iOS下拉、上拉刷新控件的封装

iOS 封装下拉、上拉刷新控件，首先看下效果图：

简单阐述一下：自定义头部、尾部刷新视图，继承UIView，通过KVO监听scrollView的滑动，通过偏移量设置刷新状态，通过修改状态修改scrollView的滚动位置。建一个UIScrollView的分类，添加上拉、下拉刷新及回调的方法，可以让UITableView、UICollectionView直接调用。现在很多应用是在滑动到底部自动进行上拉加载超做，可以在scrollViewDidScroll这个代理方法中手动调用尾部刷新。

下面贴上主要相关代码：

控制器ViewController：

#import <UIKit/UIKit.h>

@interface ViewController : UIViewController

@end

/*** ---------------分割线--------------- ***/

#import "ViewController.h"
#import "HWRefresh.h"

@interface ViewController ()<UITableViewDataSource, UITableViewDelegate>

@property (nonatomic, strong) NSMutableArray *array;
@property (nonatomic, strong) UITableView *tableView;
@property (nonatomic, assign) NSInteger page;

@end

@implementation ViewController

- (NSMutableArray *)array
{
 if (!_array) {
  _array = [NSMutableArray array];
 }

 return _array;
}

- (void)viewDidLoad {
 [super viewDidLoad];

 self.view.backgroundColor = [UIColor blackColor];
 self.page = 1;

 //模拟获取信息
 [self getInfo];

 //创建控件
 [self creatControl];

 //添加头部刷新
 [self addHeaderRefresh];

 //添加尾部刷新
 [self addFooterRefresh];
}

- (void)getInfo
{
 NSArray *array = @[@"iOS HERO博客", @"iOS HERO博客", @"iOS HERO博客", @"iOS HERO博客", @"http://blog.csdn.net/hero_wqb"];
 dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(2.0f * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{
  if (self.page == 1) {
   self.array = [NSMutableArray arrayWithArray:array];
  }else{
   [self.array addObjectsFromArray:array];
  }
  [_tableView reloadData];
  [_tableView headerEndRefreshing];
  [_tableView footerEndRefreshing];
  NSLog(@"已经刷新好了");
 });
}

- (void)creatControl
{
 //列表视图
 _tableView = [[UITableView alloc] initWithFrame:CGRectMake(20, 64, [[UIScreen mainScreen] bounds].size.width - 100, [[UIScreen mainScreen] bounds].size.height - 164) style:UITableViewStylePlain];
 _tableView.dataSource = self;
 _tableView.delegate = self;
 [self.view addSubview:_tableView];
}

- (void)addHeaderRefresh
{
 __weak typeof(self) weakSelf = self;
 [_tableView addHeaderRefreshWithCallback:^{
  __strong typeof(weakSelf) strongSelf = weakSelf;
  strongSelf.page = 1;
  [strongSelf getInfo];
 }];
}

- (void)addFooterRefresh
{
 __weak typeof(self) weakSelf = self;
 [_tableView addFooterRefreshWithCallback:^{
  __strong typeof(weakSelf) strongSelf = weakSelf;
  strongSelf.page ++;
  [strongSelf getInfo];
 }];
}

#pragma mark - UITableViewDataSource
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
 return self.array.count;
}

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
 static NSString *identifier = @"refreshTest";
 UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:identifier];
 if (!cell) {
  cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:identifier];
 }
 cell.textLabel.text = [_array[indexPath.row] stringByAppendingString:[NSString stringWithFormat:@"_%ld", indexPath.row]];

 return cell;
}

- (void)scrollViewDidScroll:(UIScrollView *)scrollView
{
 //滑动到底部自动刷新
 if (_tableView.contentSize.height > _tableView.frame.size.height && _tableView.contentOffset.y + _tableView.frame.size.height > _tableView.contentSize.height - 40 && _page < 50) {
  [_tableView footerBeginRefreshing];
 }
}

