Question

我正在制作一个涉及画线的多人游戏。我有10个不同的自定义UIViews，我使用Core Graphics以独特的颜色绘制一条线。所有视图彼此堆叠在一起并且是半透明的。我在相应的UIView中绘制每种颜色而不是单个颜色的原因是因为我想让用户能够清除特定的视图。但是，如果我同时绘制所有这些视图，则会出现大量滞后。如果我检查时间分析器，大部分时间都花在绘图上。但它并没有那么糟糕，不应该导致那么多的滞后。那么，有没有办法让我在多个UIViews（或其他东西）中绘制，而不会造成这种滞后。是我的代码导致这种滞后还是UIView？

- (void)drawRect:(CGRect)rect {
//create a image reference from the bitmap and then draw it in the context of the UIView. 

CGContextRef context = UIGraphicsGetCurrentContext();

CGImageRef cacheImage = CGBitmapContextCreateImage(cacheContext);

  CGContextDrawImage(context, self.bounds, cacheImage);
   CGImageRelease(cacheImage);
}

-(void)draw{
 //drawing code. Could ignore the Beizer curve algorithm here.

 CGContextSetStrokeColorWithColor(cacheContext, [color CGColor]);
 CGContextSetFillColorWithColor(cacheContext, [[UIColor blueColor] CGColor]);

 CGContextSetLineCap(cacheContext, kCGLineCapButt);
 CGContextSetLineWidth(cacheContext, 6+thickness);

        point0 = point1;
        point1 = point2; // previous previous point
        point2 = pos; // previous touch point
        point3 = currentpos;

        double x0 = (point0.x > -1) ? point0.x : point1.x; //after 4 touches we should have a back anchor point, if not, use the current anchor point
        double y0 = (point0.y > -1) ? point0.y : point1.y; //after 4 touches we should have a back anchor point, if not, use the current anchor point
        double x1 = point1.x;
        double  y1 =  point1.y;
        double x2 =  point2.x;
        double  y2 =  point2.y;
        double  x3 = point3.x;
        double  y3 = point3.y;



    // Assume we need to calculate the control
    // points between (x1,y1) and (x2,y2).
    // Then x0,y0 - the previous vertex,
    //      x3,y3 - the next one.

    double xc1 = (x0 + x1) / 2.0;
    double yc1 = (y0 + y1) / 2.0;
    double xc2 = (x1 + x2) / 2.0;
    double yc2 = (y1 + y2) / 2.0;
    double xc3 = (x2 + x3) / 2.0;
    double yc3 = (y2 + y3) / 2.0;

    double len1 = sqrt((x1-x0) * (x1-x0) + (y1-y0) * (y1-y0));
    double len2 = sqrt((x2-x1) * (x2-x1) + (y2-y1) * (y2-y1));
    double len3 = sqrt((x3-x2) * (x3-x2) + (y3-y2) * (y3-y2));

    double k1 = len1 / (len1 + len2);
    double k2 = len2 / (len2 + len3);

    double xm1 = xc1 + (xc2 - xc1) * k1;
    double ym1 = yc1 + (yc2 - yc1) * k1;

    double xm2 = xc2 + (xc3 - xc2) * k2;
    double ym2 = yc2 + (yc3 - yc2) * k2;
    double smooth_value = 0.8;
    // Resulting control points. Here smooth_value is mentioned
    // above coefficient K whose value should be in range [0...1].
    float ctrl1_x = xm1 + (xc2 - xm1) * smooth_value + x1 - xm1;
    float ctrl1_y = ym1 + (yc2 - ym1) * smooth_value + y1 - ym1;

    float ctrl2_x = xm2 + (xc2 - xm2) * smooth_value + x2 - xm2;
    float ctrl2_y = ym2 + (yc2 - ym2) * smooth_value + y2 - ym2;



        CGContextMoveToPoint(cacheContext, point1.x, point1.y);
        CGContextAddCurveToPoint(cacheContext, ctrl1_x, ctrl1_y, ctrl2_x, ctrl2_y, point2.x, point2.y);
        CGContextStrokePath(cacheContext);




    CGRect dirtyPoint1 = CGRectMake(point1.x-(8+thickness)/2, point1.y-(8+thickness)/2, (8+thickness), (8+thickness));
    CGRect dirtyPoint2 = CGRectMake(point2.x-(8+thickness)/2, point2.y-(8+thickness)/2, (8+thickness), (8+thickness));

    [self setNeedsDisplayInRect:CGRectUnion(dirtyPoint1, dirtyPoint2)];

}

绘制多个UIViews导致滞后。为什么？

0 个答案: