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iOS开发 下拉刷新上拉加载更多详解

iOS开发 下拉刷新上拉加载更多详解

作者: MrZhaoCn | 来源:发表于2017-01-21 13:44 被阅读402次

    下拉刷新(上拉加载更多)是大家经常用到的功能,本篇文章将带大家详细介绍下拉刷新原理,一步步实现下拉刷新效果。下拉刷新的核心原理是先自定义一个refreshView,然后将自定义的view添加到tableView(collectionView上)监听tableView(或者collectionView)的contentOffset属性,根据偏移量动态修改refreshView的子控件即可。下面一步步实现。
    1.给UIScroolVIew添加一个分类UIScrollView+ZCRefresh.h,在该文件中添加如下代码:

    //  UIScrollView+ZCRefresh.h  
    //  ZCRefreshExample  
    //  Created by MrZhao on 16/6/28.  
    //  Copyright (c) 2016年 MrZhao. All rights reserved.  
    #import <UIKit/UIKit.h>  
    @class ZCHeaderRefreshView,ZCFooterRefreshView;  
    @interface UIScrollView (ZCRefresh)  
    /* 
     * 下拉刷新 
     */  
    @property (nonatomic,strong)ZCHeaderRefreshView *zc_headerRefreshView;  
      
    /* 
     * 上拉加载更多 
     */  
    @property (nonatomic,strong)ZCFooterRefreshView *zc_footerRefreshView;  
    @end  
    

    在UIScrollView+ZCRefresh.m文件中添加如下代码:

    //  UIScrollView+ZCRefresh.m  
    //  ZCRefreshExample  
    //  Created by MrZhao on 16/6/28.  
    //  Copyright (c) 2016年 MrZhao. All rights reserved.  
    #import "UIScrollView+ZCRefresh.h"  
    #import "ZCHeaderRefreshView.h"  
    #import "ZCFooterRefreshView.h"  
    #import <objc/runtime.h>  
    static const voidvoid *zc_headerRefresh_key = @"zc_headerRefresh_key";  
    static const voidvoid *zc_footerRefresh_key = @"zc_footerRefresh_key";  
    @implementation UIScrollView (ZCRefresh)  
      
    #pragma mark 实现下拉刷新控件的get set 方法  
    - (void)setZc_headerRefreshView:(ZCHeaderRefreshView *)zc_headerRefreshView {  
        if (zc_headerRefreshView != self.zc_headerRefreshView) {  
              
            //先删除旧的  
            [self.zc_headerRefreshView removeFromSuperview];  
            [self insertSubview:zc_headerRefreshView atIndex:0];        
            //添加新的  
            objc_setAssociatedObject(self, zc_headerRefresh_key, zc_headerRefreshView, OBJC_ASSOCIATION_RETAIN_NONATOMIC);   
        }  
    }  
    - (ZCHeaderRefreshView *)zc_headerRefreshView {  
        return objc_getAssociatedObject(self, zc_headerRefresh_key);  
    }  
    - (void)setZc_footerRefreshView:(ZCFooterRefreshView *)zc_footerRefreshView {  
        if (zc_footerRefreshView != self.zc_footerRefreshView) {  
              
            [self.zc_footerRefreshView removeFromSuperview];  
            [self addSubview:zc_footerRefreshView];    
            //添加新的  
            objc_setAssociatedObject(self, zc_footerRefresh_key, zc_footerRefreshView, OBJC_ASSOCIATION_RETAIN_NONATOMIC);     
        }  
    }  
    - (ZCFooterRefreshView *)zc_footerRefreshView {  
        return objc_getAssociatedObject(self, zc_footerRefresh_key);  
    }  
    @end
    

    添加分类的目的是在使用时,可直接是self.tableView.zc_headerRefresh = ***,这样使用。其中用到了runtime里面的部分api,主要就是关联相关的api,大家不熟悉可以自行查找相关文档学习下。
    2.自定义下拉刷新的View,ZCHeaderRefreshView.h,其中下拉的子控件和布局可以根据公司具体需求改动。ZCHeaderRefreshView.h中的代码如下。

    //  ZCRefreshExample  
    //  Created by MrZhao on 16/6/26.  
    //  Copyright (c) 2016年 MrZhao. All rights reserved.  
    //   git:https://github.com/MrZhaoCn/Refresh  
    #import <UIKit/UIKit.h>  
    #import <Foundation/Foundation.h>  
    @interface ZCHeaderRefreshView : UIView  
    /* 
     *提供有个工厂方法 
     */  
    + (instancetype)addHeaderRefreshViewWithTarget:(id)target action:(SEL)action;  
    /* 
     *开始下拉刷新 
     */  
    - (void)beginRefreshing;  
    /* 
     *结束下拉刷新 
     */  
    - (void)endHeaderRefreshing;  
    /* 
     *设置下拉刷新相关图片 
     */  
    //正常状态的图片  
    - (void)setHeaderNormorlImageWithName:(NSString *)imageName;  
    /* 
     *设置pullin状态关图片 
     */  
    - (void)setHeaderPullingImageWithName:(NSString *)imageName;  
    /* 
     *设置动画图片 
     */  
    - (void)setAnimantionImages:(NSArray *)images;  
    @end 
    

    ZCHeaderRefreshView.m中的代码如下:

    
    //  
    //  ZCRefreshExample  
    //  
    //  Created by MrZhao on 16/6/26.  
    //  Copyright (c) 2016年 MrZhao. All rights reserved.  
    //  
      
    #import "ZCHeaderRefreshView.h"  
    #import <objc/message.h>  
    #define ZCContentOffset  @"contentOffset"  
    #define ScreenWidth  [UIScreen mainScreen].bounds.size.width  
    const static int headerRefreshHeight = 60 ;  
    /* 
     *枚举下拉刷新的几种状态 
     */  
    typedef enum {  
        kZCStateNomorl = 0, //默认状态  
        kZCStatePulling,    //下拉状态  
        kZCStateRefreshing  //正在刷新状态  
    } state;  
    @interface ZCHeaderRefreshView ()  
    /* 
     *用于设置图片 
     */  
    @property (nonatomic,weak)UIImageView *imageView;  
    /* 
     *用于设置文字 
     */  
    @property (nonatomic,weak)UILabel *label;  
    /* 
     *菊花控件 
     */  
    @property (nonatomic,weak)UIActivityIndicatorView *activityView;  
    /* 
     * 记录当前状态 
     */  
    @property (nonatomic, assign)int currentState;  
    /* 
     * 父控件 
     */  
    @property (nonatomic,weak)UIScrollView *superview;  
    /* 
     * 记录父控件初始时的偏移量,用于判定是否含有导航栏 
     */  
    @property (nonatomic,assign)CGFloat contentOffSetY;  
    /* 
     * 目标 
     */  
    @property(nonatomic,weak)id target;  
    /* 
     * 目标的方法,即刷新即将调用的方法 
     */  
    @property(nonatomic,assign)SEL action;  
    /* 
     *下拉刷新正常时的图片设置图片 
     */  
    @property(nonatomic,strong)UIImage *headerNormoalImage;  
    /* 
     *下拉时的图片设置图片 
     */  
    @property(nonatomic,strong)UIImage *headerPullingImage;  
    /* 
     *执行动画时的图片数组 
     */  
    @property(nonatomic,strong)NSArray *animationImages;  
    @end  
    @implementation ZCHeaderRefreshView  
    //工厂方法  
    + (instancetype)addHeaderRefreshViewWithTarget:(id)target action:(SEL)action {  
        ZCHeaderRefreshView *refreash = [[self alloc] init];  
        refreash.frame = CGRectMake(0, -headerRefreshHeight, ScreenWidth, headerRefreshHeight);  
        //背景颜色可根据需求设置或者取消  
        refreash.backgroundColor = [UIColor colorWithRed:230/255.0 green:230/255.0 blue:230/255.0 alpha:1.0];  
        refreash.currentState = kZCStateNomorl;  
        if (target != nil &&action != nil) {  
            refreash.target = target;  
            refreash.action = action;  
        }else {   
            NSLog(@"请设置刷新时调用的方法!!!");  
        }  
        return refreash;  
    } 
    #pragma mark子控件布局  
    - (void)layoutSubviews {  
        [super layoutSubviews];
        //图片位置  
        CGFloat imagViewWH = 40;  
        //做了简单的适配  
        CGFloat imagViewX = ScreenWidth * 0.3;  
        self.imageView.frame = CGRectMake(  imagViewX, (self.frame.size.height - imagViewWH) / 2, imagViewWH, imagViewWH);  
        //文字位置  
        CGFloat labelX = CGRectGetMaxX(self.imageView.frame);  
        self.label.frame = CGRectMake(labelX , (self.frame.size.height - imagViewWH) / 2, 100, imagViewWH);  
        //菊花位置  
        self.activityView.frame = CGRectMake(  imagViewX, (self.frame.size.height - imagViewWH) / 2, imagViewWH, imagViewWH);  
    }  
    #pragma 加到父控件时会调用该方法  
    - (void)willMoveToSuperview:(UIView *)newSuperview {  
        //是可以滚动的SCroolView才可以监听滚动事件  
        if ([newSuperview isKindOfClass:[UIScrollView class]]) {   
            //刷新控件添加的到的父控件  
            self.superview = (UIScrollView *)newSuperview;  
            //为父控件添加观察者,观察父控件的contentOffset.y值的变化。  
            [newSuperview addObserver:self forKeyPath:ZCContentOffset options:NSKeyValueObservingOptionNew context:nil];  
        }  
    }  
    - (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:  (NSDictionary *)change context:(voidvoid *)context {  
        if ([keyPath isEqualToString:ZCContentOffset]) {  
            [self adjustRefreshView];  
        }  
    }  
    #pragma 当正在操作下拉刷新控件时调用该方法  
    - (void)adjustRefreshView {  
        //主要用来区别控制器有无导航栏  
        if (self.superview.contentInset.top == 64.000000) {  
            static dispatch_once_t one;  
            dispatch_once(&one, ^{  
                self.contentOffSetY = self.superview.contentInset.top;  
            });     
        }  
        CGFloat y = self.superview.contentOffset.y;  
        if (self.superview.isDragging) { //正在拖动  
            if (y<  -self.contentOffSetY &&y> -self.contentOffSetY - headerRefreshHeight && self.currentState ==kZCStatePulling) { //正常状态->下拉  
                self.currentState = kZCStateNomorl;        
            }else if (y <= -self.contentOffSetY - headerRefreshHeight && self.currentState == kZCStateNomorl)//下拉->正常  
            {  
                self.currentState = kZCStatePulling;  
            }  
        }else if(self.currentState ==kZCStatePulling &&y <= -self.contentOffSetY - headerRefreshHeight) { //手释放      
            self.currentState = kZCStateRefreshing;  
        }  
    }  
    #pragma 重写setState方法,在该方法中修改文字,图片  
        if (_currentState == currentState) { //相等直接返回  
            return;  
        }  
        _currentState = currentState;  
        if (_currentState ==kZCStateNomorl) {//默认状态什么都不  
              
            self.imageView.hidden = NO;  
            [self.activityView stopAnimating];  
            self.activityView.hidden = YES;  
            [UIView animateWithDuration:0.5 animations:^{  
                [self.imageView stopAnimating];  
                self.label.text = @"下拉刷新";  
                //如果没有设置动画图片  
                if (self.animationImages == nil)  {  
                    if (self.headerNormoalImage == nil) {//没有设置正常图片,则采用默认的  
                        self.imageView.image = [UIImage imageNamed:@"down"];  
                    }   else {//采用设置的图片  
                        self.imageView.image = self.headerNormoalImage;  
                    }  
                } else {//   如果设置了动画,则采用第一张做正常时的图片  
                    self.imageView.image = self.animationImages[0];       
                }  
            }];        
        }else if (_currentState ==kZCStatePulling){//下拉状态  
            self.imageView.hidden = NO;  
            [self.activityView stopAnimating];  
            self.activityView.hidden = YES;  
            [UIView animateWithDuration:0.5 animations:^{     
                [self.imageView stopAnimating];  
                self.label.text= @"释放立即刷新";  
                //如果没有设置动画图片  
                if (self.animationImages == nil)  {  
                    if (self.headerPullingImage == nil) {//没有设置下拉图片,则采用默认的  
                        self.imageView.image = [UIImage imageNamed:@"up"];  
                    } else {//采用设置的图片  
                        self.imageView.image = self.headerPullingImage;  
                    }         
                } else {  
                    //   如果设置了动画,则采用第一张做下拉时的图片  
                    self.imageView.image = self.animationImages[0];  
                }  
            }];  
        } else if (_currentState == kZCStateRefreshing){ //释放刷新  
            self.label.text = @"正在刷新...";  
            //没有动画图片,默认采用菊花控件  
            if (self.animationImages == nil) {  
                self.activityView.hidden = NO;  
                self.imageView.hidden = YES;  
                [self.activityView startAnimating];       
            } else {  
                self.imageView.hidden = NO;  
                self.activityView.hidden = YES;  
                self.imageView.animationDuration = 0.1 * self.animationImages.count;  
                [self.imageView startAnimating];       
            }  
            //放手之后不能立即返回  
            [UIView animateWithDuration:0.25 animations:^{  
                self.superview.contentInset = UIEdgeInsetsMake(self.superview.contentInset.top + headerRefreshHeight, self.superview.contentInset.left, self.superview.contentInset.bottom, self.superview.contentInset.right);  
            }];  
            //不能直接调用objec.msgSend()  
            void (*action)(id, SEL) = (void (*)(id, SEL)) objc_msgSend;  
            action(self.target,self.action);      
        }  
    }  
    #pragma 开始刷新  
    - (void)beginRefreshing {   
        self.currentState = kZCStateRefreshing;  
    }  
    #pragma 结束下拉刷新  
    - (void)endHeaderRefreshing {     
        if (self.currentState == kZCStateRefreshing) {  
            self.currentState = kZCStateNomorl;  
            [UIView animateWithDuration:0.25 animations:^{  
                self.superview.contentInset = UIEdgeInsetsMake(self.superview.contentInset.top - headerRefreshHeight, self.superview.contentInset.left, self.superview.contentInset.bottom, self.superview.contentInset.right);  
            }];  
        }  
    }  
    #pragma mark 一定要记得移除观察者,不然会崩  
    - (void)dealloc  {  
        [self.superview removeObserver:self forKeyPath:ZCContentOffset];  
    }  
    #pragma mark 设置图片相关方法  
    - (void)setHeaderNormorlImageWithName:(NSString *)imageName {  
        self.headerNormoalImage = [UIImage imageNamed:imageName];  
    }  
    - (void)setHeaderPullingImageWithName:(NSString *)imageName {   
        self.headerPullingImage = [UIImage imageNamed:imageName];  
    }  
    - (void)setAnimantionImages:(NSArray *)images {    
        self.animationImages = images;  
        self.imageView.animationImages = self.animationImages;  
    }  
    #pragma mark懒加载子控件,放到最后这样不影响主逻辑  
    // 1 图片控件  
    - (UIImageView *)imageView {  
        if (_imageView == nil) {    
            UIImageView *imageView = [[UIImageView alloc] init];  
            //如果没有设置动画图片  
            if (self.animationImages == nil)  
            {  
                if (self.headerNormoalImage == nil) {//没有设置正常图片,则采用默认的  
                    imageView.image = [UIImage imageNamed:@"down"];  
                }  
                else {//采用设置的图片  
                    imageView.image = self.headerNormoalImage;  
                }         
            }else {//   如果设置了动画,则采用第一张做正常时的图片  
                imageView.image = self.animationImages[0];  
            }  
            imageView.autoresizingMask = UIViewAutoresizingFlexibleLeftMargin | UIViewAutoresizingFlexibleRightMargin; 
            [self addSubview: imageView];  
            _imageView = imageView;  
        }  
        return _imageView;  
    }   
    //2 文本控件  
    - (UILabel *)label {  
        if (_label == nil) { 
            //2 文本控件  
            UILabel *label = [[UILabel alloc] init];  
            label.textColor = [UIColor darkGrayColor];  
            label.font = [UIFont systemFontOfSize:13];  
            label.backgroundColor = [UIColor clearColor];  
            label.textAlignment = NSTextAlignmentCenter;  
            label.text = @"下拉刷新";  
            [label sizeToFit];  
            [self addSubview:label];  
            _label = label;  
        }  
        return _label;  
    } 
    //菊花控件  
    - (UIActivityIndicatorView *)activityView {  
        if (_activityView == nil) {  
            UIActivityIndicatorView *activityView = [[UIActivityIndicatorView alloc] init];  
            self.activityView = activityView;  
            activityView.bounds = self.imageView.bounds;  
            activityView.autoresizingMask = self.imageView.autoresizingMask;  
            [self addSubview: activityView];   
        }  
        return _activityView;  
    }  
    @end  
    

