Question

我正在尝试编写一个程序，允许用户每次在框架内单击时绘制一条线来绘制多边形。在第一次单击时，应绘制一个小方块。每次点击后，都应该从最后一行的终点到用户点击的位置绘制一条线。一旦用户在最初制作的正方形内点击，多边形将完成，正方形将消失。我的代码如下;它运行但它无法正常运行。

import java.awt.Rectangle;
import java.awt.event.ActionListener;
import java.awt.event.MouseEvent;    
import java.awt.event.MouseListener;
import java.awt.geom.Point2D;
import java.awt.geom.Point2D.Double;
import java.util.ArrayList;
import javax.swing.JFrame;

public class DrawPolygonComponent {

public static void main(String[] args) {
    final JFrame frame = new JFrame();
    frame.setSize(300, 400);
    frame.setTitle("Draw a Polygon");
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    final ArrayList<Point2D.Double> path = new ArrayList();

    //addRectangle(frame, 10, 10);
    //

    class ClickListener implements MouseListener {
        @Override
        public void mouseClicked(MouseEvent me) {
            if (path.isEmpty()) {
                System.out.println("First");
                addRectangle(frame, me.getX(),me.getY());
                path.add(new Point2D.Double(me.getX(),me.getY()));
            } else {
                System.out.println("Second");
                Point2D.Double prev = path.get(path.size()-1);
                addLine(frame, (int) prev.x, (int) prev.y,me.getX(),me.getY());
                path.add(new Point2D.Double(me.getX(),me.getY()));


                frame.repaint();
            }

        }

        public void mousePressed(MouseEvent me) {}
        public void mouseReleased(MouseEvent me) {}
        public void mouseEntered(MouseEvent me) {}
        public void mouseExited(MouseEvent me) {}
    }
    MouseListener listener = new ClickListener();
    frame.addMouseListener (listener);
    frame.setVisible (true);

}
public static void addRectangle(JFrame frame, int x , int y) {
    RectangleComponent r = new RectangleComponent(x, y, 10, 10);
    frame.add(r);
}
public static void addLine(JFrame frame, int x1, int y1, int x2, int y2) {
    LineComponent line = new LineComponent(x1, y1, x2, y2);
    frame.add(line);
}

}

/////////other

import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Rectangle;
import javax.swing.JComponent;

public class LineComponent extends JComponent {
private int px;
private int py;
private int x;
private int y;

public LineComponent(int px, int py, int x, int y){
  this.px=px;
  this.py=py;
this.x=x;
this.y=y;
}

@Override
public void paintComponent(Graphics g){
Graphics2D g2 = (Graphics2D)g;
g2.drawLine(px,py,x,y);
}

}


 ////////other
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Rectangle;
import javax.swing.JComponent;

public class RectangleComponent extends JComponent {
private Rectangle box;

public RectangleComponent(int x,int y, int l, int w){
box = new Rectangle(x,y,l,w);
}

public void paintComponent(Graphics g){
Graphics2D g2 = (Graphics2D)g;
g2.fill(box);
g2.draw(box);
}


}

Answer 1

您已将鼠标侦听器附加到框架上，但未提供框架绘制路径的任何方法......
您已设置为“明显”绘制多边形的组件尚未添加到框架中。

相反。

使用JPanel之类的内容创建自定义组件。将鼠标侦听器附加到此组件。覆盖它的paintComponent方法。当鼠标事件发生时（应生成新行），请调用repaint以请求更新组件。

在paintComponent方法中，重新绘制所有行。

查看Java Applet Polygon array和How can I draw a polygon using path2d and see if a point is within it's area?以及drawPolygon keeps drawing lines from starting (mousePressed) location to current (mouseDragged) location了解一些概念

Ps 您可能还想查看Performing Custom Painting

根据点击绘制多边形

1 个答案: