Iphone 如何使用1000+；子视图？

我正在努力编写一个应用程序的一部分，它的行为应该与本机iphone照片应用程序类似。查看Oriely的iphone sdk应用程序开发书，书中给出了实现这种所谓页面翻转的示例代码。那里的代码首先创建所有子视图，然后隐藏/取消隐藏它们。在给定时间内，只有3个子视图可见，其余子视图隐藏。经过很多努力，我得到了它的应用程序，在那个时候只有约15页工作

当我添加了300页后，很明显，预分配这么多子视图的方法存在性能/内存问题。然后我想，对于我的情况，我应该只分配3个子视图，而不是隐藏/取消隐藏它们。也许我应该在运行时删除/添加子视图。但无法确定UIScrollView是否可以动态更新内容。例如，如UIScrollView所理解的，在开始时，屏幕上有3个不同x偏移（0320640）的帧。一旦用户移动到第3页，我如何确保我能够添加第4页和删除第1页，而UIScrollView不会感到困惑

---

希望能有一个标准的解决方案来解决这类问题……有人可以指导吗？

UIScrollView只是UIView的一个子类，因此可以在运行时添加和删除子视图。假设你有固定宽度的照片（320px）并且有300张，那么你的主视图将是300*320像素宽。创建滚动视图时，将帧初始化为该宽度

因此，滚动视图的框架的尺寸为（0,0）到（96000480）。无论何时添加子视图，都必须更改其框架，使其适合其父视图中的正确位置

比如说，我们正在将第四张照片添加到滚动视图中。它的帧从（960480）到（1280480）。这很容易计算，如果你能以某种方式将索引与每张图片关联起来。然后使用此值计算图片的帧，其中索引从0开始：

Top-Left -- (320 * (index - 1), 0)

到

---

删除第一个图片/子视图应该很容易。保持屏幕上当前有3个子视图的数组。无论何时向屏幕添加新的子视图，也要将其添加到此数组的末尾，然后将此数组中的第一个子视图也从屏幕中删除。

按照前面所说的，您可以使用有限的资源显示数千个元素（是的，这确实有点像飞锤模式）。这里有一些代码可以帮助你做你想做的事情

UntitledViewController类只包含一个UIScroll，并将自身设置为其委托。我们有一个NSArray，其中包含NSString实例作为数据模型（其中可能有数千个NSString），我们希望使用水平滚动在UILabel中显示每个实例。当用户滚动时，我们移动UILabel，将一个放在左侧，另一个放在右侧，以便为下一个滚动事件做好准备

以下是界面，非常简单：

@interface UntitledViewController : UIViewController <UIScrollViewDelegate>
{
@private
    UIScrollView *_scrollView;

    NSArray *_objects;

    UILabel *_detailLabel1;
    UILabel *_detailLabel2;
    UILabel *_detailLabel3;
}

@end

@interface UntitledViewController:UIViewController
{
@私人的
UIScrollView*\u滚动视图；
NSArray*_对象；
UILabel*_详细标签1；
UILabel*\u详细标签2；
UILabel*_详细标签3；
}
@结束

下面是该类的实现：

@interface UntitledViewController ()
- (void)replaceHiddenLabels;
- (void)displayLabelsAroundIndex:(NSInteger)index;
@end

@implementation UntitledViewController

- (void)dealloc 
{
    [_objects release];
    [_scrollView release];
    [_detailLabel1 release];
    [_detailLabel2 release];
    [_detailLabel3 release];
    [super dealloc];
}

- (void)viewDidLoad 
{
    [super viewDidLoad];

    _objects = [[NSArray alloc] initWithObjects:@"first", @"second", @"third", 
                @"fourth", @"fifth", @"sixth", @"seventh", @"eight", @"ninth", @"tenth", nil];

    _scrollView = [[UIScrollView alloc] initWithFrame:CGRectMake(0.0, 0.0, 320.0, 460.0)];
    _scrollView.contentSize = CGSizeMake(320.0 * [_objects count], 460.0);
    _scrollView.showsVerticalScrollIndicator = NO;
    _scrollView.showsHorizontalScrollIndicator = YES;
    _scrollView.alwaysBounceHorizontal = YES;
    _scrollView.alwaysBounceVertical = NO;
    _scrollView.pagingEnabled = YES;
    _scrollView.delegate = self;

    _detailLabel1 = [[UILabel alloc] initWithFrame:CGRectMake(0.0, 0.0, 320.0, 460.0)];
    _detailLabel1.textAlignment = UITextAlignmentCenter;
    _detailLabel1.font = [UIFont boldSystemFontOfSize:30.0];
    _detailLabel2 = [[UILabel alloc] initWithFrame:CGRectMake(320.0, 0.0, 320.0, 460.0)];
    _detailLabel2.textAlignment = UITextAlignmentCenter;
    _detailLabel2.font = [UIFont boldSystemFontOfSize:30.0];
    _detailLabel3 = [[UILabel alloc] initWithFrame:CGRectMake(640.0, 0.0, 320.0, 460.0)];
    _detailLabel3.textAlignment = UITextAlignmentCenter;
    _detailLabel3.font = [UIFont boldSystemFontOfSize:30.0];

    // We are going to show all the contents of the _objects array
    // using only these three UILabel instances, making them jump 
    // right and left, replacing them as required:
    [_scrollView addSubview:_detailLabel1];
    [_scrollView addSubview:_detailLabel2];
    [_scrollView addSubview:_detailLabel3];

    [self.view addSubview:_scrollView];
}

- (void)viewDidAppear:(BOOL)animated
{
    [super viewDidAppear:animated];
    [_scrollView flashScrollIndicators];
}

- (void)viewWillAppear:(BOOL)animated
{
    [super viewWillAppear:animated];
    [self displayLabelsAroundIndex:0];
}

- (void)didReceiveMemoryWarning 
{
    // Here you could release the data source, but make sure
    // you rebuild it in a lazy-loading way as soon as you need it again...
    [super didReceiveMemoryWarning];
}

#pragma mark -
#pragma mark UIScrollViewDelegate methods

- (void)scrollViewWillBeginDragging:(UIScrollView *)scrollView
{
    // Do some initialization here, before the scroll view starts moving!
}

- (void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView
{
    [self replaceHiddenLabels];
}

- (void)displayLabelsAroundIndex:(NSInteger)index
{
    NSInteger count = [_objects count];
    if (index >= 0 && index < count)
    {
        NSString *text = [_objects objectAtIndex:index];
        _detailLabel1.frame = CGRectMake(320.0 * index, 0.0, 320.0, 460.0);
        _detailLabel1.text = text;
        [_scrollView scrollRectToVisible:CGRectMake(320.0 * index, 0.0, 320.0, 460.0) animated:NO];

        if (index < (count - 1))
        {
            text = [_objects objectAtIndex:(index + 1)];
            _detailLabel2.frame = CGRectMake(320.0 * (index + 1), 0.0, 320.0, 460.0);
            _detailLabel2.text = text;
        }

        if (index > 0)
        {
            text = [_objects objectAtIndex:(index - 1)];
            _detailLabel3.frame = CGRectMake(320.0 * (index - 1), 0.0, 320.0, 460.0);
            _detailLabel3.text = text;
        }
    }
}

- (void)replaceHiddenLabels
{
    static const double pageWidth = 320.0;
    NSInteger currentIndex = ((_scrollView.contentOffset.x - pageWidth) / pageWidth) + 1;

    UILabel *currentLabel = nil;
    UILabel *previousLabel = nil;
    UILabel *nextLabel = nil;

    if (CGRectContainsPoint(_detailLabel1.frame, _scrollView.contentOffset))
    {
        currentLabel = _detailLabel1;
        previousLabel = _detailLabel2;
        nextLabel = _detailLabel3;
    }
    else if (CGRectContainsPoint(_detailLabel2.frame, _scrollView.contentOffset))
    {
        currentLabel = _detailLabel2;
        previousLabel = _detailLabel1;
        nextLabel = _detailLabel3;
    }
    else
    {
        currentLabel = _detailLabel3;
        previousLabel = _detailLabel1;
        nextLabel = _detailLabel2;
    }

    currentLabel.frame = CGRectMake(320.0 * currentIndex, 0.0, 320.0, 460.0);
    currentLabel.text = [_objects objectAtIndex:currentIndex];

    // Now move the other ones around
    // and set them ready for the next scroll
    if (currentIndex < [_objects count] - 1)
    {
        nextLabel.frame = CGRectMake(320.0 * (currentIndex + 1), 0.0, 320.0, 460.0);
        nextLabel.text = [_objects objectAtIndex:(currentIndex + 1)];
    }

    if (currentIndex >= 1)
    {
        previousLabel.frame = CGRectMake(320.0 * (currentIndex - 1), 0.0, 320.0, 460.0);
        previousLabel.text = [_objects objectAtIndex:(currentIndex - 1)];
    }
}

@end

@interface UntitledViewController（）
-（无效）替换隐藏标签；
-（void）displaylabaroundex：（NSInteger）索引；
@结束
@实现无标签的IEWController
-（无效）解除锁定
{
[_物体释放]；
[_scrollView发布]；
[_detailLabel1发布]；
[_detailLabel2发布]；
[_detailLabel3发布]；
[super dealoc]；
}
-（无效）viewDidLoad
{
[超级视图下载]；
_objects=[[NSArray alloc]initWithObjects:@“第一”，“第二”，“第三”，
@“第四”、“第五”、“第六”、“第七”、“第八”、“第九”、“第十”、“无”；
_scrollView=[[UIScrollView alloc]initWithFrame:CGRectMake（0.0,0.0320.0460.0）]；
_scrollView.contentSize=CGSizeMake（320.0*[\u对象计数]，460.0）；
_scrollView.showsVerticalScrollIndicator=否；
_scrollView.showsHorizontalScrollIndicator=是；
_scrollView.alwaysBounceHorizontal=是；
_scrollView.alwaysBounceVertical=否；
_scrollView.PaginEnabled=是；
_scrollView.delegate=self；
_detailLabel1=[[UILabel alloc]initWithFrame:CGRectMake（0.0,0.0320.0460.0）]；
_detailLabel1.textAlignment=UITextAlignmentCenter；
_detailLabel1.font=[UIFont boldSystemFontOfSize:30.0]；
_detailLabel2=[[UILabel alloc]initWithFrame:CGRectMake（320.0,0.0,320.0,460.0）]；
_detailLabel2.textAlignment=UITextAlignmentCenter；
_detailLabel2.font=[UIFont boldSystemFontOfSize:30.0]；
_detailLabel3=[[UILabel alloc]initWithFrame:CGRectMake（640.0,0.0320.0460.0）]；
_detailLabel3.textAlignment=UITextAlignmentCenter；
_detailLabel3.font=[UIFont boldSystemFontOfSize:30.0]；
//我们将显示_objects数组的所有内容
//仅使用这三个UILabel实例，使它们跳转
//左右两侧，根据需要更换：
[_scrollviewaddsubview:_detailLabel1]；
[_scrollviewaddsubview:_detailLabel2]；
[_scrollviewaddsubview:_detailLabel3]；
[self.view addSubview:_scrollView]；
}
-（无效）视图显示：（BOOL）动画
{
[超级视图显示：动画]；
[_ScrollViewFlashScrollIndicators]；
}
-（无效）视图将显示：（BOOL）动画
{
[超级视图将显示：动画]；
[自显示标签aroundex:0]；
}
-（无效）未收到记忆警告
{
//在这里，您可以释放数据源，但请确保
//一旦您再次需要它，您就以延迟加载的方式重新构建它。。。
[超级记忆警告]；
}
#布拉格标记-
#pragma标记UIScrollViewDelegate方法
-（无效）scrollView将开始刷新：（UIScrollView*）scrollView
{
//在滚动视图开始移动之前，在此执行一些初始化！
}
-（无效）ScrollViewDiEndDecelling：（UI）
@interface UntitledViewController ()
- (void)replaceHiddenLabels;
- (void)displayLabelsAroundIndex:(NSInteger)index;
@end

@implementation UntitledViewController

- (void)dealloc 
{
    [_objects release];
    [_scrollView release];
    [_detailLabel1 release];
    [_detailLabel2 release];
    [_detailLabel3 release];
    [super dealloc];
}

- (void)viewDidLoad 
{
    [super viewDidLoad];

    _objects = [[NSArray alloc] initWithObjects:@"first", @"second", @"third", 
                @"fourth", @"fifth", @"sixth", @"seventh", @"eight", @"ninth", @"tenth", nil];

    _scrollView = [[UIScrollView alloc] initWithFrame:CGRectMake(0.0, 0.0, 320.0, 460.0)];
    _scrollView.contentSize = CGSizeMake(320.0 * [_objects count], 460.0);
    _scrollView.showsVerticalScrollIndicator = NO;
    _scrollView.showsHorizontalScrollIndicator = YES;
    _scrollView.alwaysBounceHorizontal = YES;
    _scrollView.alwaysBounceVertical = NO;
    _scrollView.pagingEnabled = YES;
    _scrollView.delegate = self;

    _detailLabel1 = [[UILabel alloc] initWithFrame:CGRectMake(0.0, 0.0, 320.0, 460.0)];
    _detailLabel1.textAlignment = UITextAlignmentCenter;
    _detailLabel1.font = [UIFont boldSystemFontOfSize:30.0];
    _detailLabel2 = [[UILabel alloc] initWithFrame:CGRectMake(320.0, 0.0, 320.0, 460.0)];
    _detailLabel2.textAlignment = UITextAlignmentCenter;
    _detailLabel2.font = [UIFont boldSystemFontOfSize:30.0];
    _detailLabel3 = [[UILabel alloc] initWithFrame:CGRectMake(640.0, 0.0, 320.0, 460.0)];
    _detailLabel3.textAlignment = UITextAlignmentCenter;
    _detailLabel3.font = [UIFont boldSystemFontOfSize:30.0];

