[iOS]下拉刷新的简单源码（适用于UICollectionView）

两个源码文件：

1.PullRefreshTableViewController.h

//
//  PullRefreshTableViewController.h
//  Plancast
//
//  Created by Leah Culver on 7/2/10.
//  Copyright (c) 2010 Leah Culver
//
//  Permission is hereby granted, free of charge, to any person
//  obtaining a copy of this software and associated documentation
//  files (the "Software"), to deal in the Software without
//  restriction, including without limitation the rights to use,
//  copy, modify, merge, publish, distribute, sublicense, and/or sell
//  copies of the Software, and to permit persons to whom the
//  Software is furnished to do so, subject to the following
//  conditions:
//
//  The above copyright notice and this permission notice shall be
//  included in all copies or substantial portions of the Software.
//
//  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
//  EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
//  OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
//  NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
//  HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
//  WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
//  FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
//  OTHER DEALINGS IN THE SOFTWARE.
//

#import <UIKit/UIKit.h>


@interface PullRefreshTableViewController : UIViewController {
    UIView *refreshHeaderView;
    UILabel *refreshLabel;
    UIImageView *refreshArrow;
    UIActivityIndicatorView *refreshSpinner;
    BOOL isDragging;
    BOOL isLoading;
    NSString *textPull;
    NSString *textRelease;
    NSString *textLoading;
}

@property (nonatomic, strong) UIView *refreshHeaderView;
@property (nonatomic, strong) UILabel *refreshLabel;
@property (nonatomic, strong) UIImageView *refreshArrow;
@property (nonatomic, strong) UIActivityIndicatorView *refreshSpinner;
@property (nonatomic, strong) NSString *textPull;
@property (nonatomic, strong) NSString *textRelease;
@property (nonatomic, strong) NSString *textLoading;


@property (nonatomic, strong) UICollectionView *myRefreshview;




- (void)setupStrings;
- (void)addPullToRefreshHeader;
- (void)startLoading;
- (void)stopRefreshing;
- (void)refresh;

@end

2.PullRefreshTableViewController.m

//
//  PullRefreshTableViewController.m
//  Plancast
//
//  Created by Leah Culver on 7/2/10.
//  Copyright (c) 2010 Leah Culver
//
//  Permission is hereby granted, free of charge, to any person
//  obtaining a copy of this software and associated documentation
//  files (the "Software"), to deal in the Software without
//  restriction, including without limitation the rights to use,
//  copy, modify, merge, publish, distribute, sublicense, and/or sell
//  copies of the Software, and to permit persons to whom the
//  Software is furnished to do so, subject to the following
//  conditions:
//
//  The above copyright notice and this permission notice shall be
//  included in all copies or substantial portions of the Software.
//
//  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
//  EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
//  OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
//  NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
//  HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
//  WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
//  FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
//  OTHER DEALINGS IN THE SOFTWARE.
//

#import <QuartzCore/QuartzCore.h>
#import "PullRefreshTableViewController.h"

#define REFRESH_HEADER_HEIGHT 52.0f


@implementation PullRefreshTableViewController

@synthesize textPull, textRelease, textLoading, refreshHeaderView, refreshLabel, refreshArrow, refreshSpinner;

-(void)viewDidLoad{
    [super viewDidLoad];
}



-(void)viewWillAppear:(BOOL)animated{
    [self addPullToRefreshHeader];
    [self setupStrings];
    [self.myRefreshview setAlwaysBounceVertical:YES];
}


- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil {
  self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
  if (self != nil) {
    [self setupStrings];
  }
  return self;
}


- (void)setupStrings{
  textPull = @"下拉刷新...";
  textRelease = @"松开刷新...";
  textLoading = @"加载中...";
}

- (void)addPullToRefreshHeader {
    refreshHeaderView = [[UIView alloc] initWithFrame:CGRectMake(0, 0 - REFRESH_HEADER_HEIGHT, 320, REFRESH_HEADER_HEIGHT)];
    refreshHeaderView.backgroundColor = [UIColor clearColor];

    refreshLabel = [[UILabel alloc] initWithFrame:CGRectMake(0, 0, 320, REFRESH_HEADER_HEIGHT)];
    refreshLabel.backgroundColor = [UIColor clearColor];
    refreshLabel.font = [UIFont boldSystemFontOfSize:12.0];
    refreshLabel.textAlignment = NSTextAlignmentCenter;

