Swing FocusListener接口
接口focusListener的用於接收鍵盤焦點事件。過程焦點事件的類需要實現這個接口。
類聲明
以下是聲明 java.awt.event.FocusListener接口：
public interface FocusListener extends EventListener
接口方法
S.N.
方法 & 描述
1
void focusGained(FocusEvent e)
Invoked when a component gains the keyboard focus.
2
void focusLost(FocusEvent e)
Invoked when a component loses the keyboard focus.
方法繼承
這個類方法從下面的接口繼承：
- java.awt.event.EventListener
FocusListener 例子
選擇使用任何編輯器創建以下java程序在 D:/ > SWING > com > yiibai > gui >
SwingListenerDemo.java
package com.yiibai.gui; import java.awt.*; import java.awt.event.*; import javax.swing.*; public class SwingListenerDemo { private JFrame mainFrame; private JLabel headerLabel; private JLabel statusLabel; private JPanel controlPanel; public SwingListenerDemo(){ prepareGUI(); } public static void main(String[] args){ SwingListenerDemo swingListenerDemo = new SwingListenerDemo(); swingListenerDemo.showFocusListenerDemo(); } private void prepareGUI(){ mainFrame = new JFrame("Java SWING Examples"); mainFrame.setSize(400,400); mainFrame.setLayout(new GridLayout(3, 1)); headerLabel = new JLabel("",JLabel.CENTER ); statusLabel = new JLabel("",JLabel.CENTER); statusLabel.setSize(350,100); mainFrame.addWindowListener(new WindowAdapter() { public void windowClosing(WindowEvent windowEvent){ System.exit(0); } }); controlPanel = new JPanel(); controlPanel.setLayout(new FlowLayout()); mainFrame.add(headerLabel); mainFrame.add(controlPanel); mainFrame.add(statusLabel); mainFrame.setVisible(true); } private void showFocusListenerDemo(){ headerLabel.setText("Listener in action: FocusListener"); JButton okButton = new JButton("OK"); JButton cancelButton = new JButton("Cancel"); okButton.addFocusListener(new CustomFocusListener()); cancelButton.addFocusListener(new CustomFocusListener()); controlPanel.add(okButton); controlPanel.add(cancelButton); mainFrame.setVisible(true); } class CustomFocusListener implements FocusListener{ public void focusGained(FocusEvent e) { statusLabel.setText(statusLabel.getText() + e.getComponent().getClass().getSimpleName() + " gained focus. "); } public void focusLost(FocusEvent e) { statusLabel.setText(statusLabel.getText() + e.getComponent().getClass().getSimpleName() + " lost focus. "); } } }
編譯程序，使用命令提示符。到 D:/ > SWING 然後輸出以下命令。
D:SWING>javac comyiibaiguiSwingListenerDemo.java
如果沒有錯誤出現，這意味着編譯成功。使用下面的命令來運行程序。
D:SWING>java com.yiibai.gui.SwingListenerDemo
驗證下面的輸出