    // We are going to show all the contents of the _objects array
    // using only these three UILabel instances, making them jump 
    // right and left, replacing them as required:
    [_scrollView addSubview:_detailLabel1];
    [_scrollView addSubview:_detailLabel2];
    [_scrollView addSubview:_detailLabel3];

    [self.view addSubview:_scrollView];
}

- (void)viewDidAppear:(BOOL)animated
{
    [super viewDidAppear:animated];
    [_scrollView flashScrollIndicators];
}

- (void)viewWillAppear:(BOOL)animated
{
    [super viewWillAppear:animated];
    [self displayLabelsAroundIndex:0];
}

- (void)didReceiveMemoryWarning 
{
    // Here you could release the data source, but make sure
    // you rebuild it in a lazy-loading way as soon as you need it again...
    [super didReceiveMemoryWarning];
}

#pragma mark -
#pragma mark UIScrollViewDelegate methods

- (void)scrollViewWillBeginDragging:(UIScrollView *)scrollView
{
    // Do some initialization here, before the scroll view starts moving!
}

- (void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView
{
    [self replaceHiddenLabels];
}

- (void)displayLabelsAroundIndex:(NSInteger)index
{
    NSInteger count = [_objects count];
    if (index >= 0 && index < count)
    {
        NSString *text = [_objects objectAtIndex:index];
        _detailLabel1.frame = CGRectMake(320.0 * index, 0.0, 320.0, 460.0);
        _detailLabel1.text = text;
        [_scrollView scrollRectToVisible:CGRectMake(320.0 * index, 0.0, 320.0, 460.0) animated:NO];

        if (index < (count - 1))
        {
            text = [_objects objectAtIndex:(index + 1)];
            _detailLabel2.frame = CGRectMake(320.0 * (index + 1), 0.0, 320.0, 460.0);
            _detailLabel2.text = text;
        }

        if (index > 0)
        {
            text = [_objects objectAtIndex:(index - 1)];
            _detailLabel3.frame = CGRectMake(320.0 * (index - 1), 0.0, 320.0, 460.0);
            _detailLabel3.text = text;
        }
    }
}

- (void)replaceHiddenLabels
{
    static const double pageWidth = 320.0;
    NSInteger currentIndex = ((_scrollView.contentOffset.x - pageWidth) / pageWidth) + 1;

    UILabel *currentLabel = nil;
    UILabel *previousLabel = nil;
    UILabel *nextLabel = nil;

    if (CGRectContainsPoint(_detailLabel1.frame, _scrollView.contentOffset))
    {
        currentLabel = _detailLabel1;
        previousLabel = _detailLabel2;
        nextLabel = _detailLabel3;
    }
    else if (CGRectContainsPoint(_detailLabel2.frame, _scrollView.contentOffset))
    {
        currentLabel = _detailLabel2;
        previousLabel = _detailLabel1;
        nextLabel = _detailLabel3;
    }
    else
    {
        currentLabel = _detailLabel3;
        previousLabel = _detailLabel1;
        nextLabel = _detailLabel2;
    }

    currentLabel.frame = CGRectMake(320.0 * currentIndex, 0.0, 320.0, 460.0);
    currentLabel.text = [_objects objectAtIndex:currentIndex];

    // Now move the other ones around
    // and set them ready for the next scroll
    if (currentIndex < [_objects count] - 1)
    {
        nextLabel.frame = CGRectMake(320.0 * (currentIndex + 1), 0.0, 320.0, 460.0);
        nextLabel.text = [_objects objectAtIndex:(currentIndex + 1)];
    }

    if (currentIndex >= 1)
    {
        previousLabel.frame = CGRectMake(320.0 * (currentIndex - 1), 0.0, 320.0, 460.0);
        previousLabel.text = [_objects objectAtIndex:(currentIndex - 1)];
    }
}

@end

int refPage, currentPage;

refpage = 0; 
curentPage = 0;

- (void)scrollViewDidScroll:(UIScrollView *)sender{
    int currentPosition = floor(_scrollView.contentOffset.x);
    currentPage = MAX(0,floor(currentPosition / 340)); 
//340 is the width of the scrollview...
    if(currentPage != refPage)  { 
        refPage = currentPage;
        [self replaceHiddenLabels];
        }
    }