Question

我在这个java代码中遇到了问题。我想做一个画家程序，但每当我选择一个形状并绘制它之前绘制的所有形状都与此形状相同。这是代码。我知道问题来自paintComponent中的for语句，但是我可以用什么替换它？

class inner extends JPanel implements MouseListener,MouseMotionListener{
        private int oldx,oldy,newx,newy;
        private Point point1,point2;
        private Shape newRec,line1;
        Rectangle currRec;
        private Vector shape;
        private boolean status,status1;
        private int count=0;
        private Object line;
        inner(){
            point1=point2=new Point(0,0);
            shape = new Vector();
            addMouseListener(this);
            addMouseMotionListener(this);
        }

        public void mouseDragged(MouseEvent event) {

            point2=event.getPoint();
            newx = point2.x;
            newy = point2.y;
            if(Universal==7){
            line = new Object(oldx,oldy,newx,newy);
            status = true;
            repaint();
            }


            currRec = new Rectangle(Math.min(point1.x,point2.x),Math.min(point1.y,point2.y),Math.abs(point1.x-point2.x),Math.abs(point1.y-point2.y));   
            status = true;
            repaint();

        }

        @Override
        public void mouseMoved(MouseEvent arg0) {}
        public void mouseClicked(MouseEvent arg0) {}                
        public void mouseEntered(MouseEvent arg0) {}
        @Override
        public void mouseExited(MouseEvent arg0) {}


        public void mousePressed(MouseEvent event) {

            point1=event.getPoint();
            oldx=event.getX();
            oldy=event.getY();
        }

        @Override
        public void mouseReleased(MouseEvent event) {

            point2=event.getPoint();
            newx=event.getX();
            newy=event.getY();
            //count++;


        if(Universal==7){
                line1 = new Shape(point1.x,point1.y,point2.x,point2.y);
                shape.add(line1);
                //Graphics g = getGraphics();
                //g.setColor(colour);
                //g.drawLine(point1.x,point1.y,point2.x,point2.y);

                count++;
                repaint();
            }
        else if(Universal==1||Universal==2||Universal==3||Universal==4||Universal==5||Universal==6){
                newRec = new Shape(Math.min(point1.x,point2.x),Math.min(point1.y,point2.y),Math.abs(point1.x-point2.x),Math.abs(point1.y-point2.y));
                shape.add(newRec);
                count++;
                repaint();  
            }
        }

    ///// the problem is in here    
        public void paintComponent(Graphics g){
            super.paintComponent(g);
            Shape c;
            g.setColor(colour);
            for(int i=0;i<shape.size();i++){
                c = (Shape) shape.get(i);

            if(Universal==1){

                g.drawRect(c.x, c.y, c.w, c.h);
                if(status){
                    g.drawRect(currRec.x, currRec.y, currRec.width, currRec.height);
                }
            }

            if(Universal==2){
                g.fillRect(c.x, c.y, c.w, c.h);

                if(status){
                    g.fillRect(currRec.x, currRec.y, currRec.width, currRec.height);

                }
            }

            if(Universal==3){
                g.drawRoundRect(c.x, c.y, c.w, c.h, c.w/4, c.h/4);

                if(status){
                    g.drawRoundRect(currRec.x, currRec.y, currRec.width, currRec.height,currRec.width/4,currRec.height/4);

                }
            }

            if(Universal==4){
                g.fillRoundRect(c.x, c.y, c.w, c.h, c.w/4, c.h/4);

                if(status){
                    g.fillRoundRect(currRec.x, currRec.y, currRec.width, currRec.height,currRec.width/4,currRec.height/4);

                }
            }

                if(Universal==5){

                    g.drawOval(c.x, c.y, c.w, c.h);

                    if(status){
                        g.drawOval(currRec.x, currRec.y, currRec.width, currRec.height);
                    }
                }

                if(Universal==6){

                    g.fillOval(c.x, c.y, c.w, c.h);

                    if(status){
                        g.fillOval(currRec.x, currRec.y, currRec.width, currRec.height);
                    }
                }

                if(Universal==7){

                    g.drawLine(c.x, c.y, c.w, c.h);

                    if(status){
                        g.drawLine(line1.x, line1.y, line1.w,line1.h);
                    }
                }

                if(Universal==8){
                    shape.clear();
                }
            }
        }

Answer 1

Universal在任何特定时间都只是一个给定的值。

油漆不是累积的，它们具有破坏性。

也就是说，每次调用paintComponent时，所有先前的内容都会被删除/擦除，并且您需要“重新绘制”内容。

您应该将Shape添加到某种List，而不是依赖于单个标记，并在调用paintComponent时重新绘制它们。同样，您只需将“类型”（int）添加到List并在每次重绘时处理该列表

请查看Painting in AWT in Swing以获取有关绘画过程的说明

Answer 2

有两种不同的方法，请参阅Custom Painting Approaches：

向List添加形状，然后每次调用paintComponent（）时重新绘制列表中的所有Shapes。
将形状绘制到BufferedImage，然后在调用paintComponent（）时重新绘制图像。

这两个例子都没有完全符合您的要求，它只向您展示方法。

Java画家程序绘图形状

2 个答案: