[java] 繞著圓心走的同心圓座標

之前有寫一篇，怎樣算出一個繞著一點走的圓，

接下來我用程式來實現，程式在座標的計算上與數學常用的座標不太一樣。

//半徑
int r = 150;
//座標的矩陣
slidepoint = new int[360][2];
//圓心位址
int x0 = 225;
int y0 = 225;
//計算
for (int i = 1; i < 361; i++) {
    int x1 = (int) (x0 + r * Math.cos(Math.toRadians(i)));
    int y1 = (int) (y0 + r * Math.sin(Math.toRadians(i)));

   slidepoint[360 - i][0] = x1;
   slidepoint[360 - i][1] = y1;
  //draw angle string
   if (i % 10 ==0)
 g.drawString(String.valueOf(i), x1, y1);
}

我先用swing做個示範，每隔10度畫出角度在座標上

你會發現跟我們習慣的角度好像方向不同，我們做個轉換

class DrawPane extends JPanel {
  public void paintComponent(Graphics g) {
                      //畫大圓
   g.drawOval(0, 0, 450, 450);
                       //大圓
   int r = 150;
                        //座標的矩陣
   slidepoint = new int[360][2];
                        //圓心位址
   int x0 = 225;
   int y0 = 225;
                       //計算
   for (int i = 1; i < 361; i++) {
             int x1 = (int) (x0 + r * Math.cos(Math.toRadians(i)));
      int y1 = (int) (y0 + r * Math.sin(Math.toRadians(i)));

    slidepoint[360 - i][0] = x1;
    slidepoint[360 - i][1] = y1;
    
   }
                        //轉換
   for (int i = 0; i < 360; i++) {
    int x1 = slidepoint[i][0];
    int y1 = slidepoint[i][1];
                                //繪圓
    if (i%10==0)
     g.drawString(String.valueOf(i), x1, y1);
   
   }

  }
 }