如何根据给定的度数旋转直线

Question

我用 Graphics 对象绘制了一条线。我想根据鼠标拖动的程度将这条线旋转一定的角度。我可以获得旋转它所需的度数，但是我如何根据该角度旋转线呢？

谢谢你！

Answer 1

Line2D您可以为原始线创建一个对象。然后您可以使用AffineTransform#getRotateInstance它来获取AffineTransform围绕某个点旋转某个角度的 。使用它AffineTransform，您可以创建一个旋转的Line2D对象来绘制。所以你的绘画代码大致如下所示：

protected void paintComponent(Graphics gr) {
    super.paintComponent(gr);
    Graphics2D g = (Graphics2D)gr; 

    // Create the original line, starting at the origin,
    // and extending along the x-axis
    Line2D line = new Line2D.Double(0,0,100,0);

    // Obtain an AffineTransform that describes a rotation
    // about a certain angle (given in radians!), around
    // the start point of the line. (Here, this is the
    // origin, so this could be simplified. But in this
    // form, it's more generic)
    AffineTransform at = 
        AffineTransform.getRotateInstance(
            Math.toRadians(angleInDegrees), line.getX1(), line.getY1());

    // Draw the rotated line
    g.draw(at.createTransformedShape(line));
}