@end

刷新基类HWRefreshBaseView：

#import <UIKit/UIKit.h>

#define HWRefreshContentOffset @"contentOffset"

typedef enum {
 HWRefreshStateNormal = 0, //普通状态
 HWRefreshStatePulling,  //释放即可刷新的状态
 HWRefreshStateRefreshing, //正在刷新中的状态
} HWRefreshState;

@interface HWRefreshBaseView : UIView

@property (nonatomic, weak) UIScrollView *scrollView;
@property (nonatomic, copy) NSString *pullToRefreshText;
@property (nonatomic, copy) NSString *releaseToRefreshText;
@property (nonatomic, copy) NSString *refreshingText;
@property (nonatomic, copy) void (^refreshingCallback)();
@property (nonatomic, assign) HWRefreshState state;
@property (nonatomic, assign) UIEdgeInsets scrollViewOriginalInset;

- (void)beginRefreshing;
- (void)endRefreshing;

@end

/*** ---------------分割线--------------- ***/

#import "HWRefreshBaseView.h"

#define KHWRefreshViewHeight 44.0f
#define KImageW 30.0f
#define KLabelW 100.0f

@interface HWRefreshBaseView ()

@property (nonatomic, weak) UILabel *rLabel;
@property (nonatomic, weak) UIImageView *rImageView;

@end

@implementation HWRefreshBaseView

- (instancetype)initWithFrame:(CGRect)frame
{
 frame.size.height = KHWRefreshViewHeight;
 if (self = [super initWithFrame:frame]) {
  CGFloat imageH = 30.f;
  CGFloat labelH = 20.f;
  CGFloat imageX = ([UIScreen mainScreen].bounds.size.width - KImageW - KLabelW) * 0.5;
  CGFloat imageY = (KHWRefreshViewHeight - imageH) * 0.5;
  CGFloat labelY = (KHWRefreshViewHeight - labelH) * 0.5;

  //图片
  UIImageView *rImageView = [[UIImageView alloc] initWithFrame:CGRectMake(imageX, imageY, KImageW, imageH)];
  rImageView.image = [UIImage imageNamed:@"refreshing.jpg"];
  [self addSubview:rImageView];
  self.rImageView = rImageView;

  //标签
  UILabel *rLabel = [[UILabel alloc] initWithFrame:CGRectMake(CGRectGetMaxX(rImageView.frame), labelY, KLabelW, labelH)];
  rLabel.text = self.pullToRefreshText;
  rLabel.font = [UIFont systemFontOfSize:14.0f];
  rLabel.textAlignment = NSTextAlignmentCenter;
  [self addSubview:rLabel];
  self.rLabel = rLabel;
 }

 return self;
}

- (void)willMoveToSuperview:(UIView *)newSuperview
{
 [super willMoveToSuperview:newSuperview];

 //旧的父控件
 [self.superview removeObserver:self forKeyPath:HWRefreshContentOffset context:nil];

 //新的父控件
 if (newSuperview) {
  [newSuperview addObserver:self forKeyPath:HWRefreshContentOffset options:NSKeyValueObservingOptionNew context:nil];

  //记录UIScrollView
  _scrollView = (UIScrollView *)newSuperview;

  //记录UIScrollView最开始的contentInset
  _scrollViewOriginalInset = _scrollView.contentInset;
 }

 //居中显示图片、提示信息
 CGRect temFrame = _rImageView.frame;
 temFrame.origin.x = (newSuperview.frame.size.width - KImageW - KLabelW) * 0.5;
 _rImageView.frame = temFrame;

 CGRect tf = _rLabel.frame;
 tf.origin.x = CGRectGetMaxX(_rImageView.frame);
 _rLabel.frame = tf;
}

