iOS开发中关于键盘的处理

一、通过接收键盘弹出、回退时发出的通知来进行键盘的相关的处理：

- (void)viewDidLoad {
    [super viewDidLoad];

    //键盘弹出时接收通知
    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(keyboardShow:) name:UIKeyboardWillShowNotification object:nil];

    //键盘回退时接收通知
    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(keyboardHide:) name:UIKeyboardWillHideNotification object:nil];
}

//收到键盘弹出通知
-(void)keyboardShow:(NSNotification *)note
{
    CGRect keyboardRect = [note.userInfo[UIKeyboardFrameEndUserInfoKey] CGRectValue];
    self.toolBottomDistance.constant = keyboardRect.size.height;

    [UIView animateWithDuration:0.25 animations:^{
        [self.view layoutIfNeeded];
    }];
}
//收到键盘回退的通知
-(void)keyboardHide:(NSNotification *)note
{
    self.toolBottomDistance.constant = 0;

    [UIView animateWithDuration:0.25 animations:^{
        [self.view layoutIfNeeded];
    }];
}

//滑动屏幕时回退键盘
-(void)scrollViewWillBeginDragging:(UIScrollView *)scrollView
{
    [self.view endEditing:YES];
}

//当有键盘弹出、回退时，都会发通知，如果此控制器已销毁，通知会根据原来的地址找此控制器，程序会崩溃
-(void)dealloc
{
    [[NSNotificationCenter defaultCenter] removeObserver:self];
}

其中 toolBottomDistance 为工具条底部和 view 底部之间的约束。

二、通过接收键盘 frame 改变时发出的通知来进行相关的键盘处理：

- (void)viewDidLoad {
    [super viewDidLoad];

    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(keyboardAction:) name:UIKeyboardWillChangeFrameNotification object:nil];
}

-(void)keyboardAction:(NSNotification *)note
{
    CGRect rect = [note.userInfo[UIKeyboardFrameEndUserInfoKey] CGRectValue];
    CGFloat duration = [note.userInfo[UIKeyboardAnimationDurationUserInfoKey] floatValue];

    self.toolBottomDistance.constant = [UIScreen mainScreen].bounds.size.height - rect.origin.y;

    [UIView animateWithDuration:duration animations:^{
        [self.view layoutIfNeeded];
    }];
}

//滑动屏幕时回退键盘
-(void)scrollViewWillBeginDragging:(UIScrollView *)scrollView
{
    [self.view endEditing:YES];
}

//当有键盘弹出、回退时，都会发通知，如果此控制器已销毁，通知会根据原来的地址找此控制器，程序会崩溃
-(void)dealloc
{
    [[NSNotificationCenter defaultCenter] removeObserver:self];
}

以上改约束的方法还可以通过改 transform 来实现：

-(void)keyboardAction:(NSNotification *)note
{
    CGRect rect = [note.userInfo[UIKeyboardFrameEndUserInfoKey] CGRectValue];
    CGFloat duration = [note.userInfo[UIKeyboardAnimationDurationUserInfoKey] floatValue];

    //清空 transform
    self.view.transform = CGAffineTransformIdentity;

    CGFloat ty = [UIScreen mainScreen].bounds.size.height - rect.origin.y;

    [UIView animateWithDuration:duration animations:^{
        self.view.transform = CGAffineTransformMakeTranslation(0, -ty);
    }];
}

其它：回退键盘的三种方式：

• 方式一：注销第一响应者

[self.messageField resignFirstResponder];

• 方式二：停止编辑模式

[self.messageField endEditing:YES];

• 方式三：view 中所有控件停止编辑模式

[self.view endEditing:YES];

第三种方式使用比较方便，建议使用