1、绘制下载进度按钮

• 具体实现代码见 GitHub 源码 QExtension

• QProgressButton.h

      @interface QProgressButton : UIButton
  
      /// 进度值，范围 0 ～ 1
      @property (nonatomic, assign) CGFloat progress;
  
      /// 进度终止状态标题，一旦设置了此标题进度条就会停止
      @property (nonatomic, strong) NSString *stopTitle;
  
      /**
       *  创建带进度条的按钮
       *
       *  @param frame        按钮的 frame 值
       *  @param title        进按钮的标题
       *  @param lineWidth    进度条的线宽，default is 2
       *  @param lineColor    进度条线的颜色，default is greenColor
       *  @param textColor    进度值的颜色，default is blackColor
       *  @param backColor    按钮的背景颜色，default is clearColor
       *  @param isRound      按钮是否显示为圆形，default is YES
       *
       *  @return 带进度条的按钮
       */
      + (instancetype)q_progressButtonWithFrame:(CGRect)frame
                                          title:(NSString *)title
                                      lineWidth:(CGFloat)lineWidth
                                      lineColor:(nullable UIColor *)lineColor
                                      textColor:(nullable UIColor *)textColor
                                      backColor:(nullable UIColor *)backColor
                                        isRound:(BOOL)isRound;
  
      @end

• QProgressButton.m

      @interface QProgressButton ()
  
      /// 进度条的线宽
      @property (nonatomic, assign) CGFloat lineWidth;
  
      /// 进度条线的颜色
      @property (nonatomic, strong) UIColor *lineColor;
  
      /// 按钮的背景颜色
      @property (nonatomic, strong) UIColor *backColor;
  
      /// 按钮是否显示为圆形
      @property (nonatomic, assign, getter=isRound) BOOL round;
  
      @end
  
      @implementation QProgressButton
  
      /// 创建带进度条的按钮
      + (instancetype)q_progressButtonWithFrame:(CGRect)frame
                                          title:(NSString *)title
                                      lineWidth:(CGFloat)lineWidth
                                      lineColor:(nullable UIColor *)lineColor
                                      textColor:(nullable UIColor *)textColor
                                      backColor:(nullable UIColor *)backColor
                                        isRound:(BOOL)isRound {
  
          QProgressButton *progressButton = [[self alloc] init];
  
          progressButton.lineWidth = lineWidth ? : 2;
          progressButton.lineColor = lineColor ? : [UIColor colorWithRed:76/255.0 green:217/255.0 blue:100/255.0 alpha:1.0];
          progressButton.backColor = backColor ? : [UIColor clearColor];
          progressButton.round = isRound;
  
          // 设置按钮的实际 frame
          if (isRound) {
              CGRect tmpFrame = frame;
              tmpFrame.origin.y = frame.origin.y - (frame.size.width - frame.size.height) * 0.5;
              tmpFrame.size.height = frame.size.width;
              progressButton.frame = tmpFrame;
          } else {
              progressButton.frame = frame;
          }
  
          // 设置显示的标题和颜色
          [progressButton setTitle:title forState:UIControlStateNormal];
          [progressButton setTitleColor:(textColor ? : [UIColor blackColor]) forState:UIControlStateNormal];
  
          return progressButton;
      }
  
      /// 绘制进度条
      - (void)drawRect:(CGRect)rect {
  
          // 设置按钮圆角
          self.layer.masksToBounds = YES;
          self.layer.cornerRadius = rect.size.height * 0.5;
  
          // 绘制按钮的背景颜色
          UIBezierPath *path = [UIBezierPath bezierPathWithRect:rect];
          [self.backColor set];
          [path fill];
  
          // 设置进度终止时显示的内容
          if (self.stopTitle) {
  
              // 设置下载完成后的标题
              [self setTitle:self.stopTitle forState:UIControlStateNormal];
              return;
          }
  
          if (self.progress <= 0) {
              return;
          }
  
          // 清除按钮背景图片
          [self setBackgroundImage:nil forState:UIControlStateNormal];
  
          // 设置进度值
          [self setTitle:[NSString stringWithFormat:@"%.2f%%", self.progress * 100] forState:UIControlStateNormal];
  
          if (self.isRound) {
  
              CGPoint center = CGPointMake(rect.size.height * 0.5, rect.size.height * 0.5);
              CGFloat radius = (rect.size.height - self.lineWidth) * 0.5;
              CGFloat startA = - M_PI_2;
              CGFloat endA = startA + self.progress * 2 * M_PI;
  
              // 绘制进度条背景
              path = [UIBezierPath bezierPathWithArcCenter:center
                                                    radius:radius
                                                startAngle:0
                                                  endAngle:2 * M_PI
                                                 clockwise:YES];
              [[[UIColor lightGrayColor] colorWithAlphaComponent:0.5] set];
              path.lineWidth = self.lineWidth;
              [path stroke];
  
              // 绘制进度条
              path = [UIBezierPath bezierPathWithArcCenter:center
                                                    radius:radius
                                                startAngle:startA
                                                  endAngle:endA
                                                 clockwise:YES];
              path.lineWidth = self.lineWidth;
              path.lineCapStyle = kCGLineCapRound;
              [self.lineColor set];
              [path stroke];
  
          } else {
  
              CGFloat w = self.progress * rect.size.width;
              CGFloat h = rect.size.height;
  
              // 绘制进度条背景
              path = [UIBezierPath bezierPathWithRect:CGRectMake(0, 0, rect.size.width, rect.size.height)];
              [[[UIColor lightGrayColor] colorWithAlphaComponent:0.5] set];
              [path fill];
  
              // 绘制进度条
              path = [UIBezierPath bezierPathWithRect:CGRectMake(0, 0, w, h)];
              [self.lineColor set];
              [path fill];
          }
      }
  
      /// 设置进度值
      - (void)setProgress:(CGFloat)progress {
  
          _progress = progress;
  
          [self setNeedsDisplay];
      }
  
      /// 设置进度终止状态标题
      - (void)setStopTitle:(NSString *)stopTitle {
  
          _stopTitle = stopTitle;
  
          [self setNeedsDisplay];
      }
  
      @end

• ViewController.m

      // 创建进度按钮
      QProgressButton *progressButton = [QProgressButton q_progressButtonWithFrame:CGRectMake(100, 100, 100, 50)
                                                                             title:@"开始下载"
                                                                         lineWidth:10
                                                                         lineColor:[UIColor blueColor]
                                                                         textColor:[UIColor redColor]
                                                                         backColor:[UIColor yellowColor]
                                                                           isRound:YES];
  
      // 设置按钮点击事件
      [progressButton addTarget:self action:@selector(progressUpdate:) forControlEvents:UIControlEventTouchUpInside];
  
      // 将按钮添加到当前控件显示
      [self.view addSubview:progressButton];
  
      // 设置按钮的进度值
      self.progressButton.progress = progress;
  
      // 设置按钮的进度终止标题，一旦设置了此标题进度条就会停止
      self.progressButton.stopTitle = @"下载完成";

• 效果