JApplet 和调用paint/paintComponent 的问题 [英] Trouble with JApplets and calling paint/paintComponent

问题描述

所以我只是在这里为期末考试做一些学习，但我无法让它发挥作用.我以前一直做的是调用paintComponent(Graphics g)事情进展顺利.但是现在我在编译时收到paintComponent has protected access in JComponent"错误.我可以让它编译的唯一方法是告诉它调用paint.但即使它编译，paint 也永远不会在小程序窗口中被调用.我在这里没有看到什么?

So I'm just doing some studying for finals here, and I'm having trouble getting this to work. What I have always done previously is call paintComponent(Graphics g) and things have worked just peachy. But now I'm getting a "paintComponent has protected access in JComponent" error when I go to compile. The only way I could get it to compile was to tell it to call paint. But even if it compiles, paint never gets called in the applet window. What am I not seeing here?

 public class LineDraw extends JComponent
 {
private final Point p1;
private final Point p2;
private final JApplet callingWindow;
private final ArrayList<Line2D.Double> lines;

public LineDraw(JApplet callingWindow)
{
    this.p1 = new Point();
    this.p2 = new Point();
    this.callingWindow = callingWindow;
    this.lines = new ArrayList<Line2D.Double>();
    MouseListener mouse = new MouseHandler();
    callingWindow.addMouseListener(mouse);
}

public class MouseHandler extends MouseAdapter
{
    private boolean firstClick;
    public MouseHandler()
    {
        firstClick = true;
    }
    public void mouseClicked(MouseEvent e)
    {
        if(firstClick)
        {
            p1.setLocation(e.getPoint());
            firstClick = false;
        }
        else    
        {
            p2.setLocation(e.getPoint());
            lines.add(new Line2D.Double(p1, p2));
            p2.setLocation(p1.getLocation());
            callingWindow.repaint();        
        }
    }

    public void paintComponent(Graphics2D g2)
    {
        for(Line2D.Double e: lines)
        {
            g2.draw(e);
        }
    }
}

}

和小程序类本身

    public class AppletWin extends JApplet
    {
private LineDraw lineDrawer;

public void init()
{
    setBackground(Color.white);
    lineDrawer = new LineDraw(this);
}

public void paint(Graphics h)
{
    Graphics2D g = (Graphics2D)h;
    //Clear background
    g.setColor(getBackground());
    g.fillRect(1, 1, getWidth(), getHeight());
    lineDrawer.paintComponent(g);  
}
    }

推荐答案

这段代码的问题是LineDraw中的paintComponent方法在内部类MouseHandler里面.

Problem with this code is that the paintComponent method in LineDraw is inside the inner class MouseHandler.

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