Question

我有以下代码（基于this回答）来创建'morphable'圈＆lt;＆gt;正方形。

它在iPhone上运行良好：

但在iPad上运行不太好（运行相同版本的iOS - 10）：

代码是：

-(UIBezierPath*)circlePathWithCenter:(CGPoint)center andRadius:(CGFloat)radius {
    UIBezierPath *circlePath = [UIBezierPath bezierPath];
    [circlePath addArcWithCenter:center radius:radius startAngle:-M_PI endAngle:-M_PI/2 clockwise:YES];
    [circlePath addArcWithCenter:center radius:radius startAngle:-M_PI/2 endAngle:0 clockwise:YES];
    [circlePath addArcWithCenter:center radius:radius startAngle:0 endAngle:M_PI/2 clockwise:YES];
    [circlePath addArcWithCenter:center radius:radius startAngle:M_PI/2 endAngle:M_PI clockwise:YES];
    [circlePath closePath];

    NSLog(@"%@", [circlePath debugDescription]);

    return circlePath;
}

- (UIBezierPath *)squarePathWithCenter:(CGPoint)center andSize:(CGFloat)size
{
    CGFloat startX = center.x-size/2;
    CGFloat startY = center.y-size/2;

    UIBezierPath *squarePath = [UIBezierPath bezierPath];
    [squarePath moveToPoint:CGPointMake(startX, startY)];
    [squarePath addLineToPoint:squarePath.currentPoint];
    [squarePath addLineToPoint:CGPointMake(startX+size, startY)];
    [squarePath addLineToPoint:squarePath.currentPoint];
    [squarePath addLineToPoint:CGPointMake(startX+size, startY+size)];
    [squarePath addLineToPoint:squarePath.currentPoint];
    [squarePath addLineToPoint:CGPointMake(startX, startY+size)];
    [squarePath addLineToPoint:squarePath.currentPoint];
    [squarePath closePath];

    NSLog(@"%@", [squarePath debugDescription]);

    return squarePath;
}

动画代码是：

CABasicAnimation *animation = [CABasicAnimation animationWithKeyPath:@"path"];
animation.duration = 0.5;
animation.timingFunction = [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionEaseInEaseOut];

animation.fromValue = (__bridge id)(_innerShape.path);
animation.toValue = (__bridge id)(_innerSquare.CGPath);
_innerShape.path = _innerSquare.CGPath;

[_innerShape addAnimation:animation forKey:@"animatePath"];

仔细检查路径后，我注意到iPad版本上有更多'curveto'点（运行相同的代码）。从上一期的讨论来看，我认为控制点的数量必须相同才能实现平稳过渡。

设备之间预期的点数是否不同？是否有更可靠的方法来实现可变形状？

圈子的iPad调试：

<UIBezierPath: 0x6c4f0d0; <MoveTo {13.5, 45.000004}>,
 <CurveTo {44.999996, 13.5} {13.499998, 27.603035} {27.603027, 13.500002}>,
 <CurveTo {45, 13.5} {44.999996, 13.5} {45, 13.5}>,
 <LineTo {45, 13.5}>,
 <CurveTo {76.5, 45} {62.396969, 13.499999} {76.5, 27.603031}>,
 <CurveTo {76.5, 45} {76.5, 45} {76.5, 45}>,
 <LineTo {76.5, 45}>,
 <CurveTo {45, 76.5} {76.5, 62.396969} {62.396969, 76.5}>,
 <CurveTo {45, 76.5} {45, 76.5} {45, 76.5}>,
 <LineTo {45, 76.5}>,
 <CurveTo {13.5, 45} {27.603031, 76.5} {13.499999, 62.396969}>,
 <CurveTo {13.5, 44.999996} {13.5, 45} {13.5, 44.999996}>,
 <Close>

iPhone版：

<UIBezierPath: 0x6180000b24e0; <MoveTo {13.5, 44.999999999999993}>,
 <CurveTo {45, 13.5} {13.500000000000002, 27.603030380330004} {27.603030380330011, 13.499999999999998}>,
 <LineTo {45, 13.5}>,
 <CurveTo {76.5, 45} {62.396969619669989, 13.500000000000002} {76.5, 27.603030380330011}>,
 <LineTo {76.5, 45}>,
 <CurveTo {45, 76.5} {76.5, 62.396969619669989} {62.396969619669989, 76.5}>,
 <LineTo {45, 76.5}>,
 <CurveTo {13.5, 45.000000000000007} {27.603030380330011, 76.5} {13.500000000000002, 62.396969619669996}>,
 <Close>

两者都是正方形：

<UIBezierPath: 0x6000000b0f80; <MoveTo {29.25, 29.25}>,
 <LineTo {29.25, 29.25}>,
 <LineTo {60.75, 29.25}>,
 <LineTo {60.75, 29.25}>,
 <LineTo {60.75, 60.75}>,
 <LineTo {60.75, 60.75}>,
 <LineTo {29.25, 60.75}>,
 <LineTo {29.25, 60.75}>,
 <Close>

Answer 1

如果在两条路径之间进行转换，那么它们具有相同数量的分段非常重要。

有两种基本方法：

一种方法是将圆圈创建为多个线段，然后组成相同数量的线段的平方。您只需使用足够多的段，使圆圈呈现圆形：

static NSInteger segments = 360;

