+ (UIImage *)croppedImage:(UIImage *)image fraction:(CGFloat)fractonPart{
 CGFloat width = image.size.width * fractonPart * image.scale;
 CGRect newFrame = CGRectMake(0, 0, width , image.size.height * image.scale);
 CGImageRef resultImage = CGImageCreateWithImageInRect(image.CGImage, newFrame);
 UIImage *result = [UIImage imageWithCGImage:resultImage scale:image.scale orientation:image.imageOrientation];
 CGImageRelease(resultImage);
 return result;
}

- (void)setFractionPart:(CGFloat)fractionPart{
 if (fractionPart == 0) {
 return;
 }
 UIImage *image = [CDZStarButton croppedImage:self.highlightedImage fraction:fractionPart];
 self.imageView.contentMode = UIViewContentModeScaleAspectFit;
 self.contentHorizontalAlignment = UIControlContentHorizontalAlignmentLeft;
 self.contentVerticalAlignment = UIControlContentVerticalAlignmentFill;
 [self setImage:image forState:UIControlStateHighlighted];
 [self setBackgroundImage:self.normalImage forState:UIControlStateHighlighted];
 self.selected = NO;
 self.highlighted = YES;
}

- (void)setHighlightedImage:(UIImage *)highlightedImage{
 _highlightedImage = [CDZStarButton reSizeImage:highlightedImage toSize:self.frame.size];
 [self setImage:_highlightedImage forState:UIControlStateSelected];
}

- (CGFloat)fractionPartOfPoint:(CGPoint)point{
 CGFloat fractionPart = (point.x - self.frame.origin.x) / self.frame.size.width;
 return round(fractionPart * 10) / 10;
}

- (void)setupView {
 for (NSInteger index = 0; index < self.numberOfStars; index++) {
  CDZStarButton *starButton = [CDZStarButton.alloc initWithSize:self.starSize];
  starButton.tag = index;
  starButton.normalImage = self.normalStarImage;
  starButton.highlightedImage = self.highlightedStarImage;
  starButton.userInteractionEnabled = NO;//关闭事件响应，交由UIControl本身处理
  [self addSubview:starButton];
 }
}

- (void)layoutSubviews {
 [super layoutSubviews];
 for (NSInteger index = 0; index < self.numberOfStars; index ++) {
  CDZStarButton *starButton = [self starForTag:index];
  CGFloat newY = (self.frame.size.height - self.starSize.height) / 2;
  CGFloat margin = 0;
  if (self.numberOfStars > 1) {
   margin = (self.frame.size.width - self.starSize.width * self.numberOfStars) / (self.numberOfStars - 1);
  }
  starButton.frame = CGRectMake((self.starSize.width + margin) * index, newY, self.starSize.width, self.starSize.height);
 }
}

- (CDZStarButton *)starForPoint:(CGPoint)point {
 for (NSInteger i = 0; i < self.numberOfStars; i++) {
  CDZStarButton *starButton = [self starForTag:i];
  if (CGRectContainsPoint(starButton.frame, point)) {
   return starButton;
  }
 }
 return nil;
}

- (CDZStarButton *)starForTag:(NSInteger)tag {
 __block UIView *target;
 [self.subviews enumerateObjectsUsingBlock:^(__kindof UIView * _Nonnull obj, NSUInteger idx, BOOL * _Nonnull stop) {
  if (obj.tag == tag) {
   target = obj;
   *stop = YES;
  }
 }];
 return (CDZStarButton *)target;
}

- (void)starsDownToIndex:(NSInteger)index {
 for (NSInteger i = self.numberOfStars; i > index; --i) {
  CDZStarButton *starButton = [self starForTag:i];
  starButton.selected = NO;
  starButton.highlighted = NO;
 }
}

- (void)starsUpToIndex:(NSInteger)index {
 for (NSInteger i = 0; i <= index; i++) {
  CDZStarButton *starButton = [self starForTag:i];
  starButton.selected = YES;
  starButton.highlighted = NO;
 }
}

