PullToChange.m

//
//  PullToChange.m
//  PullTemperatures
//
//  Created by SCOTT ASHMORE on 07/03/2012.
//  Copyright (c) 2012 __MyCompanyName__. All rights reserved.
//

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

#define REFRESH_HEADER_HEIGHT 52.0f

@implementation PullRefreshTableViewController

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

- (id)initWithStyle:(UITableViewStyle)style 
{
    self = [super initWithStyle:style];
    if (self != nil) 
    {
        [self setupStrings];
    }
    return self;
}

- (id)initWithCoder:(NSCoder *)aDecoder 
{
    self = [super initWithCoder:aDecoder];
    if (self != nil) 
    {
        [self setupStrings];
    }
    return self;
}

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

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

- (void)setupStrings
{
    textPull = [[NSString alloc] initWithString:@"Pull down to change measurement..."];
    textRelease = [[NSString alloc] initWithString:@"Release to change measurement..."];
    textLoading = [[NSString alloc] initWithString:@"Loading new measurement..."];
}

- (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 = UITextAlignmentCenter;
    
    refreshArrow = [[UIImageView alloc] initWithImage:[UIImage imageNamed:@"blackArrow.png"]];
    refreshArrow.frame = CGRectMake(floorf((REFRESH_HEADER_HEIGHT - 22) / 2), (floorf(REFRESH_HEADER_HEIGHT - 44) / 2), 22, 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.tableView 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.tableView.contentInset = UIEdgeInsetsZero;
        else if (scrollView.contentOffset.y >= -REFRESH_HEADER_HEIGHT)
            self.tableView.contentInset = UIEdgeInsetsMake(-scrollView.contentOffset.y, 0, 0, 0);
    } 
    else if (isDragging && scrollView.contentOffset.y < 0) 
    {
        // Update the arrow direction and label
        [UIView beginAnimations:nil context:NULL];
        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);
        }
        [UIView commitAnimations];
    }
}

- (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 beginAnimations:nil context:NULL];
    [UIView setAnimationDuration:0.3];
    self.tableView.contentInset = UIEdgeInsetsMake(REFRESH_HEADER_HEIGHT, 0, 0, 0);
    refreshLabel.text = self.textLoading;
    refreshArrow.hidden = YES;
    [refreshSpinner startAnimating];
    [UIView commitAnimations];
    
    // Refresh action!
    [self refresh];
}

- (void)stopLoading 
{
    isLoading = NO;
    
    // Hide the header
    [UIView beginAnimations:nil context:NULL];
    [UIView setAnimationDelegate:self];
    [UIView setAnimationDuration:0.3];
    [UIView setAnimationDidStopSelector:@selector(stopLoadingComplete:finished:context:)];
    self.tableView.contentInset = UIEdgeInsetsZero;
    UIEdgeInsets tableContentInset = self.tableView.contentInset;
    tableContentInset.top = 0.0;
    self.tableView.contentInset = tableContentInset;
    [refreshArrow layer].transform = CATransform3DMakeRotation(M_PI * 2, 0, 0, 1);
    [UIView commitAnimations];
}

- (void)stopLoadingComplete:(NSString *)animationID finished:(NSNumber *)finished context:(void *)context 
{
    // 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(stopLoading) withObject:nil afterDelay:1.0];
}

@end