- (void)setPullToRefreshText:(NSString *)pullToRefreshText
{
 _pullToRefreshText = pullToRefreshText;

 self.rLabel.text = pullToRefreshText;
}

- (void)setState:(HWRefreshState)state
{
 if (_state == state) return;

 switch (state) {
  case HWRefreshStateNormal: {
   [self stopAnimating];
   self.rLabel.text = self.pullToRefreshText;
   break;
  }

  case HWRefreshStatePulling: {
   self.rLabel.text = self.releaseToRefreshText;
   break;
  }

  case HWRefreshStateRefreshing: {
   [self startAnimating];
   self.rLabel.text = self.refreshingText;
   if (self.refreshingCallback) self.refreshingCallback();
   break;
  }

  default:
   break;
 }

 _state = state;
}

//开始刷新
- (void)beginRefreshing
{
 self.state = HWRefreshStateRefreshing;
}

//结束刷新
- (void)endRefreshing
{
 self.state = HWRefreshStateNormal;
}

//开始动画
- (void)startAnimating
{
 NSMutableArray *array = [NSMutableArray array];
 for (int i = 0; i < 2; i++) {
  NSString *imageName = [NSString stringWithFormat:@"refreshing%02d.jpg", i + 1];
  UIImage *image = [UIImage imageNamed:imageName];
  [array addObject:image];
 }

 [_rImageView setAnimationImages:array];
 [_rImageView setAnimationDuration:0.3f];
 [_rImageView startAnimating];
}

//结束动画
- (void)stopAnimating
{
 if (_rImageView.isAnimating) {
  [_rImageView stopAnimating];
  [_rImageView performSelector:@selector(setAnimationImages:) withObject:nil afterDelay:0];
 }
}

@end

头部刷新HWRefreshHeader：

#import "HWRefreshBaseView.h"

@interface HWRefreshHeader : HWRefreshBaseView

+ (instancetype)header;

@end

/*** ---------------分割线--------------- ***/

#import "HWRefreshHeader.h"

@implementation HWRefreshHeader

+ (instancetype)header
{
 return [[HWRefreshHeader alloc] init];
}

- (instancetype)initWithFrame:(CGRect)frame
{
 if (self = [super initWithFrame:frame]) {
  self.pullToRefreshText = @"下拉即可刷新";
  self.releaseToRefreshText = @"释放即可刷新";
  self.refreshingText = @"刷新中...";
 }

 return self;
}

- (void)willMoveToSuperview:(UIView *)newSuperview
{
 [super willMoveToSuperview:newSuperview];

 //设置自己的位置和尺寸
 CGRect frame = self.frame;
 frame.origin.y = - self.frame.size.height;
 self.frame = frame;
}

- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context
{
 //不能跟用户交互或正在刷新就直接返回
 if (!self.userInteractionEnabled || self.alpha <= 0.01 || self.hidden || self.state == HWRefreshStateRefreshing) return;

 //根据偏移量设置相应状态
 if ([keyPath isEqualToString:HWRefreshContentOffset]) {
  [self setStateWithContentOffset];
 }
}

- (void)setStateWithContentOffset
{
 //当前的contentOffset
 CGFloat currentOffsetY = self.scrollView.contentOffset.y;

 //头部控件刚好出现的offsetY
 CGFloat happenOffsetY = - self.scrollViewOriginalInset.top;

 //如果是向上滚动到看不见头部控件，直接返回
 if (currentOffsetY >= happenOffsetY) return;

 //滑动时
 if (self.scrollView.isDragging) {
  //普通状态和即将刷新状态的临界点
  CGFloat normalTopullingOffsetY = happenOffsetY - self.frame.size.height;

  //转为即将刷新状态
  if (self.state == HWRefreshStateNormal && currentOffsetY < normalTopullingOffsetY) {
   self.state = HWRefreshStatePulling;

  //转为普通状态
  }else if (self.state == HWRefreshStatePulling && currentOffsetY >= normalTopullingOffsetY) {
   self.state = HWRefreshStateNormal;
  }

 //松手时，如果是松开就可以进行刷新的状态，则进行刷新
 }else if (self.state == HWRefreshStatePulling) {
  self.state = HWRefreshStateRefreshing;
 }
}

- (void)setState:(HWRefreshState)state
{
 //若状态未改变，直接返回
 if (self.state == state) return;

