iOS小技巧

1-->TableView不显示没内容的Cell怎么办?
    很简单
    self.tableView.tableFooterView = [[UIView alloc] init];
    试过的都说好.


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)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.


5-->为什么我的app老是不流畅,到底哪里出了问题?
   这个神器叫做:KMCGeigerCounter,快去github搬运吧.


6-->怎么在不新建一个Cell的情况下调整（隐藏）separaLine的位置?
   _myTableView.separatorInset = UIEdgeInsetsMake(0, screenWidth, 0, 0);
(注意: titleLabel的位置也会跟着改变)


7-->怎么点击self.view就让键盘收起,需要添加一个tapGestures么 ? NO
  - (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.


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？
    1.UIImage *image = [[UIImage imageNamed:@"xxx"] stretchableImageWithLeftCapWidth:10 topCapHeight:10];
    2.使用九切片技术


16-->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： 


17-->怎么一句话添加上拉刷新？
     使用MJRefresh 最新的已经支持gif 图和添加刷新图片了

18-->怎么把tableview里cell的小对勾的颜色改成别的颜色？
    _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-->如何修改导航返回按钮的标题（默认是上一级导航的title） ？
    // 推到下个页面之前 修改backItem标题为返回
    UIBarButtonItem *backBtn = [[UIBarButtonItem alloc] init];
    backBtn.title = @"返回";
    self.navigationItem.backBarButtonItem = backBtn;
    [self.navigationController pushViewController:zhtVC animated:YES];