前言

前段时间在研究YYModel框架时学到不少东西,尤其是下面要讲述的查看屏幕帧数的小工具.个人感觉在项目里比较实用,自己模仿写了一个,代码中有详细注释,有需要的小伙伴们可以点击这里查看, 如果star一下就更好了😆, 请看我的效果图👇

fps.gif

AxeFPSLabel实现思路

首先说下CADisplayLink, CADisplayLink是一种定时器, 系统的每一帧刷新时都会被调用. CADisplayLink中的timestamp是系统每次调用时的系统时间戳，通过计算两次时间戳的间隔，可以得到每一帧所花费的时间，既可以获取当前每秒能刷新多少帧。

下面给出YYFPSLabel源码

YYFPSLabel.h

/**
 Show Screen FPS...
 
 The maximum fps in OSX/iOS Simulator is 60.00.
 The maximum fps on iPhone is 59.97.
 The maxmium fps on iPad is 60.0.
 */
@interface YYFPSLabel : UILabel

@end

YYFPSLabel.m

#import "YYFPSLabel.h"
#import "YYWeakProxy.h"

#define kSize CGSizeMake(55, 20)

@implementation YYFPSLabel {
    CADisplayLink *_link;
    NSUInteger _count;
    NSTimeInterval _lastTime;
    UIFont *_font;
    UIFont *_subFont;
    
    NSTimeInterval _llll;
}

- (instancetype)initWithFrame:(CGRect)frame {
    if (frame.size.width == 0 && frame.size.height == 0) {
        frame.size = kSize;
    }
    self = [super initWithFrame:frame];
    
    self.layer.cornerRadius = 5;
    self.clipsToBounds = YES;
    self.textAlignment = NSTextAlignmentCenter;
    self.userInteractionEnabled = NO;
    self.backgroundColor = [UIColor colorWithWhite:0.000 alpha:0.700];
    
    _font = [UIFont fontWithName:@"Menlo" size:14];
    if (_font) {
        _subFont = [UIFont fontWithName:@"Menlo" size:4];
    } else {
        _font = [UIFont fontWithName:@"Courier" size:14];
        _subFont = [UIFont fontWithName:@"Courier" size:4];
    }
    
    // 如果直接用 self 或者 weakSelf，都不能解决循环引用问题
    _link = [CADisplayLink displayLinkWithTarget:[YYWeakProxy proxyWithTarget:self] selector:@selector(tick:)];
//    __weak typeof(self) weakSelf = self;
//    _link = [CADisplayLink displayLinkWithTarget:weakSelf selector:@selector(tick:)];
    [_link addToRunLoop:[NSRunLoop mainRunLoop] forMode:NSRunLoopCommonModes];
    return self;
}

- (void)dealloc {
    [_link invalidate];
    NSLog(@"timer release");
}

- (CGSize)sizeThatFits:(CGSize)size {
    return kSize;
}

- (void)tick:(CADisplayLink *)link {
    if (_lastTime == 0) {
        _lastTime = link.timestamp;
        return;
    }
    
    _count++;
    NSTimeInterval delta = link.timestamp - _lastTime;
    if (delta < 1) return;
    _lastTime = link.timestamp;
    float fps = _count / delta;
    _count = 0;
    
    CGFloat progress = fps / 60.0;
    UIColor *color = [UIColor colorWithHue:0.27 * (progress - 0.2) saturation:1 brightness:0.9 alpha:1];
    
    NSMutableAttributedString *text = [[NSMutableAttributedString alloc] initWithString:[NSString stringWithFormat:@"%d FPS",(int)round(fps)]];
    [text addAttribute:NSForegroundColorAttributeName value:color range:NSMakeRange(0, text.length - 3)];
    [text addAttribute:NSForegroundColorAttributeName value:[UIColor whiteColor] range:NSMakeRange(text.length - 3, 3)];
    [text addAttribute:NSFontAttributeName value:_font range:NSMakeRange(0, text.length)];
    [text addAttribute:NSFontAttributeName value:_subFont range:NSMakeRange(text.length - 4, 1)];
    self.attributedText = text;
}