Setting the Initial Focused Component in a Window : Window Event « Swing Event « Java Tutorial

1. Java Tutorial
2. Swing Event
3. Window Event

import java.awt.Component;
import java.awt.FlowLayout;
import java.awt.Window;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;

import javax.swing.JButton;
import javax.swing.JFrame;

public class Main {
  public static void main(String[] argv) throws Exception {
    JFrame frame = new JFrame();
    JButton component1 = new JButton("1");
    JButton component2 = new JButton("2");
    JButton component3 = new JButton("3");

    frame.setLayout(new FlowLayout());
    frame.add(component1);
    frame.add(component2);
    frame.add(component3);

    InitialFocusSetter.setInitialFocus(frame, component2);

    frame.pack();
    frame.setVisible(true);
  }
}

class InitialFocusSetter {
  public static void setInitialFocus(Window w, Component c) {
    w.addWindowListener(new FocusSetter(c));
  }
}

class FocusSetter extends WindowAdapter {
  Component initComp;

  FocusSetter(Component c) {
    initComp = c;
  }

  public void windowOpened(WindowEvent e) {
    initComp.requestFocus();
    e.getWindow().removeWindowListener(this);
  }
}

15.41.Window Event
	15.41.1.	The event IDs for the WindowEvent class
	15.41.2.	Making a Window Handle its Own Events
	15.41.3.	The WindowListener Interface: events reflecting changes in the state of a window
	15.41.4.	Using WindowListener
	15.41.5.	Using Adapter Classes
	15.41.6.	Listens for window iconify and deiconify events, so that it can stop the animation when the window isn't visible.
	15.41.7.	WindowListener, WindowFocusListener, WindowStateListener
	15.41.8.	extends WindowAdapter
	15.41.9.	Handle a window closing event
	15.41.10.	Setting the Initial Focused Component in a Window
	15.41.11.	int java.awt.event.WindowEvent.WINDOW_OPENED