import javax.swing.*; 
import java.awt.*; 
import java.awt.event.MouseAdapter; 
import java.awt.event.MouseWheelEvent; 
import java.awt.event.MouseWheelListener; 
 
public class jtaWheel { 
  JFrame jf; 
  JTextArea jta; 
  JScrollPane jsp; 
  MouseWheelListener sysWheel; 
  public jtaWheel(){ 
    jf = new JFrame("滾動縮放"); 
    jf.setBounds(500,500,600,400); 
    jta = new JTextArea(); 
    jsp = new JScrollPane(jta,JScrollPane.VERTICAL_SCROLLBAR_AS_NEEDED, 
        JScrollPane.HORIZONTAL_SCROLLBAR_AS_NEEDED); 
    sysWheel = jsp.getMouseWheelListeners()[0];//得到系統(tǒng)滾動事件 
    jsp.removeMouseWheelListener(sysWheel);//移除系統(tǒng)滾動，需要時添加 
    jsp.addMouseWheelListener(new event()); 
    jf.add(jsp); 
    jf.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); 
    jf.setVisible(true); 
  } 
  private class event extends MouseAdapter{ 
    @Override 
    public void mouseWheelMoved(MouseWheelEvent e){ 
      if(e.isControlDown()){//當ctrl鍵被按下，滾動為放大縮小 
        Font f = jta.getFont(); 
        if(e.getWheelRotation()<0){//如果滾動條向前就放大文本 
          jta.setFont(new Font(f.getFamily(),f.getStyle(),f.getSize()+1)); 
        }else if(e.getWheelRotation()>0){//滾動條向后就縮小文本 
          jta.setFont(new Font(f.getFamily(),f.getStyle(),f.getSize()-1)); 
        } 
      }else{//當ctrl沒有被按下，則為系統(tǒng)滾動 
        jsp.addMouseWheelListener(sysWheel); 
        sysWheel.mouseWheelMoved(e);//觸發(fā)系統(tǒng)滾動事件。 
        jsp.removeMouseWheelListener(sysWheel); 
      } 
    } 
  } 
  public static void main(String[] args){ 
    new jtaWheel(); 
  } 
}