自适应UITextView和键盘位置

在UITextView输入时视图被键盘挡住，这可是非常常见的事，这里说一个解决方案。

基本思想就是在键盘将要出现时设置UITextView的frame在弹出的键盘之上，在键盘将要消失时重置UITextView的位置。

首先在消息中心中注册自己为事件观察者：

#pragma mark - View life cycle

- (void)viewDidLoad {
    [super viewDidLoad];
    
    self.textView.keyboardDismissMode = UIScrollViewKeyboardDismissModeInteractive;
}

- (void)viewDidAppear:(BOOL)animated {
    // 当键盘出现时发送消息给self
    [[NSNotificationCenter defaultCenter] addObserver:self
                                             selector:@selector(keyboardWillShow:)
                                                 name:UIKeyboardWillShowNotification
                                               object:nil];
    
    // 当键盘消失时发送消息给self
    [[NSNotificationCenter defaultCenter] addObserver:self
                                             selector:@selector(keyboardWillHide:)
                                                 name:UIKeyboardWillHideNotification
                                               object:nil];
}

- (void)viewDidDisappear:(BOOL)animated {
    [[NSNotificationCenter defaultCenter] removeObserver:self name:UIKeyboardWillShowNotification object:nil];
    [[NSNotificationCenter defaultCenter] removeObserver:self name:UIKeyboardWillHideNotification object:nil];
}

然后是对应的方法：

#pragma mark - Keyboard management

- (void)keyboardWillShow:(NSNotification *)noti {
    [UIView beginAnimations:nil context:nil];
    [UIView setAnimationDuration:0.5];
    
    CGSize keyboardSize = [[[noti userInfo] objectForKey:UIKeyboardFrameEndUserInfoKey] CGRectValue].size;
    CGFloat height = keyboardSize.height;
    self.textView.frame = CGRectMake(0.0,
                                     20.0,
                                     self.view.bounds.size.width,
                                     self.view.bounds.size.height - height - 20.0);
    
    [UIView commitAnimations];
}

- (void)keyboardWillHide:(NSNotification *)noti {
    [UIView beginAnimations:nil context:nil];
    [UIView setAnimationDuration:0.1];
    
    self.textView.frame = CGRectMake(0.0, 20.0, self.view.bounds.size.width, self.view.bounds.size.height - 20.0);
    
    [UIView commitAnimations];
}

为了让键盘出现得自然点，这里加了点动画。

也可以将其写成宏，让代码更加简洁：

#define TEXTVIEW_DEFAULT_FRAME CGRectMake(0.0, 20.0, self.view.bounds.size.width, self.view.bounds.size.height - 20.0)

#define ADJUST_TEXTVIEW_FRAME(nofi) \
CGRectMake(0.0, 20.0, \
self.view.bounds.size.width, \
self.view.bounds.size.height -\
[[[noti userInfo] objectForKey:UIKeyboardFrameEndUserInfoKey] CGRectValue].size.height - 20.0)

TEXTVIEW_DEFAULT_FRAME表示默认情况下的位置，ADJUST_TEXTVIEW_FRAME表示键盘出现后进行调整的位置。

修改后代码为：

#pragma mark - Keyboard management

- (void)keyboardWillShow:(NSNotification *)noti {
    [UIView beginAnimations:nil context:nil];
    [UIView setAnimationDuration:0.5];
    self.textView.frame = ADJUST_TEXTVIEW_FRAME(noti);
    [UIView commitAnimations];
}

- (void)keyboardWillHide:(NSNotification *)noti {
    [UIView beginAnimations:nil context:nil];
    [UIView setAnimationDuration:0.1];
    self.textView.frame = TEXTVIEW_DEFAULT_FRAME;
    [UIView commitAnimations];
}

尝试下运行：

不足之处：

这里UITextView中隐藏键盘的方法是UIScrollViewKeyboardDismissModeInteractive，在隐藏键盘时如果有下滑手势，那么在TextView和键盘之间将会出现一段空白：