最近在準(zhǔn)備畢業(yè)論文和畢業(yè)設(shè)計(jì)的事情，也是比較忙，許久未寫博客了。之前一直想寫一個(gè)自己的無限輪播，于是乎寫出來和大家分享一下。

思路

總體思路很簡(jiǎn)單，重寫了個(gè)scrollview。里面設(shè)置三個(gè)imageview，顯示的是中間那個(gè)imageView的圖像。當(dāng)滾動(dòng)結(jié)束后，把當(dāng)前顯示的imageView的image轉(zhuǎn)給中間的imageView，并且設(shè)置好兩邊的imageView。
設(shè)置了兩個(gè)style，一個(gè)是給string，本地圖片，一個(gè)是傳url，結(jié)合SDwebImage，顯示網(wǎng)絡(luò)圖片。

typedef NS_ENUM(NSInteger, LpScrollViewStyle){
LpSCrollVIewUrlStyle ,
LpSCrollVIewStringStyle};

初始化三個(gè)imageView，設(shè)置好位置和大?。ㄓ脩屑虞d的方式）。

- (UIImageView *)leftImageView{
if (_leftImageView == nil) {
    _leftImageView = [[UIImageView alloc] initWithFrame:CGRectMake(0, 0, SCREENWIDTH, IMAGEHEIGHT)];
}
return _leftImageView;
}
- (UIImageView *)midImageView{
if (_midImageView == nil) {
    _midImageView = [[UIImageView alloc] initWithFrame:CGRectMake(SCREENWIDTH, 0, SCREENWIDTH, IMAGEHEIGHT)];
}
return _midImageView;
}
- (UIImageView *)rightImageView{
if (_rightImageView == nil) {
    _rightImageView = [[UIImageView alloc] initWithFrame:CGRectMake(SCREENWIDTH * 2, 0, SCREENWIDTH, IMAGEHEIGHT)];
}
return _rightImageView;
}

根據(jù)傳入的數(shù)組初始化每個(gè)imageView的image。
- (void)set_imageWithString{
NSInteger count = self.imageArray.count;
if (count == 1) {
self.midImageView.image = [UIImage imageNamed:self.imageArray[0]];
self.leftImageView.image = [UIImage imageNamed:self.imageArray[0]];
self.rightImageView.image = [UIImage imageNamed:self.imageArray[0]];
}else if(count == 2){
self.midImageView.image = [UIImage imageNamed:self.imageArray[0]];
self.leftImageView.image = [UIImage imageNamed:self.imageArray[1]];
self.rightImageView.image = [UIImage imageNamed:self.imageArray[1]];
}else{
self.midImageView.image = [UIImage imageNamed:self.imageArray[0]];
self.leftImageView.image = [UIImage imageNamed:self.imageArray[count - 1]];
self.rightImageView.image = [UIImage imageNamed:self.imageArray[1]];
}
}
- (void)set_imageWithUrl{
NSInteger count = self.imageArray.count;
if (count == 1) {
[self.midImageView sd_setImageWithURL:[NSURL URLWithString:self.imageArray[0]] placeholderImage:[UIImage imageNamed:@""]];
[self.leftImageView sd_setImageWithURL:[NSURL URLWithString:self.imageArray[0]] placeholderImage:[UIImage imageNamed:@""]];
[self.rightImageView sd_setImageWithURL:[NSURL URLWithString:self.imageArray[0]] placeholderImage:[UIImage imageNamed:@""]];
}else if(count == 2){
[self.midImageView sd_setImageWithURL:[NSURL URLWithString:self.imageArray[0]] placeholderImage:[UIImage imageNamed:@""]];
[self.leftImageView sd_setImageWithURL:[NSURL URLWithString:self.imageArray[1]] placeholderImage:[UIImage imageNamed:@""]];
[self.rightImageView sd_setImageWithURL:[NSURL URLWithString:self.imageArray[1]] placeholderImage:[UIImage imageNamed:@""]];
}else{
[self.midImageView sd_setImageWithURL:[NSURL URLWithString:self.imageArray[0]] placeholderImage:[UIImage imageNamed:@""]];
[self.leftImageView sd_setImageWithURL:[NSURL URLWithString:self.imageArray[count - 1]] placeholderImage:[UIImage imageNamed:@""]];
[self.rightImageView sd_setImageWithURL:[NSURL URLWithString:self.imageArray[1]] placeholderImage:[UIImage imageNamed:@""]];
}

}

設(shè)置好定時(shí)器，用于計(jì)時(shí)作用，由于有時(shí)候人為的拖動(dòng)需要重置定時(shí)器，所以設(shè)置了isTimeUp布爾類型的成員變量對(duì)他進(jìn)行控制。
- (void)set_timer{
if (self.imageArray.count != 1) {
self.timer = [NSTimer scheduledTimerWithTimeInterval:changeImageTime target:self selector:@selector(imageViewMoved) userInfo:nil repeats:YES];
isTimeUp = NO;
}
}

- (void)imageViewMoved{
[self setContentOffset:CGPointMake(SCREENWIDTH * 2, 0) animated:YES];
isTimeUp = YES;
[NSTimer scheduledTimerWithTimeInterval:0.4f target:self selector:@selector(scrollViewDidEndDecelerating:) userInfo:nil repeats:NO];
}

定時(shí)器方法調(diào)用的是UIScrollViewDelegate里的方法，當(dāng)滑動(dòng)結(jié)束后，會(huì)自動(dòng)去更新imageView顯示的內(nèi)容，并且把scrollview的contentoffset設(shè)置到中間的imageView

- (void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView{
if (self.contentOffset.x == SCREENWIDTH * 2) {
    if (index == self.imageArray.count - 1) {
        index = 0;
    }else{
        index = index + 1;
    }
}else{
    if (index == 0) {
        index = self.imageArray.count - 1;
    }else{
        index = index - 1;
    }
    }

self.pageControl.currentPage = index % 3;

if (self.lpStyle == LpSCrollVIewStringStyle) {
    [self string_Decelerating];
}else{
    [self url_decelerating];
}

self.contentOffset = CGPointMake(SCREENWIDTH, 0);

if (!isTimeUp) {
    [self.timer setFireDate:[NSDate dateWithTimeIntervalSinceNow:changeImageTime]];
}
isTimeUp = NO;
}

- (void)string_Decelerating{
NSInteger count = self.imageArray.count;
if (index == 0) {
    _leftImageView.image = [UIImage imageNamed:_imageArray[(count - 1)%count]];
    _midImageView.image = [UIImage imageNamed:_imageArray[(index )%count]];
    _rightImageView.image = [UIImage imageNamed:_imageArray[(index + 1)%count]];
}else{
    _leftImageView.image = [UIImage imageNamed:_imageArray[(index - 1)%count]];
    _midImageView.image = [UIImage imageNamed:_imageArray[(index )%count]];
    _rightImageView.image = [UIImage imageNamed:_imageArray[(index + 1)%count]];
}
}

- (void)url_decelerating{
NSInteger count = self.imageArray.count;
if (index == 0) {
    [_leftImageView sd_setImageWithURL:self.imageArray[(count-1)%count]];
    [_midImageView sd_setImageWithURL:self.imageArray[index%count]];
    [_rightImageView sd_setImageWithURL:self.imageArray[(index+1)%count]];
}else{
    [_leftImageView sd_setImageWithURL:self.imageArray[(index-1)%count]];
    [_midImageView sd_setImageWithURL:self.imageArray[index%count]];
    [_rightImageView sd_setImageWithURL:self.imageArray[(index+1)%count]];
}
}

結(jié)束語

非常感謝各位的觀看，歡迎交流，附上demo地址：https://github.com/ioscick/LpScrollview-Demo