Pull to Refresh 拖动刷新之我的实现

2021-09-18 13:14:11

项目中需要用到pull to refresh这个功能， 从网上找了下找到了这个：https://github.com/leah/PullToRefresh。
这个代码对我来说有一个很大的问题。其中拖动刷新的实现是放在TableViewControllerL里的，我要的放在
自定义UIView中的实现。经过一番改造终于实现了出来。

首先，我们整个的拖动刷新都是从拖动操作发起的，如下的方法必须予以合适的实现：

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// 拖动动作开始，如果正在获取更多信息不做任何操作
- (void)scrollViewWillBeginDragging:(UIScrollView *)scrollView;
 
 
// 拖动中。根据是否已经开始加载信息设置tableView的contentInset值
- (void)scrollViewDidScroll:(UIScrollView *)scrollView;
 
 
// 拖动完成，开始加载。如果上次的加载没有完成，不做任何操作
- (void)scrollViewDidEndDragging:(UIScrollView *)scrollView willDecelerate:(BOOL)decelerate;


拖动相关的了解之后。拖动之前需要在初始化方法里做好准备工作。
设置下什么“拖动获取更多”，“加载中。。。”之类的文字。还有箭头，ActivityIndicator之类的界面元素。

然后就是根据加载的不同状态设置界面语速的文字，位置和隐藏与否。代码：
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#pragma mark -
#pragma mark Pull to refresh methods
 
- (void)setUpStrings{
 
_textPull = [[NSString alloc]initWithString:@"拖动获取更多。。。"];
_textRelease = [[NSString alloc]initWithString:@"释放获取更多。。。"];
_textRelease = [[NSString alloc]initWithString:@"加载中。。。"];
}
 
- (void)addPullToRefreshHeader{
 
CGRect mainBounds = [[UIScreen mainScreen] bounds];
_refreshHeaderView = [[UIView alloc]initWithFrame:CGRectMake(0, 0 - REFRESH_HEADER_VIEW, mainBounds.size.width, REFRESH_HEADER_VIEW)];
_refreshHeaderView.backgroundColor = [UIColor clearColor];
 
_refreshLabel = [[UILabel alloc]initWithFrame:CGRectMake(0, 0, mainBounds.size.width, REFRESH_HEADER_VIEW)];
_refreshLabel.backgroundColor = [UIColor clearColor];
_refreshLabel.font = [UIFont boldSystemFontOfSize:12.f];
_refreshLabel.textAlignment = UITextAlignmentCenter;
 
_refreshArrow = [[UIImageView alloc]initWithImage:[UIImage imageNamed:@"arrow.png"]];
_refreshArrow.frame = CGRectMake(floorf((REFRESH_HEADER_VIEW - 20) / 2), floorf((REFRESH_HEADER_VIEW - 20) / 2), 27, 44);
 
_refreshSpinner = [[UIActivityIndicatorView alloc] initWithActivityIndicatorStyle:UIActivityIndicatorViewStyleGray];
_refreshSpinner.frame = CGRectMake(floorf((REFRESH_HEADER_VIEW - 20) / 2), floorf((REFRESH_HEADER_VIEW - 20) / 2), 27, 44);
_refreshSpinner.hidesWhenStopped = YES;
 
[_refreshHeaderView addSubview:_refreshLabel];
[_refreshHeaderView addSubview:_refreshArrow];
[_refreshHeaderView addSubview:_refreshSpinner];
[self.weiboTableView addSubview:_refreshHeaderView];
}
 
- (void)startLoading{
 
_isLoading = YES;
 
[UIView animateWithDuration:0.3f animations:^{
 
self.weiboTableView.contentInset = UIEdgeInsetsMake(REFRESH_HEADER_VIEW, 0, 0, 0);
_refreshLabel.text = self.textLoading;
_refreshArrow.hidden = YES;
[_refreshSpinner startAnimating];
}];
 
[self refresh];
}
 
- (void)stopLoadingComplete {
// Reset the header
_refreshLabel.text = self.textPull;
_refreshArrow.hidden = NO;
[_refreshSpinner stopAnimating];
}
 
- (void)stopLoading{
 
_isLoading = NO;
 
[UIView animateWithDuration:0.3f animations:^{
 
self.weiboTableView.contentInset = UIEdgeInsetsZero;
[_refreshArrow layer].transform = CATransform3DMakeRotation(M_PI * 2, 0, 0, 1);
}
completion:^(BOOL finished){
[self performSelector:@selector(stopLoadingComplete)];
}];
}
 
- (void)refresh{
 
[self performSelector:@selector(stopLoading) withObject:nil afterDelay:5.f];
}


最后最重要就是加载了。在加载方法中填充必要的代码，或者在子类的加载方法中添加（如果你要继承的话，最好还是继承一下）。示例：
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- (void)refresh{
 
// 加载功能代码
// 最后一句必不可少
[self performSelector:@selector(stopLoading) withObject:nil afterDelay:5.f];
}


完整代码如下：
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//
// ScrollRefreshPageView.h
// Sample Project
//
// Created by Bruce Li (mr_bruce).
// QQ: 1828099940
//
 
#import <UIKit/UIKit.h>
#import "TSPageView.h"
 
@interface ScrollRefreshPageView : UIView {
 
UIView *_refreshHeaderView;
UILabel *_refreshLabel;
UIImageView *_refreshArrow;
UIActivityIndicatorView *_refreshSpinner;
 
BOOL _isDragging;
BOOL _isLoading;
NSString *_textPull;
NSString *_textRelease;
NSString *_textLoading;
}
 
@property(nonatomic, copy) NSString *textPull;
@property(nonatomic, copy) NSString *textRelease;
@property(nonatomic, copy) NSString *textLoading;
 
