Java 按钮不起作用

Question

按钮正在触发事件，但未显示。它创建新的圆圈，但不绘制新的圆圈。有什么我没做的事吗？ (第一个 Java 小程序)。这可能是我错过的一些愚蠢的东西..

import java.applet.*;


    public class CircleApp extends Applet {

        public circle[] circles;
        public Button regen;

        public CircleApp(){
        }

        public void init()
        {
            this.setSize(400, 400);
            genCircles(getWidth(), getHeight());
            regen = new Button("New Circles");
            add(regen);
        }

        public boolean action(Event e, Object args)
        {
            genCircles(getWidth(), getHeight());
            return true;
        }

        public void genCircles(int wid, int hei)
        {
            circles = new circle[20];
            Random gen = new Random();
            for (int i = 0; i < 20; i++)
            {
                int x = gen.nextInt(wid);
                int y = gen.nextInt(hei);
                int rx = Math.min(x, wid - x);
                int ry = Math.min(y, hei - y);
                int r = Math.min(rx, ry);

                circles[i] = new circle(new Point(x, y), gen.nextInt(r));
            }

            for (int i = 0; i < 20; i++)
            {
                for (int j = i; j < 20; j++)
                {
                    if (circles[i].intersects(circles[j]))
                    {
                        circles[i].intersects = true;
                        break;
                    }
                }
            }
        }

        public void paint(Graphics g)
        {
            for (int i = 0; i < 20; i++)
            {
                g.setColor((circles[i].intersects) ? Color.blue : Color.magenta);
                g.drawOval(circles[i].location.x,
                        circles[i].location.y,
                        circles[i].radius,
                        circles[i].radius);
            }
        }
    }

import java.awt.Point;


public class circle {
    public Point location;
    public int radius;
    public boolean intersects;

    public circle(Point h, int radius)
    {
        this.location = h;
        this.radius = radius;
    }
    public circle()
    {
        this(new Point(0, 0), 1);
    }
    public boolean intersects(circle other)
    {
        return (this.location.distance(other.location) <
                (double)(this.radius + other.radius));
    }
}

感谢您的帮助!!

Answer 1

您需要调用repaint()生成新圆圈后重新绘制它们。

另外，与您的问题没有直接关系，但是action()已弃用 - 使用 action listener而是在按钮上。