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我正在开发一个水平滚动图像的简单 iPad 应用程序（Lion 上的 iOS 5.1.1 和 XCode 4.3.3）。它使用延迟加载，但不幸的是，由于图像大约 3/4 的内存不足，它正在崩溃。我使用 XCode 分析器和 Instruments 来查找和修复任何泄漏，但它仍然崩溃。崩溃日志如下：

Incident Identifier: 91B65E89-4CCE-4CB5-975F-365D23D802E5
CrashReporter Key:   659f640ad55a7dfbaf0305305e0b8f0fb36a6c41
Hardware Model:      iPad1,1
OS Version:          iPhone OS 5.1.1 (9B206)
Kernel Version:      Darwin Kernel Version 11.0.0: Sun Apr  8 21:51:26 PDT 2012; root:xnu-1878.11.10~1/RELEASE_ARM_S5L8930X
Date:                2012-06-29 14:51:58 -0700
Time since snapshot: 49 ms

Free pages:        610
Active pages:      0
Inactive pages:    694
Throttled pages:   43266
Purgeable pages:   0
Wired pages:       18518
Largest process:   GBTL

Processes
     Name                 UUID                    Count resident pages
        GBTL <d26b776787493174ae14f454a11b746d>   31295 (jettisoned) (active)
 debugserver <2408bf4540f63c55b656243d522df7b2>     134
    installd <0f9e14173c503a8089f7f8cd0329a1a0>     403
         atc <1e5f2a595709376b97f7f0fa29368ef1>     605 (jettisoned)
notification_pro <373a488638c436b48ef0801b212593c4>      96
notification_pro <373a488638c436b48ef0801b212593c4>      99
notification_pro <373a488638c436b48ef0801b212593c4>      96
        afcd <c3cc9d594b523fd1902fb69add11c25d>     133
  MobileMail <eed7992f4c1d3050a7fb5d04f1534030>    1004 (jettisoned)
        ptpd <62bc5573db7a352ab68409e87dc9abb9>     356 (jettisoned)
mediaserverd <f03b746f09293fd39a6079c135e7ed00>     404 (jettisoned)
        iapd <0a747292a113307abb17216274976be5>     285 (jettisoned)
  DTMobileIS <1383b8ed7d373b59a0839e89ab947089>     899
notification_pro <373a488638c436b48ef0801b212593c4>      99
 dataaccessd <473ff40f3bfd3f71b5e3b4335b2011ee>     735 (jettisoned)
springboardservi <b74f5f58317031e9aef7e95744c816ca>     283
syslog_relay <b07876a121a432d39d89daf531e8f2bd>      62
notification_pro <373a488638c436b48ef0801b212593c4>      98
syslog_relay <b07876a121a432d39d89daf531e8f2bd>      66
notification_pro <373a488638c436b48ef0801b212593c4>      98
filecoordination <0f34c714b10d35318f0d445f1d953386>      98
        geod <976e1080853233b1856b13cbd81fdcc3>     127
absinthed.K48 <04b40efabeac392ba63cba7256b86bb0>      74
     notifyd <f6a9aa19d33c3962aad3a77571017958>     181
  aosnotifyd <8cf4ef51f0c635dc920be1d4ad81b322>     369
    BTServer <31e82dfa7ccd364fb8fcc650f6194790>     186
CommCenterClassi <041d4491826e3c6b911943eddf6aaac9>     274
 SpringBoard <c74dc89dec1c3392b3f7ac891869644a>    4878 (active)
  aggregated <a12fa71e6997362c83e0c23d8b4eb5b7>     356
        apsd <e7a29f2034083510b5439c0fb5de7ef1>     630
     configd <ee72b01d85c33a24b3548fa40fbe519c>     304
fairplayd.K48 <47deae2d0fb23b6594b0128353e8b48d>     115
   fseventsd <914b28fa8f8a362fabcc47294380c81c>     175
     imagent <9c3a4f75d1303349a53fc6555ea25cd7>     361
   locationd <cf31b0cddd2d3791a2bfcd6033c99045>     833
mDNSResponder <86ccd4633a6c3c7caf44f51ce4aca96d>     188
mediaremoted <327f00bfc10b3820b4a74b9666b0c758>     201
   lockdownd <b06de06b9f6939d3afc607b968841ab9>     216
      powerd <133b7397f5603cf8bef209d4172d6c39>     133
     syslogd <7153b590e0353520a19b74a14654eaaa>      97
       wifid <3001cd0a61fe357d95f170247e5458f5>     258
UserEventAgent <dc32e6824fd33bf189b266102751314f>     362
     launchd <5fec01c378a030a8bd23062689abb07f>     123

