[英]scrollView images not centered
我試圖用UIPageControl創建一個scrollView。 這可以正常工作,但是問題是圖像不會在scrollView的每個頁面中居中。 它向右對齊。 如何始終將圖像居中?
圖片說明:
http://i.stack.imgur.com/In6t7.png
碼:
self.pageControl = UIPageControl()
self.pageControl?.frame = CGRectZero
self.pageControl?.currentPage = 0
self.pageControl?.numberOfPages = self.imageArray!.count
self.pageControl?.tintColor = UIColor.whiteColor()
self.pageControl?.userInteractionEnabled = false
self.navigationItem.titleView = self.pageControl?
for var i = 0; i<self.imageArray?.count; i++ {
self.pageViews.append(nil)
}
let pagesScrollViewSize = self.scrollView.frame.size
self.scrollView.contentSize = CGSizeMake(pagesScrollViewSize.width * CGFloat(self.imageArray!.count), pagesScrollViewSize.height)
self.loadVisiblePages()
func loadPage(page: Int) {
if page < 0 || page >= self.imageArray!.count {
// If it's outside the range of what you have to display, then do nothing
return
}
// 1
if let pageView = pageViews[page] {
// Do nothing. The view is already loaded.
} else {
// 2
let newPageView = UIImageView(image: self.imageArray![page] as UIImage)
var frame = scrollView.bounds
frame.origin.x = (frame.size.width * CGFloat(page))
frame.origin.y = 0.0
// 3
newPageView.contentMode = .ScaleAspectFit
newPageView.frame = frame
scrollView.addSubview(newPageView)
newPageView.backgroundColor = UIColor.blackColor()
// 4
pageViews[page] = newPageView
}
}
func purgePage(page: Int) {
if page < 0 || page >= self.imageArray!.count {
// If it's outside the range of what you have to display, then do nothing
return
}
// Remove a page from the scroll view and reset the container array
if let pageView = pageViews[page] {
pageView.removeFromSuperview()
pageViews[page] = nil
}
}
func loadVisiblePages() {
// First, determine which page is currently visible
let pageWidth = scrollView.frame.size.width
let page = Int(floor((scrollView.contentOffset.x * 2.0 + pageWidth) / (pageWidth * 2.0)))
// Update the page control
pageControl?.currentPage = page
// Work out which pages you want to load
let firstPage = page - 1
let lastPage = page + 1
// Purge anything before the first page
for var index = 0; index < firstPage; ++index {
purgePage(index)
}
// Load pages in our range
for var index = firstPage; index <= lastPage; ++index {
loadPage(index)
}
// Purge anything after the last page
for var index = lastPage+1; index < self.imageArray!.count; ++index {
purgePage(index)
}
}
func scrollViewDidScroll(scrollView: UIScrollView!) {
// Load the pages that are now on screen
loadVisiblePages()
}
我在這里發現您使用let
來聲明一個常量UIImageView
,我認為您應該使用var
。
let newPageView = UIImageView(image: self.imageArray![page] as UIImage)
其實,除此之外,我還能發現任何問題,我認為您之所以無法將圖片設置為居中的原因是因為此聲明之后的所有操作均不起作用,因此您無法設置正確的框架,正確的contentMode到UIImageView
。
定位scrollView的圖像視圖時,如果使用center.x
而不是origin.x
,可能會更容易。
在這種情況下,我將使用的公式:
centerX = pageNumber * 320 + 160
所以像這樣:
myImageView.center = CGPointMake(pageNumber * 320 + 160, 0);
通過我的公式,我得到以下結果:
page 0: 0 * 320 + 160 = 160
page 1: 1 * 320 + 160 = 480
page 2: 2 * 320 + 160 = 800
page 3: 3 * 320 + 160 = 1120
您可以看到每個頁面的偏移量為320(此處假設iPhone屏幕尺寸)。 您顯然可以使用它代替:
self.view.bounds.size.width
這里的320僅用於說明目的。
好的,讓我們遍歷代碼:
var frame = scrollView.bounds
frame.origin.x = (frame.size.width * CGFloat(page))
frame.origin.y = 0.0
您看到數字如何不斷增加,而不是保持不變的320嗎?
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