iOS開發(fā)的22個奇葩技巧
導讀：TableView不顯示沒內(nèi)容的Cell怎么辦？鍵盤事件寫得好煩躁，都想摔鍵盤了怎么辦？App老不流暢哪出問題了？CoreData語法又臭又長怎么辦？拉伸圖片怎么才能不變形？讓我們一起歡樂地學習一下iOS開發(fā)的各種小技巧吧。
1. TableView不顯示沒內(nèi)容的Cell怎么辦？
加 ? self.tableView.tableFooterView ?= ?[[UIView alloc] init];
2.自定義了leftBarbuttonItem左滑返回手勢失效了怎么辦？
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劃到頂怎么辦？
self.automaticallyAdjustsScrollViewInsets = NO;
4.鍵盤事件寫得好煩躁，都想摔鍵盤了怎么辦？
使用IQKeyboardManager
5.為什么我的App老是不流暢，到底哪里出了問題？
KMCGeigerCounter，快去GitHub上搬運吧。
6.怎么在不新建一個Cell的情況下調(diào)整separaLine的位置？
_myTableView.separatorInset = UIEdgeInsetsMake(0, 100, 0, 0);
7.怎么點擊self.view就讓鍵盤收起，需要添加一個tapGestures么？
- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
{
? ? ? ? ? [self.view endEditing:YES];
}
8.怎么給每個ViewController設定默認的背景圖片？
使用基類
9.想在代碼里改在xib里添加的layoutAttributes，但該怎么用代碼找？
像拉Button一樣地拉你的約束，nslayoutattribute也是可以拉線的。
10.怎么像Safari一樣滑動的時候隱藏navigationbar？
navigationController.hidesBarsOnSwipe = Yes
11.導航條返回鍵帶的title太討厭了，怎么讓它消失？
[[UIBarButtonItem appearance] setBackButtonTitlePositionAdjustment:UIOffsetMake(0, -60) ?forBarMetrics:UIBarMetricsDefault];
12. CoreData用起來好煩，語法又臭又長怎么辦？
MagicRecord
13. CollectionView怎么實現(xiàn)tableview那種懸停的header？
CSStickyHeaderFlowLayout
14.能不能只用一個pan手勢來代替UISwipegesture的各個方向？
- (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.拉伸圖片的時候怎么才能讓圖片不變形？
方法一：
UIImage *image = [[UIImage imageNamed:@"xxx"] stretchableImageWithLeftCapWidth:10 topCapHeight:10];
注：有開發(fā)者提醒這個已經(jīng)棄用，現(xiàn)在的方法叫resizableImageWithCapInsets。
16.怎么播放GIF的時候這么卡，有沒有好點的庫？
FlipBoard出品的FLAnimatedImage太適合你了。
17.怎么一句話添加上拉刷新？
使用SVPullToRefresh庫：
[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的小對勾顏色改成別的顏色？
_mTableView.tintColor = [UIColor redColor];
19.本來我的statusbar是lightcontent的，結果用UIImagePickerController會導致我的statusbar的樣式變成黑色，怎么辦？
- (void)navigationController:(UINavigationController *)navigationController willShowViewController:(UIViewController *)viewController animated:(BOOL)animated
{
[[UIApplication sharedApplication] setStatusBarStyle:UIStatusBarStyleLightContent];
}
20.怎么把我的navigationbar弄成透明的而不是帶模糊的效果？
[self.navigationBar setBackgroundImage:[UIImage new]
forBarMetrics:UIBarMetricsDefault];
self.navigationBar.shadowImage = [UIImage new];
self.navigationBar.translucent = YES;
21.怎么改變uitextfield placeholder的顏色和位置？
繼承uitextfield，重寫這個方法：
- (void) drawPlaceholderInRect:(CGRect)rect {
[[UIColor blueColor] setFill];
[self.placeholder drawInRect:rect withFont:self.font lineBreakMode:UILineBreakModeTailTruncation alignment:self.textAlignment];
}
