AFNetworking EXC_BAD_ACCESS (code=2, address=0x0) in downloadTask

Posted 2023-03-12

【中文标题】AFNetworking EXC_BAD_ACCESS (code=2, address=0x0) in downloadTask

【英文标题】：

【发布时间】：2014-03-20 03:49:54

【问题描述】：

我有一个应用程序，它在登录后为客户编译客户特定报告列表。这些报告正在显示，我已经放置了一个“查看”按钮，该按钮应该下载 PDF 文件，并在应用程序中显示它。

在这个阶段，按下查看按钮时似乎出现了内存问题，我不知道如何找到问题所在。这是我的代码：

#import "reportsTestViewController.h"
#import "ReportsDataObject.h"
#import "Session.h"
#import "AFNetworking.h"
@interface reportsTestViewController ()

@end

@implementation reportsTestViewController

@synthesize response;

@synthesize myDataIvar;

@synthesize viewReportPressed;


- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil

    self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
    if (self) 
        // Custom initialization
    
    return self;


- (void)viewDidLoad

    reportsTable.delegate = self;
    reportsTable.dataSource = self;
    self.sections = [[NSMutableDictionary alloc] init];

    [super viewDidLoad];


- (void)viewWillAppear:(BOOL)animated

    [super viewWillAppear:animated];

#pragma mark NSURLConnection Delegate Methods
//    

    //Create your request pointing to the test page
   NSURLRequest *request = [NSURLRequest requestWithURL:[NSURL URLWithString:@"http://www.tesg.com.au/allCustBuild.php"] cachePolicy:NSURLRequestUseProtocolCachePolicy timeoutInterval:15.0];


    NSURLConnection *connection = [[NSURLConnection alloc] initWithRequest:request delegate:self];

    //initialize it when you create your connection
    if (connection)
        self.myDataIvar = [[NSMutableData alloc] init];
    


    -(void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response
        [self.myDataIvar setLength:0];
    

    -(void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data
        [self.myDataIvar appendData:data];

    

    -(void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error
        NSLog(@"Connection Failed: %@", error.userInfo);
    

-(void)connectionDidFinishLoading:(NSURLConnection *)connection
    //this is where you would parse the data received back from the server
    NSString *responseString = [[NSString alloc] initWithData:self.myDataIvar encoding:NSUTF8StringEncoding];
    NSLog(@"Received Data: %@",responseString);
    [self setupReportsFromJSONArray:self.myDataIvar];



-(void)connectionWasASuccess:(NSData *)data
    [self setupReportsFromJSONArray:data];





-(void)setupReportsFromJSONArray:(NSData*)dataFromReportsArray
    BOOL found;
    NSError *error;
   // NSMutableArray *reportsArray = [[NSMutableArray alloc] init];
    NSArray *arrayFromServer = [NSJSONSerialization JSONObjectWithData:dataFromReportsArray options:0 error:&error];

    if(error)
        NSLog(@"error parsing the json data from server with error description - %@", [error localizedDescription]);
    

    else 
        reportsArray = [[NSMutableArray alloc] init];
        for(NSDictionary *eachReport in arrayFromServer)
        

            ReportsDataObject *report = [[ReportsDataObject alloc] initWithJSONData:eachReport];

            [reportsArray addObject:report];
            NSString *c = [[eachReport objectForKey:@"title"] substringToIndex:3];
                      found = NO;

            for (NSString *str in [self.sections allKeys])
            
                if ([str isEqualToString:c])
                
                    found = YES;
                
            

            if (!found)
            
                [self.sections setValue:[[NSMutableArray alloc] init] forKey:c];
            
        

        
        NSLog(@"Array Populated");
        NSLog(@"%u reports found",reportsArray.count);
        //Now you have your reportsArray filled up with all your data objects



for (NSDictionary *eachReport in arrayFromServer)

   [[self.sections objectForKey:[[eachReport objectForKey:@"title"] substringToIndex:3]] addObject:eachReport];


// Sort each section array
for (NSString *key in [self.sections allKeys])

    [[self.sections objectForKey:key] sortUsingDescriptors:[NSArray arrayWithObject:[NSSortDescriptor sortDescriptorWithKey:@"title" ascending:YES]]];




[reportsTable reloadData];



-(void)didReceiveMemoryWarning

    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.


-(void)viewReportPressed:(UIButton*)button 

    NSLog(@"Button successfully Pressed");
    NSURLSessionConfiguration *configuration = [NSURLSessionConfiguration defaultSessionConfiguration];
    AFURLSessionManager *manager = [[AFURLSessionManager alloc] initWithSessionConfiguration:configuration];

    NSURL *URL = [NSURL URLWithString:@"http://tesg.com.au/portal/media/reports/1367365180_367 Collins Passive April 2013.pdf"];
    NSURLRequest *request = [NSURLRequest requestWithURL:URL];

    NSURLSessionDownloadTask *downloadTask = [manager downloadTaskWithRequest:request progress:nil destination:^NSURL *(NSURL *targetPath, NSURLResponse *theResponse) 
        NSURL *documentsDirectoryPath = [NSURL fileURLWithPath:[NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) firstObject]];
        return [documentsDirectoryPath URLByAppendingPathComponent:[theResponse suggestedFilename]];
     completionHandler:^(NSURLResponse *response, NSURL *filePath, NSError *error) 
        NSLog(@"File downloaded to: %@", filePath);
    ];
    [downloadTask resume];

