iOS無限循環(huán)滾動實(shí)現(xiàn)

昨天將以前寫的一個循環(huán)滾動視圖重新整理了一下。以后還會繼續(xù)完善這個demo，github托管地址：
https://github.com/JerryLMJ/LMJEndlessLoopScrollView
如果此demo幫助到你，請賜給一顆star，你的鼓勵是我coding的動力

主要講一下核心的代碼什么的，具體的下載下來自己來看吧。

原理

主要是利用UIScrollView實(shí)現(xiàn)，設(shè)置scrollVIew的contentSize為三倍控件寬度，不斷重置添加在scrollView上的三個內(nèi)容子視圖，從而實(shí)現(xiàn)無限循環(huán)。

用到的類別

先說一下用到的兩個自定義類別：

  • NSTimer (ForLMJEndlessLoopScrollView)
// 暫停
- (void)pause;
// 重新開始
- (void)restart;
// 延遲一定時間啟動
- (void)restartAfterTimeInterval:(NSTimeInterval)interval;

- (void)pause{
    if ([self isValid]) {
        [self setFireDate:[NSDate distantFuture]];
    }
}

- (void)restart{
    if ([self isValid]) {
        [self setFireDate:[NSDate date]];
    }
}

- (void)restartAfterTimeInterval:(NSTimeInterval)interval{
    if ([self isValid]) {
        [self setFireDate:[NSDate dateWithTimeIntervalSinceNow:interval]];
    }
}
  • UIView (ForLMJEndlessLoopScrollView)
- (UIView *)copyView; // 復(fù)制一個相同的UIView

- (UIView *)copyView{
    NSData * tempArchive = [NSKeyedArchiver archivedDataWithRootObject:self];
    return [NSKeyedUnarchiver unarchiveObjectWithData:tempArchive];
}

代理

@protocol LMJEndlessLoopScrollViewDelegate <NSObject>

@required
// 要添加的內(nèi)容子視圖的個數(shù) 
- (NSInteger)numberOfContentViewsInLoopScrollView:(LMJEndlessLoopScrollView *)loopScrollView;
// 每一個序號位置對應(yīng)的內(nèi)容子視圖（這個代理會調(diào)用很多次）
- (UIView *)loopScrollView:(LMJEndlessLoopScrollView *)loopScrollView contentViewAtIndex:(NSInteger)index;

@optional
// 滾動到當(dāng)前內(nèi)容子視圖的序號
- (void)loopScrollView:(LMJEndlessLoopScrollView *)loopScrollView currentContentViewAtIndex:(NSInteger)index;
// 點(diǎn)擊了某個內(nèi)容子視圖
- (void)loopScrollView:(LMJEndlessLoopScrollView *)loopScrollView didSelectContentViewAtIndex:(NSInteger)index;

@end

核心代碼

.h文件

@interface LMJEndlessLoopScrollView : UIView 

@property (nonatomic,assign) id<LMJEndlessLoopScrollViewDelegate> delegate;

// 當(dāng)duration<=0時，默認(rèn)不自動滾動
- (id)initWithFrame:(CGRect)frame animationScrollDuration:(NSTimeInterval)duration;

- (void)reloadData;

@end

.m文件

#define SelfWidth_LMJ     (self.frame.size.width)
#define SelfHeight_LMJ    (self.frame.size.height)

@interface LMJEndlessLoopScrollView () <UIScrollViewDelegate>
{
    UIScrollView   * _scrollView;
    
    NSInteger        _totalPageCount;
    NSInteger        _currentPageIndex;
    
    NSTimer        * _animationTimer;
    NSTimeInterval   _animationDuration;
}
@end

@implementation LMJEndlessLoopScrollView

- (id)initWithFrame:(CGRect)frame animationScrollDuration:(NSTimeInterval)duration{
    self = [super initWithFrame:frame];
    if (self) {
        
        [self initData];
        
        [self initAnimationScrollTimerWithDuration:duration];
        
        [self buildScrollView];
    }
    
    return self;
}
#pragma mark - Init

- (void)initData{
    _animationTimer    = nil;
    _animationDuration = 0;
}

- (void)initAnimationScrollTimerWithDuration:(NSTimeInterval)duration{
    
    _animationDuration = duration;
    
    if (duration > 0) {
        _animationTimer = [NSTimer scheduledTimerWithTimeInterval:duration
                                                           target:self
                                                         selector:@selector(startScroll:)
                                                         userInfo:nil
                                                          repeats:YES];
        // 將timer加入到currentRunLoop中主要是防止在操作UI的時候影響到timer驅(qū)動的自動滾動
        NSRunLoop *main = [NSRunLoop currentRunLoop];
        [main addTimer:_animationTimer forMode:NSRunLoopCommonModes];
        
        [_animationTimer pause];
        
