ios - 当我在滚动 UITableview 期间显示文档目录中的图像时，内存不断增加然后应用程序崩溃

Question

我的要求是下载应用程序内存中的所有图像，并在可用时从本地显示。

下面是我从本地访问图像的代码，如果它不可用，那么它将下载然后显示。

[cell.imgProfilePic processImageDataWithURLString:cData.PICTURE];

我制作了自定义的 UIImageView 类

DImageView.h

    #import <UIKit/UIKit.h>
    @interface DImageView : UIImageView
    @property (nonatomic, strong) UIActivityIndicatorView *activityView;
    - (void)processImageDataWithURLString:(NSString *)urlString;
    + (UIImage *)getSavedImage :(NSString *)fileName;
    @end

DImageView.m

#import "DImageView.h"
#define IMAGES_FOLDER_NAME  @"DImages"

@implementation DImageView

- (id)initWithFrame:(CGRect)frame
{
    self = [super initWithFrame:frame];
    if (self)
    {    }
    return self;
}
- (void)dealloc
{
    self.activityView = nil;
    [super dealloc];
}
- (id)initWithCoder:(NSCoder *)aDecoder
{
    self = [super initWithCoder:aDecoder];
    if (self)
    {
        [self initWithFrame:[self frame]];
    }
    return self;
}
- (void)processImageDataWithURLString:(NSString *)urlString
{
    @autoreleasepool
    {
    UIImage * saveImg =[DImageView getSavedImage:urlString];
    if (saveImg)
    {
        @autoreleasepool
        {
        dispatch_queue_t callerQueue = dispatch_get_main_queue();
        dispatch_async(callerQueue, ^{

            @autoreleasepool{
            [self setImage:saveImg];
            }
        });
    }
    }
    else
    {
        [self showActivityIndicator];
        NSURL *url = [NSURL URLWithString:[urlString stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding]];

        dispatch_queue_t callerQueue = dispatch_get_main_queue();
        dispatch_queue_t downloadQueue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH,0);
        __block NSError* error = nil;
        dispatch_async(downloadQueue, ^{

            @autoreleasepool
            {
                NSData * imageData = [NSData dataWithContentsOfURL:url options:NSDataReadingUncached error:&error];
                if (!error)
                {
                    dispatch_async(callerQueue, ^{
                        @autoreleasepool {
                        UIImage *image = [UIImage imageWithData:imageData];
                        [self setImage:image];
                        [self hideActivityIndicator];
                        [self saveImageWithFolderName:IMAGES_FOLDER_NAME AndFileName:urlString AndImage:imageData];
                        }
                    });
                }
            }
        });
        dispatch_release(downloadQueue);
    }
    }
}
- (void) showActivityIndicator
{
    self.activityView = [[UIActivityIndicatorView alloc]initWithFrame:CGRectMake(0, 0, self.frame.size.width, self.frame.size.height)];
    self.activityView.autoresizingMask = UIViewAutoresizingFlexibleLeftMargin | UIViewAutoresizingFlexibleTopMargin | UIViewAutoresizingFlexibleRightMargin | UIViewAutoresizingFlexibleBottomMargin;
    self.activityView.hidesWhenStopped = TRUE;
    self.activityView.backgroundColor = [UIColor clearColor];
    self.activityView.activityIndicatorViewStyle = UIActivityIndicatorViewStyleGray;

    [self addSubview:self.activityView];
    [self.activityView startAnimating];
}
- (void) hideActivityIndicator
{
    CAAnimation *animation = [NSClassFromString(@"CATransition") animation];
    [animation setValue:@"kCATransitionFade" forKey:@"type"];
    animation.duration = 0.4;;
    [self.layer addAnimation:animation forKey:nil];
    [self.activityView stopAnimating];
    [self.activityView removeFromSuperview];

    for (UIView * view in self.subviews)
    {
        if([view isKindOfClass:[UIActivityIndicatorView class]])
            [view removeFromSuperview];
    }
}
- (void)saveImageWithFolderName:(NSString *)folderName AndFileName:(NSString *)fileName AndImage:(NSData *) imageData
{
    @autoreleasepool{
    NSFileManager *fileManger = [[NSFileManager defaultManager] autorelease];
    NSString *directoryPath =  [[NSString stringWithFormat:@"%@/%@",[DImageView  applicationDocumentsDirectory],folderName] autorelease];

    if (![fileManger fileExistsAtPath:directoryPath])
    {
        NSError *error = nil;
        [fileManger createDirectoryAtPath:directoryPath withIntermediateDirectories:YES attributes:nil error:&error];
    }
    fileName = [DImageView fileNameValidate:fileName];
    NSString *filePath = [[NSString stringWithFormat:@"%@/%@",directoryPath,fileName] autorelease];

    BOOL isSaved = [imageData writeToFile:filePath atomically:YES];
    if (!isSaved)DLog(@" ** Img Not Saved");
    }
}

+ (NSString *)applicationDocumentsDirectory
{
    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
    NSString *basePath = ([paths count] > 0) ? [paths objectAtIndex:0] : nil;
    return basePath;
}

+ (UIImage *)getSavedImage :(NSString *)fileName
{
    NSAutoreleasePool* pool = [[NSAutoreleasePool alloc] init];
    fileName = [DImageView fileNameValidate:fileName];

    NSFileManager * fileManger = [[NSFileManager defaultManager] autorelease];
    NSString * directoryPath =  [[NSString stringWithFormat:@"%@/%@",[DImageView applicationDocumentsDirectory],IMAGES_FOLDER_NAME] autorelease];
    NSString * filePath = [[NSString stringWithFormat:@"%@/%@",directoryPath,fileName] autorelease];

    if ([fileManger fileExistsAtPath:directoryPath])
    {
        UIImage *image = [[[UIImage imageWithContentsOfFile:filePath] retain]autorelease];
        if (image)
            return image;
        else
            return nil;
    }
    [pool release];
    return nil;
}

+ (NSString*) fileNameValidate : (NSString*) name
{
    name = [name stringByReplacingOccurrencesOfString:@"://" withString:@"##"];
    name = [name stringByReplacingOccurrencesOfString:@"/" withString:@"#"];
    name = [name stringByReplacingOccurrencesOfString:@"%20" withString:@""];
    return name;
}
@end

一切正常，平滑滚动以及后台异步图像下载。

问题是当我滚动 UITableview 应用程序内存不断增加，一段时间后我得到 Receive memory waring 2/3 时间然后应用程序崩溃。

当我使用 AsyncImageView 类时，内存不会增加并且工作正常。但由于应用程序要求，我将所有图像保存到 Document Directory 并在可用时从中显示。

我已经尝试使用 @autoreleasepool 和 release 一些变量但没有成功。

如果有人有管理内存管理的解决方案，我将不胜感激。

 **ARC is off in my application.** 

Answer 1

UIImagePNGRepresentation 可能会返回非自动释放的对象 - 您可以尝试释放它并查看是否会导致崩溃。显然你没有发布任何东西，但除了图像表示之外没有什么是显而易见的。

一些其他评论:

• 使用 ObjectAlloc 工具在 Instruments 中运行您的应用程序，应该会立即清楚哪些对象没有被释放。如果您不了解 Instruments，那么现在是时候学习它了。

• 您可以“跟踪”对象并在使用 ObjectTracker 释放对象时收到消息- 但是它是为 ARC 设计的，因此您可能需要对其进行调整。如果您使用它，您会在每个对象被释放时看到一条消息

• 当表格 View 完成一个单元格时，您可以接收一个委托(delegate)方法来告诉您，然后您可以 nil(释放)单元格保留的对象

• 您对 downloadQueue 的使用很奇怪 - 在您的实例中将其作为 ivar 创建一次，根据需要使用它，然后在 dealloc 中释放它

• 您将事件微调器隐藏在主队列中，但不要在主队列中启动它

• 您命令事件 View 将其自身从其父 View 中移除，但随后在 subview 中查找并尝试将其移除:

[self.activityView removeFromSuperview];

for (UIView * view in self.subviews)
{
    if([view isKindOfClass:[UIActivityIndicatorView class]])
        [view removeFromSuperview];
}

最后，Instruments 就是您想要的。你可以在这里阅读更多关于它的信息，或者只是谷歌，你一定会找到大量的博客来阅读。