**End**

这是相关的代码：

#import "GBTLViewController.h"

@implementation GBTLViewController

@synthesize scrollView;
@synthesize pageControl;
@synthesize pageImages;
@synthesize pageViews;

- (void)scrollViewDidScroll:(UIScrollView *)scrollView {
    [self loadVisiblePages];

    if (!pageControlBeingUsed) {
        // Update the page when more than 50% of the previous/next page is visible
        CGFloat pageWidth = self.scrollView.frame.size.width;
        int page = floor((self.scrollView.contentOffset.x - pageWidth / 2) / pageWidth) + 1;
        self.pageControl.currentPage = page;
    }
}

- (IBAction)changePage {
    // update the scroll view to the appropriate page
    CGRect frame;
    frame.origin.x = self.scrollView.frame.size.width * self.pageControl.currentPage;
    frame.origin.y = 0;
    frame.size = self.scrollView.frame.size;
    [self.scrollView scrollRectToVisible:frame animated:YES];

    pageControlBeingUsed = YES;
}

- (void)scrollViewWillBeginDragging:(UIScrollView *)scrollView {
    pageControlBeingUsed = NO;
}

- (void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView {
    pageControlBeingUsed = NO;
}

- (void)loadVisiblePages {
    // First, determine which page is currently visible
    CGFloat pageWidth = self.scrollView.frame.size.width;
    NSInteger page = (NSInteger)floor((self.scrollView.contentOffset.x * 2.0f + pageWidth) / (pageWidth * 2.0f));

    // Update the page control
    self.pageControl.currentPage = page;

    // Work out which pages you want to load
    NSInteger firstPage = page - 1;
    NSInteger lastPage = page + 1;

    // Purge anything before the first page
    for (NSInteger i=0; i<firstPage; i++) {
        [self purgePage:i];
    }

    // Load pages in our range
    for (NSInteger i=firstPage; i<=lastPage; i++) {
        [self loadPage:i];
    }

    // Purge anything after the last page
    for (NSInteger i=lastPage+1; i<self.pageImages.count; i++) {
        [self purgePage:i];
    }
}

- (void)loadPage:(NSInteger)page {
    if (page < 0 || page >= self.pageImages.count) {
        // If it's outside the range of what you have to display, then do nothing
        return;
    }

    UIView *pageView = [self.pageViews objectAtIndex:page];
    if ((NSNull*)pageView == [NSNull null]) {

        CGRect frame = self.scrollView.bounds;
        frame.origin.x = frame.size.width * page;
        frame.origin.y = 0.0f;

        UIImageView *newPageView = [[UIImageView alloc] initWithImage:[self.pageImages objectAtIndex:page]];
        newPageView.contentMode = UIViewContentModeScaleAspectFit;
        newPageView.frame = frame;
        [self.scrollView addSubview:newPageView];
        [newPageView release];

        [self.pageViews replaceObjectAtIndex:page withObject:newPageView];
    }
}

- (void)purgePage:(NSInteger)page {
    if (page < 0 || page >= self.pageImages.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
    UIView *pageView = [self.pageViews objectAtIndex:page];
    if ((NSNull*)pageView != [NSNull null]) {
        [pageView removeFromSuperview];
        [self.pageViews replaceObjectAtIndex:page withObject:[NSNull null]];
    }
}

// Implement viewDidLoad to do additional setup after loading the view, typically from a     nib.
- (void)viewDidLoad {
    [super viewDidLoad];

    pageControlBeingUsed = NO;

    scrollView.delegate = self;
    [self.scrollView setBackgroundColor:[UIColor blackColor]];
    scrollView.indicatorStyle = UIScrollViewIndicatorStyleWhite;
    scrollView.clipsToBounds = NO;
    scrollView.scrollEnabled = YES;
    scrollView.pagingEnabled = NO;

