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文章目录
一、前情概要
系统提供UISlider，但在开发过程中经常需要自定义，本次需求内容是实现一个拥有渐变色的滑动条，且渐变色随着手指touch的位置不同改变区域，类似如下
可以使用CAGradientLayer实现渐变效果，但是发现手指滑动的快时会有不跟手的情况。我们可以重写左侧有渐变色的UIView的drawRect: 方法来绘制渐变色
二、具体实现
左侧的渐变色UIView
HLProgressView.h
@interface HLProgressView : UIView @property (nonatomic, assign) CGSize viewSize; @end HLProgressView.m
@implementation HLProgressView - (instancetype)initWithFrame:(CGRect)frame{ self = [super initWithFrame:frame]; if (self) { } return self; } - (void)setViewSize:(CGSize)viewSize { _viewSize = viewSize; self.frame = CGRectMake(0, 0, viewSize.width, viewSize.height); // setNeedsDisplay会自动调用drawRect方法 [self setNeedsDisplay]; } - (void)drawRect:(CGRect)rect { CGSize size = self.bounds.size; // 获取图形上下文对象CGContextRef CGContextRef context = UIGraphicsGetCurrentContext(); // 创建一个颜色空间 CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB(); // 设置的颜色 每四个元素表示一种颜色，值的范围0~1，分别表示R、G、B、透明度 CGFloat colors[] = { 55.0/255.0, 180.0/255.0, 255.0/255.0, 1.0, 55.0/255.0, 80.0/255.0, 255.0/255.0, 1.0 }; // 渐变的位置信息范围0~1 0表示开始的位置 1表示结束的位置 CGFloat gradientLocations[] = {0, 1}; // 渐变的个数 size_t locationCount = 2; // 创建渐变 CGGradientRef gradient = CGGradientCreateWithColorComponents(colorSpace, colors, gradientLocations, locationCount); // 指定渐变的开始位置和结束位置 这里设置完效果是整块区域的水平方向的渐变 CGPoint gradientStartPoint = CGPointMake(0, size.height/2); CGPoint gradientEndPoint = CGPointMake(size.width, size.height/2); // 将渐变画到上下文中，最后一个参数表示发散的方式 CGContextDrawLinearGradient(context, gradient, gradientStartPoint, gradientEndPoint, kCGGradientDrawsBeforeStartLocation); // 释放内存 CGGradientRelease(gradient); CGColorSpaceRelease(colorSpace); } @end 滑动条
UICustomSlider.h
@interface UICustomSlider : UIView @end UICustomSlider.m
@interface UICustomSlider () @property (nonatomic, strong) HLProgressView *progressView; @end @implementation UICustomSlider - (instancetype)initWithFrame:(CGRect)frame { self = [super initWithFrame:frame]; if (self) { self.backgroundColor = [UIColor grayColor]; self.clipsToBounds = YES; //不显示超过父视图的内容 self.layer.cornerRadius = 8; self.progressView = [[HLProgressView alloc] initWithFrame:CGRectMake(0, 0, 140, 44)]; [self addSubview:self.progressView]; } return self; } - (void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event { CGPoint point = [touches.anyObject locationInView:self]; self.progressView.viewSize = CGSizeMake(point.x, self.bounds.size.height); } - (void)touchesMoved:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event { CGPoint point = [touches.anyObject locationInView:self]; self.progressView.viewSize = CGSizeMake(point.x, self.bounds.size.height); } - (void)touchesEnded:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event { CGPoint point = [touches.anyObject locationInView:self]; self.progressView.viewSize = CGSizeMake(point.x, self.bounds.size.height); } @end 调用滑动条
ViewController.m
#import "GradientSlider.h" @interface ViewController () @end @implementation ViewController - (void)viewDidLoad { [super viewDidLoad]; UICustomSlider *customSlider = [[UICustomSlider alloc] initWithFrame:CGRectMake(20, 100, 280, 44)]; [self.view addSubview:customSlider]; } 