学习知识点总结(一)

1.当第一次用到这个类的时候就会掉用以下方法:

+ (void)initialize {

}

2.push和pop的使用:

#pragma mark -  拦截所有push方法
- (void)pushViewController:(UIViewController *)viewController animated:(BOOL)animated {
    
    if (self.viewControllers.count > 0) {
        // 如果navigationController的字控制器个数大于两个就隐藏
        viewController.hidesBottomBarWhenPushed = YES;
        
        viewController.navigationItem.leftBarButtonItem = [[UIBarButtonItem alloc] initWithTitle:@"返回" style:UIBarButtonItemStyleDone target:self action:@selector(back)];
    }
    [super pushViewController:viewController animated:YES];
}

#pragma mark -  拦截所有pop方法
- (void)back {
    [super popViewControllerAnimated:YES];
}

3.实现拖拽表视图的时候隐藏导航栏和标签栏:

- (void)scrollViewWillBeginDragging:(UIScrollView *)scrollView {
    [UIView animateWithDuration:1 animations:^{

                //改变标签栏的fram,隐藏
        self.tabBarController.tabBar.transform = CGAffineTransformMakeTranslation(0, 49);
        [UIView animateWithDuration:5 animations:^{

               //改变导航栏的透明度
            self.navigationController.navigationBar.alpha = 0;
        }];
    }];

}

- (void)scrollViewDidEndDragging:(UIScrollView *)scrollView willDecelerate:(BOOL)decelerate {
    [UIView animateWithDuration:1 animations:^{
        self.tabBarController.tabBar.transform = CGAffineTransformIdentity;
        self.navigationController.navigationBar.alpha = 1;
    }];
}

4.实现下拉表视图表头图片的等比放大,停止滑动图片还原大小至滑走:

#pragma mark -  重点的地方在这里 滚动时候进行计算
-(void)scrollViewDidScroll:(UIScrollView *)scrollView {
    CGFloat offsetY = scrollView.contentOffset.y;  //-264
    NSLog(@"%f",offsetY);
    
    //取得偏移的高度
    CGFloat offsetH = imageBGHeight + offsetY;
    
    //往下拉
    if (offsetH < 0) {
        CGRect frame = self.imageBG.frame;

        //改变图片的高度
        frame.size.height = imageBGHeight - offsetH;
        
        //图片的y要往上走
        frame.origin.y = -imageBGHeight + offsetH;
        self.imageBG.frame = frame;
    }
    
    CGFloat alpha = offsetH / imageBGHeight;
    
    [self.navigationController.navigationBar setBackgroundImage:[self imageWithColor:[[UIColor cyanColor] colorWithAlphaComponent:alpha]] forBarMetrics:UIBarMetricsDefault];
    self.titleLabel.alpha = alpha;
}

#pragma mark - 返回一张纯色图片
/** 返回一张纯色图片 */
- (UIImage *)imageWithColor:(UIColor *)color {
    // 描述矩形
    CGRect rect = CGRectMake(0.0f, 0.0f, 1.0f, 1.0f);
    // 开启位图上下文
    UIGraphicsBeginImageContext(rect.size);
    // 获取位图上下文
    CGContextRef context = UIGraphicsGetCurrentContext();
    // 使用color演示填充上下文
    CGContextSetFillColorWithColor(context, [color CGColor]);
    // 渲染上下文
    CGContextFillRect(context, rect);
    // 从上下文中获取图片
    UIImage *theImage = UIGraphicsGetImageFromCurrentImageContext();
    // 结束上下文
    UIGraphicsEndImageContext();
    return theImage;
}

5.实现十六进制转颜色的宏定义:

#define UIColorFromRGB(rgbValue) [UIColor colorWithRed:((float)((rgbValue & 0xFF0000) >> 16))/255.0 green:((float)((rgbValue & 0xFF00) >> 8))/255.0 blue:((float)(rgbValue & 0xFF))/255.0 alpha:1.0]

6.去掉导航分割线:

// 去掉导航分割线
    [self.navigationBar setBackgroundImage:[[UIImage alloc] init] forBarMetrics:UIBarMetricsDefault];
    [self.navigationBar setShadowImage:[[UIImage alloc] init]];