iOS开发的一些奇巧淫技

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TableView不显示没内容的Cell怎么办?

类似这种,我不想让下面那些空的显示.

很简单.

self.tableView.tableFooterView = [[UIView alloc] init];

试过的都说好.

加完这句之后就变成了这样.

自定义了leftBarbuttonItem左滑返回手势失效了怎么办?

self.navigationItem.leftBarButtonItem = [[UIBarButtonItem alloc]                                         initWithImage:img                                         style:UIBarButtonItemStylePlain                                         target:self                                         action:@selector(onBack:)];self.navigationController.interactivePopGestureRecognizer.delegate = (id)self;

ScrollView莫名其妙不能在viewController划到顶怎么办?

self.automaticallyAdjustsScrollViewInsets = NO;

键盘事件写的好烦躁,都想摔键盘了,怎么办?

1.买个结实的键盘.

2.使用IQKeyboardManager(github上可搜索),用完之后腰也不疼了,腿也不酸了.

为什么我的app老是不流畅,到底哪里出了问题?

如图

这个神器叫做:KMCGeigerCounter,快去github搬运吧.

怎么在不新建一个Cell的情况下调整separaLine的位置?

_myTableView.separatorInset = UIEdgeInsetsMake(0, 100, 0, 0);

怎么点击self.view就让键盘收起,需要添加一个tapGestures么?

- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event{   [self.view endEditing:YES];}

怎么给每个ViewController设定默认的背景图片?

使用基类啊,少年。

想在代码里改在xib里添加的layoutAttributes,但是怎么用代码找啊?

像拉button一样的拉你的约束.nslayoutattribute也是可以拉线的.

怎么像safari一样滑动的时候隐藏navigationbar?

navigationController.hidesBarsOnSwipe = Yes

导航条返回键带的title太讨厌了,怎么让它消失!

[[UIBarButtonItem appearance] setBackButtonTitlePositionAdjustment:UIOffsetMake(0, -60)                                                     forBarMetrics:UIBarMetricsDefault];

CoreData用起来好烦,语法又臭又长,怎么办?

MagicRecord

CollectionView 怎么实现tableview那种悬停的header?

CSStickyHeaderFlowLayou

能不能只用一个pan手势来代替UISwipegesture的各个方向?

- (void)pan:(UIPanGestureRecognizer *)sender{typedef NS_ENUM(NSUInteger, UIPanGestureRecognizerDirection) {    UIPanGestureRecognizerDirectionUndefined,    UIPanGestureRecognizerDirectionUp,    UIPanGestureRecognizerDirectionDown,    UIPanGestureRecognizerDirectionLeft,    UIPanGestureRecognizerDirectionRight};static UIPanGestureRecognizerDirection direction = UIPanGestureRecognizerDirectionUndefined;switch (sender.state) {    case UIGestureRecognizerStateBegan: {        if (direction == UIPanGestureRecognizerDirectionUndefined) {            CGPoint velocity = [sender velocityInView:recognizer.view];            BOOL isVerticalGesture = fabs(velocity.y) > fabs(velocity.x);            if (isVerticalGesture) {                if (velocity.y > 0) {                    direction = UIPanGestureRecognizerDirectionDown;                } else {                    direction = UIPanGestureRecognizerDirectionUp;                }            }            else {                if (velocity.x > 0) {                    direction = UIPanGestureRecognizerDirectionRight;                } else {                    direction = UIPanGestureRecognizerDirectionLeft;                }            }        }        break;    }    case UIGestureRecognizerStateChanged: {        switch (direction) {            case UIPanGestureRecognizerDirectionUp: {                [self handleUpwardsGesture:sender];                break;            }            case UIPanGestureRecognizerDirectionDown: {                [self handleDownwardsGesture:sender];                break;            }            case UIPanGestureRecognizerDirectionLeft: {                [self handleLeftGesture:sender];                break;            }            case UIPanGestureRecognizerDirectionRight: {                [self handleRightGesture:sender];                break;            }            default: {                break;            }        }        break;    }    case UIGestureRecognizerStateEnded: {        direction = UIPanGestureRecognizerDirectionUndefined;           break;    }    default:        break;}}

拉伸图片的时候怎么才能让图片不变形？
1.UIImage *image = [[UIImage imageNamed:@"xxx"] stretchableImageWithLeftCapWidth:10 topCapHeight:10];

