Question

这是代码：

import java.awt.*;
import java.awt.event.*;
import java.applet.*;
import java.util.Vector;


public class PainterNN extends Applet implements MouseListener, MouseMotionListener{

    class MyShape{
    int mx;
    int my;
    Color mc;

    MyShape(int x, int y, Color c){
        mx=x;
        my=y;
        mc=c;
        }

    void Render(Graphics g){
          g.setColor(mc);
        g.fillOval (mx,my,10,10);
        }
}


    Vector<MyShape> vec = new Vector();   


    public void init() {
        }

    public void paint(Graphics g) {
        for(int i =0; i < vec.size() ; i=i+1){

        MyShape s = vec.elementAt(i);
        s.Render(g);
        }
    }

    public void mouseEntered( MouseEvent e ) {
      // called when the pointer enters the applet's rectangular area
   }
           public void mouseExited( MouseEvent e ) {
      // called when the pointer leaves the applet's rectangular area
   }
           public void mouseClicked( MouseEvent e ) {
      // called after a press and release of a mouse button
      // with no motion in between
      // (If the user presses, drags, and then releases, there will be
      // no click event generated.)
   }
           public void mousePressed( MouseEvent e ) {  // called after a button is pressed down
      repaint();
      // "Consume" the event so it won't be processed in the
      // default manner by the source which generated it.
      e.consume();
   }
   public void mouseReleased( MouseEvent e ) {  // called after a button is released
       repaint();
      e.consume();
   }
   public void mouseMoved( MouseEvent e ) {  // called during motion when no buttons are down
      e.consume();
   }
   public void mouseDragged( MouseEvent e ) {  // called during motion with buttons down
     int mx = e.getX();
     int my = e.getY();

      vec.add(new MyShape(mx,my,new Color(0,255,0)));
      repaint();
      e.consume();
   }


}

它应该在鼠标拖动时绘制圆圈，但事实并非如此。为什么呢？

Answer 1

您必须添加鼠标侦听器。

public void init()
{
    this.addMouseListener(this);
    this.addMouseMotionListener(this);
}

提示：尝试在IDE中使用 Ctrl - Shift - F 。通常，它会美化您的代码。（Eclipse和NetBeans支持此功能）

Java applet不会在鼠标事件上绘制

1 个答案: