开发过程中小的知识点梳理（三）

1.通过NSURL获取的图片->NSData->UIImage并进行压缩

UIImage *image = nil;
NSData *imageData = [NSData dataWithContentsOfURL:[NSURL URLWithString:weakSelf.shareInfoModel.image]];
image = [UIImage imageWithData:imageData];
if (!image) {
    image = [UIImage imageNamed:@"app_icon_90"];
}
content.imageData = UIImageJPEGRepresentation(image, 1.0);

2.定时器的简单使用。

//初始化一个定时器，5分钟执行一次timerAction方法
NSTimer *timer = [NSTimer timerWithTimeInterval:60*5 target:self selector:@selector(timerAction) userInfo:nil repeats:YES];
[[NSRunLoop mainRunLoop] addTimer:timer forMode:NSDefaultRunLoopMode];//关键代码

NSTimeInterval timeInterval = -[self.refreshDate timeIntervalSinceNow];
if (timeInterval >= 60*1) {  //时间间隔超过1分钟
    [timer setFireDate:[NSDate distantPast]]; //定时器立即执行
 } else {
    [timer setFireDate:[NSDate dateWithTimeIntervalSinceNow:AutoRefreshTimeInterval - timeInterval]]; //定时器开始计时
}
    //[timer setFireDate:[NSDate distantFuture]];//定时器暂停
    //[timer invalidate]; //定时器销毁

- (void)timerAction {
    NSTimeInterval timeInterval = -[self.refreshDate timeIntervalSinceNow];
    if (timeInterval >= 60*1) {//自动刷新不短于1分钟
    [self loadObjectsAtPageIndex:kFirstPageIndex];
    }
}

3.给UI控件设置横向渐变色

+ (CAGradientLayer *)gradientLayerWithCornerRadius:(CGFloat)radius
                                             width:(CGFloat)width
                                            height:(CGFloat)height
                                         leftColor:(UIColor *)leftColor
                                        rightColor:(UIColor *)rightColor{
    CAGradientLayer *gradientLayer = [CAGradientLayer layer];
    gradientLayer.cornerRadius = radius;
    gradientLayer.frame = CGRectMake(0, 0, width, height);
    gradientLayer.startPoint = CGPointMake(0, 0);
    gradientLayer.endPoint = CGPointMake(1, 0);
    gradientLayer.colors = @[(__bridge id)leftColor.CGColor,(__bridge id)rightColor.CGColor];
    return gradientLayer;
}

4.绝对布局设置指定圆角

- (void)addRoundedCorners:(UIRectCorner)corners
                withRadii:(CGSize)radii {

    UIBezierPath* rounded = [UIBezierPath bezierPathWithRoundedRect:self.bounds byRoundingCorners:corners cornerRadii:radii];
    CAShapeLayer* shape = [[CAShapeLayer alloc] init];
    [shape setPath:rounded.CGPath];

    self.layer.mask = shape;
}

5.相对布局设置指定圆角

- (void)addRoundedCorners:(UIRectCorner)corners
                withRadii:(CGSize)radii
                 viewRect:(CGRect)rect {

    UIBezierPath* rounded = [UIBezierPath bezierPathWithRoundedRect:rect byRoundingCorners:corners cornerRadii:radii];
    CAShapeLayer* shape = [[CAShapeLayer alloc] init];
    [shape setPath:rounded.CGPath];

    self.layer.mask = shape;
}