这次主要讲解EGOTableViewPullRefresh下拉的实现原理，并对EGOTableViewPullRefresh源代码进行讲解，至于如何使用EGOTableViewPullRefresh，可以参考我上传的Demo。
，并把下拉的箭头图标向上。
此时若用户松开手，停止下拉，HeaderView的状态就改为等待数据的状态，如下图所示（下图的contentoffset.y=0标错了，是=-60）
以上就是顶部下拉刷新数据的原理了，根据这个原理也就不难写出底部上拉刷新数据的实现了。
下面我们来分析下EGOTableViewPullRefresh的代码。
EGOTableViewPullRefresh的代码结构
EGORefreshTableHeaderView.h的代码
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#import
<QuartzCore/QuartzCore.h>
//下拉状态
typedef enum{
EGOOPullRefreshPulling
= 0,
EGOOPullRefreshNormal,
EGOOPullRefreshLoading,
} EGOPullRefreshState;
@protocol EGORefreshTableHeaderDelegate;
@interface EGORefreshTableHeaderView
: UIView {
id _delegate;
EGOPullRefreshState
_state;//下拉状态
UILabel *_lastUpdatedLabel;//显示最后更新的时间
UILabel *_statusLabel;//显示下拉状态
CALayer *_arrowImage;//显示下拉图标
UIActivityIndicatorView
*_activityView;//等待指示器
}
@property(nonatomic,assign) id
<EGORefreshTableHeaderDelegate>
delegate;
- (id)initWithFrame:(CGRect)frame arrowImageName:(NSString *)arrow
textColor:(UIColor *)textColor;
//刷新最后更新时间
- (void)refreshLastUpdatedDate;
//UIScrollView
滑动时调用该方法
- (void)egoRefreshScrollViewDidScroll:(UIScrollView *)scrollView;
//UIScrollView
停止拖拽时调用该方法
- (void)egoRefreshScrollViewDidEndDragging:(UIScrollView *)scrollView;
//数据载入完成时调用此方法
- (void)egoRefreshScrollViewDataSourceDidFinishedLoading:(UIScrollView *)scrollView;
@end
//下拉委托
@protocol EGORefreshTableHeaderDelegate
//指示开始刷新数据
- (void)egoRefreshTableHeaderDidTriggerRefresh:(EGORefreshTableHeaderView*)view;
//是否正在载入数据
- (BOOL)egoRefreshTableHeaderDataSourceIsLoading:(EGORefreshTableHeaderView*)view;
@optional
//返回最后更新时间
- (NSDate*)egoRefreshTableHeaderDataSourceLastUpdated:(EGORefreshTableHeaderView*)view;
@end |
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#define TEXT_COLOR [UIColor
colorWithRed:87.0/255.0 green:108.0/255.0 blue:137.0/255.0
alpha:1.0]
#define
FLIP_ANIMATION_DURATION 0.18f
@interface EGORefreshTableHeaderView
(Private)
//设置下拉状态
- (void)setState:(EGOPullRefreshState)aState;
@end
@implementation EGORefreshTableHeaderView
@synthesize delegate=_delegate;
- (id)initWithFrame:(CGRect)frame arrowImageName:(NSString *)arrow
textColor:(UIColor *)textColor {
if((self =
[super initWithFrame:frame])) {
//设置UIView为的缩放模式
self.autoresizingMask = UIViewAutoresizingFlexibleWidth;
self.backgroundColor = [UIColor
colorWithRed:226.0/255.0 green:231.0/255.0 blue:237.0/255.0 alpha:1.0];
//初始化
用来显示最后更新日期的控件
UILabel *label =
[[UILabel alloc] initWithFrame:CGRectMake(0.0f, frame.size.height
- 30.0f, self.frame.size.width, 20.0f)];
label.autoresizingMask = UIViewAutoresizingFlexibleWidth;
label.font =
[UIFont systemFontOfSize:12.0f];
label.textColor = textColor;
label.shadowColor = [UIColor
colorWithWhite:0.9f
alpha:1.0f];
label.shadowOffset = CGSizeMake(0.0f,
1.0f);
label.backgroundColor = [UIColor
clearColor];
label.textAlignment = UITextAlignmentCenter;
[self addSubview:label];
_lastUpdatedLabel=label;
[label release];
//初始化
用来显示下拉状态的控件
label = [[UILabel
alloc] initWithFrame:CGRectMake(0.0f, frame.size.height
- 48.0f, self.frame.size.width, 20.0f)];
label.autoresizingMask = UIViewAutoresizingFlexibleWidth;
label.font =
[UIFont boldSystemFontOfSize:13.0f];
label.textColor = textColor;
label.shadowColor = [UIColor
colorWithWhite:0.9f
alpha:1.0f];
label.shadowOffset = CGSizeMake(0.0f,
1.0f);
label.backgroundColor = [UIColor
clearColor];
label.textAlignment = UITextAlignmentCenter;
[self addSubview:label];
_statusLabel=label;
[label release];
//初始化
用来显示指示图标的图层
CALayer *layer =
[CALayer layer];
layer.frame =
CGRectMake(25.0f, frame.size.height
- 65.0f, 30.0f,
55.0f);
layer.contentsGravity = kCAGravityResizeAspect;//图像显示模式
layer.contents =
(id)[UIImage imageNamed:arrow].CGImage;
#if
__IPHONE_OS_VERSION_MAX_ALLOWED >= 40000
if ([[UIScreen mainScreen] respondsToSelector:@selector(scale)]) {
layer.contentsScale = [[UIScreen mainScreen] scale];
}
#endif
[[self layer]
addSublayer:layer];
_arrowImage=layer;
//初始化 等待指示器
UIActivityIndicatorView
*view = [[UIActivityIndicatorView alloc] initWithActivityIndicatorStyle:UIActivityIndicatorViewStyleGray];
view.frame =
CGRectMake(25.0f, frame.size.height
- 38.0f, 20.0f,
20.0f);
[self addSubview:view];
_activityView = view;
[view release];
//初始化下拉状态
[self setState:EGOOPullRefreshNormal];
}
return self;
}
- (id)initWithFrame:(CGRect)frame {
return [self initWithFrame:frame arrowImageName:@"blueArrow.png" textColor:TEXT_COLOR];
}
#pragma mark -
#pragma mark
Setters
//更新最后刷新时间
- (void)refreshLastUpdatedDate {
if ([_delegate respondsToSelector:@selector(egoRefreshTableHeaderDataSourceLastUpdated:)]) {
//通过委托egoRefreshTableHeaderDataSourceLastUpdated：返回时间，并格式化时间
NSDate *date =
[_delegate egoRefreshTableHeaderDataSourceLastUpdated:self];
[NSDateFormatter setDefaultFormatterBehavior:NSDateFormatterBehaviorDefault];
NSDateFormatter *dateFormatter = [[[NSDateFormatter alloc]
init] autorelease];
// [dateFormatter
setDateStyle:NSDateFormatterShortStyle];
// [dateFormatter
setTimeStyle:NSDateFormatterShortStyle];
[dateFormatter setDateFormat:@"yyyy-MM-dd HH:mm:ss"];
//更新最后显示的时间
NSString *lastUpdated = NSLocalizedString(@"last updated", @"");
_lastUpdatedLabel.text =
[NSString stringWithFormat:@"%@ %@",lastUpdated, [dateFormatter stringFromDate:date]];
//保存最后刷新的时间，以便下次打开应用的时候还有
[[NSUserDefaults standardUserDefaults] setObject:_lastUpdatedLabel.text forKey:@"EGORefreshTableView_LastRefresh"];
[[NSUserDefaults standardUserDefaults] synchronize];
} else {
_lastUpdatedLabel.text =
nil;
}
}
//设置下拉状态
- (void)setState:(EGOPullRefreshState)aState{
switch (aState)
{
case EGOOPullRefreshPulling://如果是下拉状态，则更新_statusLabel内容，并把下拉图标旋转180度
// _statusLabel.text =
NSLocalizedString(@"Release to refresh...", @"Release to refresh
status");
_statusLabel.text =
NSLocalizedString(@"release to refresh", @"");
[CATransaction begin];
[CATransaction setAnimationDuration:FLIP_ANIMATION_DURATION];
_arrowImage.transform = CATransform3DMakeRotation((M_PI /
180.0) * 180.0f,
0.0f, 0.0f, 1.0f);
[CATransaction commit];
break;
case EGOOPullRefreshNormal://普通状态，恢复默认值
if (_state ==
EGOOPullRefreshPulling)
{
[CATransaction begin];
[CATransaction setAnimationDuration:FLIP_ANIMATION_DURATION];
_arrowImage.transform = CATransform3DIdentity;//把transform设为默认值
[CATransaction commit];
}
// _statusLabel.text =
NSLocalizedString(@"Pull down to refresh...", @"Pull down to refresh
status");
_statusLabel.text =