    }else{
        /* 
         注意： 當(dāng) duration <= 0 時，_animationTimer為nil，由于在NSTimer擴(kuò)展的方法中進(jìn)行了空對象判斷，所以本頁代碼中都沒有進(jìn)行空判斷，也就是說此時對_animationTimer的操作都無效
         */
    }
}

- (void)buildScrollView{
    _scrollView = [[UIScrollView alloc] initWithFrame:CGRectMake(0, 0, SelfWidth_LMJ, SelfHeight_LMJ)];
    _scrollView.delegate         = self;
    _scrollView.contentSize      = CGSizeMake(SelfWidth_LMJ *3, SelfHeight_LMJ);
    _scrollView.contentOffset    = CGPointMake(SelfWidth_LMJ, 0);
    _scrollView.pagingEnabled    = YES;
    _scrollView.showsHorizontalScrollIndicator = NO;
    _scrollView.showsVerticalScrollIndicator   = NO;
    [self addSubview:_scrollView];
}

#pragma mark - Set

- (void)setDelegate:(id<LMJEndlessLoopScrollViewDelegate>)delegate{
    _delegate = delegate;
    
/*
 為什么要在delegate的set函數(shù)中reloadData，主要是因?yàn)樵趓eload的過程中需要調(diào)用代理獲取數(shù)據(jù)源，所以只有設(shè)置了代理之后才可以調(diào)用代理函數(shù)
*/
    [self reloadData]; 
}

#pragma mark - ReloadData

- (void)reloadData{
    _currentPageIndex  = 0;
    _totalPageCount    = 0;
    
    if ([self.delegate respondsToSelector:@selector(numberOfContentViewsInLoopScrollView:)]) {
        _totalPageCount = [self.delegate numberOfContentViewsInLoopScrollView:self];
    }else{
        NSAssert(NO, @"請實(shí)現(xiàn)numberOfContentViewsInLoopScrollView:代理函數(shù)");
    }
    
    [self resetContentViews];
    [_animationTimer restartAfterTimeInterval:_animationDuration];
}

#pragma mark - Methods
- (void)resetContentViews{
    // 移除scrollView上的所有子視圖
    [_scrollView.subviews makeObjectsPerformSelector:@selector(removeFromSuperview)];
    
    NSInteger previousPageIndex = [self getPreviousPageIndexWithCurrentPageIndex:_currentPageIndex];
    NSInteger currentPageIndex  = _currentPageIndex;
    NSInteger nextPageIndex     = [self getNextPageIndexWithCurrentPageIndex:_currentPageIndex];
    
    UIView * previousContentView;
    UIView * currentContentView;
    UIView * nextContentView;
    
    if ([self.delegate respondsToSelector:@selector(loopScrollView:contentViewAtIndex:)]) {
        
        previousContentView = [self.delegate loopScrollView:self contentViewAtIndex:previousPageIndex];
        currentContentView  = [self.delegate loopScrollView:self contentViewAtIndex:currentPageIndex];
        nextContentView     = [self.delegate loopScrollView:self contentViewAtIndex:nextPageIndex];
        
        NSArray * viewsArr = @[[previousContentView copyView],[currentContentView copyView],[nextContentView copyView]]; // copy操作主要是為了只有兩張內(nèi)容視圖的情況
        
        for (int i = 0; i < viewsArr.count; i++) {
            UIView * contentView = viewsArr[i];
            
            [contentView setFrame:CGRectMake(SelfWidth_LMJ*i, 0, contentView.frame.size.width, contentView.frame.size.height)];
            contentView.userInteractionEnabled = YES;
            
            UITapGestureRecognizer *tapGesture = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(tapContentView:)];
            [contentView addGestureRecognizer:tapGesture];
            
            [_scrollView addSubview:contentView];
        }
        
        [_scrollView setContentOffset:CGPointMake(SelfWidth_LMJ, 0)];
        
    }else{
//        NSAssert(NO, @"請實(shí)現(xiàn)loopScrollView:contentViewAtIndex:代理函數(shù)");
    }
}

// 獲取當(dāng)前頁上一頁的序號
- (NSInteger)getPreviousPageIndexWithCurrentPageIndex:(NSInteger)currentIndex{
    if (currentIndex == 0) {
        return _totalPageCount -1;
    }else{
        return currentIndex -1;
    }
}

// 獲取當(dāng)前頁下一頁的序號
- (NSInteger)getNextPageIndexWithCurrentPageIndex:(NSInteger)currentIndex{
    if (currentIndex == _totalPageCount -1) {
        return 0;
    }else{
        return currentIndex +1;
    }
}