- (UIBezierPath*)circlePathWithCenter:(CGPoint)center andRadius:(CGFloat)radius {

    CGFloat startAngle = -M_PI * 3.0 / 4.0;
    CGPoint point = CGPointMake(radius * cos(startAngle) + center.x, radius * sinf(startAngle) + center.y);

    UIBezierPath *path = [UIBezierPath bezierPath];
    [path moveToPoint:point];

    for (NSInteger angle = 1; angle <= segments; angle++) {
        point = CGPointMake(radius * cos(startAngle + ((CGFloat)angle / 360.0 * M_PI * 2.0)) + center.x,
                            radius * sin(startAngle + ((CGFloat)angle / 360.0 * M_PI * 2.0)) + center.y);
        [path addLineToPoint:point];
    }

    return path;
}

- (UIBezierPath *)squarePathWithCenter:(CGPoint)center andSize:(CGFloat)size {
    CGFloat startX = center.x-size/2;
    CGFloat startY = center.y-size/2;

    CGFloat endX = startX+size;
    CGFloat endY = startY;

    UIBezierPath *path = [UIBezierPath bezierPath];
    CGPoint point = CGPointMake(startX, startY);
    [path moveToPoint:point];

    for (NSInteger i = 1; i <= segments / 4; i++) {
        CGPoint point = CGPointMake(startX + (endX - startX) * (CGFloat) i / 90.0,
                                    startY + (endY - startY) * (CGFloat) i / 90.0);
        [path addLineToPoint:point];
    }

    startX = endX; startY = endY;
    endY += size;

    for (NSInteger i = 1; i <= segments / 4; i++) {
        CGPoint point = CGPointMake(startX + (endX - startX) * (CGFloat) i / 90.0,
                                    startY + (endY - startY) * (CGFloat) i / 90.0);
        [path addLineToPoint:point];
    }

    startX = endX; startY = endY;
    endX -= size;

    for (NSInteger i = 1; i <= segments / 4; i++) {
        CGPoint point = CGPointMake(startX + (endX - startX) * (CGFloat) i / 90.0,
                                    startY + (endY - startY) * (CGFloat) i / 90.0);
        [path addLineToPoint:point];
    }

    startX = endX; startY = endY;
    endY -= size;

    for (NSInteger i = 1; i <= segments / 4; i++) {
        CGPoint point = CGPointMake(startX + (endX - startX) * (CGFloat) i / 90.0,
                                    startY + (endY - startY) * (CGFloat) i / 90.0);
        [path addLineToPoint:point];
    }

    return path;
}

或者，您可以使用弧，但您可能希望确保两个路径中的线段和弧一对一匹配。例如，我可以将正方形渲染为一系列零半径圆弧，并在它们之间有线段，并将圆形渲染为一系列全尺寸圆弧，它们之间具有零长度线段。这样，每次拨打moveToPoint，addArcWithCenter和addLineToPoint都会有一对一的对应关系：

- (UIBezierPath*)circlePathWithCenter:(CGPoint)center andRadius:(CGFloat)radius {
    UIBezierPath *path = [UIBezierPath bezierPath];

    CGFloat startAngle = -M_PI;

    [path moveToPoint:CGPointMake(center.x - radius, center.y)];

    for (NSInteger angle = 0; angle < 4; angle++) {
        [path addArcWithCenter:center radius:radius startAngle:startAngle endAngle:startAngle + M_PI_2 clockwise:true];
        [path addLineToPoint:path.currentPoint];
        startAngle += M_PI_2;
    }

    return path;
}

- (UIBezierPath *)squarePathWithCenter:(CGPoint)center andSize:(CGFloat)size {
    CGFloat startX = center.x-size/2;
    CGFloat startY = center.y-size/2;
    CGFloat angle = -M_PI;

    CGFloat endX = startX+size;
    CGFloat endY = startY;

    UIBezierPath *path = [UIBezierPath bezierPath];
    CGPoint point = CGPointMake(startX, startY);
    [path moveToPoint:point];

    [path addArcWithCenter:point radius:0 startAngle:angle endAngle:angle + M_PI_2 clockwise:true];
    point = CGPointMake(endX, endY);
    [path addLineToPoint:point];

    angle += M_PI_2;
    startX = endX; startY = endY;
    endY += size;

    [path addArcWithCenter:point radius:0 startAngle:angle endAngle:angle + M_PI_2 clockwise:true];
    point = CGPointMake(endX, endY);
    [path addLineToPoint:point];

    angle += M_PI_2;
    startX = endX; startY = endY;
    endX -= size;

    [path addArcWithCenter:point radius:0 startAngle:angle endAngle:angle + M_PI_2 clockwise:true];
    point = CGPointMake(endX, endY);
    [path addLineToPoint:point];

    angle += M_PI_2;
    startX = endX; startY = endY;
    endY -= size;

    [path addArcWithCenter:point radius:0 startAngle:angle endAngle:angle + M_PI_2 clockwise:true];
    point = CGPointMake(endX, endY);
    [path addLineToPoint:point];

    return path;
}

产量：

这两种产生不同的效果，所以它取决于你的目标。

UIBezierPath：iPad上创建的控制点多于iPhone？

1 个答案: