You must know: 22 weird tricks for iOS development

Combining his own practical development experience, he summarized 22 small tips for iOS development, and used a very cheerful tone to easily solve various difficult problems encountered in the development process. Just reading it makes you laugh.

1. What should I do if TableView does not display cells with no content?

Similar to Figure 1, I don't want the blanks below to show up. It's very simple, add "self.tableView.tableFooterView = [[UIView alloc] init];" and it works. After adding this sentence, it becomes what Figure 2 looks like.

2. What should I do if the left swipe back gesture of the customized leftBarbuttonItem fails?

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

3. What should I do if ScrollView cannot be scrolled to the top in viewController for unknown reasons?

 self.automaticallyAdjustsScrollViewInsets = NO;

4. I am so annoyed writing keyboard events that I want to throw the keyboard. What should I do?

Buy a solid keyboard;
After using IQKeyboardManager (searchable on GitHub), my waist and legs no longer hurt.

5. Why is my app always not running smoothly? What’s the problem?

As shown in the figure:

This artifact is called: KMCGeigerCounter, go to GitHub and copy it.

6. How to adjust the position of separaLine without creating a new Cell?

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

7. How to close the keyboard by clicking on self.view? Do I need to add a tapGestures?

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

8. How to set a default background image for each ViewController?

Use the base class, boy.

9. I want to change the layoutAttributes added in the xib in code, but how can I find it in code?

Pull your constraints like you pull a Button, NSLayoutAttribute can also pull lines.

10. How to hide the navigationbar when scrolling like Safari?

 navigationController.hidesBarsOnSwipe = Yes

11. The title of the back button on the navigation bar is so annoying, how can I make it disappear?

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

12. CoreData is annoying to use. What should I do if the syntax is long and boring?

MagicRecord

13. How does CollectionView implement a hovering header like tableview?

CSStickyHeaderFlowLayout

14. Can I use only one pan gesture to replace all directions of UISwipegesture?

 - ( 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. How can I keep the image from being deformed when stretching it?

Method 1:

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

Note: Some developers have reminded that this method has been deprecated and is now called resizableImageWithCapInsets.

Method 2, as shown in the figure:

16. Why is there so much lag when playing GIF? Is there a better library?

FLAnimatedImage by FlipBoard is perfect for you.

17. How to add pull-to-refresh in one sentence?

Using SVPullToRefresh library:

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

18. How to change the color of the small check mark in the Cell in the tableview to another color?

 _mTableView.tintColor = [UIColor redColor];

19. Originally my statusbar was lightcontent, but using UIImagePickerController caused the style of my statusbar to turn black. What should I do?

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

20. How can I make my navigationbar transparent instead of blurry?

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

21. How to change the color and position of UITextField placeholder?

Inherit UITextField and override this method:

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

22. Why do you know so many strange tricks?

Go ask questions on Stack Overflow, boy!