封裝類

package com.wb.applet;

import java.awt.Color;
import java.awt.TextField;
import java.awt.event.FocusEvent;
import java.awt.event.FocusListener;

/**
 * 默认文字提示功能
 * @author User
 *
 */
public class TextFieldHintListener implements FocusListener{
	
	private String hintText;
	private TextField textField;
	
	public TextFieldHintListener(TextField TextField,String hintText) {
		this.textField = TextField;
		this.hintText = hintText;
		TextField.setText(hintText);  //默认直接显示
		TextField.setForeground(Color.GRAY);
	}

	@Override
	public void focusGained(FocusEvent e) {
		//获取焦点时，清空提示内容
		String temp = textField.getText();
		if(temp.equals(hintText)) {
			textField.setText("");
			textField.setForeground(Color.BLACK);
		}
	}

	@Override
	public void focusLost(FocusEvent e) {
		//失去焦点时，没有输入内容，显示提示内容
		String temp = textField.getText();
		if(temp.equals("")) {
			textField.setForeground(Color.GRAY);
			textField.setText(hintText);
		}
	}

}

继承的是Frame

private TextField textField1 = new TextField(8);
textField1 .setBounds(630, 185, 150, 30);
textField1 .setFont(font);
textField1 .addFocusListener(new TextFieldHintListener(tf_color_card, "請輸入色卡"));
add(tf_color_card);