我查看了StdDraw
您正在使用的课程,看起来您想要的是
StdDRaw.show(int)
方法,此方法注释说明:
/**
* 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
*/
在这个库中,任何时候你调用一个draw方法,line
或者circle
它有条件地重新绘制框架。通过将int
参数传递给该draw
方法,它会将所有绘画方法转换为“动画模式”并推迟重新绘制帧,直到您调用draw()
(无参数)。
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,每一帧都需要与前一帧不同。您可以通过在循环外部使用变量来将每个帧偏移一小部分来做到这一点。我会打电话给这个offset
使用此信息,您可以将循环更改为:
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
}
代码中的一些改进
1在你的循环中,你绘制每个“点”,你正在增加.5
. 因为那个 X 值实际上是 1 个像素,所以你不会通过去.5
而不是获得任何东西1
。1 实际上是您在此环境中可以视觉看到的最小的。我建议至少让它成为x+=1
for (double x = -450; x <= 450; x += 1)
2您正在使用该.line
方法,但绘制到同一点。您可以通过仅计算每 3 个像素的 Y 值并连接点来显着加快您的程序。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,但在该StdDraw.init
方法中您可以设置一些渲染提示以允许更清晰的线条。这应该使它看起来更好
offscreen.setRenderingHint(RenderingHints.KEY_STROKE_CONTROL,
RenderingHints.VALUE_STROKE_PURE);
把所有这些东西结合起来就是我写的
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();
}
}
我没有动画录像机所以这里有一张照片