java - 如何在 JPanel 和 JFrame 范围内绘图？

Question

我有代码假设在 JPanel 内的随机位置绘制环，但由于某种原因，我的环有时会超出此范围，例如，它出现在下半切中。据我了解，我有 JPanel 位于 JFrame 内，为了在这个边界内绘制，我的环应该用这个表达式绘制:

xRing = (int)((frameWidth -ringSize)* (Math.random()));
yRing = (int)((frameHeight-ringSize)*(Math.random()));
setParamsRing(xRing, yRing, ringSize); 

有什么问题吗？这是所有代码:

public class mull extends JPanel implements ActionListener{

    private static JPanel p;
      Timer timer;
      ActionListener updateProBar;
      private double esize;
      private double maxSize = 0;
      private boolean initialize = true;
        private int squareX = 50;
        private int squareY = 50;
        private int squareSize = 200;  
        private int ringX = 50;
        private int ringY = 50;
        private int ringSize = 100;
        private static int frameWidth = 300;
        private static int frameHeight = 300;
        private int jPanelHeight;
        private int jPanelWidth;
        private int i = 0;

      public mull() {
            timer = new Timer(200, this);
            timer.setInitialDelay(200);
            timer.start();
          }
      int xRing;
      int yRing;
          @Override
          public void actionPerformed(ActionEvent e) {
               xRing = (int)((frameWidth -ringSize)* (Math.random()));
               yRing = (int)((frameHeight-ringSize)*(Math.random()));
              setParamsRing(xRing, yRing, ringSize);
              repaint();

          }
//  public void getJPanelSize(){
//      Rectangle r = p.getBounds();
//        jPanelHeight = r.height;
//        jPanelWidth = r.width;
//  }
    public void setParamsRing(int xpos, int ypos, int size){
        this.ringX = xpos;
        this.ringY = ypos;
        this.ringSize = size;
    }
    public void setParamsSquare(int xpos, int ypos, int size){
        this.squareX = xpos;
        this.squareY = ypos;
        this.squareSize = size; 
    }
    protected void paintComponent(Graphics g) {
        super.paintComponent(g);       
      g.setColor(Color.BLACK);
      g.drawOval(ringX, ringY, ringSize, ringSize);
      g.setColor(Color.BLUE );
      g.fillOval(ringX, ringY, ringSize, ringSize);

//        g.setColor(Color.BLACK);
//    g.drawRect(ringX, ringY, ringSize, ringSize);
//    g.setColor(Color.BLUE );
//    g.fillRect(ringX, ringY, ringSize, ringSize);

    } 



public static void main(String[] args) throws InterruptedException  {

        JFrame f = new JFrame("Swing Paint Demo");
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); 
        p = new JPanel();

        p.addMouseListener(new MouseAdapter() {
          public void mousePressed(MouseEvent e) {
//              moveSquare(e.getX(),e.getY());
          }
      });

        f.add(p);
        f.add(new mull());
        f.setSize(frameWidth, frameHeight);
        f.setLocationRelativeTo(null);
        f.setVisible(true);
    }

}

<小时/>

感谢这种方法有效!

我需要绘制圆环和正方形，但不要彼此重叠。有什么问题吗？我的代码似乎不起作用(尽管它似乎是正确的):

@Override
public void actionPerformed(ActionEvent e) {
xRing = (int)((getWidth()  -ringSize)* (Math.random()));
yRing = (int)((getHeight()-ringSize)*(Math.random()));     
xSquare = (int)((getWidth() -squareSize)* (Math.random()));
ySquare = (int)((getHeight()-squareSize)*(Math.random()));

while( (xSquare>=xRing && xSquare<=ringSize) && (ySquare>=yRing && ySquare<=ringSize)  ){
xSquare = (int)((getWidth() -squareSize)* (Math.random()));
ySquare = (int)((getHeight()-squareSize)*(Math.random()));
               } 
setParamsRing(xRing, yRing, ringSize);
setParamsSquare(xSquare, ySquare, squareSize);
repaint();

 }

Answer 1

代码中的问题是，您正在绘制的面板的尺寸不是frameWidthxframeHeight，而是更小。框架的边界设置为这些值，但您必须考虑标题栏和边框，这使得您的实际面板比这要小一些。

您可以使用面板的宽度和高度:

xRing = (int) ((getWidth() - ringSize) * Math.random());
yRing = (int) ((getHeight() - ringSize) * Math.random());
setParamsRing(xRing, yRing, ringSize);