UIScrollvie 里 keyboard遮挡问题

防止键盘遮挡的方式有很多，在一个UIScrollView 中，可以进行如下处理。
关键是拿到textfield的bottom，然后和键盘通知里的键盘高度做计算。

#define ScreenWidth         [[UIScreen mainScreen] bounds].size.width
#define ScreenHeight        [[UIScreen mainScreen] bounds].size.height
#import "ViewController.h"
#import "UIView+Positioning.h"
@interface ViewController ()<UIScrollViewDelegate,UITextViewDelegate>

@property (nonatomic,strong) UIScrollView *scrollView;

@property (nonatomic,strong) UITextView *textView;

@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
    [self.view addSubview:self.scrollView];


    _textView = [[UITextView alloc]initWithFrame:CGRectMake(0, 400, ScreenWidth, 50)];
    _textView.backgroundColor = [UIColor lightGrayColor];
    _textView.delegate =self;
    [self.scrollView addSubview:_textView];


    UITapGestureRecognizer  *tapGR=[[UITapGestureRecognizer alloc]initWithTarget:self action:@selector(tap)];
    tapGR.numberOfTapsRequired=1;
    [self.view addGestureRecognizer:tapGR];
}

-(void)tap{
    [_textView resignFirstResponder];
}

- (void)viewWillAppear:(BOOL)animated
{
    [super viewWillAppear:animated];

    [[NSNotificationCenter defaultCenter] addObserver:self
                                             selector:@selector(keyboardWillShow:)
                                                 name:UIKeyboardWillShowNotification
                                               object:nil];
    [[NSNotificationCenter defaultCenter] addObserver:self
                                             selector:@selector(keyboardWillShow:)
                                                 name:UIKeyboardWillHideNotification
                                               object:nil];
}

- (void)viewDidDisappear:(BOOL)animated
{
    [super viewDidDisappear:animated];

    [[NSNotificationCenter defaultCenter] removeObserver:self
                                                        name:UIKeyboardWillHideNotification
                                                      object:nil];
    [[NSNotificationCenter defaultCenter] removeObserver:self
                                                        name:UIKeyboardWillShowNotification
                                                      object:nil];
}

- (void)keyboardWillShow:(NSNotification *)aNotification
{
    CGFloat contentOffY = self.scrollView.contentOffset.y;
    UIViewAnimationCurve curve = [aNotification.userInfo[UIKeyboardAnimationCurveUserInfoKey]integerValue];
    NSNumber *duration = aNotification.userInfo[UIKeyboardAnimationDurationUserInfoKey];
     CGSize size = [aNotification.userInfo[UIKeyboardFrameEndUserInfoKey] CGRectValue].size;
    float keyboardHeight = size.height;
    CGFloat spaceY = self.textView.bottom - (ScreenHeight-keyboardHeight)-contentOffY;
    [UIView animateWithDuration:[duration doubleValue] delay:0 options:(curve << 16) animations: ^{
        if (spaceY>0) {
            CGFloat space =_scrollView.contentOffset.y + spaceY;
            [_scrollView setContentOffset:CGPointMake(0, space) animated:YES];
        }

    } completion:^(BOOL finished) {
    }];
}

-(UIScrollView *)scrollView{
    if (!_scrollView) {
        _scrollView = [[UIScrollView alloc] initWithFrame:CGRectMake(0, 0, ScreenWidth, ScreenHeight - 64)];
        _scrollView.contentSize = CGSizeMake(ScreenWidth, 800);
        _scrollView.delegate = self;
        _scrollView.alwaysBounceVertical = YES;
    }
    return _scrollView;
}


- (void)didReceiveMemoryWarning {
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}


@end