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IOS 类似抖音下拉刷新与自定义上拉加载

最近UICollectionView中使用了pageEnabled，MJRresh直接使用时出现偏移。这里就暂时考虑简单的做法。

首先考虑在UICollection与拖动手势之间的问题。

解决UICollectionView上添加手势不能触发。

这里使用了子类继承UICollectionView

#import "INMyCollectionView.h"

@implementation INMyCollectionView

-(void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event {
    [[self nextResponder] touchesBegan:touches withEvent:event];
    [super touchesBegan:touches withEvent:event];
}


-(void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event {
    [[self nextResponder] touchesMoved:touches withEvent:event];
    [super touchesMoved:touches withEvent:event];
}


- (void)touchesEnded:(NSSet *)touches
           withEvent:(UIEvent *)event {
    [[self nextResponder] touchesEnded:touches withEvent:event];
    [super touchesEnded:touches withEvent:event];
}

@end

在View上添加拖动手势

self.startPoint = CGPointZero;
self.isInLoading = NO;

UIPanGestureRecognizer *panGesture = [[UIPanGestureRecognizer alloc]initWithTarget:self action:@selector(panGestureHandle:)];
panGesture.minimumNumberOfTouches = 1;
panGesture.maximumNumberOfTouches = 1;
panGesture.delegate = self;
[self addGestureRecognizer:panGesture];

处理手势判断

-(BOOL)gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer shouldRecognizeSimultaneouslyWithGestureRecognizer:(UIGestureRecognizer *)otherGestureRecognizer {
    return YES;
}

// 给加的手势设置代理, 并实现此协议方法

- (BOOL)gestureRecognizerShouldBegin:(UIGestureRecognizer *)gestureRecognizer {
    if ([gestureRecognizer isKindOfClass:[UIPanGestureRecognizer class]]) {
        
        UIPanGestureRecognizer *pan = (UIPanGestureRecognizer *)gestureRecognizer;
        CGPoint pos = [pan velocityInView:pan.view];
        if (pos.y > 0) {
            return YES;
        }
    }
    
    return NO;
}

在处理拖动手势

 (void)panGestureHandle:(UIPanGestureRecognizer *)pan{
    if (self.collectionView.contentOffset.y > 0) {
        return;
    }
    
    DebugLog(@"panGestureHandle");
    if (self.isInLoading) {
        return;
    }
    
    if (pan.state == UIGestureRecognizerStateBegan) {
        DebugLog(@"UIGestureRecognizerStateBegan");
        self.startPoint = [pan translationInView:self];
        self.collectionView.scrollEnabled = NO;
    } if (pan.state == UIGestureRecognizerStateChanged) {
        DebugLog(@"UIGestureRecognizerStateChanged");
        CGPoint point = [pan translationInView:self];
        CGFloat distance = point.y - self.startPoint.y;
        if (distance > 0) {
            self.refreshStateLabel.text = @"下拉刷新";
            CGFloat scale = distance/KMaxScrollRefreshHeight;
            if (scale > 1.0) {
                scale = 1.0;
            }
            
            self.refreshStateLabel.alpha = scale;
            self.navbarView.alpha = (1-scale);
            self.refreshStateLabel.frame = CGRectMake(0.0, scale*(kStatusBarHeight + [BaseView baseSafeAreaEdgeInsets].top) + 5.0, CGRectGetWidth(self.bounds), 44.0);
            if (distance > KMaxScrollRefreshHeight) {
                DebugLog(@"可以下拉刷新");
            }
        } else {
            DebugLog(@"上拉操作");
            self.refreshStateLabel.alpha = 0.0;
        }
        
    } else if (pan.state == UIGestureRecognizerStateEnded || pan.state == UIGestureRecognizerStateCancelled || pan.state == UIGestureRecognizerStateFailed) {
        DebugLog(@"UIGestureRecognizerStateEnded");
        self.collectionView.scrollEnabled = YES;
        CGPoint point = [pan translationInView:self];
        CGFloat distance = point.y - self.startPoint.y;
        self.refreshStateLabel.text = @"";
        if (distance > 0) {
            if (distance > KMaxScrollRefreshHeight) {
                DebugLog(@"加载中...");
                self.refreshStateLabel.text = @"加载中...";
                self.refreshStateLabel.alpha = 1.0;
                self.isInLoading = YES;
                if (self.actionDelegate && [self.actionDelegate respondsToSelector:@selector(refreshLoadingData)]) {
                    [self.actionDelegate refreshLoadingData];
                }
            }
        }
    }
}

