用Objective中的NSNotificationCenter实现按键盘在屏幕上显示和隐藏ScrollView(上下键)

Question

假设我有一个屏幕，在这个屏幕上我有10个文本字段，现在我的问题是当键盘打开时，键盘在我的3个文本字段上打开。那么我该如何使用UIScrollView和NSNotification中心来管理它呢？

Answer 1

是的，我有一个代码这一点，我相信这肯定是你的工作。

 [[NSNotificationCenter defaultCenter] addObserver:self
                                         selector:@selector(keyboardWasShown:)
                                             name:UIKeyboardDidShowNotification object:nil];
[[NSNotificationCenter defaultCenter] addObserver:self
                                         selector:@selector(keyboardWillBeHidden:)
                                             name:UIKeyboardWillHideNotification object:nil];

// Called when the UIKeyboardDidShowNotification is sent.
- (void)keyboardWasShown:(NSNotification*)aNotification
{
    NSDictionary* info = [aNotification userInfo];
   CGSize kbSize = [[info objectForKey:UIKeyboardFrameBeginUserInfoKey]   CGRectValue].size;
   UIEdgeInsets contentInsets = UIEdgeInsetsMake(0.0, 0.0, kbSize.height, 0.0);
   MyScrollView.contentInset = contentInsets;
   MyScrollView.scrollIndicatorInsets = contentInsets;
 }

// Called when the UIKeyboardWillHideNotification is sent
- (void)keyboardWillBeHidden:(NSNotification*)aNotification
{
   UIEdgeInsets contentInsets = UIEdgeInsetsZero;
   MyScrollView.contentInset = contentInsets;
   MyScrollView.scrollIndicatorInsets = contentInsets;
}

Answer 2

您可以创建一个UIView类别，使其能够观察UIKeyboardWillShowNotification和UIKeyboardWillHideNotification通知

如下所示

@implementation UIView (PFInputViewControl)

-(void)setupKeyboardShow:(void(^)(NSNotification *notifacation))showblock hide:(void (^)(NSNotification *notifacation))hideblock {
      NSNotificationCenter *notificationCenter = [NSNotificationCenter defaultCenter];
      NSOperationQueue *mainQuene = [NSOperationQueue mainQueue];
      [notificationCenter addObserverForName:UIKeyboardWillShowNotification object:nil queue:mainQuene usingBlock:showblock];

      [notificationCenter addObserverForName:UIKeyboardWillHideNotification object:nil queue:mainQuene usingBlock:hideblock];

     //Setting tap hid gesture when the keyboard is showed and remove the tap gesture when it disappear
     [self setupForDismissKeyboard];
}

-(void)setupForDismissKeyboard{
     NSNotificationCenter *notificationCenter = [NSNotificationCenter defaultCenter];
     UITapGestureRecognizer *singleTap = [[UITapGestureRecognizer alloc]initWithTarget:self action:@selector(tapHidAction)];

     __weak typeof(self)weakSelf = self;
     NSOperationQueue *mainQuene = [NSOperationQueue mainQueue];
     [notificationCenter addObserverForName:UIKeyboardWillShowNotification object:nil queue:mainQuene usingBlock:^(NSNotification * _Nonnull note) {
         [weakSelf addGestureRecognizer:singleTap];
     }];

     [notificationCenter addObserverForName:UIKeyboardWillHideNotification object:nil queue:mainQuene usingBlock:^(NSNotification * _Nonnull note) {
         [weakSelf removeGestureRecognizer:singleTap];
     }];
 }

@end

在您的使用中，您只需要导入类别文件，然后设置代码

    [self.view setupKeyboardShow:^(NSNotification *notification) {

         //========== do your action when keyboard is show ==========
         //....
         //
         //such as
         NSDictionary* info = [notification userInfo];
         //get the size of key board
         CGSize kbSize = [[info objectForKey:UIKeyboardFrameEndUserInfoKey] CGRectValue].size;
         //make transform when key board show
         self.view.y = - kbSize.height;

     } hide:^(NSNotification *notification) {
         //.... key board hid action
         self.view.y = 0;
         //....
     }];


     //setup keyboard dismiss when touch the screen out side the keyboard
     [self.view setupForDismissKeyboard];