如何在打开JFrame的Java Applet中创建一个按钮？

Question

I've made a few JFrames and I want to call them from a JApplet. What is the best way to do this? Could I just instantiate my JFrames in my init method and then call them whenever a button is pushed?

Answer 1

How do I make a button in a Java Applet that opens a JFrame?

You probably shouldn't do this, but rather if you want to open another window from the JApplet, create and show a JDialog. They are created and displayed similar to a JFrame, but uses different constructors. You will need to get the applet's Window for the "owner" parameter of the JDialog, and this can be obtained via:

Window w = (Window) SwingUtilities.getAncestorOfClass(Window.class, comp); 

Where comp is a visible component in the JApplet.

Answer 2

Ok, it sounds like you initialize a JFrame on initialization and you store it. You don't need to re-instantiate the JFrame from initalization. Instead just store it in a field of your Applet and use it when ever the button is pressed.

OR you can use Singletons and lazy initialization:

class JFrameToOpen extends JFrame {
    private static JFrame frame = null;
    private JFrameToOpen() {
        //init
    }
    public static GetJFrame() {
        if(frame==null) {
            frame=new JFrameToOpen();
        }
        return frame;
    }
}

But singletons are ugly and many people choose to avoid them.

Answer 3

You can just create JFrame with its default constructor and then show it:

JFrame frame = new JFrame();
JLabel label = new JLabel("Welcome");
frame.add(label);
frame.pack();
frame.setVisible(true);

This code forks from the applet similar way as from the standalone program. No need for any special tricks. The applet itself then can only contain buttons like "press to launch the application".