当然，类似抖音的下拉，在ScrollDidScoll处理了下
- (void)scrollViewDidScroll:(UIScrollView *)scrollView {
    if (scrollView.contentOffset.y < 0) {
        [scrollView setContentOffset:CGPointMake(0.0, 0.0)];
    } else {
        // 向上拖动，向上拖动的指定位置后加载更多数据
        DebugLog(@"向上拖动，向上拖动的指定位置后加载更多数据");
    }
}

第二部分

自己处理上拉加载更多，这里代码如下
INUpwardRefreshView.h

@protocol INUpwardRefreshViewDelegate;

@interface INUpwardRefreshView : BaseView

@property (nonatomic, weak) id<INUpwardRefreshViewDelegate>delegate;
@property (nonatomic, strong) UIScrollView *scrollView;

- (instancetype)initWithTarget:(UIScrollView *)scrollView;

- (void)endRefreshing;

@end

@protocol INUpwardRefreshViewDelegate <NSObject>

- (void)pullUpwardRefreshDidFinish;

@end

INUpwardRefreshView.m

//
//  INUpwardRefreshView.m
//  Views
//
//  Created by ABC on 2019/7/26.
//

#import "INUpwardRefreshView.h"
#import "Color.h"
#import "NSString+size.h"

NSString *const RefreshUpKeyPathContentOffset = @"contentOffset";
NSString *const RefreshUpKeyPathContentSize = @"contentSize";

CGFloat const FooterUpHeight = 80;

@interface INUpwardRefreshView ()

@property (nonatomic, strong) UIActivityIndicatorView *activityView;
@property (nonatomic, strong) UIImageView *arrowView;
@property (nonatomic, strong) UILabel *stateLable;
@property (nonatomic, assign) BOOL isRefresh;
@property (nonatomic, assign) CGFloat lastOffSet;

@end

@implementation INUpwardRefreshView

- (instancetype)initWithTarget:(UIScrollView *)scrollView {
    self = [super init];
    if (self) {
        self.backgroundColor = [UIColor clearColor];
        
        _scrollView = scrollView;
        
        self.frame = CGRectMake(0, 0, 0, FooterUpHeight);
        [_scrollView addSubview:self];
        
        [self addObserver];
    }
    return self;
    
}

- (void)layoutSubviews{
    [super layoutSubviews];
    
    CGSize statelabelSize = [self.stateLable.text sizeWithFont:self.stateLable.font forMaxSize:CGSizeMake(MAXFLOAT, 40)];
    
    self.stateLable.frame = CGRectMake((CGRectGetWidth(self.bounds) - statelabelSize.width)/2 + 10.0, 0.0, statelabelSize.width, 40);
    
    self.arrowView.frame = CGRectMake(CGRectGetMinX(self.stateLable.frame) - CGRectGetWidth(self.arrowView.frame) - 10.0, 0.0, CGRectGetWidth(self.arrowView.frame), 40);
    
    self.activityView.frame = CGRectMake(CGRectGetMinX(self.stateLable.frame) - CGRectGetWidth(self.arrowView.frame) - 10.0, (40.0 - 20.0)/2, 20, 20);
}

- (void)setCurrentFrame {
    [self setFrame:CGRectMake(0, MAX(self.scrollView.contentSize.height, CGRectGetHeight(self.scrollView.frame)), self.scrollView.size.width, FooterUpHeight)];
    [self setNeedsLayout];
}

- (void)setFrameHeight:(CGFloat)height {
    [self setFrame:CGRectMake(0, MAX(self.scrollView.contentSize.height, CGRectGetHeight(self.scrollView.frame)), self.scrollView.size.width, height)];
    DebugLog(@"frameHeight:%f",height);
}

#pragma mark setter
- (UIActivityIndicatorView *)activityView{
    if (!_activityView) {
        _activityView = [[UIActivityIndicatorView alloc] initWithActivityIndicatorStyle:UIActivityIndicatorViewStyleWhite];
        _activityView.hidesWhenStopped = YES;
        [self addSubview:_activityView];
    }
    return _activityView;
}

- (UIImageView *)arrowView{
    if (!_arrowView) {
        _arrowView = [[UIImageView alloc] initWithFrame:CGRectMake(0, 0, 15, 40)];
        _arrowView.image = [UIImage imageNamed:@"refresh_up_arrow"];
        //[self addSubview:_arrowView];
    }
    return _arrowView;
}

- (UILabel *)stateLable{
    if (!_stateLable) {
        _stateLable = [[UILabel alloc] initWithFrame:CGRectMake(0, 0, 90, 40)];
        _stateLable.backgroundColor = [UIColor clearColor];
        _stateLable.font = [UIFont systemFontOfSize:12];
        _stateLable.textAlignment = NSTextAlignmentLeft;
        _stateLable.textColor = [UIColor whiteColor];
        [self addSubview:_stateLable];
    }
    return _stateLable;
}