    refreshArrow = [[UIImageView alloc] initWithImage:[UIImage imageNamed:@"arrow.png"]];
    refreshArrow.frame = CGRectMake(floorf((REFRESH_HEADER_HEIGHT - 27) / 2),
                                    (floorf(REFRESH_HEADER_HEIGHT - 44) / 2),
                                    27, 44);

    refreshSpinner = [[UIActivityIndicatorView alloc] initWithActivityIndicatorStyle:UIActivityIndicatorViewStyleGray];
    refreshSpinner.frame = CGRectMake(floorf(floorf(REFRESH_HEADER_HEIGHT - 20) / 2), floorf((REFRESH_HEADER_HEIGHT - 20) / 2), 20, 20);
    refreshSpinner.hidesWhenStopped = YES;

    [refreshHeaderView addSubview:refreshLabel];
    [refreshHeaderView addSubview:refreshArrow];
    [refreshHeaderView addSubview:refreshSpinner];
    [self.myRefreshview addSubview:refreshHeaderView];
}

- (void)scrollViewWillBeginDragging:(UIScrollView *)scrollView {
    if (isLoading) return;
    isDragging = YES;
}

- (void)scrollViewDidScroll:(UIScrollView *)scrollView {
    if (isLoading) {
        // Update the content inset, good for section headers
        if (scrollView.contentOffset.y > 0)
            self.myRefreshview.contentInset = UIEdgeInsetsZero;
        else if (scrollView.contentOffset.y >= -REFRESH_HEADER_HEIGHT)
            self.myRefreshview.contentInset = UIEdgeInsetsMake(-scrollView.contentOffset.y, 0, 0, 0);
    } else if (isDragging && scrollView.contentOffset.y < 0) {
        // Update the arrow direction and label
        [UIView animateWithDuration:0.25 animations:^{
            if (scrollView.contentOffset.y < -REFRESH_HEADER_HEIGHT) {
                // User is scrolling above the header
                refreshLabel.text = self.textRelease;
                [refreshArrow layer].transform = CATransform3DMakeRotation(M_PI, 0, 0, 1);
            } else { 
                // User is scrolling somewhere within the header
                refreshLabel.text = self.textPull;
                [refreshArrow layer].transform = CATransform3DMakeRotation(M_PI * 2, 0, 0, 1);
            }
        }];
    }
}

- (void)scrollViewDidEndDragging:(UIScrollView *)scrollView willDecelerate:(BOOL)decelerate {
    if (isLoading) return;
    isDragging = NO;
    if (scrollView.contentOffset.y <= -REFRESH_HEADER_HEIGHT) {
        // Released above the header
        [self startLoading];
    }
}

- (void)startLoading {
    isLoading = YES;
    
    // Show the header
    [UIView animateWithDuration:0.3 animations:^{
        self.myRefreshview.contentInset = UIEdgeInsetsMake(REFRESH_HEADER_HEIGHT, 0, 0, 0);
        refreshLabel.text = self.textLoading;
        refreshArrow.hidden = YES;
        [refreshSpinner startAnimating];
    }];
    
    // Refresh action!
    [self refresh];
}

- (void)stopRefreshing {
    isLoading = NO;
    // Hide the header
    [UIView animateWithDuration:0.3 animations:^{
        self.myRefreshview.contentInset = UIEdgeInsetsZero;
        [refreshArrow layer].transform = CATransform3DMakeRotation(M_PI * 2, 0, 0, 1);
    } 
                     completion:^(BOOL finished) {
                         [self performSelector:@selector(stopLoadingComplete)];
                     }];
}

- (void)stopLoadingComplete {
    // Reset the header
    refreshLabel.text = self.textPull;
    refreshArrow.hidden = NO;
    [refreshSpinner stopAnimating];
}

- (void)refresh {
    // This is just a demo. Override this method with your custom reload action.
    // Don't forget to call stopLoading at the end.
    [self performSelector:@selector(stopRefreshing) withObject:nil afterDelay:2.0];
}


@end

在引用的时候，继承自上面的类，同时在头文件声明且在xib或storyboard中链接：

@property (weak, nonatomic) IBOutlet UICollectionView *faxsView;

重写父类中的refresh函数：

- (void)refresh {
    
    [self performSelector:@selector(addItem) withObject:nil afterDelay:2.0];
    [super refresh];
}

- (void)addItem {
    NSLog(@"!!!!!!!!!!!!!!!!!!");
}