打开开源中国iOS客户端应用程序第一步就是加载数据,经常我们在第二次以后打开的时候,我们界面显示的是上一次更新的数据,此时我们想看最新内容就需要去刷新数据加载这些内容,加载需要一个等待过程,如何能让用户在等待过程中不焦急,能够等待这个过程完成,这就需要给用户一个心里安慰,让用户知道该软件正在很努力很努力的执行自己命令,这就需要我们为自己应用程序添加一些特效;
开源中国iOS客户端用到了不少特效,这些特效在当前很多应用软件中都比较流行,基本上这些特效都属于第三方类库,本次想说的是下拉刷新特效,EGOTableViewPullRefresh最开始是在Twitter中使用,最后做了开源,然后很多应用添加这个特效,常作为加载数据时将等待时间作为一个动画来过渡;
下拉刷新类库EGOTableViewPullRefresh资源文件下载地址:
https://github.com/enormego/EGOTableViewPullRefresh/tree/
先这个特效的效果图
在EGOTableViewPullRefresh资源文件中有两个文件,.m和.h文件,还有资源图片,就是下拉刷新箭头
资源图片一共4种色,可以根据喜好选用不同色的箭头,只需在EGORefreshTableHeaderView.m文件中修改一下。按照大小尺寸又可分两种,较大尺寸是用于iPad上使用的。
针对这些第三方类库,我们没必要去深入研究它们内部实现机制原理,只要知道怎么用就可以。不过,看一看别人实现原理,学学别人的方法还是很不错的,了解下人家牛人程序是怎么写的;
EGORefreshTableHeaderView.h
#import <UIKit/UIKit.h> #import <QuartzCore/QuartzCore.h> typedef enum{ EGOOPullRefreshPulling = 0, EGOOPullRefreshNormal, EGOOPullRefreshLoading, } EGOPullRefreshState; @protocol EGORefreshTableHeaderDelegate; @interface EGORefreshTableHeaderView : UIView { id _delegate; EGOPullRefreshState _state; UILabel *_lastUpdatedLabel; UILabel *_statusLabel; CALayer *_arrowImage; UIActivityIndicatorView *_activityView; } @property(nonatomic,assign) id <EGORefreshTableHeaderDelegate> delegate; - (id)initWithFrame:(CGRect)frame arrowImageName:(NSString *)arrow textColor:(UIColor *)textColor; - (void)refreshLastUpdatedDate; - (void)egoRefreshScrollViewDidScroll:(UIScrollView *)scrollView; - (void)egoRefreshScrollViewDidEndDragging:(UIScrollView *)scrollView; - (void)egoRefreshScrollViewDataSourceDidFinishedLoading:(UIScrollView *)scrollView; @end //定义协议方法 @protocol EGORefreshTableHeaderDelegate //下拉的时候调用此方法 - (void)egoRefreshTableHeaderDidTriggerRefresh:(EGORefreshTableHeaderView*)view; //判断刷新状态情况,正在刷新或者是没刷新 - (BOOL)egoRefreshTableHeaderDataSourceIsLoading:(EGORefreshTableHeaderView*)view; @optional //返回刷新时间,回调方法 - (NSDate*)egoRefreshTableHeaderDataSourceLastUpdated:(EGORefreshTableHeaderView*)view; @end
首先是定义了一个枚举类型EGOPullRefreshState表示当前我们操作在哪种状态下,有下拉状态、正常状态、数据加载状态;
@protocol EGORefreshTableHeaderDelegate;表示声明有这个协议,该协议里面声明了一些方法,只要其他的类遵循了这个协议(也就是遵循了它的规定),就可以去实现协议里面方法,协议里的方法是留给遵循这个协议的类去实现的,也是留给外部实现接口;
EGORefreshTableHeaderView成员变量定义两个label用于提示下拉过程所处状态,和显示的刷新时间。定义的CALayer类对象装载显示图片。UIActivityIndicatorView类对象显示一个等待动画;
@property(nonatomic,assign)id <EGORefreshTableHeaderDelegate> delegate;声明一个协议对象;
接着下面的是EGORefreshTableHeaderView类成员函数,用于实现类库中下拉刷新的效果;
最后定义了4个协议方法,其中最后一个协议方法为可选实现;
下面是EGORefreshTableHeaderView.m文件,想说的都在注释里
#import "EGORefreshTableHeaderView.h" #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 //设置的一个私有接口,只能本类来使用 @interface EGORefreshTableHeaderView (Private) - (void)setState:(EGOPullRefreshState)aState; @end @implementation EGORefreshTableHeaderView @synthesize delegate=_delegate; //初始化框架属性, - (id)initWithFrame:(CGRect)frame arrowImageName:(NSString *)arrow textColor:(UIColor *)textColor { if((self = [super initWithFrame:frame])) { // self.view自动适应bounds的宽度 self.autoresizingMask = UIViewAutoresizingFlexibleWidth; // self.view背景色和透明度设置 self.backgroundColor = [UIColor colorWithRed:226.0/255.0 green:231.0/255.0 blue:237.0/255.0 alpha:1.0]; 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文本阴影颜色 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]; 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]; CALayer *layer = [CALayer layer]; layer.frame = CGRectMake(25.0f, frame.size.height - 65.0f, 30.0f, 55.0f); // 设置layer在view上以某种形式适应 layer.contentsGravity = kCAGravityResizeAspect; layer.contents = (id)[UIImage imageNamed:arrow].CGImage; // 判断设备版本,因为一些iOS特性是在最后新增的,要求设备配置高一些,所以做一下判断 #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; 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]; [self setState:EGOOPullRefreshNormal]; } return self; }
//初始化当前视图的frame - (id)initWithFrame:(CGRect)frame { return [self initWithFrame:frame arrowImageName:@"blueArrow.png" textColor:TEXT_COLOR]; } #pragma mark - #pragma mark Setters //获取最后一次更新的时间 - (void)refreshLastUpdatedDate { if ([_delegate respondsToSelector:@selector(egoRefreshTableHeaderDataSourceLastUpdated:)]) { NSDate *date = [_delegate egoRefreshTableHeaderDataSourceLastUpdated:self]; // NSDateFormatter实例创建字符串,来表示NSDate和NSCalendarDate对象,已预订格式化字符串输出 [NSDateFormatter setDefaultFormatterBehavior:NSDateFormatterBehaviorDefault]; NSDateFormatter *dateFormatter = [[[NSDateFormatter alloc] init] autorelease]; // 设置日期输出格式 [dateFormatter setDateStyle:NSDateFormatterShortStyle]; // 设置时间显示格式 [dateFormatter setTimeStyle:NSDateFormatterShortStyle]; // _lastUpdatedLabel.text = [NSString stringWithFormat:@"Last Updated: %@", [dateFormatter stringFromDate:date]]; _lastUpdatedLabel.text = [NSString stringWithFormat:@"最后更新: %@", [dateFormatter stringFromDate:date]]; // 存储_lastUpdatedLabel.text内容,放到字典中 [[NSUserDefaults standardUserDefaults] setObject:_lastUpdatedLabel.text forKey:@"EGORefreshTableView_LastRefresh"]; // 将NSUserDefaults存储数据放到磁盘 [[NSUserDefaults standardUserDefaults] synchronize]; } else { _lastUpdatedLabel.text = nil; } }
- (void)setState:(EGOPullRefreshState)aState{ switch (aState) { /*触摸屏幕下拉状态*/ case EGOOPullRefreshPulling: // _statusLabel.text = NSLocalizedString(@"Release to refresh...", @"Release to refresh status"); _statusLabel.text = @"松开即可刷新"; // 设置下拉刷新过程,箭头的图片的一个动画过程 [CATransaction begin]; // 动画时间 [CATransaction setAnimationDuration:FLIP_ANIMATION_DURATION]; // 下拉刷新箭头一个翻转过程,(M_PI / 180.0)是角度转换为弧度 _arrowImage.transform = CATransform3DMakeRotation((M_PI / 180.0) * 180.0f, 0.0f, 0.0f, 1.0f); // 动画结束 [CATransaction commit]; break; /*刚开始触摸屏幕准备下拉的时候的状态*/ case EGOOPullRefreshNormal: if (_state == EGOOPullRefreshPulling) { [CATransaction