing i need to use repaint or something?

Answer 1

Update the GUI component (JLabel) from another thread except Swing thread can not be done directly. But you can use a synchronized thread with Swing thread using SwingUtilities.invokeLater. GUI components can be updated inside a thread like this,

void appendText(String text) {
    final String Text=text;
    SwingUtilities.invokeLater(new Runnable() {
        public void run() {
            generalStatus.setText(Text);
        }
    });
}

Whenever you want to update your GUI components in any other thread except Swing thread you should use this mechanism.