scrollview的无缝循环滚动

1.循环滚动

每次滚动后都将scrollview的offset设置为中间的一页

若本次滚动是向前一页滚动，则把三页都向后放置，最后一页放到开头

若本次滚动是向后一页滚动，则把三页都向前放置，第一页放到末尾

初始化UISCrollView



float x,y,width,height;

x = WIDTH_OFF_SET;

y = HEIGHT_OFF_SET;

width = WIDTH_OFF_SET;

height = SCROLLVIEW_HEIGHT;

for (int j=0; j<3; j++) {

UIView *view = [[UIView alloc] initWithFrame:CGRectMake(x*(j), y, width, height)];

[view setTag:10+j];//view的tag为10，11，12

[view setBackgroundColor:[UIColor yellowColor]];

for (int i=0; i<count; i++) {

UIButton*pointNButton = [UIButton buttonWithType:UIButtonTypeCustom];

[pointNButton setTitle:[NSString stringWithFormat:@"%d",100+i] forState:UIControlStateNormal];

[pointNButton setBackgroundColor:[UIColor blueColor]];

[pointNButton setTag:100+i];

[pointNButton setFrame:CGRectMake(6.5+(13+65)*i, 8, 65, 65)];

[pointNButton addTarget:self action:@selector(pointBtnClicked:) forControlEvents:UIControlEventTouchUpInside];

[view addSubview:pointNButton];

}

[scrollView addSubview:view];

[view release];



}

[scrollView setDelegate:self];

[scrollView setPagingEnabled:NO];

[scrollView setContentSize:CGSizeMake(WIDTH_OFF_SET*3, 80.0)];

[scrollView setShowsHorizontalScrollIndicator:NO];

#define WIDTH_OFF_SET630.0

#define HEIGHT_OFF_SET0

#define SCROLLVIEW_WIDTH390.0

#define SCROLLVIEW_HEIGHT80.0



#define SET_FRAME(ARTICLEX) x = ARTICLEX.frame.origin.x + increase;\

if(x < 0) x = pageWidth * 2;\

if(x > pageWidth * 2) x = 0.0f;\

[ARTICLEX setFrame:CGRectMake(x, \

ARTICLEX.frame.origin.y,\

ARTICLEX.frame.size.width,\

ARTICLEX.frame.size.height)]



#pragma mark -

#pragma mark UIScrollViewDelegate

//将三个view都向右移动，并更新三个指针的指向，article1永远指向当前显示的view，article0是左边的，article2是右边的

- (void)allArticlesMoveRight:(CGFloat)pageWidth {

UIView *view0 = [scrollView viewWithTag:10];

UIView *view1 = [scrollView viewWithTag:11];

UIView *view2 = [scrollView viewWithTag:12];

UIView *tmpView = view2;

view2 = view1;

view1 = view0;

view0 = tmpView;



float increase = pageWidth;

CGFloat x = 0.0f;

SET_FRAME(view2);

SET_FRAME(view0);

SET_FRAME(view1);

}

- (void)allArticlesMoveLeft:(CGFloat)pageWidth {



UIView *view0 = [scrollView viewWithTag:10];

UIView *view1 = [scrollView viewWithTag:11];

UIView *view2 = [scrollView viewWithTag:12];



UIView *tmpView = view0;

view0 = view1;

view1 = view2;

view2 = tmpView;

float increase = -pageWidth;

CGFloat x = 0.0f;

SET_FRAME(view1);

SET_FRAME(view2);

SET_FRAME(view0);

}

- (void)scrollViewDidScroll:(UIScrollView *)theScrollView

{

CGFloat pageWidth = WIDTH_OFF_SET;

// 0 1 2

int page = floor((theScrollView.contentOffset.x - pageWidth / 2) / pageWidth) + 1;

if(page == 1) {

//用户拖动了，但是滚动事件没有生效

return;

} else if (page == 0) {

[self allArticlesMoveRight:pageWidth];

} else {

[self allArticlesMoveLeft:pageWidth];

}

CGPoint p = CGPointZero;

p.x = pageWidth;

[theScrollView setContentOffset:p animated:NO];



}





- (void)scrollViewDidEndDecelerating:(UIScrollView *)theScrollView

{

CGFloat pageWidth = WIDTH_OFF_SET;

// 0 1 2

int page = floor((theScrollView.contentOffset.x - pageWidth / 2) / pageWidth) + 1;

if(page == 1) {

//用户拖动了，但是滚动事件没有生效

return;

} else if (page == 0) {

[self allArticlesMoveRight:pageWidth];

} else {

[self allArticlesMoveLeft:pageWidth];

}

CGPoint p = CGPointZero;

p.x = pageWidth;

[theScrollView setContentOffset:p animated:NO];



}

2.种方法思想是一样的，运用scrollRectToVisible



- (void)scrollViewDidEndDecelerating:(UIScrollView *)_scrollView

{



float currentPage =scrollView.contentOffset.x;

NSLog(@"=======bao===scrollViewDidEndDragging==currentPage=%d",currentPage);

if (currentPage >WIDTH_OFF_SET&¤tPage<WIDTH_OFF_SET*2) {

[scrollView scrollRectToVisible:CGRectMake(0,0,SCROLLVIEW_WIDTH,SCROLLVIEW_HEIGHT) animated:NO];

} else if (currentPage<0) {

[scrollView scrollRectToVisible:CGRectMake(WIDTH_OFF_SET,0,SCROLLVIEW_WIDTH,SCROLLVIEW_HEIGHT) animated:NO];

}



}

3。改变conentOffset



#pragma mark UIScrollViewDelegate

- (void)scrollViewDidScroll:(UIScrollView *)_scrollView

{

int currentPage =(int)scrollView.contentOffset.x;

if (currentPage >WIDTH_OFF_SET) {

scrollView.contentOffset = CGPointMake(abs(currentPage-WIDTH_OFF_SET), HEIGHT_OFF_SET);

} else if (currentPage<0) {

scrollView.contentOffset = CGPointMake(currentPage+WIDTH_OFF_SET,HEIGHT_OFF_SET);

}

}

- (void)scrollViewDidEndDecelerating:(UIScrollView *)_scrollView

{



int x= (int)scrollView.contentOffset.x/BUTTON_OFFSET*BUTTON_OFFSET;

[scrollView setContentOffset:CGPointMake(x, HEIGHT_OFF_SET) animated:YES];

}

- (void)scrollViewDidEndDragging:(UIScrollView *)_scrollView willDecelerate:(BOOL)decelerate {

if (!decelerate) {

int x = (int)scrollView.contentOffset.y/BUTTON_OFFSET*BUTTON_OFFSET;

[scrollView setContentOffset:CGPointMake(x, HEIGHT_OFF_SET) animated:YES];

}

}



总之要想实现无缝链接就必须准备三屏你的数据，通过改变offset或是view的frame的的横纵坐标进而实现循环滚动