#pragma mark private
- (void)scrollViewContentOffsetDidChange:(NSDictionary *)change{
    _stateLable.hidden = NO;
    CGFloat yOffSet = _scrollView.contentOffset.y;
    DebugLog(@"yOffSet:%f",yOffSet);
    CGFloat contentSizeHeight = _scrollView.contentSize.height;
    CGFloat frameHeight = CGRectGetHeight(_scrollView.frame);
    if (contentSizeHeight > 0 && contentSizeHeight < frameHeight) {
        CGFloat insetTop = frameHeight - contentSizeHeight;
        if (yOffSet+insetTop > 0.0) {
            //正在拖拽中
            if (self.scrollView.isDragging) {
                
                [UIView animateWithDuration:0.3 animations:^{
                    self.arrowView.hidden = NO;
                    if (yOffSet+insetTop > 100.0) {
                        self.arrowView.transform =  CGAffineTransformMakeRotation(M_PI);
                        self.stateLable.text = @"松开夹子";
                    }else{
                        self.arrowView.transform =  CGAffineTransformMakeRotation(M_PI*2);
                        self.stateLable.text = @"继续滑动";
                    }
                }];
                
                [self setFrameHeight:(yOffSet+insetTop)];
            } else {
                if (yOffSet+insetTop > 100.0) {
                    [self beginRefreshing];
                }
            }
        }
        
    } else {
        //正在拖拽中
        CGFloat aYBottom = yOffSet - (contentSizeHeight - frameHeight);
        if (self.scrollView.isDragging) {
            
            [UIView animateWithDuration:0.3 animations:^{
                self.arrowView.hidden = NO;
                if (aYBottom > 100.0) {
                    self.arrowView.transform =  CGAffineTransformMakeRotation(M_PI);
                    self.stateLable.text = @"松开加载";
                }else{
                    self.arrowView.transform =  CGAffineTransformMakeRotation(M_PI*2);
                    self.stateLable.text = @"继续滑动";
                }
            }];
            
            [self setFrameHeight:yOffSet];
        } else {
            if (contentSizeHeight > 0 && aYBottom > 100.0) {
                [self beginRefreshing];
            }
        }
    }
}

#pragma mark publick
- (void)beginRefreshing{
    [self setFrameHeight:FooterUpHeight];
    
    if (!_isRefresh) {
        
        _isRefresh = YES;
        CGFloat insetTop = _scrollView.contentInset.top;
        //设置偏移量,衔接加载的更多数据
         [UIView animateWithDuration:0.35 animations:^{
             //[self.scrollView setContentInset:UIEdgeInsetsMake(insetTop, 0, FooterUpHeight, 0)];
             [self.activityView startAnimating];
             self.arrowView.hidden = YES;
             self.stateLable.text = @"加载中";
         } completion:^(BOOL finished) {
             [self startBeginRefresh];
         }];
    }
}

- (void)startBeginRefresh {
    // Refresh action!
    if ([self.delegate respondsToSelector:@selector(pullUpwardRefreshDidFinish)]) {
        [self.delegate performSelector:@selector(pullUpwardRefreshDidFinish) withObject:nil];
    }
}

- (void)endRefreshing {
    _isRefresh = NO;
    
    [UIView animateWithDuration:0.3 animations:^{
        [self.activityView stopAnimating];
        self.arrowView.hidden = YES;
        self.arrowView.transform =  CGAffineTransformMakeRotation(M_PI*2);
    }];
}

#pragma mark KVO
- (void)addObserver{
    NSKeyValueObservingOptions options = NSKeyValueObservingOptionNew | NSKeyValueObservingOptionOld;
    [_scrollView addObserver:self forKeyPath:RefreshUpKeyPathContentOffset options:options context:nil];
    
    [_scrollView addObserver:self forKeyPath:RefreshUpKeyPathContentSize options:options context:nil];
}

- (void)removeObserver{
    [_scrollView removeObserver:self forKeyPath:RefreshUpKeyPathContentOffset];
    [_scrollView removeObserver:self forKeyPath:RefreshUpKeyPathContentSize];
}

- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context{
    if ([keyPath isEqualToString:RefreshUpKeyPathContentOffset]) {
        [self scrollViewContentOffsetDidChange:change];
    } else if ([keyPath isEqualToString:RefreshUpKeyPathContentSize]) {
        [self setCurrentFrame];
    } else {
        [super observeValueForKeyPath:keyPath ofObject:object change:change context:context];
    }
}

- (void)dealloc{
    [self removeObserver];
}

@end

使用上拉加载的shih
在collection创建的时候，设置下即可

_upwardRefreshView = [[INUpwardRefreshView alloc] initWithTarget:_collectionView];
 _upwardRefreshView.delegate = self;

源码地址：

https://github.com/goodbruce/DouyinRefresh