• 在iOS上有兩個(gè)通知可以監(jiān)聽鍵盤彈出和收回：

UIKeyboardWillShowNotification（彈出）和UIKeyboardWillHideNotification（收回）。可以分別監(jiān)聽兩個(gè)通知調(diào)整輸入框的位置。但也有一個(gè)監(jiān)聽起來更為方便的通知UIKeyboardWillChangeFrameNotification（直接監(jiān)聽鍵盤的frame改變，彈出或收回）代碼如下：

//監(jiān)聽鍵盤彈出或收回通知
[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(keyboardChange:) name:UIKeyboardWillChangeFrameNotification object:nil];

• 當(dāng)鍵盤frame改變(彈出和收回)時(shí)的操作：

- (void)keyboardChange:(NSNotification *)note{
    
    //拿到鍵盤彈出的frame
    CGRect frame = [note.userInfo[UIKeyboardFrameEndUserInfoKey] CGRectValue];
    
    //修改底部輸入框的約束
    self.bottomConstrain.constant = [UIScreen mainScreen].bounds.size.height - frame.origin.y;
    
    //鍵盤彈出所需時(shí)長
    CGFloat duration = [note.userInfo[UIKeyboardAnimationDurationUserInfoKey] doubleValue];
    
    //添加輸入框彈出和收回動畫
    [UIView animateWithDuration:duration animations:^{
       
        //立即刷新進(jìn)行重新布局
        [self.view layoutIfNeeded];
    }];
}

• 移除通知

//移除通知
- (void)dealloc{
    
    [[NSNotificationCenter defaultCenter] removeObserver:self];
}

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