我的 UIScrollView 实现是否泄漏了内存？答案

【问题标题】：Am I leaking memory in my UIScrollView implementation?我的 UIScrollView 实现是否泄漏了内存？
【发布时间】：2011-05-16 21:23:00
【问题描述】：

我正在开发一个使用 UIScrollView 滚动浏览一堆幻灯片的应用程序。当应用程序打开时，它会创建幻灯片并将它们传递给滚动视图。我的应用程序还有一个计时器，它会导致 UIScrollView 在幻灯片中滚动。

我还有一个设置按钮。当我按下该按钮时，它会打开设置面板。计时器无效并设置为nil。当设置面板打开时，用户可以更改应用程序主题、幻灯片和动画方向等内容。

当设置面板关闭时，将应用设置：从 UIScrollView 中删除幻灯片，并为 UIScrollView 提供一个新的 NSArray 幻灯片以供使用。 UIScrollView 然后以正确的顺序和方向布置新幻灯片。计时器已重置。

大约每 14-16 次，应用程序在运行 dismissAndRestart（“关闭”代码）时崩溃。我不确定为什么。我以为我在泄漏内存，显然我是，但我不知道在哪里。

这是我的代码：

这在启动时运行：

    - (void)viewDidLoad {    
        [scrollView setPagingEnabled:YES];
    }

    - (void) viewWillAppear:(BOOL)animated{
        [self prepareViews];
        [self applyTheme];  
    }

    - (void) viewDidAppear:(BOOL)animated{
        [self createTimerWithInterval:kScrollInterval];
    }

将视图加载到滚动条中的主力方法。（它也会删除旧的）：

- (void)loadViews:(NSArray *)views IntoScroller:(UIScrollView *)scroller withDirection:(NSString *)direction{
    [scrollView.subviews makeObjectsPerformSelector:@selector(removeFromSuperview)];
    [scrollView setShowsHorizontalScrollIndicator: NO];
    [scrollView setShowsVerticalScrollIndicator:NO];
    scrollView.scrollsToTop = NO;

    if([direction isEqualToString:@"horizontal"]){
        scrollView.frame = CGRectMake(0, 0, 1024, 768);
        scrollView.contentSize = CGSizeMake(scrollView.frame.size.width * [[NSNumber numberWithUnsignedInt:[views count]] floatValue], scrollView.frame.size.height);
    }else if([direction isEqualToString:@"vertical"]){
        scrollView.frame = CGRectMake(0, 0, 1024, 768);
        scrollView.contentSize = CGSizeMake(scrollView.frame.size.width, scrollView.frame.size.height * [[NSNumber numberWithUnsignedInt:[views count]] floatValue]);
    }

    for (int i=0; i<[[NSNumber numberWithUnsignedInt:[views count]] intValue]; i++) {

        [[[views objectAtIndex:[[NSNumber numberWithInt:i] unsignedIntValue]] view] setFrame:scrollView.frame];

        if([direction isEqualToString:@"horizontal"]){
            [[[views objectAtIndex:[[NSNumber numberWithInt:i] unsignedIntValue]] view] setFrame:CGRectMake(i * [[views objectAtIndex:[[NSNumber numberWithInt:i] unsignedIntValue]] view].frame.size.width, 0, scrollView.frame.size.width, scrollView.frame.size.height)];//CGRectMake(i * announcementView.view.frame.size.width, -scrollView.frame.origin.x, scrollView.frame.size.width, scrollView.frame.size.height)];
        }else if([direction isEqualToString:@"vertical"]){
            [[[views objectAtIndex:[[NSNumber numberWithInt:i] unsignedIntValue]] view] setFrame:CGRectMake(0, i * [[views objectAtIndex:[[NSNumber numberWithInt:i] unsignedIntValue]] view].frame.size.height, scrollView.frame.size.width, scrollView.frame.size.height)];
        }

        [scrollView addSubview:[[views objectAtIndex:[[NSNumber numberWithInt:i] unsignedIntValue]] view]];
    }
}

为自动滚动创建计时器：

#pragma mark -
#pragma mark Create the Timer to automate scrolling

- (void) createTimerWithInterval:(float)interval{
    self.timer = [NSTimer scheduledTimerWithTimeInterval:interval target:self selector:@selector(scrollWrapperForTimer) userInfo:nil repeats:YES];
}

定时器函数的包装函数。（在方向是 NSUserDefault 之前这是必需的，现在我不应该需要它了。）

#pragma mark -
#pragma mark Scroll Automatically Every N seconds

- (void) scrollWrapperForTimer{
    [self scrollToNewViewInDirection:kDirection];
}

- (void)scrollToNewViewInDirection:(NSString *)direction{
    if([[NSUserDefaults standardUserDefaults] boolForKey:@"animated_scrolling"] == YES){
        if([direction isEqualToString:@"horizontal"]){
            if([[NSNumber numberWithFloat:scrollView.contentOffset.x] compare:[NSNumber numberWithFloat:scrollView.contentSize.width - scrollView.frame.size.width]] == (NSOrderedAscending)){
                [scrollView scrollRectToVisible:CGRectMake(scrollView.contentOffset.x + scrollView.frame.size.width, 0, scrollView.frame.size.width, scrollView.frame.size.height) animated:YES];
            }else if([[NSNumber numberWithFloat:scrollView.contentOffset.x] compare:[NSNumber numberWithFloat:scrollView.contentSize.width - scrollView.frame.size.width]] == (NSOrderedSame)){
                [scrollView scrollRectToVisible:CGRectMake(0, 0, scrollView.frame.size.width, scrollView.frame.size.height) animated:YES];
            }
        }else if([direction isEqualToString:@"vertical"]){
            if([[NSNumber numberWithFloat:scrollView.contentOffset.y] compare:[NSNumber numberWithFloat:scrollView.contentSize.height - scrollView.frame.size.height]] == (NSOrderedAscending)){
                [scrollView scrollRectToVisible:CGRectMake(0, scrollView.contentOffset.y + scrollView.frame.size.height, scrollView.frame.size.width, scrollView.frame.size.height) animated:YES];
            }else if([[NSNumber numberWithFloat:scrollView.contentOffset.y] compare:[NSNumber numberWithFloat:scrollView.contentSize.height - scrollView.frame.size.height]] == (NSOrderedSame)){
                [scrollView scrollRectToVisible:CGRectMake(0, 0, scrollView.frame.size.width, scrollView.frame.size.height) animated:YES];
            }
        }
    }else {
        if([direction isEqualToString:@"horizontal"]){
            if([[NSNumber numberWithFloat:scrollView.contentOffset.x] compare:[NSNumber numberWithFloat:scrollView.contentSize.width - scrollView.frame.size.width]] == (NSOrderedAscending)){
                [scrollView scrollRectToVisible:CGRectMake(scrollView.contentOffset.x + scrollView.frame.size.width, 0, scrollView.frame.size.width, scrollView.frame.size.height) animated:NO];
            }else if([[NSNumber numberWithFloat:scrollView.contentOffset.x] compare:[NSNumber numberWithFloat:scrollView.contentSize.width - scrollView.frame.size.width]] == (NSOrderedSame)){
                [scrollView scrollRectToVisible:CGRectMake(0, 0, scrollView.frame.size.width, scrollView.frame.size.height) animated:NO];
            }
        }else if([direction isEqualToString:@"vertical"]){
            if([[NSNumber numberWithFloat:scrollView.contentOffset.y] compare:[NSNumber numberWithFloat:scrollView.contentSize.height - scrollView.frame.size.height]] == (NSOrderedAscending)){
                [scrollView scrollRectToVisible:CGRectMake(0, scrollView.contentOffset.y + scrollView.frame.size.height, scrollView.frame.size.width, scrollView.frame.size.height) animated:NO];
            }else if([[NSNumber numberWithFloat:scrollView.contentOffset.y] compare:[NSNumber numberWithFloat:scrollView.contentSize.height - scrollView.frame.size.height]] == (NSOrderedSame)){
                [scrollView scrollRectToVisible:CGRectMake(0, 0, scrollView.frame.size.width, scrollView.frame.size.height) animated:NO];
            }
        }
    }

}

当在设置面板中按下完成按钮时调用此方法。

#pragma mark -
#pragma mark Restart the program

- (void) dismissAndRestart{
    [self prepareViews];
    [self applyTheme];
    [self dismissModalViewControllerAnimated:YES];
    [self createTimerWithInterval:kScrollInterval];
}

这会创建正确的图像文件并将它们加载到位：

#pragma mark -
#pragma mark Apply the theme to the main view

- (void) applyTheme{

    //Front panel
    UIImage *frontImage = [[UIImage alloc] initWithContentsOfFile:[[NSBundle mainBundle] pathForResource:[[NSString stringWithFormat:@"%@_front", kTheme]description] ofType:@"png"]];  
    [self.overlayImage setImage:frontImage];
    [frontImage release];

    //Back Panel
    if([kTheme isEqualToString:@"walnut"]){
        [self.backgroundImage setHidden:NO];
        UIImage *backImage = [[UIImage alloc] initWithContentsOfFile:[[NSBundle mainBundle] pathForResource:[[NSString stringWithFormat:@"%@_back", kTheme]description] ofType:@"png"]];    
        [self.backgroundImage setImage:backImage];
        [backImage release];            
    }else if([kTheme isEqualToString:@"metal"]){
        [self.backgroundImage setHidden:YES];
        [self.view setBackgroundColor: [UIColor scrollViewTexturedBackgroundColor]];
    }

    //Gabbai Button
    UIImage *gabbaiImage = [[UIImage alloc] initWithContentsOfFile:[[NSBundle mainBundle] pathForResource:[[NSString stringWithFormat:@"%@_settings_button", kTheme]description] ofType:@"png"]];   
    [self.gabbaiButton setImage:gabbaiImage forState:UIControlStateNormal];
    [gabbaiImage release];  


}

另一个需要重构的包装函数：

#pragma mark -
#pragma mark Slide View related

- (void) prepareViews{
    [self loadViews:[self createandReturnViews] IntoScroller:scrollView withDirection:kDirection];
}

创建幻灯片数组以传递给滚动条：

//recreation of the views causes a delay each time the admin panel is closed.
- (NSArray*) createandReturnViews{

    NSMutableArray *announcements = [NSMutableArray array];
    NSArray *announcementsArray = [NSArray arrayWithObjects: @"Welcome to\nGabbai HD!",
                                   @"First slide",
                                   @"Second Slide",
                                   @"Third Slide",
                                   @"etc.",
                                   nil];
    for (int i = 0; i<[[NSNumber numberWithUnsignedInteger:[announcementsArray count]] intValue]; i++) {
        MBAnnouncementViewController *announcement = [[MBAnnouncementViewController alloc] initWithNibName:@"MBAnnouncementViewController" bundle:nil];
        [announcement setAnnouncementText:[announcementsArray objectAtIndex:[[NSNumber numberWithInt:i] unsignedIntegerValue]]];
        [announcements addObject:announcement];
        [announcement release];
    }

    return announcements;
}

为什么我的设置面板会在关闭时使应用程序崩溃？

【问题讨论】：

标签： iphone ipad memory-management uiscrollview

【解决方案1】：

你也可以通过window+shift+a使用xcode分析器来找出内存泄漏。

【讨论】：

【解决方案2】：

您展示的代码有几个 alloc 调用。在每个之后，您设置一个属性，然后释放。我假设该属性被声明为retain。

如果是这样，那么最终，您需要释放这些属性。通常在dealloc消息实现中。

具有保留属性的类需要像这样的 dealloc

 -(void) dealloc() {
    self.prop = nil; // calls release
    self.prop2 = nil;
    [super dealloc];
 }

如果你的属性是这样声明的

  @property (nonatomic, retain) Type* prop;

然后，当您使用set 消息或self.prop 语法重新分配属性时，先前的值已对其调用释放。如果你只是使用prop = newVal;，那么你是直接访问该字段而不是调用set消息，所以不会调用release。

通常，始终使用set 消息或点语法，这样您就不必担心它——这是您将属性声明为保留的主要原因，因此请充分利用它。

【讨论】：

dealloc 在应用程序执行结束时被调用。我正在尝试重置属性。我明白你在说什么。
dealloc 可以在此之前调用。它在其定义的对象的保留计数降至 1 以下后的某个时间被调用。
但是如何释放我想重新分配其他内容的属性？
哦，我是在调用 release，而不是 dealloc。
你不调用dealloc，你实现dealloc，当retainCount变为0时调用它。我更新了答案以提供更多信息

【解决方案3】：

我没有阅读你的代码，但可能是你试图释放一个已经被释放的对象。我建议你在开发的时候打开zombies，但是在编译release版本的时候记得关闭它，因为当zombies开启时，内存不会被释放。调试时真的很有帮助，如果你的代码试图访问一个不再存在的对象。谷歌“启用僵尸 xcode”或类似的东西

【讨论】：

我知道如何开启 NSZombie，但是如何查看 Zombies 的保留数？
Zombies 的 retainCount 始终为 0——这就是它试图帮助你解决的问题——向可能被释放的对象发送消息。如果您向僵尸发送消息，您将在控制台中看到消息。