使用 NSTimer 进行幻灯片放映时出现问题

发布于 2024-09-25 06:40:08 字数 1777 浏览 4 评论 0原文

我正在尝试使用 NSTimer 创建幻灯片...但以下代码不会定期滚动图像...

- (void)tilePages

{

// Calculate which pages are visible
CGRect visibleBounds = pagingScrollView.bounds;
int firstNeededPageIndex = floorf(CGRectGetMinX(visibleBounds) / CGRectGetWidth(visibleBounds));
int lastNeededPageIndex  = floorf((CGRectGetMaxX(visibleBounds)-1) / CGRectGetWidth(visibleBounds));
firstNeededPageIndex = MAX(firstNeededPageIndex, 0);
lastNeededPageIndex  = MIN(lastNeededPageIndex, [self imageCount] - 1);

// Recycle no-longer-visible pages 
for (ImageScrollView *page in visiblePages) {
    if (page.index < firstNeededPageIndex || page.index > lastNeededPageIndex) {
        [recycledPages addObject:page];
        [page removeFromSuperview];
    }
}
[visiblePages minusSet:recycledPages];

// add missing pages
for (int index = firstNeededPageIndex; index <= lastNeededPageIndex; index++) {
    if (![self isDisplayingPageForIndex:index]) {
        ImageScrollView *page = [self dequeueRecycledPage];
        if (page == nil) {
            page = [[[ImageScrollView alloc] init] autorelease];
        }
        [self configurePage:page forIndex:index];
        [pagingScrollView addSubview:page];
        [visiblePages addObject:page];

    }


}

}

在我使用的 ViewWillAppear 方法中...

timer = [NSTimer scheduledTimerWithTimeInterval:3.0 target:self selector:@selector(timerFired:) userInfo:nil repeats:YES];

并

调用要每隔一段时间触发的事件 i已经使用过...

-(void)timerFired:(NSTimer *)timer

{

[self tilePages];

}

我尝试过调试。该事件在 3 秒后被触发，但tilePages 没有被调用。我对scrollViewDidScroll方法使用了相同的方法，其中tilePages执行得很好......可能是什么问题？？？请帮忙...

原文

I am trying to create a slide show using NSTimer... But the following code is not scrolling the images at regular intervals...

- (void)tilePages

{

// Calculate which pages are visible
CGRect visibleBounds = pagingScrollView.bounds;
int firstNeededPageIndex = floorf(CGRectGetMinX(visibleBounds) / CGRectGetWidth(visibleBounds));
int lastNeededPageIndex  = floorf((CGRectGetMaxX(visibleBounds)-1) / CGRectGetWidth(visibleBounds));
firstNeededPageIndex = MAX(firstNeededPageIndex, 0);
lastNeededPageIndex  = MIN(lastNeededPageIndex, [self imageCount] - 1);

// Recycle no-longer-visible pages 
for (ImageScrollView *page in visiblePages) {
    if (page.index < firstNeededPageIndex || page.index > lastNeededPageIndex) {
        [recycledPages addObject:page];
        [page removeFromSuperview];
    }
}
[visiblePages minusSet:recycledPages];

// add missing pages
for (int index = firstNeededPageIndex; index <= lastNeededPageIndex; index++) {
    if (![self isDisplayingPageForIndex:index]) {
        ImageScrollView *page = [self dequeueRecycledPage];
        if (page == nil) {
            page = [[[ImageScrollView alloc] init] autorelease];
        }
        [self configurePage:page forIndex:index];
        [pagingScrollView addSubview:page];
        [visiblePages addObject:page];

    }


}

}

In ViewWillAppear method i have used...

timer = [NSTimer scheduledTimerWithTimeInterval:3.0 target:self selector:@selector(timerFired:) userInfo:nil repeats:YES];

and

to call the event to be fired at intervals i have used...

-(void)timerFired:(NSTimer *)timer

{

[self tilePages];

}

I have tried to debug. The event is getting fired at 3 secs, but the tilePages is not getting called. I have used the same for scrollViewDidScroll method where in the tilePages is getting executed well... What might be the problem??? Please help...

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回眸一笑 2024-10-02 06:40:08

调用[selftilePages]；不会显示新页面。看起来您是基于 WWDC 2010 分页和缩放图像的示例代码。因为我熟悉该代码，所以我也许可以帮助一些人。

您应该创建自己的方法来更改 pagingScrollView 的框架。然后您应该从timerFired 方法调用此方法。将 [selftilePages] 替换为 [selfchangePage] 并添加以下代码：

-(void)changePage{
   CGRect pageFrame = pagingScrollView.frame;
   pageFrame.size.width -= (2 * 10);
pageFrame.origin.x = (pagingScrollView.frame.size.width * aVariableHoldingTheCurrentPageNumber)+20;
[pagingScrollView scrollRectToVisible:pageFrame animated:YES];
}

基本上只是计算要滚动到的页框，然后调用scrollRectToVisible。

我希望这有帮助。

Calling [self tilePages]; will not show a new page. It looks like you're basing this on the WWDC 2010 sample code for paging and zooming images. Because I'm familiar with that code I may be able to help some.

You should make your own method that changes the frame of the pagingScrollView. Then you should call this method from the timerFired method. Replace [self tilePages] with [self changePage] and add the following code:

-(void)changePage{
   CGRect pageFrame = pagingScrollView.frame;
   pageFrame.size.width -= (2 * 10);
pageFrame.origin.x = (pagingScrollView.frame.size.width * aVariableHoldingTheCurrentPageNumber)+20;
[pagingScrollView scrollRectToVisible:pageFrame animated:YES];
}

Basically just calculate the page frame you want to scroll to and then call scrollRectToVisible.

I hope this helps.

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