java - 绘制旋转三角形

Question

我想在 Android 中使用 Canvas 类填充一个三角形。我目前的工作方式有效但非常滞后。我想知道是否有人有比我的方法更快的方法。谢谢!

我的代码:

public void rotate(float angle){
    if(neighbour == null)
        return;
    path.reset();
    Point origin = rotatePoint(neighbour.getX() + 64, neighbour.getY() + 128 + 16, neighbour.getX() + 64, neighbour.getY() + 64, angle);
    Point a = rotatePoint(neighbour.getX() + 64, neighbour.getY() + 128 + neighbour.getWidth() + neighbour.getHeight(), neighbour.getX() + 64, neighbour.getY() + 64, angle - 15);
    Point b = rotatePoint(neighbour.getX() + 64, neighbour.getY() + 128 + neighbour.getWidth() + neighbour.getHeight(), neighbour.getX() + 64, neighbour.getY() + 64, angle + 15);
    path.moveTo(origin.x, origin.y);
    path.lineTo(a.x, a.y);
    path.lineTo(b.x, b.y);
}

neighbor 只是一个包含 x 和 y 值的类。

旋转点法:

private Point rotatePoint(float x, float y, float px, float py, float angle){
    float s = (float)Math.sin(Math.toRadians(angle));
    float c = (float)Math.cos(Math.toRadians(angle));

    x -= px;
    y -= py;

    float xnew = x * c - y * s;
    float ynew = x * s + y * c;

    x = xnew + px;
    y = ynew + py;
    return new Point((int)x, (int)y);
}

这个三角形会非常频繁地旋转，所以我需要一种有效的方法。

Answer 1

您可以始终使用相同的路径绘制三角形，但在绘制路径之前将 Canvas 旋转到所需的旋转角度。

canvas.save();
canvas.rotate(degrees);
//draw your triangle here
canvas.restore();

还有一个

canvas.rotate(degrees, x, y);

如果你需要给它一个轴心点。