NSLocalizedString(@"pull down to refresh", @"");
[_activityView stopAnimating];
[CATransaction begin];
[CATransaction setValue:(id)kCFBooleanTrue forKey:kCATransactionDisableActions];
_arrowImage.hidden =
NO;
_arrowImage.transform = CATransform3DIdentity;
[CATransaction commit];
[self refreshLastUpdatedDate];
break;
case EGOOPullRefreshLoading://如果是下拉状态，则显示为载入中，显示等待指示器，并隐藏箭头
// _statusLabel.text =
NSLocalizedString(@"Loading...", @"Loading Status");
_statusLabel.text =
NSLocalizedString(@"loading", @"");
[_activityView startAnimating];
[CATransaction begin];
[CATransaction setValue:(id)kCFBooleanTrue forKey:kCATransactionDisableActions];
_arrowImage.hidden =
YES;
[CATransaction commit];
break;
default:
break;
}
_state = aState;
}
#pragma mark -
#pragma mark ScrollView
Methods
//UIScrollView
滑动时调用该方法
- (void)egoRefreshScrollViewDidScroll:(UIScrollView *)scrollView {
if (_state ==
EGOOPullRefreshLoading)
{//如果正在载入中，则判断如果是上拉则不改变scrollView，如果是下拉，则保持HeaderView在顶部
CGFloat offset
= MAX(scrollView.contentOffset.y * -1, 0);
offset = MIN(offset, 60);
scrollView.contentInset = UIEdgeInsetsMake(offset, 0.0f, 0.0f, 0.0f);
} else if (scrollView.isDragging) {//scrollView停止拖拽时计算下拉状态
BOOL _loading = NO;
//委托egoRefreshTableHeaderDataSourceIsLoading：返回用户载入数据的情况
if ([_delegate respondsToSelector:@selector(egoRefreshTableHeaderDataSourceIsLoading:)]) {
_loading =
[_delegate egoRefreshTableHeaderDataSourceIsLoading:self];
}
//如果现在时上拉状态，并且没有数据在载入中，则恢复默认状态
if (_state ==
EGOOPullRefreshPulling && scrollView.contentOffset.y > -65.0f && scrollView.contentOffset.y < 0.0f && !_loading)
{
[self setState:EGOOPullRefreshNormal];
} //如果当前为默认状态，下拉大于65，并且不是在载入数据状态，则设置为Pull状态
else if (_state
== EGOOPullRefreshNormal
&& scrollView.contentOffset.y <
-65.0f && !_loading) {
[self setState:EGOOPullRefreshPulling];
}
if (scrollView.contentInset.top !=
0) {
scrollView.contentInset = UIEdgeInsetsZero;
}
}
}
//UIScrollView
停止拖拽时调用该方法
- (void)egoRefreshScrollViewDidEndDragging:(UIScrollView *)scrollView {
BOOL _loading = NO;
if ([_delegate respondsToSelector:@selector(egoRefreshTableHeaderDataSourceIsLoading:)]) {
_loading =
[_delegate egoRefreshTableHeaderDataSourceIsLoading:self];
}
//如果还没有载入数据，则通知载入数据
if (scrollView.contentOffset.y <=
- 65.0f && !_loading) {
if ([_delegate respondsToSelector:@selector(egoRefreshTableHeaderDidTriggerRefresh:)]) {
[_delegate egoRefreshTableHeaderDidTriggerRefresh:self];
}
[self setState:EGOOPullRefreshLoading];
[UIView beginAnimations:nil context:NULL];
[UIView setAnimationDuration:0.2];
scrollView.contentInset = UIEdgeInsetsMake(60.0f, 0.0f, 0.0f, 0.0f);
[UIView commitAnimations];
}
}
//数据载入完成是调用此方法
- (void)egoRefreshScrollViewDataSourceDidFinishedLoading:(UIScrollView *)scrollView {
[UIView beginAnimations:nil context:NULL];
[UIView setAnimationDuration:.3];
[scrollView setContentInset:UIEdgeInsetsMake(0.0f,
0.0f, 0.0f, 0.0f)];
[UIView commitAnimations];
[self setState:EGOOPullRefreshNormal];
}
#pragma mark -
#pragma mark
Dealloc
- (void)dealloc {
_delegate=nil;
_activityView = nil;
_statusLabel = nil;
_arrowImage = nil;
_lastUpdatedLabel
= nil;
[super dealloc];
}
@end |
原文：http://www.cnblogs.com/yulang314/p/3721770.html