- (void)setUpStrings;
- (void)addPullToRefreshHeader;
- (void)startLoading;
- (void)stopLoading;
- (void)refresh;
 
@end


.m
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#import "ScrollRefreshPageView.h"
#import <QuartzCore/QuartzCore.h>
 
#define REFRESH_HEADER_VIEW 90.f
 
 
@implementation ScrollRefreshPageView
 
@synthesize textPull = _textPull;
@synthesize textRelease = _textRelease;
@synthesize textLoading = _textLoading;
 
- (id)initWithFrame:(CGRect)frame
{
self = [super initWithFrame:frame];
if (self) {
[self setUpStrings];
[self addPullToRefreshHeader];
}
return self;
}
 
- (void)dealloc{
 
[_refreshHeaderView release];
[_refreshLabel release];
[_refreshArrow release];
[_refreshSpinner release];
[_textPull release];
[_textRelease release];
[_textLoading release];
[super dealloc];
}
 
#pragma mark -
#pragma mark Scroll view delegate
 
- (void)scrollViewWillBeginDragging:(UIScrollView *)scrollView{
 
if (_isLoading) {
return;
}
 
_isDragging = YES;
}
 
- (void)scrollViewDidScroll:(UIScrollView *)scrollView{
 
if (_isLoading) {
if (scrollView.contentOffset.y > 0) {
self.weiboTableView.contentInset = UIEdgeInsetsZero;
}else if (scrollView.contentOffset.y >= -REFRESH_HEADER_VIEW) {
self.weiboTableView.contentInset = UIEdgeInsetsMake(-scrollView.contentOffset.y, 0, 0, 0);
}
}else if (_isDragging && scrollView.contentOffset.y < 0) {
[UIView animateWithDuration:0.25f animations:^{
 
if (scrollView.contentOffset.y < -REFRESH_HEADER_VIEW) {
_refreshLabel.text = self.textRelease;
[_refreshArrow layer].transform = CATransform3DMakeRotation(M_PI, 0, 0, 1);
}
else {
_refreshLabel.text = self.textPull;
[_refreshArrow layer].transform = CATransform3DMakeRotation(M_PI * 2, 0, 0, 1);
}
}];
}
}
 
- (void)scrollViewDidEndDragging:(UIScrollView *)scrollView willDecelerate:(BOOL)decelerate{
 
if (_isLoading) {
return;
}
 
_isDragging = NO;
 
if (scrollView.contentOffset.y <= -REFRESH_HEADER_VIEW) {
[self startLoading];
}
}
 
#pragma mark -
#pragma mark Pull to refresh methods
 
- (void)setUpStrings{
 
_textPull = [[NSString alloc]initWithString:@"拖动获取更多。。。"];
_textRelease = [[NSString alloc]initWithString:@"释放获取更多。。。"];
_textRelease = [[NSString alloc]initWithString:@"加载中。。。"];
}
 
- (void)addPullToRefreshHeader{
 
CGRect mainBounds = [[UIScreen mainScreen] bounds];
_refreshHeaderView = [[UIView alloc]initWithFrame:CGRectMake(0, 0 - REFRESH_HEADER_VIEW, mainBounds.size.width, REFRESH_HEADER_VIEW)];
_refreshHeaderView.backgroundColor = [UIColor clearColor];
 
_refreshLabel = [[UILabel alloc]initWithFrame:CGRectMake(0, 0, mainBounds.size.width, REFRESH_HEADER_VIEW)];
_refreshLabel.backgroundColor = [UIColor clearColor];
_refreshLabel.font = [UIFont boldSystemFontOfSize:12.f];
_refreshLabel.textAlignment = UITextAlignmentCenter;
 
_refreshArrow = [[UIImageView alloc]initWithImage:[UIImage imageNamed:@"arrow.png"]];
_refreshArrow.frame = CGRectMake(floorf((REFRESH_HEADER_VIEW - 20) / 2), floorf((REFRESH_HEADER_VIEW - 20) / 2), 27, 44);
 
_refreshSpinner = [[UIActivityIndicatorView alloc] initWithActivityIndicatorStyle:UIActivityIndicatorViewStyleGray];
_refreshSpinner.frame = CGRectMake(floorf((REFRESH_HEADER_VIEW - 20) / 2), floorf((REFRESH_HEADER_VIEW - 20) / 2), 27, 44);
_refreshSpinner.hidesWhenStopped = YES;
 
[_refreshHeaderView addSubview:_refreshLabel];
[_refreshHeaderView addSubview:_refreshArrow];
[_refreshHeaderView addSubview:_refreshSpinner];
[self.weiboTableView addSubview:_refreshHeaderView];
}
 
- (void)startLoading{
 
_isLoading = YES;
 
[UIView animateWithDuration:0.3f animations:^{
 
self.weiboTableView.contentInset = UIEdgeInsetsMake(REFRESH_HEADER_VIEW, 0, 0, 0);
_refreshLabel.text = self.textLoading;
_refreshArrow.hidden = YES;
[_refreshSpinner startAnimating];
}];
 
[self refresh];
}
 
- (void)stopLoadingComplete {
// Reset the header
_refreshLabel.text = self.textPull;
_refreshArrow.hidden = NO;
[_refreshSpinner stopAnimating];
}
 
- (void)stopLoading{
 
_isLoading = NO;
 
[UIView animateWithDuration:0.3f animations:^{
 
self.weiboTableView.contentInset = UIEdgeInsetsZero;
[_refreshArrow layer].transform = CATransform3DMakeRotation(M_PI * 2, 0, 0, 1);
}
completion:^(BOOL finished){
[self performSelector:@selector(stopLoadingComplete)];
}];
}
 
- (void)refresh{
 
[self performSelector:@selector(stopLoading) withObject:nil afterDelay:5.f];
}
 
@end
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