#pragma mark - UIScrollView Delegate
- (void)scrollViewWillBeginDragging:(UIScrollView *)scrollView{
    // 當(dāng)手動滑動時 暫停定時器
    [_animationTimer pause];
}
- (void)scrollViewDidEndDragging:(UIScrollView *)scrollView willDecelerate:(BOOL)decelerate{
    // 當(dāng)手動滑動結(jié)束時 開啟定時器
    [_animationTimer restartAfterTimeInterval:_animationDuration];
}
- (void)scrollViewDidScroll:(UIScrollView *)scrollView{
    
    int contentOffsetX = scrollView.contentOffset.x;
    
    if(contentOffsetX >= (2 * SelfWidth_LMJ)) {
        _currentPageIndex = [self getNextPageIndexWithCurrentPageIndex:_currentPageIndex];
        
        // 調(diào)用代理函數(shù) 當(dāng)前頁面序號
        if ([self.delegate respondsToSelector:@selector(loopScrollView:currentContentViewAtIndex:)]) {
            [self.delegate loopScrollView:self currentContentViewAtIndex:_currentPageIndex];
        }
        
        [self resetContentViews];
    }
    
    
    if(contentOffsetX <= 0) {
        _currentPageIndex = [self getPreviousPageIndexWithCurrentPageIndex:_currentPageIndex];
        
        // 調(diào)用代理函數(shù) 當(dāng)前頁面序號
        if ([self.delegate respondsToSelector:@selector(loopScrollView:currentContentViewAtIndex:)]) {
            [self.delegate loopScrollView:self currentContentViewAtIndex:_currentPageIndex];
        }
        
        [self resetContentViews];
    }
}

- (void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView{
    [scrollView setContentOffset:CGPointMake(SelfWidth_LMJ, 0) animated:YES];
}

#pragma mark - Action
- (void)startScroll:(NSTimer *)timer{
    // 主要為了處理沒有滑完整頁的情況
    CGFloat contentOffsetX = ( (int)(_scrollView.contentOffset.x +SelfWidth_LMJ) / (int)SelfWidth_LMJ ) * SelfWidth_LMJ;
    CGPoint newOffset = CGPointMake(contentOffsetX, 0);
    [_scrollView setContentOffset:newOffset animated:YES];
}

#pragma mark - TapAction
- (void)tapContentView:(UITapGestureRecognizer *)gesture{
    
    if ([self.delegate respondsToSelector:@selector(loopScrollView:didSelectContentViewAtIndex:)]) {
        [self.delegate loopScrollView:self didSelectContentViewAtIndex:_currentPageIndex];
    }
}

使用

#import "LMJEndlessLoopScrollView.h"

@interface ViewController () <LMJEndlessLoopScrollViewDelegate>
{
    NSMutableArray * _contentViewsDataArr;
}
@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    
    self.view.backgroundColor = [UIColor lightGrayColor];
    
    _contentViewsDataArr = [NSMutableArray array];
    NSArray *colorArray = @[[UIColor cyanColor],[UIColor blueColor],[UIColor greenColor],[UIColor yellowColor],[UIColor purpleColor]];
    for (int i = 0; i < 2; i++) {
        UILabel *tempLabel = [[UILabel alloc] initWithFrame:CGRectMake(0, 0, 280, 200)];
        tempLabel.backgroundColor = colorArray[i];
        tempLabel.textAlignment   = NSTextAlignmentCenter;
        tempLabel.text            = [NSString stringWithFormat:@"%d",i];
        tempLabel.font            = [UIFont boldSystemFontOfSize:50];
        [_contentViewsDataArr addObject:tempLabel];
    }
    
    
    
    
    
    
    LMJEndlessLoopScrollView * scrollView = [[LMJEndlessLoopScrollView alloc] initWithFrame:CGRectMake(20, 100, 280, 200) animationScrollDuration:3];
    scrollView.delegate        = self;
    scrollView.backgroundColor = [UIColor whiteColor];
    [self.view addSubview:scrollView];
    

    
}

#pragma mark - LMJEndlessLoopScrollView Delegate
- (NSInteger)numberOfContentViewsInLoopScrollView:(LMJEndlessLoopScrollView *)loopScrollView{
    return _contentViewsDataArr.count;
}

- (UIView *)loopScrollView:(LMJEndlessLoopScrollView *)loopScrollView contentViewAtIndex:(NSInteger)index{
    return _contentViewsDataArr[index];
}

- (void)loopScrollView:(LMJEndlessLoopScrollView *)loopScrollView didSelectContentViewAtIndex:(NSInteger)index{
    NSLog(@"----點(diǎn)擊-----%ld",index);
}

- (void)loopScrollView:(LMJEndlessLoopScrollView *)loopScrollView currentContentViewAtIndex:(NSInteger)index{
    NSLog(@"----當(dāng)前-----%ld",index);
}

@end

github托管地址：
https://github.com/JerryLMJ/LMJEndlessLoopScrollView
如果此demo幫助到你，請賜給一顆star，你的鼓勵是我coding的動力

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