iOS开发的22个巧技

摘要：TableView不显示没内容的Cell怎么办？键盘事件写得好烦躁，都想摔键盘了怎么办？App老不流畅哪出问题了？CoreData语法又臭又长怎么办？拉伸图片怎么才能不变形？让我们一起欢乐地学习一下iOS开发的各种小技巧吧。

本文作者@叶孤城___，他结合自身的实践开发经验总结出了22个iOS开发的小技巧，以非常欢乐的语调轻松解决开发过程中所遇到的各种苦逼难题，光读着便已忍俊不禁。

1. TableView不显示没内容的Cell怎么办？

类似于图1，我不想让下面的那些空显示。很简单，添加“self.tableView.tableFooterView = [[UIView alloc]    init];”试过都说好，加完这句之后就变成了图2的样子。

2. 自定义了leftBarbuttonItem左滑返回手势失效了怎么办？

[cpp] view plaincopyprint?

1. self.navigationItem.leftBarButtonItem = [[UIBarButtonItem alloc] 
2.               initWithImage:img 
3.               style:UIBarButtonItemStylePlain 
4.               target:self 
5.               action:@selector(onBack:)]; 
6. self.navigationController.interactivePopGestureRecognizer.delegate = (id<UIGestureRecognizerDelegate>)self; 

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

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

[cpp] view plaincopyprint?

1. self.automaticallyAdjustsScrollViewInsets = NO; 

self.automaticallyAdjustsScrollViewInsets = NO;

4. 键盘事件写得好烦躁，都想摔键盘了怎么办？

• 买个结实的键盘；
• 使用IQKeyboardManager（GitHub上可搜索），用完之后腰也不疼了，腿也不酸了。

5. 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上搬运吧。

6. 怎么在不新建一个Cell的情况下调整separaLine的位置？

[cpp] view plaincopyprint?

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

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

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

[cpp] view plaincopyprint?

1. - (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event 
2. { 
3.    [self.view endEditing:YES]; 
4. } 

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

8. 怎么给每个ViewController设定默认的背景图片？

使用基类啊，少年。

9. 想在代码里改在xib里添加的layoutAttributes，但该怎么用代码找？

像拉Button一样地拉你的约束，nslayoutattribute也是可以拉线的。

10. 怎么像Safari一样滑动的时候隐藏navigationbar？

[cpp] view plaincopyprint?

1. navigationController.hidesBarsOnSwipe = Yes 

navigationController.hidesBarsOnSwipe = Yes

11. 导航条返回键带的title太讨厌了，怎么让它消失？

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

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

12. CoreData用起来好烦，语法又臭又长怎么办？

MagicRecord

13. CollectionView怎么实现tableview那种悬停的header？

CSStickyHeaderFlowLayout

 

 

 

14. 能不能只用一个pan手势来代替UISwipegesture的各个方向？

[cpp] view plain copy print ?

1. - (void)pan:(UIPanGestureRecognizer *)sender 
2. { 
3. typedef NS_ENUM(NSUInteger, UIPanGestureRecognizerDirection) { 
4.     UIPanGestureRecognizerDirectionUndefined, 
5.     UIPanGestureRecognizerDirectionUp, 
6.     UIPanGestureRecognizerDirectionDown, 
7.     UIPanGestureRecognizerDirectionLeft, 
8.     UIPanGestureRecognizerDirectionRight 
9. }; 
10. static UIPanGestureRecognizerDirection direction = UIPanGestureRecognizerDirectionUndefined; 
11. switch (sender.state) { 
12.     case UIGestureRecognizerStateBegan: { 
13.         if (direction == UIPanGestureRecognizerDirectionUndefined) { 
14.             CGPoint velocity = [sender velocityInView:recognizer.view]; 
15.             BOOL isVerticalGesture = fabs(velocity.y) > fabs(velocity.x); 
16.             if (isVerticalGesture) { 
17.                 if (velocity.y > 0) { 
18.                     direction = UIPanGestureRecognizerDirectionDown; 
19.                 } else { 
20.                     direction = UIPanGestureRecognizerDirectionUp; 
21.                 } 
22.             } 
23.             else { 
24.                 if (velocity.x > 0) { 
25.                     direction = UIPanGestureRecognizerDirectionRight; 
26.                 } else { 
27.                     direction = UIPanGestureRecognizerDirectionLeft; 
28.                 } 
29.             } 
30.         } 
31.         break; 
32.     } 
33.     case UIGestureRecognizerStateChanged: { 
34.         switch (direction) { 
35.             case UIPanGestureRecognizerDirectionUp: { 
36.                 [self handleUpwardsGesture:sender]; 
37.                 break; 
38.             } 
39.             case UIPanGestureRecognizerDirectionDown: { 
40.                 [self handleDownwardsGesture:sender]; 
41.                 break; 
42.             } 
43.             case UIPanGestureRecognizerDirectionLeft: { 
44.                 [self handleLeftGesture:sender]; 
45.                 break; 
46.             } 
47.             case UIPanGestureRecognizerDirectionRight: { 
48.                 [self handleRightGesture:sender]; 
49.                 break; 
50.             } 
51.             default: { 
52.                 break; 
53.             } 
54.         } 
55.         break; 
56.     } 
57.     case UIGestureRecognizerStateEnded: { 
58.         direction = UIPanGestureRecognizerDirectionUndefined;    
59.         break; 
60.     } 
61.     default: 
62.         break; 
63. } 
64. } 

- (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;
}
}

15. 拉伸图片的时候怎么才能让图片不变形？

方法一：

[cpp] view plain copy print ?

1. UIImage *image = [[UIImage imageNamed:@"xxx"] stretchableImageWithLeftCapWidth:10 topCapHeight:10]; 

UIImage *image = [[UIImage imageNamed:@"xxx"] stretchableImageWithLeftCapWidth:10 topCapHeight:10];

注：有开发者提醒这个已经弃用，现在的方法叫resizableImageWithCapInsets。

方法二，如图：

16. 怎么播放GIF的时候这么卡，有没有好点的库？

FlipBoard出品的FLAnimatedImage太适合你了。

17. 怎么一句话添加上拉刷新？

使用SVPullToRefresh库：

[cpp] view plain copy print ?

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

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

18. 怎么把tableview里Cell的小对勾颜色改成别的颜色？

[cpp] view plain copy print ?

1. _mTableView.tintColor = [UIColor redColor]; 

_mTableView.tintColor = [UIColor redColor];

19. 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？

[cpp] view plain copy print ?

1. - (void)navigationController:(UINavigationController *)navigationController willShowViewController:(UIViewController *)viewController animated:(BOOL)animated 
2. { 
3.     [[UIApplication sharedApplication] setStatusBarStyle:UIStatusBarStyleLightContent]; 
4. } 

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

20. 怎么把我的navigationbar弄成透明的而不是带模糊的效果？

[cpp] view plain copy print ?

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

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

21. 怎么改变uitextfield placeholder的颜色和位置？

继承uitextfield，重写这个方法：

[cpp] view plain copy print ?

1. - (void) drawPlaceholderInRect:(CGRect)rect { 
2.     [[UIColor blueColor] setFill]; 
3.     [self.placeholder drawInRect:rect withFont:self.font lineBreakMode:UILineBreakModeTailTruncation alignment:self.textAlignment]; 
4. } 

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

22. 你为什么知道这么多奇怪的花招？

去Stack Overflow刷问题啊，少年！