iOS开发的22个奇葩技巧
导读：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。
1. TableView不显示没内容的Cell怎么办？
加 self.tableView.tableFooterView = [[UIView alloc] init];
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
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？
使用IQKeyboardManager
5.为什么我的App老是不流畅，到底哪里出了问题？
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
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。
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];
}