FocusListener 接口

介紹

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。

類的聲明

以下是聲明爲java.awt.event.FocusListener接口：

public interface FocusListener extends EventListener

接口中的方法

S.N.

方法＆說明

void focusGained(FocusEvent e)
Invoked when a component gains the keyboard focus.

void focusLost(FocusEvent e)
Invoked when a component loses the keyboard focus.

繼承的方法

這個類繼承的方法從下面的接口：

java.awt.event.EventListener

AdjustmentListener示例

選擇使用任何編輯器創建以下java程序 D:/ > AWT > com > yiibai > gui >

AwtListenerDemo

package com.yiibai.gui; import java.awt.*; import java.awt.event.*; public class AwtListenerDemo { private Frame mainFrame; private Label headerLabel; private Label statusLabel; private Panel controlPanel; public AwtListenerDemo(){ prepareGUI(); } public static void main(String[] args){ AwtListenerDemo awtListenerDemo = new AwtListenerDemo(); awtListenerDemo.showFocusListenerDemo(); } private void prepareGUI(){ mainFrame = new Frame("Java AWT Examples"); mainFrame.setSize(400,400); mainFrame.setLayout(new GridLayout(3, 1)); mainFrame.addWindowListener(new WindowAdapter() { public void windowClosing(WindowEvent windowEvent){ System.exit(0); } }); headerLabel = new Label(); headerLabel.setAlignment(Label.CENTER); statusLabel = new Label(); statusLabel.setAlignment(Label.CENTER); statusLabel.setSize(350,100); controlPanel = new Panel(); 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"); Button okButton = new Button("OK"); Button cancelButton = new Button("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。進入到D:/> AWT，然後鍵入以下命令。

D:AWT>javac comyiibaiguiAwtListenerDemo.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:AWT>java com.yiibai.gui.AwtListenerDemo

驗證下面的輸出