- (void)setScore:(CGFloat)score{
 if (_score == score) {
  return;
 }
 _score = score;
 NSInteger index = floor(score);
 CGFloat fractionPart = score - index;;
 if (!self.isAllowFraction || fractionPart == 0) {
  index -= 1;
 }
 CDZStarButton *starButton = [self starForTag:index];
 if (starButton.selected) {
  [self starsDownToIndex:index];
 }
 else{
  [self starsUpToIndex:index];
 }
 starButton.fractionPart = fractionPart;
}

- (BOOL)beginTrackingWithTouch:(UITouch *)touch withEvent:(UIEvent *)event {
 CGPoint point = [touch locationInView:self];
 CDZStarButton *pressedStar = [self starForPoint:point];
 if (pressedStar) {
  self.currentStar = pressedStar;
  NSInteger index = pressedStar.tag;
  CGFloat fractionPart = 1;
  if (self.isAllowFraction) {
   fractionPart = [pressedStar fractionPartOfPoint:point];
  }
  self.score = index + fractionPart;
 }
 return YES;
}

- (BOOL)continueTrackingWithTouch:(UITouch *)touch withEvent:(UIEvent *)event {
 CGPoint point = [touch locationInView:self];
 CDZStarButton *pressedStar = [self starForPoint:point];
 if (pressedStar) {
  self.currentStar = pressedStar;
  NSInteger index = pressedStar.tag;
  CGFloat fractionPart = 1;
  if (self.isAllowFraction) {
   fractionPart = [pressedStar fractionPartOfPoint:point];
  }
  self.score = index + fractionPart;
 }
 else{
   //移到了当前星星的左边
  if (point.x < self.currentStar.frame.origin.x) {
   self.score = self.currentStar.tag;
  }
   //移到了当前星星的右边
  else if (point.x > (self.currentStar.frame.origin.x + self.currentStar.frame.size.width)){
   self.score = self.currentStar.tag + 1;
  }
 }
 return YES;
}

@protocol CDZStarsControlDelegate<NSObject>
@optional

/**
 回调星星改变后的分数

 @param starsControl 星星组件
 @param score 分数
 */
- (void)starsControl:(CDZStarsControl *)starsControl didChangeScore:(CGFloat)score;
@end

- (void)endTrackingWithTouch:(UITouch *)touch withEvent:(UIEvent *)event {
 [super endTrackingWithTouch:touch withEvent:event];
 if ([self.delegate respondsToSelector:@selector(starsControl:didChangeScore:)]) {
  [self.delegate starsControl:self didChangeScore:self.score];
 }
}

 

- (void)cancelTrackingWithEvent:(UIEvent *)event {
 [super cancelTrackingWithEvent:event];
 if ([self.delegate respondsToSelector:@selector(starsControl:didChangeScore:)]) {
  [self.delegate starsControl:self didChangeScore:self.score];
 }
}

- (instancetype)initWithFrame:(CGRect)frame
      stars:(NSInteger)number
      starSize:(CGSize)size
    noramlStarImage:(UIImage *)normalImage
   highlightedStarImage:(UIImage *)highlightedImage{
 if (self = [super initWithFrame:frame]) {
  _numberOfStars = number;
  _normalStarImage = normalImage;
  _highlightedStarImage = highlightedImage;
  _starSize = size;
  _allowFraction = NO;
  self.clipsToBounds = YES;
  self.backgroundColor = [UIColor clearColor];
  [self setupView];
 }
 return self;
}

 CDZStarsControl *starsControl = [CDZStarsControl.alloc initWithFrame:CGRectMake(0, 100, self.view.frame.size.width, 50) stars:5 starSize:CGSizeMake(50, 50) noramlStarImage:[UIImage imageNamed:@"star_normal"] highlightedStarImage:[UIImage imageNamed:@"star_highlighted"]];
 starsControl.delegate = self;
 starsControl.allowFraction = YES;
 starsControl.score = 2.6f;
 [self.view addSubview:starsControl];