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Delegate

Each delegate is responsible for a specific role or task to keep the system simple and clean.Whenever an object needs to perform a certain task, it depends on another object to handle it. This is usually known as “separation of concerns” in software design.
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viewWillAppear不执行的解决办法

UITableViewController或UIViewController中使() 后viewWillAppear:(BOOL)animated不执行 解决方法如下： 先在 *.h 头文件里加上<UINavigationControllerDelegate> 接着在*.m 文件里加上相关代码 self.navigationController.delegate=self; 再使用此时navigationController的代理函数，就OK了。 -(void)navigationController:(UINavigationController *)navigationController willShowViewController:(UIViewController *)viewController animated:(BOOL)animated { [viewController viewWillAppear:animated]; } -(void)viewWillAppear:(BOOL)animated { NSLog(@"现在可以使用了"); } 代码实例： MyOrders.h @interface MyOrders : UIViewControllerlegate>{ } @property(nonatomic,retain)IBOutlet UITableView *table; MyOrders.m - (void)viewDidLoad { [super viewDidLoad]; self.navigationController.delegate=self; } -(void)navigationController:(UINavigationController *)navigationController willShowViewController:(UIViewController *)viewController animated:(BOOL)animated { [viewController viewWillAppear:animated]; } -(void)viewWillAppear:(BOOL)a...
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图片旋转时的边缘抗锯齿的三种方法以及性能

首先，系统给出的layer中的抗锯齿方法，简单粗暴，一个开关就搞定了。 layer.allowsEdgeAntialiasing = true 第二种，在info.plist中加入键值： "Renders with edge antialiasing" YES 即可。 第三种，给图像加上1px的透明，UIImage的category方法如下所示： - (UIImage *)antiAlias { CGFloat border = 1.0f; CGRect rect = CGRectMake(border, border, self.size.width-2*border, self.size.height-2*border); UIImage *img = nil; UIGraphicsBeginImageContext(CGSizeMake(rect.size.width,rect.size.height)); [self drawInRect:CGRectMake(-1, -1, self.size.width, self.size.height)]; img = UIGraphicsGetImageFromCurrentImageContext(); UIGraphicsEndImageContext(); UIGraphicsBeginImageContext(self.size); [img drawInRect:rect]; UIImage* antiImage = UIGraphicsGetImageFromCurrentImageContext(); UIGraphicsEndImageContext(); return antiImage; } 前两种是系统给出的方法，简单粗暴，但是第三种比较另类但是如果屏幕上出现大批量图片的时候，该方法可以提供更好的性能。 在第三种方法中，不能只用UIGraphicsBeginImageContext(imageRect.size);否则图像会变模糊。 应该再使用UIGraphicsBeginImageContextWithOptions
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