UITableView 和 UINavigationController 中的内存管理

Posted 2023-03-04

【中文标题】UITableView 和 UINavigationController 中的内存管理

【英文标题】：Memory management in UITableView and UINavigationController

【发布时间】：2012-02-06 04:35:40

【问题描述】：

更新

我已经更新了代码，我发现我可以 nil iconDownLoader 或 downloadArray 但不能同时使用它们。

我认为 unload 中的 nil 与 dealloc 中的 release 不同？而 self.xxx = nil 是必要的吗？我已经更新了代码。它工作正常（虽然它没有释放所有内存）但我不太明白。

你能解释一下为什么吗？谢谢

---

我搜索了很多，但仍然无法解决这个内存管理问题。希望有人可以帮助我解决它并理解其原理。

我有一个 UIViewController，里面有一个 UITableView。表格视图加载自定义单元格和图像。它每次都会消耗大量内存，并且在我 popViewControllerAnimated 后不会释放内存。多次push和popviewController后内存会增加到200m。

这是一些代码，任何帮助将不胜感激。

- (void)didReceiveMemoryWarning

    [super didReceiveMemoryWarning];


#pragma mark - View lifecycle

- (void)viewDidUnload

    self.newsArray = nil;
    self.newsTableView = nil;
    self.indicatorView = nil;
//  self.iconDownLoader = nil;
    self.downloadArray = nil;

    [super viewDidUnload];


... 

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath

    static NSString *CellIdentifier = @"NewsCellIdentifier";

    UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
    if (cell == nil) 
        [[NSBundle mainBundle] loadNibNamed:@"NewsTableViewCell" owner:self options:nil];
        cell = self.newsTableViewCell;
        self.newsTableViewCell = nil;
    

    // read from newsModel
    NewsModel *news = [newsArray objectAtIndex:indexPath.row];

    UILabel *label;
    label = (UILabel *)[cell viewWithTag:10];
    label.text = [NSString stringWithString:news.title];
    label = nil;
    label = (UILabel *)[cell viewWithTag:11];
    label.text = [NSString stringWithString:news.description];
    UIImageView *imageView = (UIImageView *)[cell viewWithTag:12];
    imageView.image = news.image;

    if (news.image == nil)
    
        imageView.image = [UIImage imageNamed:IconPlaceHolder];

        IconDownLoader *iconDownLoader = [[IconDownLoader alloc] init];
        iconDownLoader.url = news.imageUrl;
        iconDownLoader.delegate = self;
        iconDownLoader.indexPath = indexPath;
        if (appDelegate.ip4 == YES)
        
            iconDownLoader.width = 300;
            iconDownLoader.height = 150;
        
        else
        
            iconDownLoader.width = 150;
            iconDownLoader.height = 75;
        
        [downloadArray addObject:iconDownLoader];
        [iconDownLoader start];
    
    return cell;


#pragma mark - IconDownLoaderDelegate

- (void)iconDownLoadFinsh:(NSData *)imageData row:(NSIndexPath *)indexPath 

    UITableViewCell *cell = [newsTableView cellForRowAtIndexPath:indexPath];
    UIImageView *imageView = (UIImageView *)[cell viewWithTag:12];
    if (imageData != 0)
    
        imageView.image = [UIImage imageWithData:imageData];
    
    else
    
        imageView.image = [UIImage imageNamed:@"icon57"];
    
    NewsModel *newsModel = [newsArray objectAtIndex:indexPath.row];
    newsModel.image = [UIImage imageWithData:imageData];

这是 IconDownloader

#import "IconDownLoader.h"
#import "ASIHTTPRequest.h"

@implementation IconDownLoader

@synthesize delegate = _delegate;
@synthesize url = _url;
@synthesize indexPath = _indexPath;
@synthesize width = _width;
@synthesize height = _height;
@synthesize request = _request;

- (void)start 

    NSString *originalString = @"width=%s&height=%s";
    NSString *newString = [NSString stringWithFormat:@"width=%d&height=%d&type=jpg", self.width, self.height];

    NSString *resizedURL = [self.url stringByReplacingOccurrencesOfString:originalString withString:newString];

    NSURL *url = [NSURL URLWithString:[resizedURL stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding]];
    _request = [ASIHTTPRequest requestWithURL:url];
    if (_indexPath) 
        _request.userInfo = [NSDictionary dictionaryWithObject:_indexPath forKey:@"indexPath"];
    
    [_request setDelegate:self];
    [_request startAsynchronous];


- (void)requestFinished:(ASIHTTPRequest *)request 

    NSInteger statusCode = request.responseStatusCode;
    switch (statusCode) 
        case 401: // Not Authorized: either you need to provide authentication credentials, or the credentials provided aren't valid.
            break;

        case 200: 
            NSData *responseData = [request responseData];
            if (!responseData) 
                UIAlertView *alertView;
                alertView = [[UIAlertView alloc] initWithTitle:@"Oops" message:[NSString stringWithFormat:@"Download failed in row %d", _indexPath.row] delegate:nil cancelButtonTitle:@"OK" otherButtonTitles:nil];
                return;
            
            [_delegate iconDownLoadFinsh:responseData row:[request.userInfo objectForKey:@"indexPath"]];
        
            break;

        case 304: // Not Modified: there was no new data to return.
            break;
        case 400: // Bad Request: your request is invalid, and we'll return an error message that tells you why. This is the status code returned if you've exceeded the rate limit
            break;
        case 403: // Forbidden: we understand your request, but are refusing to fulfill it.  An accompanying error message should explain why.
            break;

        case 404: // Not Found: either you're requesting an invalid URI or the resource in question doesn't exist (ex: no such user). 
        
            UIAlertView *alertView;
            alertView = [[UIAlertView alloc] initWithTitle:@"Oops" message:@"Classical 404, please contact with your administer" delegate:nil cancelButtonTitle:@"OK" otherButtonTitles:nil];
        
            break;
        case 500: // Internal Server Error: we did something wrong.  Please post to the group about it and the Weibo team will investigate.
        case 502: // Bad Gateway: returned if Weibo is down or being upgraded.
        case 503: // Service Unavailable: the Weibo servers are up, but are overloaded with requests.  Try again later.
        
            UIAlertView *alertView;
            alertView = [[UIAlertView alloc] initWithTitle:@"Oops" message:@"503 error, service unavailable" delegate:nil cancelButtonTitle:@"OK" otherButtonTitles:nil];
        
        default:

        
    


- (void)dealloc 
    if (_request != nil) 
        [_request clearDelegatesAndCancel];
    


@end

【问题讨论】：

你没有释放IconDownLoader。

你说的太对了，答对了，你就能得到我的十美分：)

【参考方案1】：

你没有释放IconDownLoader。

【讨论】：

一个简单的问题，如果我没有 iconDownLoader，那么在 downloadArray 中是什么，因为在 downloadArray 中有很多 iconDownloader。 ([downloadArray addObject:iconDownLoader];) 我应该按顺序将它们归零吗？

如果我同时做这些，就会有一个 exc_bad_access。 self.iconDownLoader = nil; self.downloadArray = nil;

@ThinkChris：等等，你在用 ARC 吗？

rm -rf：是的，为什么要问？刚试过，如果我删除 self.downloadArray = nil; 就没有 exc_bad_access。 downloadArray 是在 initWithNibName 中创建的。

@ThinkChris：那我的回答实际上是无效的。 ARC应该会为你发布。关于您的第一个问题，如果您稍后访问downloadArray（顺便说一下，您应该使用self.downloadArray 设置它）那么您不不想取消它。