在java中使用鼠标在画布上绘制线而不使用Swing

Question

我的问题与这个问题类似

Drawing lines with mouse on canvas : Java awt

我的问题是，当窗口最小化和最大化时，绘制的线条每次都消失了

但我的工作方式完全不同，因为我只使用awt组件，没有使用swing

import java.awt.*;
import java.awt.event.*;
class Drawing extends WindowAdapter implements MouseMotionListener, MouseListener, ComponentListener {

    Frame f;
    Canvas c;
    int X=400,Y=400;
    int px=-1,py=-1;
    int x,y;

    public Drawing() {
        f=new Frame("Drawing - Canvas");
        f.addWindowListener(this);
        f.addComponentListener(this);
        f.setSize(X,Y);
        c=new Canvas();
        f.add(c);
        c.addMouseMotionListener(this);
        c.addMouseListener(this);
        f.setVisible(true);
    }

    public void componentResized(ComponentEvent e) {}
    public void componentHidden(ComponentEvent e) {}
    public void componentMoved(ComponentEvent e) {}
    public void componentShown(ComponentEvent e) {}

    public void mouseMoved(MouseEvent e) {}
    public void mouseClicked(MouseEvent e) {}
    public void mouseEntered(MouseEvent e) {}
    public void mousePressed(MouseEvent e) {}
    public void mouseExited(MouseEvent e) {}

    public void mouseDragged(MouseEvent e) {
        int x,y;
        x=e.getX();
        y=e.getY();
        Graphics g=c.getGraphics();

        if(px!=-1) {    
            g.drawLine(px,py,x,y);
        }
        else {
            g.drawLine(x,y,x,y);
        }

        px=x;
        py=y;
    }

    public void mouseReleased(MouseEvent e) {
        this.X=400; this.Y=400;
        this.px=-1; this.py=-1;
    }

    public void windowClosing(WindowEvent e) {
        f.dispose();
    }

    public static void main(String[] args) {
      Drawing c=new Drawing();
    }   
}

Can someone help me out on these problems ?

Answer 1

getGraphics从来不是执行自定义绘制的写入方式

从通读Painting in AWT and Swing和Performing Custom Painting开始，更好地理解绘画是如何工作的，以及你应该如何使用它

简单的答案是，您需要维护已绘制内容的模型，以便在每次绘制过程中可以重新绘制

例如Resize the panel without revalidation、Draw trail of circles with mouseDragged、Why is my line not drawing?