 //保存旧状态
 HWRefreshState oldState = self.state;

 //调用父类方法
 [super setState:state];

 switch (state) {
  case HWRefreshStateNormal: {
   //如果由刷新状态返回到普通状态
   if (oldState == HWRefreshStateRefreshing) {
    [UIView animateWithDuration:0.25f animations:^{
     UIEdgeInsets inset = self.scrollView.contentInset;
     inset.top -= self.frame.size.height;
     self.scrollView.contentInset = inset;
    }];
   }
   break;
  }

  case HWRefreshStatePulling: {
   break;
  }

  case HWRefreshStateRefreshing: {
   //执行动画
   [UIView animateWithDuration:0.25f animations:^{
    CGFloat top = self.scrollViewOriginalInset.top + self.frame.size.height;

    //增加滚动区域
    UIEdgeInsets inset = self.scrollView.contentInset;
    inset.top = top;
    self.scrollView.contentInset = inset;

    //设置滚动位置
    CGPoint offset = self.scrollView.contentOffset;
    offset.y = - top;
    self.scrollView.contentOffset = offset;
   }];
   break;
  }

  default:
   break;
 }

 self.state = state;
}

@end

分类UIScrollView+HWRefresh：

#import <UIKit/UIKit.h>

@interface UIScrollView (HWRefresh)

//添加下拉刷新回调
- (void)addHeaderRefreshWithCallback:(void (^)())callback;

//让下拉刷新控件停止刷新
- (void)headerEndRefreshing;

//添加上拉刷新回调
- (void)addFooterRefreshWithCallback:(void (^)())callback;

//让上拉刷新控件开始刷新
- (void)footerBeginRefreshing;

//让上拉刷新控件停止刷新
- (void)footerEndRefreshing;

@end

/*** ---------------分割线--------------- ***/

#import "UIScrollView+HWRefresh.h"
#import "HWRefreshHeader.h"
#import "HWRefreshFooter.h"
#import <objc/runtime.h>

@interface UIScrollView ()

@property (nonatomic, weak) HWRefreshHeader *header;
@property (weak, nonatomic) HWRefreshFooter *footer;

@end

@implementation UIScrollView (HWRefresh)

static char HWRefreshHeaderKey;
static char HWRefreshFooterKey;

- (void)setHeader:(HWRefreshHeader *)header
{
 [self willChangeValueForKey:@"HWRefreshHeaderKey"];
 objc_setAssociatedObject(self, &HWRefreshHeaderKey, header, OBJC_ASSOCIATION_ASSIGN);
 [self didChangeValueForKey:@"HWRefreshHeaderKey"];
}

- (HWRefreshHeader *)header
{
 return objc_getAssociatedObject(self, &HWRefreshHeaderKey);
}

- (void)setFooter:(HWRefreshFooter *)footer
{
 [self willChangeValueForKey:@"HWRefreshFooterKey"];
 objc_setAssociatedObject(self, &HWRefreshFooterKey, footer, OBJC_ASSOCIATION_ASSIGN);
 [self didChangeValueForKey:@"HWRefreshFooterKey"];
}

- (HWRefreshFooter *)footer
{
 return objc_getAssociatedObject(self, &HWRefreshFooterKey);
}

- (void)addHeaderRefreshWithCallback:(void (^)())callback
{
 if (!self.header) {
  HWRefreshHeader *header = [HWRefreshHeader header];
  [self addSubview:header];
  self.header = header;
 }

 self.header.refreshingCallback = callback;
}

- (void)headerEndRefreshing
{
 [self.header endRefreshing];
}

- (void)addFooterRefreshWithCallback:(void (^)())callback
{
 if (!self.footer) {
  HWRefreshFooter *footer = [HWRefreshFooter footer];
  [self addSubview:footer];
  self.footer = footer;
 }

 self.footer.refreshingCallback = callback;
}

- (void)footerBeginRefreshing
{
 [self.footer beginRefreshing];
}

- (void)footerEndRefreshing
{
 [self.footer endRefreshing];
}

@end

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