Java动画以及覆盖绘制和更新方法

Question

So at the moment I'm trying to animate different orders of bezier curves and the midpoints that make them up, but I am pretty new to graphics in Java. I understand how paint and repaint work but I can't figure out how to get out of this situation.

The bezier curve points are decided by user clicks here, and repaint() is called at the mouseEvent.

public void paint(Graphics g) {
    initgr();
    int left = iX(-rWidth / 2), right = iX(rWidth / 2), bottom = iY(-rHeight / 2), top = iY(rHeight / 2);
    g.drawRect(left, top, right - left, bottom - top);

    for (int i = 0; i < np; i++) {
        // Show tiny rectangle around point:
        g.drawRect(iX(P[i].x) - 2, iY(P[i].y) - 2, 4, 4);
        if (i > 0)
            // Draw line P[i-1]P[i]:
            g.drawLine(iX(P[i - 1].x), iY(P[i - 1].y), iX(P[i].x),
                    iY(P[i].y));
    }

    if (np == 2 && order == 1)
        bezier1(g, P, gran);
    if (np == 3 && order == 2)
        bezier2(g, P, gran);
    if (np == 4 && order == 3)
        bezier3(g, P, gran);
    if (np == 5 && order == 4)
        bezier4(g, P, gran);
    if (np == 6 && order == 5)
        bezier5(g, P, gran);
}

The functions called at the bottom go to the calculated and drawn bezier curves here.

void bezier3(Graphics g, Point2D[] p, int n) {
    javax.swing.Timer timer = new javax.swing.Timer(100,
            new TimerListener());
    timer.setDelay(39);
    timer.start();
    float dt = 1.0F / n, cx3 = -p[0].x + 3 * (p[1].x - p[2].x) + p[3].x, cy3 = -p[0].y
            + 3 * (p[1].y - p[2].y) + p[3].y, cx2 = 3 * (p[0].x - 2
            * p[1].x + p[2].x), cy2 = 3 * (p[0].y - 2 * p[1].y + p[2].y), cx1 = 3 * (p[1].x - p[0].x), cy1 = 3 * (p[1].y - p[0].y), cx0 = p[0].x, cy0 = p[0].y, x = p[0].x, y = p[0].y, x0, y0, x2, y2;
    for (int i = 1; i <= n; i++) {

        float t = i * dt;

        x0 = x;
        y0 = y;
        x = ((cx3 * t + cx2) * t + cx1) * t + cx0;
        y = ((cy3 * t + cy2) * t + cy1) * t + cy0;
        // x2 = ((cx3 * (.5F*t) + cx2) * (.5F*t) + cx1) * (.5F*t) + cx0;
        // y2 = ((cy3 * (.5F*t) + cy2) * (.5F*t) + cy1) * (.5F*t) + cy0;
        x2 = p[1].x * t;
        y2 = p[1].y * t;

        Point2D A = tcalc(P[0], P[1], t), B = tcalc(P[2], P[3], t), C = tcalc(
                P[1], P[2], t), A1 = tcalc(A, C, t), B1 = tcalc(C, B, t);

        g.setColor(Color.red);
        g.drawLine(iX(x0), iY(y0), iX(x), iY(y));
        // paint(g);
        g.setColor(Color.green);
        g.drawLine(iX(A.x), iY(A.y), iX(C.x), iY(C.y));
        g.drawLine(iX(C.x), iY(C.y), iX(B.x), iY(B.y));
        g.setColor(Color.blue);
        g.drawLine(iX(A1.x), iY(A1.y), iX(B1.x), iY(B1.y));
    }
}

So I know I shouldn't be drawing inside of these methods, but rather in paint. However, I have 5 of these functions that I'm not sure how to put in paint, and if I change the other method to update, it's just never going to erase the points the user clicked when I want to move on to the next selection of points. You can see I tried to put a basic swing timer in, but I'm not even sure if that will work in this situation for the animation.

Is there any way to get this to work inside of the bezier functions? I just don't see how I can get the drawlines out. My 5th order one has something like 11 midpoints being constantly calculated. Obviously, my understanding of this part of java graphics is shaky at best, so any point in the right direction would be greatly appreciated. If I find anything in my research I will update the question.

Thanks for any help.

Answer 1

Forget the timer. Try paintComponent.

Object Oriented would help keeping an overview, simplifying the number of variables.

• Make a base class Bezier with a paint(Graphics) {} and onMouse(MouseEvent){}.
• Derive Bezier1, ~2, ~3 and so on.
• And have variables Bezier bezier2 = new Bezier2(); ...
• And in your paintCompont call bezier2.paint(g).

Then try repaint(10L) or so in your mouse handling. Experiment to learn (paintImmediate and so on).