怎么播放GIF的时候这么卡，有没有好点的库？

FlipBoard出品的太适合你了：https://github.com/Flipboard/FLAnimatedImage

怎么一句话添加上拉刷新？

https://github.com/samvermette/SVPullToRefresh

[tableView addPullToRefreshWithActionHandler:^{// prepend data to dataSource, insert cells at top of table view// call [tableView.pullToRefreshView stopAnimating] when done} position:SVPullToRefreshPositionBottom];

怎么把tableview里cell的小对勾的颜色改成别的颜色？

_mTableView.tintColor = [UIColor redColor];

本来我的statusbar是lightcontent的，结果用UIImagePickerController会导致我的statusbar的样式变成黑色，怎么办？

- (void)navigationController:(UINavigationController *)navigationController willShowViewController:(UIViewController *)viewController animated:(BOOL)animated{    [[UIApplication sharedApplication] setStatusBarStyle:UIStatusBarStyleLightContent];}

怎么把我的navigationbar弄成透明的而不是带模糊的效果？

[self.navigationBar setBackgroundImage:[UIImage new]                         forBarMetrics:UIBarMetricsDefault];self.navigationBar.shadowImage = [UIImage new];self.navigationBar.translucent = YES;

怎么改变uitextfield placeholder的颜色和位置？

继承uitextfield，重写这个方法

- (void) drawPlaceholderInRect:(CGRect)rect {    [[UIColor blueColor] setFill];    [self.placeholder drawInRect:rect withFont:self.font lineBreakMode:UILineBreakModeTailTruncation alignment:self.textAlignment];}

你为什么知道这么多奇怪的花招？

去stackoverflow刷问题啊，少年！

能不能只用一个pan手势来代替UISwipegesture的各个方向?

- (void)pan:(UIPanGestureRecognizer *)sender{ typedef NS_ENUM(NSUInteger, UIPanGestureRecognizerDirection) {    UIPanGestureRecognizerDirectionUndefined,    UIPanGestureRecognizerDirectionUp,    UIPanGestureRecognizerDirectionDown,    UIPanGestureRecognizerDirectionLeft,    UIPanGestureRecognizerDirectionRight}; static UIPanGestureRecognizerDirection direction = UIPanGestureRecognizerDirectionUndefined; switch (sender.state) {     case UIGestureRecognizerStateBegan: {         if (direction == UIPanGestureRecognizerDirectionUndefined) {             CGPoint velocity = [sender velocityInView:recognizer.view];             BOOL isVerticalGesture = fabs(velocity.y) > fabs(velocity.x);             if (isVerticalGesture) {                if (velocity.y > 0) {                    direction = UIPanGestureRecognizerDirectionDown;                } else {                    direction = UIPanGestureRecognizerDirectionUp;                }            }             else {                if (velocity.x > 0) {                    direction = UIPanGestureRecognizerDirectionRight;                } else {                    direction = UIPanGestureRecognizerDirectionLeft;                }            }        }         break;    }     case UIGestureRecognizerStateChanged: {        switch (direction) {            case UIPanGestureRecognizerDirectionUp: {                [self handleUpwardsGesture:sender];                break;            }            case UIPanGestureRecognizerDirectionDown: {                [self handleDownwardsGesture:sender];                break;            }            case UIPanGestureRecognizerDirectionLeft: {                [self handleLeftGesture:sender];                break;            }            case UIPanGestureRecognizerDirectionRight: {                [self handleRightGesture:sender];                break;            }            default: {                break;            }        }        break;    }     case UIGestureRecognizerStateEnded: {        direction = UIPanGestureRecognizerDirectionUndefined;           break;    }     default:        break;} }

拉伸图片的时候怎么才能让图片不变形？

1. UIImage *image = [[UIImage imageNamed:@"xxx"] stretchableImageWithLeftCapWidth:10 topCapHeight:10];
(刚才有人提醒这个已经deprecated了哈,现在的方法叫resizableImageWithCapInsets).

