AffineTransform

Question

好吧，我使用这段代码来绘制我的图的边，如果用户想要在它的流动模式下看到图，我画箭头而不是线，所有的工作都很完美，直到我改变窗口大小，然后箭头的起点(x1，y1)与我的节点不同步地移动，使它们没有连接，而drawLine()工作得很完美。

这跟AffineTransform有什么关系吗？

(箭头画法取自here)

    void drawArrow(Graphics g1, int x1, int y1, int x2, int y2) {
    Graphics2D g = (Graphics2D) g1.create();
    int arrowSize = 5;
    double dx = x2 - x1, dy = y2 - y1;
    double angle = Math.atan2(dy, dx);
    int len = (int) Math.sqrt(dx*dx + dy*dy);
    AffineTransform at = AffineTransform.getTranslateInstance(x1, y1);
    at.concatenate(AffineTransform.getRotateInstance(angle));
    g.setTransform(at);
    g.drawLine(0, 0, len, 0);
    g.setStroke(new BasicStroke(1));
    g.drawLine(len/3, arrowSize , len/3-3*arrowSize, 0);
    g.drawLine(len/3, -arrowSize , len/3-3*arrowSize, 0);
}

对于那些漫步于paint Edge方法外观的人：

    public void paintEdge(Graphics g) {
    Point uCenter = u.getCenter();
    Point vCenter = v.getCenter();
    g.setColor(color);
    Graphics2D g2=(Graphics2D) g;
    g2.setStroke(new BasicStroke(3));
    if (mode==Mode.FLOW) {
        int minx=Math.min(uCenter.x, vCenter.x),miny=Math.min(uCenter.y, vCenter.y);
        int maxx=Math.max(uCenter.x, vCenter.x),maxy=Math.max(uCenter.y, vCenter.y);
        g2.drawString(""+ f + " / " + c,10+minx + (maxx-minx)/2,10+miny+ (maxy- miny)/2);
        drawArrow(g2,uCenter.x, uCenter.y, vCenter.x, vCenter.y);
    } else {
        g2.drawLine(uCenter.x, uCenter.y, vCenter.x, vCenter.y);
    }
    g2.setStroke(new BasicStroke(1));
}

Answer 1

void drawArrow(Graphics2D g, int x1, int y1, int x2, int y2) {
    AffineTransform prev = g.getTransform();
    int arrowSize = 5;
    double dx = x2 - x1, dy = y2 - y1;
    double angle = Math.atan2(dy, dx);
    int len = (int) Math.sqrt(dx*dx + dy*dy);
    AffineTransform at = AffineTransform.getTranslateInstance(x1, y1);
    at.rotate(angle);
    g.transform(at);
    g.drawLine(0, 0, len, 0);
    g.setStroke(new BasicStroke(1));
    g.drawLine(len/3, arrowSize , len/3-3*arrowSize, 0);
    g.drawLine(len/3, -arrowSize , len/3-3*arrowSize, 0);
    g.setTransform(prev);
}

这就是它是如何做到的，对于那些想知道的人。

问题是，我使用了g.setTransform(at)；而不是g.transform(at)；这是一个很难的问题。