简述
SKAutoScrollLabel是一个同时支持水平/垂直两种类型的“跑马灯”效果的自动滚动UILabel。在滚动的边缘使用了梯度褪色来解决滚动边缘生硬的效果问题，总体效果呈现出混然天成的感觉，并且使用简单方便。如果你觉得还不错，请star支持一下吧~
效果图
如何开始
1.从GitHub上Clone-->SKAutoScrollLabel，然后查看Demo
2.直接将目录下的SKAutoScrollLabel拷贝到工程中，或在podfile文件夹中添加 pod 'SKAutoScrollLabel'
使用方法
初始化
SKAutoScrollLabel * leftLabel = [[SKAutoScrollLabel alloc] initWithFrame:CGRectMake(50, 50, [UIScreen mainScreen].bounds.size.width - 100, 50)];
[self.view addSubview:leftLabel];
基本设置
leftLabel.backgroundColor = [UIColor blackColor];// 背景色
leftLabel.textColor = [UIColor whiteColor];// 字体颜色
leftLabel.font = [UIFont systemFontOfSize:16];// 字体大小
leftLabel.direction = SK_AUTOSCROLL_DIRECTION_LEFT;// 滚动方向，这是向左滚动
leftLabel.text = text;// 显示内容
实现
※ 这里仅列出关键步骤，具体方法请查阅源码
- 我们需要创建一个数组，来存放我们滚动时所需要展示的label，这里我们只创建两个label存放到数组中即可（滚动只需要两个即可达成持续跑马灯的效果）
// 创建label数组
NSMutableSet * labelSet = [[NSMutableSet alloc] init];
for (NSInteger i = 0; i < kLabelCount; i++) {
UILabel * label = [UILabel new];
label.backgroundColor = [UIColor clearColor];
label.autoresizingMask = self.autoresizingMask;
label.frame = CGRectMake(0, 0, 50, 50);
[self.scrollView addSubview:label];
[labelSet addObject:label];
}
self.labels = [labelSet.allObjects copy];
2.区分水平和垂直的UILabel
static void each_object(NSArray *objects, void (^block)(UILabel * label)) {
for (UILabel * label in objects) {
block(label);
}
}
__block float offset = 0;
// 遍历label数组中的元素
each_object(self.labels, ^(UILabel *label) {
[label sizeToFit];
CGRect frame = label.frame;
// 垂直
if (self.direction != SK_AUTOSCROLL_DIRECTION_RIGHT && self.direction != SK_AUTOSCROLL_DIRECTION_LEFT) {
// 动态获取长度和高度, 以此达到将label垂直的目的
NSDictionary * attribute = [NSDictionary dictionaryWithObjectsAndKeys:self.font,NSFontAttributeName, nil];
CGSize sizeWord = [@"一" boundingRectWithSize:self.bounds.size options:NSStringDrawingUsesFontLeading | NSStringDrawingUsesLineFragmentOrigin attributes:attribute context:nil].size;
CGFloat wordWidth = sizeWord.width;
CGSize sizeStr = [self.text boundingRectWithSize:CGSizeMake(wordWidth, CGFLOAT_MAX) options:NSStringDrawingUsesFontLeading | NSStringDrawingUsesLineFragmentOrigin attributes:attribute context:nil].size;
CGFloat wordHeight = sizeStr.height;
frame.origin = CGPointMake((CGRectGetWidth(self.frame) / 2) - (wordWidth / 2), offset);
frame.size = CGSizeMake(wordWidth, wordHeight);
label.frame = frame;
label.numberOfLines = 0;
offset += CGRectGetHeight(label.bounds) + self.labelSpacing;
} else {// 水平
frame.origin = CGPointMake(offset, 0);
frame.size.height = CGRectGetHeight(self.bounds);
label.frame = frame;
offset += CGRectGetWidth(label.bounds) + self.labelSpacing;
// 重新定位label在scrollview中的位置
label.center = CGPointMake(label.center.x, roundf(self.center.y - CGRectGetMinY(self.frame)));
}
});
3.判断滚动条件，是否允许滚动
// (水平方向) 判断当前scrollLabel是否大于self的宽度，如果是就开始滚动
if (CGRectGetWidth(self.scrollLabel.bounds) > CGRectGetWidth(self.bounds)) {
CGSize size = CGSizeMake(CGRectGetWidth(self.scrollLabel.bounds) + CGRectGetWidth(self.bounds) + self.labelSpacing, CGRectGetHeight(self.bounds));
self.scrollView.contentSize = size;
EACH_LABEL(hidden, NO);
[self applyGradientMaskForFadeLength:kDefaultFadeLength enableFade:self.scrolling];
[self scrollLabelIfNeeded];
} else if (CGRectGetHeight(self.scrollLabel.bounds) > CGRectGetHeight(self.bounds)) {// (垂直方向) 判断当前scrollLabel是否大于self的高度，如果是就开始滚动
CGSize size = CGSizeMake(CGRectGetWidth(self.bounds), CGRectGetHeight(self.scrollLabel.bounds) + self.labelSpacing);
self.scrollView.contentSize = size;
EACH_LABEL(hidden, NO);
