UITableView 下拉刷新

UITableView继承UIScrollView; 所以首先来学习下UIScrollView的一些属性和方法.

scrollView1.contentOffset = CGPointMake(100,0);

可以用来控制UIScrollView的显示位置;

当contentOffset改变的时候会调用:

- (void)scrollViewDidScroll:(UIScrollView *)scrollView;

- (void)scrollViewDidEndDragging:(UIScrollView *)scrollView willDecelerate:(BOOL)decelerate;

当手离开屏幕时, 停止拖拽的时候会调用.

@interface PullRefreshTableViewController :UITableViewController {

UIView *refreshHeaderView;

UILabel *refreshLabel;

UIImageView *refreshArrow;

UIActivityIndicatorView *refreshSpinner;

BOOL isDragging;

BOOL isLoading;

NSString *textPull;

NSString *textRelease;

NSString *textLoading;

}

@property (nonatomic,retain)UIView *refreshHeaderView;

@property (nonatomic,retain)UILabel *refreshLabel;

@property (nonatomic,retain)UIImageView *refreshArrow;

@property (nonatomic,retain)UIActivityIndicatorView *refreshSpinner;

@property (nonatomic,copy)NSString *textPull;

@property (nonatomic,copy)NSString *textRelease;

@property (nonatomic,copy)NSString *textLoading;

- (void)addPullToRefreshHeader;

- (void)startLoading;

- (void)stopLoading;

- (void)refresh;

@end

#define REFRESH_HEADER_HEIGHT52.0f

@implementation PullRefreshTableViewController

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

- (id)initWithStyle:(UITableViewStyle)style {

self = [superinitWithStyle:style];

if (self != nil) {

textPull = [[NSStringalloc]initWithString:@"Pull down to refresh..."];

textRelease = [[NSStringalloc]initWithString:@"Release to refresh..."];

textLoading = [[NSStringalloc]initWithString:@"Loading..."];

}

returnself;

}

- (void)viewDidLoad {

[superviewDidLoad];

[selfaddPullToRefreshHeader];

}

- (void)addPullToRefreshHeader {

//

refreshHeaderView = [[UIViewalloc]initWithFrame:CGRectMake(0,0 -REFRESH_HEADER_HEIGHT,320,REFRESH_HEADER_HEIGHT)];

refreshHeaderView.backgroundColor = [UIColorclearColor];

refreshLabel = [[UILabelalloc]initWithFrame:CGRectMake(0,0,320,REFRESH_HEADER_HEIGHT)];

refreshLabel.backgroundColor = [UIColorclearColor];

refreshLabel.font = [UIFontboldSystemFontOfSize:12.0];

refreshLabel.textAlignment = UITextAlignmentCenter;

refreshArrow = [[UIImageViewalloc]initWithImage:[UIImageimageNamed:@"arrow.png"]];

refreshArrow.frame = CGRectMake((REFRESH_HEADER_HEIGHT - 27) /2,

(REFRESH_HEADER_HEIGHT -44) /2,

27,44);

refreshSpinner = [[UIActivityIndicatorViewalloc]initWithActivityIndicatorStyle:UIActivityIndicatorViewStyleGray];

refreshSpinner.frame = CGRectMake((REFRESH_HEADER_HEIGHT - 20) /2, (REFRESH_HEADER_HEIGHT - 20) /2,20,20);

refreshSpinner.hidesWhenStopped = YES;

[refreshHeaderViewaddSubview:refreshLabel];

[refreshHeaderViewaddSubview:refreshArrow];

[refreshHeaderViewaddSubview:refreshSpinner];

[self.tableViewaddSubview: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;

elseif (scrollView.contentOffset.y >= -REFRESH_HEADER_HEIGHT)

self.tableView.contentInset = UIEdgeInsetsMake(-scrollView.contentOffset.y,0,0,0);

}elseif (isDragging && scrollView.contentOffset.y < 0) {

// Update the arrow direction and label

[UIViewbeginAnimations:nilcontext:NULL];

if (scrollView.contentOffset.y < -REFRESH_HEADER_HEIGHT) {

//改变文字和图片

refreshLabel.text = self.textRelease;

[refreshArrowlayer].transform = CATransform3DMakeRotation(M_PI,0,0,1);

}else {// User is scrolling somewhere within the header

refreshLabel.text = self.textPull;

[refreshArrowlayer].transform =CATransform3DMakeRotation(M_PI * 2,0,0,1);

}

[UIViewcommitAnimations];

}

}

- (void)scrollViewDidEndDragging:(UIScrollView *)scrollView willDecelerate:(BOOL)decelerate {

//这里是用户拖动,所以放开后只会进来一次

if (isLoading)return;

isDragging = NO;

// contentOffset表示上面的内容变成可见了,默认的是contentOffset为CGPointZero

if (scrollView.contentOffset.y <= -REFRESH_HEADER_HEIGHT) {

// Released above the header

[selfstartLoading];

}

}

- (void)startLoading {

isLoading = YES;

// Show the header

[UIViewbeginAnimations:nilcontext:NULL];

[UIViewsetAnimationDuration:0.3];

self.tableView.contentInset = UIEdgeInsetsMake(REFRESH_HEADER_HEIGHT,0,0,0);

refreshLabel.text = self.textLoading;

refreshArrow.hidden = YES;

[refreshSpinnerstartAnimating];

[UIViewcommitAnimations];

// Refresh action!

[selfrefresh];

}

- (void)stopLoading {

isLoading = NO;

// Hide the header

[UIViewbeginAnimations:nilcontext:NULL];

[UIViewsetAnimationDelegate:self];

[UIViewsetAnimationDuration:0.3];

[UIViewsetAnimationDidStopSelector:@selector(stopLoadingComplete:finished:context:)];

self.tableView.contentInset = UIEdgeInsetsZero;

[refreshArrowlayer].transform = CATransform3DMakeRotation(M_PI * 2,0,0,1);

[UIViewcommitAnimations];

}

- (void)stopLoadingComplete:(NSString *)animationID finished:(NSNumber *)finished context:(void *)context {

// Reset the header

refreshLabel.text = self.textPull;

refreshArrow.hidden = NO;

[refreshSpinnerstopAnimating];

}

- (void)refresh {

// This is just a demo. Override this method with your custom reload action.

// Don't forget to call stopLoading at the end.

[selfperformSelector:@selector(stopLoading)withObject:nilafterDelay:2.0];

}