iOS开发 下拉刷新上拉加载更多详解
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
@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
//
// 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
static const void *zc_headerRefresh_key = @"zc_headerRefresh_key";
static const void *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
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
#import
@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
//
// ZCRefreshExample
//
// Created by MrZhao on 16/6/26.
// Copyright (c) 2016年 MrZhao. All rights reserved.
//
#import "ZCHeaderRefreshView.h"
#import
#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:(void *)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
- (void)setCurrentState:(int)currentState {
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 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.
