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:

 1 #pragma mark -  拦截所有push方法
 2 - (void)pushViewController:(UIViewController *)viewController animated:(BOOL)animated {
 3     
 4     if (self.viewControllers.count > 0) {
 5         // 如果navigationController的字控制器个数大于两个就隐藏
 6         viewController.hidesBottomBarWhenPushed = YES;
 7         
 8         viewController.navigationItem.leftBarButtonItem = [[UIBarButtonItem alloc] initWithTitle:@"返回" style:UIBarButtonItemStyleDone target:self action:@selector(back)];
 9     }
10     [super pushViewController:viewController animated:YES];
11 }
12 
13 #pragma mark -  拦截所有pop方法
14 - (void)back {
15     [super popViewControllerAnimated:YES];
16 }

3.实现拖拽表视图的时候隐藏导航栏和标签栏:

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

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

               //改变导航栏的透明度
 5             self.navigationController.navigationBar.alpha = 0;
 6         }];
 7     }];
 8 
 9 }
10 
11 - (void)scrollViewDidEndDragging:(UIScrollView *)scrollView willDecelerate:(BOOL)decelerate {
12     [UIView animateWithDuration:1 animations:^{
13         self.tabBarController.tabBar.transform = CGAffineTransformIdentity;
14         self.navigationController.navigationBar.alpha = 1;
15     }];
16 }

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:

 1 #pragma mark -  重点的地方在这里 滚动时候进行计算
 2 -(void)scrollViewDidScroll:(UIScrollView *)scrollView {
 3     CGFloat offsetY = scrollView.contentOffset.y;  //-264
 4     NSLog(@"%f",offsetY);
 5     
 6     //取得偏移的高度
 7     CGFloat offsetH = imageBGHeight + offsetY;
 8     
 9     //往下拉
10     if (offsetH < 0) {
11         CGRect frame = self.imageBG.frame;
12 
13         //改变图片的高度
14         frame.size.height = imageBGHeight - offsetH;
15         
16         //图片的y要往上走
17         frame.origin.y = -imageBGHeight + offsetH;
18         self.imageBG.frame = frame;
19     }
20     
21     CGFloat alpha = offsetH / imageBGHeight;
22     
23     [self.navigationController.navigationBar setBackgroundImage:[self imageWithColor:[[UIColor cyanColor] colorWithAlphaComponent:alpha]] forBarMetrics:UIBarMetricsDefault];
24     self.titleLabel.alpha = alpha;
25 }
26 
27 #pragma mark - 返回一张纯色图片
28 /** 返回一张纯色图片 */
29 - (UIImage *)imageWithColor:(UIColor *)color {
30     // 描述矩形
31     CGRect rect = CGRectMake(0.0f, 0.0f, 1.0f, 1.0f);
32     // 开启位图上下文
33     UIGraphicsBeginImageContext(rect.size);
34     // 获取位图上下文
35     CGContextRef context = UIGraphicsGetCurrentContext();
36     // 使用color演示填充上下文
37     CGContextSetFillColorWithColor(context, [color CGColor]);
38     // 渲染上下文
39     CGContextFillRect(context, rect);
40     // 从上下文中获取图片
41     UIImage *theImage = UIGraphicsGetImageFromCurrentImageContext();
42     // 结束上下文
43     UIGraphicsEndImageContext();
44     return theImage;
45 }

5.实现十六进制转颜色的宏定义:

1 #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:

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