                                              


- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView


    NSUInteger count = [[self.sections allKeys] count];
    NSLog(@"Number of sections: %d", count);
    return count;





- (NSString *)tableView:(UITableView *)tableView titleForHeaderInSection:(NSInteger)section

    return [[[self.sections allKeys] sortedArrayUsingSelector:@selector(localizedCaseInsensitiveCompare:)] objectAtIndex:section];



- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
    //We check against table to make sure we are displaying the right number of cells
    // for the appropriate table. This is so that things will work even if one day you
    //decide that you want to have two tables instead of one.

    
        NSUInteger count = [[self.sections valueForKey:[[[self.sections allKeys] sortedArrayUsingSelector:@selector(localizedCaseInsensitiveCompare:)] objectAtIndex:section]] count];
        NSLog(@"Number of rows in section: %d", count);
        return count;
    

//- (NSArray *)sectionIndexTitlesForTableView:(UITableView *)tableView 
        //return [[self.sections allKeys] sortedArrayUsingSelector:@selector(localizedCaseInsensitiveCompare:)];
   // 





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




    static NSString *cellIdentifier = @"Cell";



    UITableViewCell *cell =[tableView dequeueReusableCellWithIdentifier:cellIdentifier];
    if (!cell)
    


        cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleSubtitle reuseIdentifier:cellIdentifier];

    

        //The beauty of this is that you have all your data in one object and grab WHATEVER you like
    //This way in the future you can add another field without doing much.
    NSUInteger count = [[self.sections allKeys] count];
    if(count == 0)
        cell.textLabel.text = @"no reports to show";
    
    else
        NSDictionary *Reports = [[self.sections valueForKey:[[[self.sections allKeys] sortedArrayUsingSelector:@selector(localizedCaseInsensitiveCompare:)] objectAtIndex:indexPath.section]] objectAtIndex:indexPath.row];

        cell.textLabel.text = [Reports objectForKey:@"title"];
        cell.detailTextLabel.text = [Reports objectForKey:@"building"];








        UIButton *button = [UIButton buttonWithType:UIButtonTypeRoundedRect];
        [button addTarget:self action:@selector(viewReportPressed:) forControlEvents:UIControlEventTouchUpInside];
        [button setTitle:@"View" forState:UIControlStateNormal];

        button.frame = CGRectMake(180.0f, 5.0f, 150.0f, 30.0f);
        [cell addSubview:button];


        // in the future you can grab whatever data you need like this
        //[currentReport buildingName], or [currentReport reportName];
    


    return(cell);

        




@end

当在任何单元格中按下视图按钮时，我得到 NSLog 说“按钮已成功按下”，但它在出现错误后立即崩溃

[downloadTask resume];             Thread 1:EXC_BAD_ACCESS (code=2, address=0x0)

任何想法如何解决这个问题？

【问题讨论】：

保留异常断点，以便找到问题的根源。

我有一个异常断点，但它似乎没有做任何事情。它仍然出现此错误

似乎崩溃发生在线程 1 的 [reportsTestViewController viewReportPressed:] 但我找不到原因。找出问题的最佳方法是什么？

在 [NSObject performSelector:withObject:withObject:] 下显示了一个问题

很好的总结，感谢您的帮助！我会牢记这一点:-)

【参考方案1】：

如果您得到地址为0x0 的EXC_BAD_ACCESS，这通常意味着在不允许nil 的上下文中使用了nil 值。

在这种情况下，这是因为您的 URL 字符串无效。不允许有空格。因此，您得到的URL 变量是nil，这将导致您描述的行为。您可能希望对 URL 字符串进行百分比转义，例如：

NSString *URLString = @"http://tesg.com.au/portal/media/reports/1367365180_367 Collins Passive April 2013.pdf";
NSURL *URL = [NSURL URLWithString:[URLString stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding]];

要在将来识别此类异常，您可以使用exception breakpoints，这通常有助于识别有问题的代码行。或者只是仔细检查您的代码代码，看看您可能无意中将 nil 值传递给了不接受它的方法。

---

但是，如果您得到的EXC_BAD_ACCESS 的值不是0x0，这通常是由于尝试使用以前释放的对象而导致的。 （并非总是如此，但经常发生。幸运的是，ARC 使此类问题变得不那么常见。）显然，这里不是这种情况，但您询问如何识别您尝试使用以前释放的对象的情况。

要诊断这种情况，您通常会打开“僵尸”（请参阅​​Running Your Application with Diagnostics）。顺便说一句，一旦完成对僵尸的诊断，请确保将其关闭，因为您不想让僵尸保持开启状态（尤其是在生产应用中）。

无论如何，在这种情况下，因为地址是0x0，所以它不是释放对象的结果，而是问题是由于无效的 URL 导致的 nil 值的错误使用。

【讨论】：

您好，谢谢您的回复。晚饭后我会继续做这个，让你知道我的进展！