JTextField setText（）方法不更新Field

Question

I am attempting to update the JTextField text via the setText() method. However, when I attempt to do this, nothing appears to happen. I walked through with the debugger and determined this is indeed the case. payField is the JTextField instance I am using.

Here is the code:

public void payBill(double payment) {

    if((this.bill - payment) > 0)
        payField.setText("Bill not completely paid! You still owe " + "$" + (this.bill - payment));
    else {
        payField.setText("Thank you for choosing Team Turbo!");//Not updating!
        try {
            Thread.sleep(1500);
        } catch (InterruptedException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        payFrame.setVisible(false);
        System.exit(0);
    }


}

Visually, nothing happens after this method is called:

Any idea what is going on here? The entire GUI is ran inside a SwingUtilities.invokeLater thread, just for clarification.

Answer 1

This...

try {
    Thread.sleep(1500);
} catch (InterruptedException e) {
    // TODO Auto-generated catch block
    e.printStackTrace();
}
payFrame.setVisible(false);
System.exit(0);

is highly suspect.

Swing is a single threaded API. That is, any long running or blocking operation will prevent the UI from been updated.

In your case, I might recommend a Swing Timer instead, which will trigger a callback after a specified delay, without blocking the UI.

Start by taking a look at Concurrency in Swing and How to Use Swing Timers for more details