java - 使正弦图移动

public class SimpleHarmonic {
    public static void main(String[] args) {
        StdDraw.setXscale(0,900);
        StdDraw.setYscale(0,700);

        while (true) {
            StdDraw.setPenColor(StdDraw.BLACK);
            StdDraw.line(0,350,900,350); // x-axis
            StdDraw.line(450,0,450,900); // y-axis
            StdDraw.setPenColor(StdDraw.RED);

            for (double x = -450; x <= 450; x += 0.5) {
                double y = 50 * Math.sin(x * (Math.PI / 180));
                int Y = (int) y;
                int X = (int) x;
                StdDraw.line(450 + X, 350 - Y, 450 + X, 350 - Y);
            }
            StdDraw.clear();

        }
    }
}

在这段代码中，我试图模拟简单的谐波运动。但是，我只能绘制静态图形，但是我需要它连续移动。

我相信我需要使用循环来连续地重画点，但是我不确定该怎么做。

如何使当前的正弦图连续移动？

编辑：投票关闭为非编程？什么？

最佳答案

我看了看您正在使用的StdDraw类，看起来您想要的是

StdDRaw.show(int)方法，此方法注释指出：

/**
 * Display on screen, pause for t milliseconds, and turn on
 * <em>animation mode</em>: subsequent calls to
 * drawing methods such as {@code line()}, {@code circle()}, and {@code square()}
 * will not be displayed on screen until the next call to {@code show()}.
 * This is useful for producing animations (clear the screen, draw a bunch of shapes,
 * display on screen for a fixed amount of time, and repeat). It also speeds up
 * drawing a huge number of shapes (call {@code show(0)} to defer drawing
 * on screen, draw the shapes, and call {@code show(0)} to display them all
 * on screen at once).
 * @param t number of milliseconds
 */

在此库中，任何时候调用诸如line或circle之类的绘制方法时，它都会有条件地重新绘制框架。通过将int参数传递给draw方法，它将把所有绘制方法都变为“动画模式”，并推迟重新绘制框架，直到调用draw()（无参数）为止。



要使其具有动画效果，您必须对while循环1动画帧进行每次迭代，每个帧都必须与前一个不同。您可以通过在循环外使用变量将每个帧偏移一小步来实现。叫这个offset

使用此信息，您可以将循环更改为如下所示：

    double offset = 0;
    while (true) {
        offset+=1; // move the frame slightly
        StdDraw.show(10); // defer repainting for 10 milisecoinds

        StdDraw.clear(); // clear before painting

        StdDraw.setPenColor(StdDraw.BLACK);
        StdDraw.line(0,350,900,350); // x-axis
        StdDraw.line(450,0,450,900); // y-axis
        StdDraw.setPenColor(StdDraw.RED);

        for (double x = -450; x <= 450; x += 0.5) {
            // apply the offset inside of calculation of Y only such that it
            // slowly "moves" the sin wave
            double y = 50 * Math.sin((offset+x) * (Math.PI / 180));
            int Y = (int) y;
            int X = (int) x;
            StdDraw.line(450 + X, 350 - Y, 450 + X, 350 - Y);
        }

        StdDraw.show(); // end animation frame. force a repaint
    }

代码方面的一些改进

1在循环中绘制每个“点”的地方是.5。因为该X值实际上是1像素，所以您通过转到.5而不是1不会获得任何收益。 1确实是您在该环境中可以直观看到的最小值。我建议至少设为x+=1

for (double x = -450; x <= 450; x += 1)

2您正在使用.line方法，但是绘制到同一点。通过仅计算每个第3个像素的Y值并连接点，可以大大提高程序速度。例如

double prevX = -450;
double prevY = 50 * Math.sin((prevX+offset) * (Math.PI / 180)); // seed the previous Y to start
for (double x = 0; x <= 450; x += 3) {
    double y = 50 * Math.sin((x+offset) * (Math.PI / 180));
    StdDraw.line(450 + (int)prevX, 350 - (int)prevY, 450 + (int)x, 350 - (int)y);
    prevX = x;
    prevY = y;
}

3这不是您的代码，但是在StdDraw.init方法中，您可以设置一些渲染提示以使线条更清晰。这应该使它看起来更好

offscreen.setRenderingHint(RenderingHints.KEY_STROKE_CONTROL,
                           RenderingHints.VALUE_STROKE_PURE);

结合所有这些东西，这就是我写的

public static void main(String[] args) {
    StdDraw.setXscale(0,900);
    StdDraw.setYscale(0,700);

    double offset = 0;
    while (true) {
        StdDraw.show(10);
        StdDraw.clear();
        offset-=1;

        StdDraw.setPenColor(StdDraw.BLACK);
        StdDraw.line(0,350,900,350); // x-axis
        StdDraw.line(450,0,450,900); // y-axis
        StdDraw.setPenColor(StdDraw.RED);


        double prevX = 0;
        double prevY = 50 * Math.sin((prevX+offset) * (Math.PI / 180)); // seed the previous Y to start
        StdDraw.filledCircle(450 + prevX, 350 - prevY, 5);

        for (double x = 0; x <= 450; x += 3) {
            double y = 50 * Math.sin((x+offset) * (Math.PI / 180));
            StdDraw.line(450 + (int)prevX, 350 - (int)prevY, 450 + (int)x, 350 - (int)y);
            prevX = x;
            prevY = y;
        }
        StdDraw.show();

    }
}

我没有动画录制器，所以这是一张照片