Question

我一直在敲打这个好几个小时。我试着阅读并搜索答案。我甚至尝试过＆＃34;走开，然后回到它后面＆＃34;方法，它没有工作。我甚至尝试过瑜伽和冥想！我没有胜过......

专家，请赐教。

我试图获取一份不在drawRect中的CGPath副本：

CGMutablePathRef path = CGPathCreateMutable();
CGPathMoveToPoint(path, ......);
CGPathAddLineToPoint(path, ....);
CGPathAddLineToPoint(path, ....);
CGPathAddLineToPoint(path, ....);
CGPathAddLineToPoint(path, ....);

最后：
CGPathCloseSubpath(path); CGContextAddPath(context, path); 这不起作用，所以我尝试使用而不是上面的2个调用： CGPathCreateMutableCopy(path); 最终 - 我只是希望能够获得此路径并将其作为CAShapeLayer中的路径插入并通过进行此调用来设置动画：

animation.toValue = [UIBezierPath bezierPathWithCGPath:path];

所以在我尝试在没有降落伞的情况下尝试另一项放松活动，例如Sky Diving，希望能够清醒我的思绪并最终能够做到这一点，请你帮我一下，向我展示一些例子？除此之外，您能否使用以下功能向我详细解释正确的方法：

CGPathCloseSubpath(path); CGContextAddPath(context, path); CGPathCreateMutableCopy(path);

提前致谢。

Answer 1

CGPath是具有C风格API的C风格数据结构。基本上它是构成路径的点列表。
CGContext也是一种C风格的数据结构（可能更大一些）来绘制图像，即将点转换为彩色像素。

我将我的代码段放入一个函数中，您可以将其复制并粘贴到单个屏幕xcode项目中。您将在代码中找到解释作为注释，并且可以深入调试和探索CGPath对象的两个函数（我从https://github.com/erica/iOS-6-Cookbook获得了一些补充）。

#import "ViewController.h"
#import "OverlayView.h"
#import <QuartzCore/QuartzCore.h>

@implementation ViewController

- (void)viewDidLoad
{
    [super viewDidLoad];

    // create a graphics context with the C-API of the QuartzCore framework
    // the graphics context is only required for drawing the path
    CGRect compositionBounds = CGRectMake(30, 30, 300, 508);
    UIGraphicsBeginImageContext(compositionBounds.size);
    CGContextRef ctx = UIGraphicsGetCurrentContext();

    // create a mutable path with QuartzCore
    CGMutablePathRef p1 = CGPathCreateMutable();

    // create a CGPath with UIKit classes using Obj-C
    UIBezierPath *bp = [UIBezierPath bezierPath];
    [bp moveToPoint:(CGPoint){180, 120}];
    [bp addLineToPoint:(CGPoint){30, 170}];
    [bp addLineToPoint:(CGPoint){135, 175}];
    [bp addLineToPoint:(CGPoint){105, 115}];
    // if you fill the path during drawing it gets closed implicitly
//    [bp closePath];
    // add the CGPath to our mutable path
    CGPathAddPath(p1, nil, bp.CGPath);

    // add a closed triangle as subpath to our mutable path
    CGPathMoveToPoint(p1, nil, 50, 250);
    CGPoint p2[3];
    p2[0] = CGPointMake(10, 20);
    p2[1] = (CGPoint){210, 50};
    p2[2] = (CGPoint){80, 120};
    CGPathAddLines(p1, nil, p2, 3);
    // explicitly close our last added subpath
    CGPathCloseSubpath(p1);

    // draw our mutable path (with all its subpaths) filling its area
    CGContextAddPath(ctx, p1);
    CGContextSetFillColorWithColor(ctx, [[UIColor redColor] CGColor]);
    CGContextFillPath(ctx);

    // draw our mutable path (with all its subpaths) stroking its outline
    CGContextAddPath(ctx, p1);
    CGContextSetRGBStrokeColor(ctx, 0, 0, 0, 1.0);
    CGContextStrokePath(ctx);

    // display our mutable path in an image view on screen
    UIImage *i = UIGraphicsGetImageFromCurrentImageContext();
    UIImageView *iv = [[UIImageView alloc] initWithImage:i];
    [self.view addSubview:iv];
    iv.frame = self.view.frame;

    // release ressources created with the C-API of QuartzCore
    CGPathRelease(p1);
    UIGraphicsEndImageContext();

    // create a mutable copy of a path and don't use it for drawing
    CGMutablePathRef p3 = CGPathCreateMutableCopy(bp.CGPath);
    NSArray *p3points = [self pointsFromCGPath:p3];
    for (NSValue *point in p3points) {
        NSLog(@"path element in p3: %@", NSStringFromCGPoint(point.CGPointValue));
    }
    // note that UIBezierPath takes care of its path itself
    CGPathRelease(p3);

}

// modified from https://github.com/erica/iOS-6-Cookbook

#define VALUE(_INDEX_) [NSValue valueWithCGPoint:points[_INDEX_]]

void getPointsFromBezier(void *info, const CGPathElement *element)
{
    NSMutableArray *bezierPoints = (__bridge NSMutableArray *)info;

    // Retrieve the path element type and its points
    CGPathElementType type = element->type;
    CGPoint *points = element->points;

    switch (type) {
        case kCGPathElementMoveToPoint:
            NSLog(@"MoveToPoint (%3.2f, %3.2f", points->x, points->y);
            break;
        case kCGPathElementAddLineToPoint:
            NSLog(@"AddLineToPoint (%3.2f, %3.2f)", points->x, points->y);
            break;
        case kCGPathElementAddQuadCurveToPoint:
            NSLog(@"AddQuadCurveToPoint (%3.2f, %3.2f), (%3.2f, %3.2f)", points->x, points->y, points[1].x, points[1].y);
            break;
        case kCGPathElementAddCurveToPoint:
            NSLog(@"AddCurveToPoint (%3.2f, %3.2f), (%3.2f, %3.2f), (%3.2f, %3.2f)", points->x, points->y, points[1].x, points[1].y, points[2].x, points[2].y);
            break;
        case kCGPathElementCloseSubpath:
            NSLog(@"CloseSubpath (%3.2f, %3.2f)", points->x, points->y);
            break;
        default:
            NSLog(@"unknown");
            break;
    }

    // Add the points if they're available (per type)
    if (type != kCGPathElementCloseSubpath)
    {
        [bezierPoints addObject:VALUE(0)];
        if ((type != kCGPathElementAddLineToPoint) &&
            (type != kCGPathElementMoveToPoint))
            [bezierPoints addObject:VALUE(1)];
    }
    if (type == kCGPathElementAddCurveToPoint)
        [bezierPoints addObject:VALUE(2)];
}

- (NSArray *)pointsFromCGPath:(CGPathRef)path
{
    NSMutableArray *points = [NSMutableArray array];
    CGPathApply(path, (__bridge void *)points, getPointsFromBezier);
    return points;
}

iOS：不在drawRect中获取CGMutablePath：并将其分配给CAShapeLayer的Path

1 个答案: