在Main中捕获所有异常代码不捕获事件异常

Question

Iam trying to put a "catch all" code to catch any exception that happens in my code so it can be sent to server. Basically, the code below is the code of my Main. This creates a Jframe with buttons. When I click on one of the buttons, I am causing a crash (dereference a null pointer). Howeever that exception is not being caught in the code below and instead is displayed in my consol.

public static void main(String args[]) {

        try {


        java.awt.EventQueue.invokeLater(new Runnable() {
            public void run() {

                    JFRAME_MAIN = new MainHomePage();
                    JFRAME_MAIN.setVisible(true);

            }
        });

        } catch (Exception ex) {

          System.out.println("Exception caught");   // <--- This is not being hit
        }

}

Any idea why or how to resolve this?

Thanks

PS: I didnt put the code of the class MainHomePage because it is big class that setup layout and add buttons with their action listeners. In one of these listeners, I have the crash happening

Answer 1

The exception is not caught because it is not thrown by the code inside your try-catch block. The button click is not handled by this code, it is handled by an ActionListener . The code in the listener is throwing the exception.

The invokeLater method simply adds a Runnable to the queue, the act of adding that Runnable is successful and does not therefore generate an exception. See this page .

Add a try-catch inside your listener code that handles your button click and you should be able to catch the exception - look for an actionPerformed method.

public void actionPerformed(ActionEvent e) {
    try{
        // your logic here
    }
    catch(Exception e){
        // do something to handle the exception here
    }
}

EDIT (responding to comment):

If you want to handle all uncaught exceptions in a single place you could do something like this:

Thread.setDefaultUncaughtExceptionHandler(new Thread.UncaughtExceptionHandler() {
    public void uncaughtException(Thread t, Throwable e) {
        System.out.println("Caught exception: "+e.getClass().getName());
        // do something else useful here
    }
});

You would place that code inside your main method.