2.如下操作：

怎么播放GIF的时候这么卡，有没有好点的库？

FlipBoard出品的太适合你了。https://github.com/Flipboard/FLAnimatedImage

怎么一句话添加上拉刷新？

https://github.com/samvermette/SVPullToRefresh

[tableView addPullToRefreshWithActionHandler:^{// prepend data to dataSource, insert cells at top of table view// call [tableView.pullToRefreshView stopAnimating] when done} position:SVPullToRefreshPositionBottom];

怎么把tableview里cell的小对勾的颜色改成别的颜色？

_mTableView.tintColor = [UIColor redColor];

本来我的statusbar是lightcontent的，结果用UIImagePickerController会导致我的statusbar的样式变成黑色，怎么办？

- (void)navigationController:(UINavigationController *)navigationController willShowViewController:(UIViewController *)viewController animated:(BOOL)animated {     [[UIApplication sharedApplication] setStatusBarStyle:UIStatusBarStyleLightContent]; }

怎么把我的navigationbar弄成透明的而不是带模糊的效果？

[self.navigationBar setBackgroundImage:[UIImage new] forBarMetrics:UIBarMetricsDefault]; self.navigationBar.shadowImage = [UIImage new]; self.navigationBar.translucent = YES;

怎么改变uitextfield placeholder的颜色和位置？

继承uitextfield，重写这个方法

- (void) drawPlaceholderInRect:(CGRect)rect {     [[UIColor blueColor] setFill];     [self.placeholder drawInRect:rect withFont:self.font lineBreakMode:UILineBreakModeTailTruncation alignment:self.textAlignment]; }

你为什么知道这么多奇怪的花招？

去stackoverflow刷问题啊，少年！

CGfloat和float的区别?

现在上架的app都要求支持64位系统,那么CGFloat和float的区别就在这里.command+左键点击CGFloat.

1
typedef CGFLOAT_TYPE CGFloat;

这里可以看到CGFloat是CGFLOAT_TYPE的宏定义,那么这个又是什么?

#if defined(__LP64__) && __LP64__# define CGFLOAT_TYPE double# define CGFLOAT_IS_DOUBLE 1# define CGFLOAT_MIN DBL_MIN# define CGFLOAT_MAX DBL_MAX#else# define CGFLOAT_TYPE float# define CGFLOAT_IS_DOUBLE 0# define CGFLOAT_MIN FLT_MIN# define CGFLOAT_MAX FLT_MAX#endif

这段话的意思就是,64位系统下,CGFLOAT是double类型,32位系统下是float类型.CGFloat能够保证你的代码在64位系统下也不容易出错,所以你的代码应该尽量使用CGFloat.尽管他可能造成一些多余的消耗.不过能保证安全.

应该使用FOUNDATION_EXPORT还是#define来定义常量?

一般iOS我们定义常量的方法有两种,来看下面例子

我的.h文件

FOUNDATION_EXPORT NSString * const kMyConstantString;  FOUNDATION_EXPORT NSString * const kMyConstantString2;

.m文件是这样定义的

NSString * const kMyConstantString = @"Hello";NSString * const kMyConstantString2 = @"World";

还有一种是常用的#define方法了

#define kMyConstantString @"Hello"

有什么区别呢?

使用第一种方法在检测字符串的值是否相等的时候更快.对于第一种你可以直接使用(stringInstance == MyFirstConstant)来比较,而define则使用的是这种.([stringInstance isEqualToString:MyFirstConstant])

哪个效率高,显而易见了.第一种直接比较的是指针地址,而第二个则是一一比较字符串的每一个字符是否相等.

static inline function是干嘛的?

如果你的.m文件需要频繁调用一个函数,可以用static inline来声明,这相当于把函数体当做一个大号的宏定义.不过这也不是百分之百有效,到底能不能把函数体转换为大号宏定义来用要看编译器心情,它要是觉得你的方法太复杂,他就不转了.他直接调用函数.

类似这种简单函数他肯定是乐意的.

static inline CGRect ScaleRect(CGRect rect, float n)

这到底是什么鬼?static void *CapturingStillImageContext = &CapturingStillImageContext;

这种声明方式常用于kvo,用来当做contenxt的key来添加.例如

[self addObserver:self forKeyPath:@"stillImageOutput.capturingStillImage" options:(NSKeyValueObservingOptionOld | NSKeyValueObservingOptionNew) context:CapturingStillImageContext];

这种声明方式可以导致a method to create a unique pointer at compile time.在编译的时候创建一个唯一的指针.因为kvo的时候context如果不小心重复了,会发生奇怪的事情.用这种方式可以避免.

如何快速定位crash的位置?