java focus_在java中擷取具有Focus的Component

另一種方法是編寫自己的TextFieldUI來實作監聽器。然而，工廠方法更優雅。

例：

import java.awt.Color;

import java.awt.EventQueue;

import java.awt.FlowLayout;

import java.awt.event.FocusEvent;

import java.awt.event.FocusListener;

import javax.swing.JComponent;

import javax.swing.JFrame;

import javax.swing.JTextField;

import javax.swing.UIManager;

import javax.swing.plaf.ComponentUI;

import javax.swing.plaf.metal.MetalTextFieldUI;

public class CustomUI extends JFrame {

public static void main(String[] args) {

EventQueue.invokeLater(new Runnable() {

public void run() {

UIManager.getDefaults().put("TextFieldUI", CustomTextFieldUI.class.getName());

new CustomUI().setVisible(true);

}

});

}

public CustomUI() {

setDefaultCloseOperation(DISPOSE_ON_CLOSE);

setLayout(new FlowLayout());

add(new JTextField(10));

add(new JTextField(10));

pack();

}

public static class CustomTextFieldUI extends MetalTextFieldUI implements FocusListener {

public static ComponentUI createUI(JComponent c) {

return new CustomTextFieldUI();

}

@Override

public void installUI(JComponent c) {

super.installUI(c);

c.addFocusListener(this);

}

public void focusGained(FocusEvent e) {

getComponent().setBackground(Color.YELLOW.brighter());

}

public void focusLost(FocusEvent e) {

getComponent().setBackground(UIManager.getColor("TextField.background"));

}

}

}