JSlider -- 需要建议

问题描述

Java 中的 JSlider 有问题我画了一个圆 A，我想把另一个圆 B 放在第一个圆 A 里面.我想把第二个圆 B 的 CENTER 放在与中心相同的坐标上第一个圆A的，然后我想用JSlider来增加或减少圆B的半径. 问题是，当你增加或减少滑块时，圆B的中心不会与A的中心对齐.基本上，我想要两个中心相同的圆圈.有人可以指出我的错误吗?

I have a problem with JSlider in Java I have drawn a circle A, and I want to put ANOTHER circle B inside the first circle A. I want to place the CENTRE of the second circle B at the same coordinate with the centre of the first circle A, and then I want to use JSlider to INCREASE or DECREASE the radius of circle B. The trouble is, when you increase or decrease the slider, the CENTRE of circle B does not stay aligned with the centre of A. Basically, I want two circles with the SAME centre. Can someone point out my mistake, please?

    slider1 = new JSlider(JSlider.HORIZONTAL,10,100,10);
    window.add(slider1);
    slider1.addChangeListener(this);

    Graphics paper = panel.getGraphics();
    int slider1Value = slider1.getValue();
    paper.setColor(Color.white);
    paper.fillRect(0, 0, 500, 500);

    paper.setColor(Color.pink);
    paper.fillOval(20,20,100,100);   // this is circle A

    paper.drawOval(60,60,slider1Value,slider1Value);  // this is circle B slider

推荐答案

因为你必须改变圆圈左上角的位置.如果你改变半径，圆圈会更大/更小，所以很明显，如果你不改变左上角的位置，两个圆圈的中心不会对齐

Because you have to change position of top-left "corner" of circle. If you change radius, the circle is bigger/smaller so it's obvious if you don't change position of top-left cornet, centers of 2 circles won't be aligned

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