JavaSE系列代码50：文本事件类TextEvent的应用

The string call method indexof (string s) retrieves the string s from the header of the current string and returns the location where the first occurrence of s occurs. If the string s is not retrieved, the value returned by the method is - 1. The indexof (string s, int startpoint) method is called to retrieve the string s from the starting point position of the current string, and return the position where s appears for the first time. If the string s is not retrieved, the value returned by the method is - 1. String calls the lastIndexOf (string s) method to retrieve the string s from the beginning of the current string’s header, and returns the location of the last s. If the string s is not retrieved, the value returned by the method is - 1.

import java.awt.*; 
import java.awt.event.*; 
public class Javase_50 extends Frame  //定义主类
{
  static TextArea ta1=new TextArea ("",6,10, TextArea.SCROLLBARS_NONE);
  static TextArea ta2=new TextArea ("",6,10, TextArea.SCROLLBARS_NONE);
  public static void main(String[] args)
  {
     Javase_50 frm=new Javase_50();    //调用构造方法
    frm.setTitle("文本事件处理TextEvent");
    frm.setSize(220,150);
    frm.setLayout(new FlowLayout(FlowLayout.CENTER)); 
    frm.setVisible(true);
  }
  public app13_5()   //构造方法
  {
    ta1.addTextListener(new MyTxListener());  
    add(ta1);
    add(ta2);
    ta2.setEditable(false);
  }
  class MyTxListener implements TextListener  //定义内部类实现TextListener接口
  {
    public void textValueChanged(TextEvent e)  //事件发生时的处理操作
    {
      String text=ta1.getText();   //获得ta1的内容
      ta2.setText(text);          //将ta1的内容放入到ta2中
    }
  }
}