[self applyGradientMaskForFadeLength:kDefaultFadeLength enableFade:self.scrolling];
[self scrollLabelIfNeeded];
} else {
// 隐藏其他label
EACH_LABEL(hidden, self.scrollLabel != label);
// 调整scrollView和scrollLabel
self.scrollView.contentSize = self.bounds.size;
self.scrollLabel.frame = self.bounds;
self.scrollLabel.hidden = NO;
self.scrollLabel.textAlignment = NSTextAlignmentCenter;
[self.scrollView.layer removeAllAnimations];
[self applyGradientMaskForFadeLength:0 enableFade:NO];
}
4.自动滚动动画
switch (self.direction) {// 滚动方向
case SK_AUTOSCROLL_DIRECTION_LEFT:
self.scrollView.contentOffset = CGPointZero;
break;
case SK_AUTOSCROLL_DIRECTION_RIGHT:
self.scrollView.contentOffset = CGPointMake(width + self.labelSpacing, 0);
break;
case SK_AUTOSCROLL_DIRECTION_TOP:
self.scrollView.contentOffset = CGPointZero;
break;
case SK_AUTOSCROLL_DIRECTION_BOTTOM:
self.scrollView.contentOffset = CGPointMake(0, height - 10 - CGRectGetHeight(self.bounds));
break;
}
// 滚动动画, UIViewAnimationOptionRepeat一直重复动画
[UIView animateWithDuration:duration delay:self.autoScrollInterval options:UIViewAnimationOptionRepeat animations:^{
switch (self.direction) {
case SK_AUTOSCROLL_DIRECTION_LEFT:
self.scrollView.contentOffset = CGPointMake(width + self.labelSpacing, 0);
break;
case SK_AUTOSCROLL_DIRECTION_RIGHT:
self.scrollView.contentOffset = CGPointZero;
break;
case SK_AUTOSCROLL_DIRECTION_TOP:
self.scrollView.contentOffset = CGPointMake(0, CGRectGetHeight(self.scrollLabel.bounds) + self.labelSpacing);
break;
case SK_AUTOSCROLL_DIRECTION_BOTTOM:
self.scrollView.contentOffset = CGPointZero;
break;
}
} completion:^(BOOL finished) {
_scrolling = NO;
// 移除阴影
[self applyGradientMaskForFadeLength:kDefaultFadeLength enableFade:NO];
// 完成后循调用
if (finished) {
[self performSelector:@selector(scrollLabelIfNeeded)];
}
}];
5.使用CAGradientLayer在滚动边缘的制造梯度褪色效果
// 创建梯度mask和消失长度
CAGradientLayer * gradientMask = [CAGradientLayer layer];
gradientMask.bounds = self.layer.bounds;
gradientMask.position = CGPointMake(CGRectGetMidX(self.bounds), CGRectGetMidY(self.bounds));
gradientMask.shouldRasterize = YES;
gradientMask.rasterizationScale = [UIScreen mainScreen].scale;
CGFloat fadePoint = 0;
// 垂直方向的梯度褪色
if (self.direction != SK_AUTOSCROLL_DIRECTION_RIGHT && self.direction != SK_AUTOSCROLL_DIRECTION_LEFT) {
gradientMask.startPoint = CGPointMake(CGRectGetMidX(self.frame), 0);
gradientMask.endPoint = CGPointMake(CGRectGetMidX(self.frame), 1);
fadePoint = fadeLength / CGRectGetHeight(self.bounds);
// 水平方向的梯度褪色
} else {
gradientMask.startPoint = CGPointMake(0, CGRectGetMidY(self.frame));
gradientMask.endPoint = CGPointMake(1, CGRectGetMidY(self.frame));
fadePoint = fadeLength / CGRectGetWidth(self.bounds);
}
// 设置渐变mask颜色和位置
id transparent = (id)[UIColor clearColor].CGColor;
id opaque = (id)[UIColor blackColor].CGColor;
gradientMask.colors = @[transparent, opaque, opaque, transparent];
// 计算褪色
NSNumber * leftFadePoint = @(fadePoint);
NSNumber * rightFadePoint = @(1 - fadePoint);
if (!fade) {
switch (self.direction) {
case SK_AUTOSCROLL_DIRECTION_LEFT:
leftFadePoint = @0;
break;
case SK_AUTOSCROLL_DIRECTION_RIGHT:
leftFadePoint = @0;
rightFadePoint = @1;
break;
case SK_AUTOSCROLL_DIRECTION_TOP:
leftFadePoint = @0;
break;
case SK_AUTOSCROLL_DIRECTION_BOTTOM:
leftFadePoint = @0;
rightFadePoint = @1;
break;
}
}
// 将计算结果交给mask
gradientMask.locations = @[@0, leftFadePoint, rightFadePoint, @1];
[CATransaction begin];
[CATransaction setDisableActions:YES];
self.layer.mask = gradientMask;
[CATransaction commit];
感谢你花时间阅读以上内容, 如果这个项目能够帮助到你，记得告诉我
Email: shevakuilin@gmail.com