    说明:
    1)子控件的多少根位置可根据需求改变。
    2)在控制器里面self.tableView.zc_headerRefresh = ***这段代码时会调用willMoveToSuperView这个方法,在这个方法中就可以拿到父视图tableView(collectionView),给tableView(collectionView)添加contOffSet观察者。
    3)根据contOffSet的变化,不断调整刷新控件里面子控件的状态,包括切换图片,动图等等.
    4)注意在不同状态下要调整tableView的contInset属性.
    3.在控制器里面可以这样用:

    //添加下拉刷新控件  
        ZCHeaderRefreshView *refreshView = [ZCHeaderRefreshView addHeaderRefreshViewWithTarget:self action:@selector(loadNewDataSoure)];  
          
        //如果没有设置动画则采用默认的菊花转,且下拉和正常状态图片由代码提供,若果不提供,则采用默认图片,  
        //如果设置了动画,则用动画转动,且下拉,和正常状态的图片采用动画的第一张图片。  
        UIImage *image1 = [UIImage imageNamed:@"icon_listheader_animation_1"];  
        UIImage *image2 = [UIImage imageNamed:@"icon_listheader_animation_2"];  
        NSArray *animationImages = @[image1,image2];  
        [refreshView setAnimantionImages:animationImages];  
        self.tableView.zc_headerRefreshView = refreshView;  
        [self.tableView.zc_headerRefreshView beginRefreshing]; 
    

    好了,以上就是下拉刷新的基本写法,下拉加载更多原理跟上拉加载更多类似,大家自行看代码。
    代码地址:https://github.com/MrZhaoCn/ZCRefresh
    仓库里还有直播类的开源项目,自动计算cell高度的代码,欢迎大家start.

    20161221175358867.png 20161221175438042.png

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