begin]; [CATransaction setAnimationDuration:FLIP_ANIMATION_DURATION]; _arrowImage.transform = CATransform3DIdentity; [CATransaction commit]; } // _statusLabel.text = NSLocalizedString(@"Pull down to refresh...", @"Pull down to refresh status"); _statusLabel.text = @"下拉可以刷新"; [_activityView stopAnimating]; [CATransaction begin]; // 因为下拉刷新完成好就不需要下拉动画,此时_activityView动画显示 // 显示事物关闭动画效果 kCFBooleanTrue关闭 kCFBooleanFalse开启 [CATransaction setValue:(id)kCFBooleanTrue forKey:kCATransactionDisableActions]; _arrowImage.hidden = NO; _arrowImage.transform = CATransform3DIdentity; [CATransaction commit]; // 更新下时间 [self refreshLastUpdatedDate]; break; /*触摸手指松开,完成下拉操作的状态*/ case EGOOPullRefreshLoading: // _statusLabel.text = NSLocalizedString(@"Loading...", @"Loading Status"); _statusLabel.text = @"加载中"; [_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 - (void)egoRefreshScrollViewDidScroll:(UIScrollView *)scrollView { if (_state == EGOOPullRefreshLoading) { 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) { BOOL _loading = NO; if ([_delegate respondsToSelector:@selector(egoRefreshTableHeaderDataSourceIsLoading:)]) { _loading = [_delegate egoRefreshTableHeaderDataSourceIsLoading:self]; } if (_state == EGOOPullRefreshPulling && scrollView.contentOffset.y > -65.0f && scrollView.contentOffset.y < 0.0f && !_loading) { [self setState:EGOOPullRefreshNormal]; } else if (_state == EGOOPullRefreshNormal && scrollView.contentOffset.y < -65.0f && !_loading) { [self setState:EGOOPullRefreshPulling]; } // 设置下拉属性scrollView框架恢复初始位置 if (scrollView.contentInset.top != 0) { // A UIEdgeInsets struct whose top, left, bottom, and right fields are all set to the value 0. scrollView.contentInset = UIEdgeInsetsZero; } } } - (void)egoRefreshScrollViewDidEndDragging:(UIScrollView *)scrollView { BOOL _loading = NO; if ([_delegate respondsToSelector:@selector(egoRefreshTableHeaderDataSourceIsLoading:)]) { _loading = [_delegate egoRefreshTableHeaderDataSourceIsLoading:self]; } 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]; } } //数据加载完成后调用此方法 - (void)egoRefreshScrollViewDataSourceDidFinishedLoading:(UIScrollView *)scrollView { [UIView beginAnimations:nil context:NULL]; [UIView setAnimationDuration:.3]; // 数据加载完成后,scrollView恢复位置大小 [scrollView setContentInset:UIEdgeInsetsMake(0.0f, 0.0f, 0.0f, 0.0f)]; [UIView commitAnimations]; // 数据加载完成, [self setState:EGOOPullRefreshNormal]; }
#pragma mark - #pragma mark Dealloc - (void)dealloc { _delegate=nil; _activityView = nil; _statusLabel = nil; _arrowImage = nil; _lastUpdatedLabel = nil; [super dealloc]; } @end
怎样让其他类来使用这里面效果,这时我们就可以委托另一个类来实现协议的方法。
选中一个协议方法,右键选择Jump to Definition就可以看到哪些类被委托了,怎样使用了这个类的协议方法:
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本文转自新风作浪 51CTO博客,原文链接:http://blog.51cto.com/duxinfeng/1208695,如需转载请自行联系原作者