iOS开发的22个奇谲巧技

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?

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?

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?

_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?

- (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?

navigationController.hidesBarsOnSwipe = Yes


11. 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];


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?

- (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:
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:
[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?

_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?

- (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?

[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:
- (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!

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转载自iaiai.iteye.com/blog/2198674
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