    self.pageImages = [NSArray arrayWithObjects:
                   [UIImage imageNamed:@"480X_cover.jpg"],
                   [UIImage imageNamed:@"GBTL1.jpg"],
                   [UIImage imageNamed:@"GBTL2.jpg"],
                   [UIImage imageNamed:@"GBTL3.jpg"],
                   [UIImage imageNamed:@"GBTL4.jpg"],
                   [UIImage imageNamed:@"GBTL5.jpg"],
                   [UIImage imageNamed:@"GBTL6.jpg"],
                   [UIImage imageNamed:@"GBTL7.jpg"],
                   [UIImage imageNamed:@"GBTL8.jpg"],
                   [UIImage imageNamed:@"GBTL9.jpg"],
                   [UIImage imageNamed:@"GBTL10.jpg"],
                   [UIImage imageNamed:@"GBTL11.jpg"],
                   [UIImage imageNamed:@"GBTL12.jpg"],
                   [UIImage imageNamed:@"GBTL13.jpg"],
                   [UIImage imageNamed:@"GBTL14.jpg"],
                   [UIImage imageNamed:@"GBTL15.jpg"],
                   [UIImage imageNamed:@"GBTL16.jpg"],
                   [UIImage imageNamed:@"GBTL17.jpg"],
                   [UIImage imageNamed:@"GBTL18.jpg"],
                   [UIImage imageNamed:@"GBTL19.jpg"],
                   [UIImage imageNamed:@"GBTL20.jpg"],
                   nil];

    NSInteger pageCount = self.pageImages.count;

    self.pageControl.currentPage = 0;
    self.pageControl.numberOfPages = pageCount;

    self.pageViews = [[[NSMutableArray alloc] init] autorelease];
    for (NSInteger i = 0; i < pageCount; ++i) {
        [self.pageViews addObject:[NSNull null]];
    }
}

- (void)viewWillAppear:(BOOL)animated {
    [super viewWillAppear:animated];

    CGSize pagesScrollViewSize = self.scrollView.frame.size;
    self.scrollView.contentSize = CGSizeMake(pagesScrollViewSize.width * self.pageImages.count, pagesScrollViewSize.height);

    [self loadVisiblePages];
}

// Override to allow orientations other than the default portrait orientation.
- (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation {
    return YES;
}

- (void)didRotateFromInterfaceOrientation:(UIInterfaceOrientation)fromInterfaceOrientation {
    NSInteger pageCount = self.pageImages.count;

    for (NSInteger i=0; i<pageCount; i++) {
    [self purgePage:i];
    }

    CGSize pagesScrollViewSize = self.scrollView.frame.size;
    self.scrollView.contentSize = CGSizeMake(pagesScrollViewSize.width * pageCount, pagesScrollViewSize.height);

    [self loadVisiblePages];
}

- (void)didReceiveMemoryWarning {
    // Releases the view if it doesn't have a superview.
    [super didReceiveMemoryWarning];

    // Release any cached data, images, etc that aren't in use.
}

- (void)viewDidUnload {
    // Release any retained subviews of the main view.
    // e.g. self.myOutlet = nil;
    self.scrollView = nil;
    self.pageControl = nil;
}

- (void)dealloc {
    [scrollView release];
    [pageControl release];
    [super dealloc];
}

@end

如果有人能弄清楚内存问题发生在哪里以及如何解决它，我将不胜感激。谢谢！

4

3 回答 3

2

不知道这些是什么尺寸的图像，但有许多策略可以处理这种情况：

1）你真的需要将图像加载到 NSArray 中吗？似乎根据您的文件命名方案，您可以构建一些逻辑以根据需要将其从包中拉出，然后在屏幕外立即丢弃。

2) 有时在 @autorelease 块中做这种事情是有利的。见这里： https ://developer.apple.com/library/mac/#documentation/Cocoa/Reference/Foundation/Classes/nsautoreleasepool_Class/Reference/Reference.html

3）您可能想查看此示例应用程序缩小低分辨率屏幕的大图像：http: //developer.apple.com/library/ios/#samplecode/LargeImageDownsizing/Introduction/Intro.html#//apple_ref/doc /uid/DTS40011173

于 2012-06-29T22:55:22.530 回答
1

一个问题是您的 loadPage 和 purgePage 方法中的以下两行：

if ((NSNull*)pageView == [NSNull null]) {
if ((NSNull*)pageView != [NSNull null]) {

右侧 ( [NSNull null]) 创建一个新对象，您正在pageView与该对象的地址进行比较。即使pageView是另一个使用 创建的对象[NSNull null]，它的地址也很可能与您在条件中创建的新对象不匹配if。nil使用它来指定尚未加载的页面会更好。您可以通过将pageViews字段设置为NSMutableDictionary(withNSUInteger作为键类型) 轻松做到这一点。除此之外，您还可以将这些检查替换为以下类型的检查：

if ([pageView isTypeOfClass:[NSNull class]]) {
if (![pageView isTypeOfClass:[NSNull class]]) {
于 2012-06-29T22:52:35.600 回答
1

那是您拥有的大量图像。也许将图像的 NSString 名称存储在一个数组中，并且屏幕上只有一两个图像处于活动状态。

于 2012-06-29T23:11:09.780 回答