iOS_使用UIBezierPath对象实现视图控件的立体阴影效果和半透明背景效果

iOS_使用UIBezierPath对象实现视图控件的立体阴影效果和半透明背景效果

说明:

• CALayer 和阴影的相关API有: shadowOpacity, shadowRadius, shadowOffset, shadowColor, shadowPath 等5个. 本篇文章要讲述的是通过设置shadowPath属性来实现特殊的UI效果

文章中尽量不使用或少使用封装, 目的是让大家清楚为了实现功能所需要的官方核心API是哪些(如果使用封装, 会在封装外面加以注释)

• 此文章由 @春雨 编写. 经 @Scott, @黑子 审核. 若转载此文章,请注明出处和作者

核心API

Class : UIBezierPath, CALayer
涉及的API:(API的官方详细注释详见本章结尾)

/** CALayer 的shadowPath属性. */
@property CGPathRef shadowPath

/** 创建UIBezierPath对象的相关类方法. */
+ (UIBezierPath *)bezierPathWithRect:(CGRect)rect
+ (UIBezierPath *)bezierPathWithRoundedRect:(CGRect)rect cornerRadius:(CGFloat)cornerRadius
+ (UIBezierPath *)bezierPathWithOvalInRect:(CGRect)rect

功能实现

1 . 椭圆形阴影效果
效果图:

2 . 半透明背景
效果图:

Code:

1 . 椭圆形阴影效果

- (void)layoutOvalShadow
{
    /** 1. 创建一个UIImageView的对象. */
    UIImage *image = [UIImage imageNamed:@"1.jpg"];
    UIImageView *imageView = [[UIImageView alloc] initWithFrame:CGRectMake(70, 200, 150, 200)];
    imageView.image = image;
    [self.view addSubview:imageView];
    [imageView release];


    /** 
     * @brief   2. 创建UIBezierPath的对象(椭圆形状).
     * @param 椭圆形状位置和大小(参考的坐标系是要设置阴影的视图)
     */
    UIBezierPath *path = [UIBezierPath bezierPathWithOvalInRect:CGRectMake(25, 230, 100, 20)];


    /** 3. 设置imageView的阴影, 制造立体效果. */
    imageView.layer.shadowPath = path.CGPath; /**< 指定path对象. */

    imageView.layer.shadowOpacity = 0.5; /**< 阴影透明度.*/

    imageView.layer.shadowRadius = 0; /**< 阴影模糊效果的半径. */

    imageView.layer.shadowColor = [UIColor grayColor].CGColor; /**< 阴影颜色.*/
}    

2 . 半透明背景

    - (void)bezierPathBackground
{
    /** 1. 创建一个UIImageView的对象, 当做背景图片. */
    UIImage *image = [UIImage imageNamed:@"33.jpg"];
    UIImageView *imageView = [[UIImageView alloc] initWithFrame:self.view.frame];
    imageView.image = image;
    [self.view addSubview:imageView];
    [imageView release];


    /** 2. 创建UILabel的对象. */
    UILabel *label = [[UILabel alloc] initWithFrame:CGRectMake(25, 50, 320, 100)];
    label.text = @"Our mind is a sponge, our heart is a stream.";
    label.font = [UIFont systemFontOfSize:30];
    label.textColor = [UIColor whiteColor];
    label.backgroundColor = [UIColor clearColor];
    label.numberOfLines = 0;
    label.textAlignment = NSTextAlignmentCenter;
    [imageView addSubview:label];
    [label release];


    /** 
     * @brief   3. 创建UIBezierPath的对象(圆角效果的矩形)
     * @param 1: 矩形的位置和大小(参考的坐标系是要设置阴影的视图)
     * @param 2: 圆角的半径
     */
    UIBezierPath *backgroundPath = [UIBezierPath bezierPathWithRoundedRect:CGRectMake(0, 0, 320, 100) cornerRadius:5];


    /** 4. 设置label的阴影, 制造半透明背景效果. */
    label.layer.shadowPath = backgroundPath.CGPath;
    label.layer.shadowOpacity = 0.4;
    label.layer.shadowRadius = 0;
    label.layer.shadowColor = [UIColor grayColor].CGColor;
}

---

API 官方注释

/**
 * @brief Creates and returns a new UIBezierPath object initialized with a rectangular path.
 * @param  The rectangle describing the path to create.
 * @return A new path object with the rectangular path.
 */
+ (UIBezierPath *)bezierPathWithRect:(CGRect)rect



/**
 * @brief Creates and returns a new UIBezierPath object initialized with an oval path inscribed in the specified rectangle
 * @ param  The rectangle in which to inscribe an oval.
 */
+ (UIBezierPath *)bezierPathWithOvalInRect:(CGRect)rect


/**
 * @brief Creates and returns a new UIBezierPath object initialized with a rounded rectangular path.
 * @param  The rectangle that defines the basic shape of the path
 * @param  The radius of each corner oval. A value of 0 results in a rectangle without rounded corners. Values larger than half the rectangle’s width or height are clamped appropriately to half the width or height.
 * @return A new path object with the rounded rectangular path.
 */
+ (UIBezierPath *)bezierPathWithRoundedRect:(CGRect)rect cornerRadius:(CGFloat)cornerRadius