Question

所以我有这个任务，但是当鼠标指针位于圆圈内部及其外部时，我还没有显示消息。这是我教科书中的问题。

（几何形状：在圆圈内？）编写一个程序，以半径50绘制以（100,60）为中心的固定圆。无论何时移动鼠标，都会显示一条消息，指示鼠标点是否在圆圈内。鼠标点或其外部，如图15.27a所示

到目前为止，这是我的代码：我没有得到任何“内圈”或“外圈”消息，半径不是50.任何输入都将非常感谢。

 import javax.swing.JFrame;
import javax.swing.JPanel;

import java.awt.*;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.awt.event.MouseMotionAdapter;
import java.awt.event.MouseMotionListener;
import java.awt.geom.Ellipse2D;

import javax.swing.*;



public class GeometryInsideACircle extends JFrame {

    private CirclePanel canvas = new CirclePanel();

    public GeometryInsideACircle() {

        JPanel panel = new JPanel();
        //JLabel label = new JLabel();
        //add(label);
        this.add(canvas , BorderLayout.CENTER);
        //addMouseListener(this);
        //this.add(panel, BorderLayout.SOUTH);


        }

    public class MouseInfo extends JPanel {
        //This is utilized to obtain the circle class because circle would have width = to its height
        Ellipse2D.Double circle = new Ellipse2D.Double(100, 60, 50, 50);//circle centered at (100, 60) radius 50

        Point p = new Point();//this will get the location of x and y

        private boolean isInCircle = false;//set to false until pointer enters the circle
        //this constructor will obtain all mouse and circle info utilizing MouseMotionListener and MouseMotionAdapter 
        public MouseInfo() {

            addMouseMotionListener(new MouseMotionAdapter() {
                public void mouseMoved(MouseEvent e) {

                    if(circle.contains(e.getPoint())) {
                        isInCircle = true;
                    }
                    else {
                        isInCircle = false;
                    }

                    p = e.getPoint();//this should obtain the x and y coordinates based upon mouse activity
                    repaint();//this will repaint the pointers locations
                }
            });
        }
        //this will create/draw a circle
        @Override
        protected void paintComponent(Graphics g) {

            super.paintComponent(g);
            Graphics2D g2 = (Graphics2D) g;
            g2.draw(circle);

            if(isInCircle) {//this should let the user know if mouse pointer is in the circle based upon x and y coordinates
                g.drawString("The mouse point is in the circle" + (int)p.getX() +"," + (int)p.getY(), (int)p.getX(), (int)p.getY() );
            }
            else {//this should let the user know if the mouse pointer is outside of the circle based upon x and y coordinates
                g.drawString("The mouse point is outside of the circle" + (int)p.getX() +"," + (int)p.getY(), (int)p.getX(), (int)p.getY() );
            }
        }

    }



    public static void main(String[] args) {

        GeometryInsideACircle frame = new GeometryInsideACircle();
        frame.setTitle("Exercise 16_19");
        frame.setLocationRelativeTo(null);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setSize(350, 350);
        frame.setVisible(true);


    }





}

Answer 1

通过简单的改变

public GeometryInsideACircle() {
    JPanel panel = new MouseInfo();
    add(panel, BorderLayout.CENTER);
}

它像宣传的那样工作。如果你阅读了Ellipse2D.Double的文档，你会发现你说的是高度和高度;不是半径。

鼠标内外圆圈事件java

1 个答案: