iOS圆形倒计时控件的实现

这两个月真的太忙了，被一堆需求压着，本来想好好学学Clang相关的知识的，但一直没时间，博客也没更了，现在终于把手上的需求都提测掉了，这几天先好好复盘一下，看看这段时间有什么收获，今天来记录一下圆形倒计时控件的实现。

先来看看demo的效果：

demo效果

实现原理：构建一个环形，环形的起始点为-π/2，终点需要讨论顺时针/逆时针、递增/递减四种情况。

设进度为progress，起始点为startA，一圈刚好为2π，现在我们需要根据clockWise和increase的四种组合情况来得出终点endA的公式，再结合UIBezierPath的接口决定是否顺时针构建环形，从而画出一个弧，结合progress即可有进度条的效果了。

---

• 顺时针递增

起始值为0，顺时针构建环形，endA与progress正相关，得：

endA = startA + progress * 2π

---

• 逆时针递减

起始值为2π，顺时针构建环形，endA与(1 - progress)正相关，得：

endA = startA + (1 - progress) * 2π

---

• 顺时针递减

起始值为2π，逆时针构建环形，endA与(1 - progress)负相关，得：

endA = startA - (1 - progress) * 2π

---

• 逆时针递增

起始值为0，逆时针构建环形，endA与progress负相关，得：

endA = startA - progress * 2π

---

通过以上分析，可以看到

1. 顺时针递增、逆时针递减都是用顺时针构建环形，否则用逆时针构建环形

2. 顺时针递增、逆时针递增，endA都是与progress相关，否则与(1-progress)相关

3. 逆时针构建环形需要与相关参数负相关

得代码：

- (void)showAnimationWithProgress:(CGFloat)progress {
    CGFloat startA = - M_PI_2;  // 设置进度条起点位置
    CGFloat endA;               // 设置进度条终点位置
    CGFloat clockWiseFlag = _clockWise ? 1 : -1;
    CGFloat progressFlag = _increase ? 1 : -1;
    CGFloat percent = _increase ? progress : (1 - progress);
    
    // 顺增、逆减，顺时针构建环形
    BOOL shouldClockWiseBulid = (clockWiseFlag * progressFlag > 0);
    
    endA = startA + M_PI * 2 * percent * clockWiseFlag * progressFlag;
    
    UIBezierPath *path = [UIBezierPath bezierPathWithArcCenter:CGPointMake(_radius / 2, _radius / 2) radius:_radius / 2 - self.lineWidth / 2 startAngle:startA endAngle:endA clockwise:shouldClockWiseBulid]; // 构建环形
    self.path = [path CGPath];
}

再加上一些可以自定义的参数（半径、填充颜色等），也可以自己根据倒计时和总计时来实现，就可以构建自己想要的倒计时环形啦！附相关代码：

//
//  HobenCountDownCircleLayer.h
//  HobenLayerDemo
//
//  Created by Hoben on 2020/8/5.
//  Copyright © 2020 Hoben. All rights reserved.
//  用于展示圆形倒计时(顺时针/逆时针/递增/递减)的Layer

#import <UIKit/UIKit.h>

NS_ASSUME_NONNULL_BEGIN

@interface HobenCountDownCircleLayer : CAShapeLayer

/**
 建立一个展示圆形倒计时的Layer
 @param strokeColor 倒计时线的颜色
 @param lineWidth   倒计时线的宽度
 @param radius      倒计时圆的半径
 */
+ (HobenCountDownCircleLayer *)layerWithStrokeColor:(UIColor *)strokeColor lineWidth:(CGFloat)lineWidth radius:(CGFloat)radius;

@property (nonatomic, assign) BOOL clockWise;   // 是否为顺时针

@property (nonatomic, assign) BOOL increase;    // 是否递增动画

@property (nonatomic, assign) CGFloat totalCountDown;   // 总计时

@property (nonatomic, assign) CGFloat radius;  // 圆的半径

/**
 根据当前倒计时展示Layer(需要实现设置totalCountDown)
 @param countDown 当前的倒计时
*/
- (void)showAnimationWithCountdown:(CGFloat)countDown;

/**
 根据当前进度展示Layer
 @param progress 当前的进度(0%-100%)
*/
- (void)showAnimationWithProgress:(CGFloat)progress;

@end

NS_ASSUME_NONNULL_END

//
//  HobenCountDownCircleLayer.m
//  HobenLayerDemo
//
//  Created by Hoben on 2020/8/5.
//  Copyright © 2020 Hoben. All rights reserved.
//

#import "HobenCountDownCircleLayer.h"

@implementation HobenCountDownCircleLayer

+ (HobenCountDownCircleLayer *)layerWithStrokeColor:(UIColor *)strokeColor lineWidth:(CGFloat)lineWidth radius:(CGFloat)radius {
    HobenCountDownCircleLayer *shapeLayer = [HobenCountDownCircleLayer layer];
    shapeLayer.strokeColor = strokeColor.CGColor;
    shapeLayer.lineWidth = lineWidth;
    shapeLayer.fillColor = [UIColor clearColor].CGColor; // 填充色为无色
    shapeLayer.lineCap = kCALineCapRound; // 指定线的边缘是圆的
    shapeLayer.totalCountDown = 1;
    shapeLayer.radius = radius;
    return shapeLayer;
}

- (void)showAnimationWithCountdown:(CGFloat)countDown {
    if (_totalCountDown <= 0) {
        NSAssert(NO, @"总计时不能为0");
        return;
    }
    [self showAnimationWithProgress:(_totalCountDown - countDown) * 1.0 / _totalCountDown];
}

- (void)showAnimationWithProgress:(CGFloat)progress {
    CGFloat startA = - M_PI_2;  // 设置进度条起点位置
    CGFloat endA;               // 设置进度条终点位置
    CGFloat clockWiseFlag = _clockWise ? 1 : -1;
    CGFloat progressFlag = _increase ? 1 : -1;
    CGFloat percent = _increase ? progress : (1 - progress);
    
    // 顺增、逆减，顺时针构建环形
    BOOL shouldClockWiseBulid = (clockWiseFlag * progressFlag > 0);
    
    endA = startA + M_PI * 2 * percent * clockWiseFlag * progressFlag;
    
    UIBezierPath *path = [UIBezierPath bezierPathWithArcCenter:CGPointMake(_radius / 2, _radius / 2) radius:_radius / 2 - self.lineWidth / 2 startAngle:startA endAngle:endA clockwise:shouldClockWiseBulid]; // 构建环形
    self.path = [path CGPath];
}

@end

Demo调用：

//
//  ViewController.m
//  HobenLayerDemo
//
//  Created by Hoben on 2020/8/19.
//  Copyright © 2020 Hoben. All rights reserved.
//

#import "ViewController.h"
#import "HobenCountDownCircleLayer.h"

#define kHobenRadius 100.f

#define kHobenTotalCountDown 20.f

@interface ViewController ()

@property (nonatomic, strong) HobenCountDownCircleLayer *circleCountDownLayer;

@property (nonatomic, strong) UIButton *circleButton;

@property (nonatomic, strong) NSTimer *timer;

@property (nonatomic, assign) NSInteger countdown;

@property (nonatomic, strong) UISwitch *clockWiseSwitch;

@property (nonatomic, strong) UISwitch *increaseSwitch;

@property (nonatomic, strong) UILabel *clockWiseLabel;

@property (nonatomic, strong) UILabel *increaseLabel;

@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view.
    
    [self.view addSubview:self.circleButton];
    [self.circleButton.layer addSublayer:self.circleCountDownLayer];
    
    [self.view addSubview:self.clockWiseLabel];
    [self.view addSubview:self.increaseLabel];
    
    [self.view addSubview:self.clockWiseSwitch];
    [self.view addSubview:self.increaseSwitch];
}

- (void)viewDidLayoutSubviews {
    [super viewDidLayoutSubviews];
    
    self.circleButton.center = self.view.center;
    self.circleCountDownLayer.frame = CGRectMake(0, 0, kHobenRadius, kHobenRadius);
    
    
    self.clockWiseLabel.frame = CGRectMake(100.f, 430.f, 20.f, 20.f);
    [self.clockWiseLabel sizeToFit];
    self.clockWiseSwitch.frame = CGRectMake(180.f, 420.f, 20.f, 20.f);
    
    self.increaseLabel.frame = CGRectMake(100.f, 480.f, 20.f, 20.f);
    [self.increaseLabel sizeToFit];
    self.increaseSwitch.frame = CGRectMake(180.f, 470.f, 20.f, 20.f);
}

- (void)stopTimer {
    if (self.timer) {
        [self.timer invalidate];
        self.timer = nil;
    }
}

#pragma mark - Action

- (void)onClockWiseChanged:(UISwitch *)switcher {
    BOOL closeWise = switcher.on;
    self.circleCountDownLayer.clockWise = closeWise;
}

- (void)onIncreaseChanged:(UISwitch *)switcher {
    BOOL increase = switcher.on;
    self.circleCountDownLayer.increase = increase;
}

- (void)startTimer {
    [self stopTimer];
    _countdown = kHobenTotalCountDown;
    __weak typeof(self) weakSelf = self;
    self.timer = [NSTimer timerWithTimeInterval:.1f repeats:YES block:^(NSTimer * _Nonnull timer) {
        weakSelf.countdown--;
    }];
    
    [[NSRunLoop currentRunLoop] addTimer:self.timer forMode:NSRunLoopCommonModes];
}

#pragma mark - Setter & Getter

- (void)setCountdown:(NSInteger)countdown {
    _countdown = countdown;
    if (countdown > 0) {
        self.circleCountDownLayer.hidden = NO;
        [self.circleCountDownLayer showAnimationWithCountdown:countdown];
    } else {
        [self stopTimer];
        self.circleCountDownLayer.hidden = YES;
    }
}

- (UIButton *)circleButton {
    if (!_circleButton) {
        _circleButton = [UIButton buttonWithType:UIButtonTypeCustom];
        _circleButton.frame = CGRectMake(0, 0, kHobenRadius, kHobenRadius);
        _circleButton.layer.cornerRadius = kHobenRadius / 2;
        _circleButton.layer.masksToBounds = YES;
        [_circleButton setTitle:@"Start" forState:UIControlStateNormal];
        _circleButton.titleLabel.font = [UIFont systemFontOfSize:16.f];
        [_circleButton setTitleColor:[UIColor greenColor] forState:UIControlStateNormal];
        [_circleButton addTarget:self action:@selector(startTimer) forControlEvents:UIControlEventTouchUpInside];
        _circleButton.backgroundColor = [UIColor blackColor];
    }
    return _circleButton;
}

- (HobenCountDownCircleLayer *)circleCountDownLayer {
    if (!_circleCountDownLayer) {
        _circleCountDownLayer = ({
            HobenCountDownCircleLayer *progressLayer = [HobenCountDownCircleLayer layerWithStrokeColor:[UIColor greenColor] lineWidth:5.f radius:kHobenRadius];
            progressLayer.clockWise = YES;
            progressLayer.increase = YES;
            progressLayer.totalCountDown = kHobenTotalCountDown;
            progressLayer;
        });
    }
    return _circleCountDownLayer;
}

- (UISwitch *)clockWiseSwitch {
    if (!_clockWiseSwitch) {
        _clockWiseSwitch = ({
            UISwitch *switcher = [[UISwitch alloc] init];
            [switcher setOn:YES];
            [switcher addTarget:self action:@selector(onClockWiseChanged:) forControlEvents:UIControlEventValueChanged];
            switcher;
        });
    }
    return _clockWiseSwitch;
}

- (UISwitch *)increaseSwitch {
    if (!_increaseSwitch) {
        _increaseSwitch = ({
            UISwitch *switcher = [[UISwitch alloc] init];
            [switcher setOn:YES];
            [switcher addTarget:self action:@selector(onIncreaseChanged:) forControlEvents:UIControlEventValueChanged];
            switcher;
        });
    }
    return _increaseSwitch;
}

- (UILabel *)clockWiseLabel {
    if (!_clockWiseLabel) {
        _clockWiseLabel = ({
            UILabel *label = [[UILabel alloc] init];
            label.font = [UIFont systemFontOfSize:14.f];
            label.text = @"是否顺时针";
            label;
        });
    }
    return _clockWiseLabel;
}

- (UILabel *)increaseLabel {
    if (!_increaseLabel) {
        _increaseLabel = ({
            UILabel *label = [[UILabel alloc] init];
            label.font = [UIFont systemFontOfSize:14.f];
            label.text = @"是否递增";
            label;
        });
    }
    return _increaseLabel;
}

@end

总的来说，构建这个环形看上去不是很难，但是实际写的时候还是有点绕的，四种情形各不相同，需要先分开分析再结合规律总结，才能造出一个比较通用的轮子~