Ios 在循环中使用dataWithContentsOfURL的内存泄漏
我使用的是Xcode 4.6.3和iOS 5.5/6.1.6 我使用后台线程将大量jpg从服务器加载到iOS设备Ios 在循环中使用dataWithContentsOfURL的内存泄漏,ios,objective-c,cocoa-touch,memory-leaks,block,Ios,Objective C,Cocoa Touch,Memory Leaks,Block,我使用的是Xcode 4.6.3和iOS 5.5/6.1.6 我使用后台线程将大量jpg从服务器加载到iOS设备 dispatch_async(kBgQueue, ^ { // get the array of filenames to download NSURL* url = [NSURL URLWithString:webPath]; NSArra
dispatch_async(kBgQueue, ^
{
// get the array of filenames to download
NSURL* url = [NSURL URLWithString:webPath];
NSArray* theArray = [NSArray arrayWithContentsOfURL:url];
if( theArray )
{
dispatch_async(dispatch_get_main_queue(), ^{
// disable screen buttons
[self setButtons:false];
});
[self loadImagesFromList:theArray sourceBundle:bundlePath destBundle:localBundlePath manager:manager];
if (!stopFlag) {
// if no memory error has occurred
NSLog(@"calling refresh after load_images");
dispatch_async(dispatch_get_main_queue(), ^{
[self refresh];
});
}
theArray = nil;
}
else
{
NSLog(@"Error loading bundle");
}
});
背景法:
-(void)loadImagesFromList:(NSArray *)theArray
sourceBundle:(NSString *)bundlePath
destBundle:(NSString *)localBundlePath
manager:(NSFileManager *)manager {
// initialize the progress and activity indicator
dispatch_async(dispatch_get_main_queue(), ^{
[self.activityIndictor startAnimating];
[UIApplication sharedApplication].networkActivityIndicatorVisible = YES;
[self.progressIndictor setProgress:0 animated:NO];
});
NSURL *url;
NSString *srcFile;
NSString *destFile;
NSError *error = nil;
int counter = 0;
float prog = 0;
float increment = 1.0 / [theArray count];
float stepSize = [theArray count] / 10;
for (NSString *file in theArray)
{
if (stopFlag) {
NSLog(@"I see stopFlag = true, counter = %d, prog = %f", counter, prog);
return;
}
srcFile = [bundlePath stringByAppendingPathComponent:file];
destFile = [localBundlePath stringByAppendingPathComponent:file];
counter += 1;
prog += increment;
if (counter == stepSize) {
dispatch_async(dispatch_get_main_queue(), ^{
self.progressIndictor.progress = prog;
});
counter = 0;
}
// only download if file isn't already here
BOOL fileExists = [manager fileExistsAtPath:destFile]; // check if we already have it
if (!fileExists) {
// jpg or folder check
if ([[destFile pathExtension] isEqualToString:@"jpg"]) {
url = [NSURL URLWithString:srcFile];
data = [NSData dataWithContentsOfURL:url
options:0
error:&error];
[data writeToFile:destFile options:NSDataWritingAtomic error:&error];
data = nil;
} else {
[manager createDirectoryAtPath:destFile withIntermediateDirectories:YES attributes:nil error:&error];
}
}
}
}
如果文件存在,循环将通过数组压缩并退出到主线程ok。
如果缺少任何文件,下载/写入部分似乎会占用RAM并触发内存不足警告。这需要数千个文件才能完成
我已经尝试在循环外声明变量,甚至在主线程中执行整个操作,以测试这是否是导致泄漏的原因。
我尝试使用替换数据with contentsofURL:options:error调用。
我试过仪器,但速度很慢而且经常崩溃。在崩溃之前,它确实显示分配在上升,上升,缓慢上升
经过几天的讨论,我被难住了。我建议的第一件事是使用
@autoreleasepool
来控制消耗的最大内存量。现在,您正在将内容作为自动释放对象下载到NSData
中,完成后,您将nil
-ing该变量,该变量将简单地标记为在自动释放池耗尽后将其释放(在loadImagesFromList
完成之前不会发生)。通过(a)在for
循环中移动变量声明;(b)将其包装在一个@autoreleasepool
中,随着个人下载的完成,您的内存将被释放
-(void)loadImagesFromList:(NSArray *)theArray
sourceBundle:(NSString *)bundlePath
destBundle:(NSString *)localBundlePath
manager:(NSFileManager *)manager {
// initialize the progress and activity indicator
dispatch_async(dispatch_get_main_queue(), ^{
// your UI update here
});
int counter = 0;
float prog = 0;
float increment = 1.0 / [theArray count];
float stepSize = [theArray count] / 10;
for (NSString *file in theArray)
{
@autoreleasepool {
if (stopFlag) {
NSLog(@"I see stopFlag = true, counter = %d, prog = %f", counter, prog);
return;
}
NSString *srcFile = [bundlePath stringByAppendingPathComponent:file];
NSString *destFile = [localBundlePath stringByAppendingPathComponent:file];
counter += 1;
prog += increment;
if (counter == stepSize) {
dispatch_async(dispatch_get_main_queue(), ^{
self.progressIndictor.progress = prog;
});
counter = 0;
}
// only download if file isn't already here
BOOL fileExists = [manager fileExistsAtPath:destFile]; // check if we already have it
if (!fileExists) {
NSError *error = nil;
// jpg or folder check
if ([[destFile pathExtension] isEqualToString:@"jpg"]) {
NSURL *url = [NSURL URLWithString:srcFile];
NSData *data = [NSData dataWithContentsOfURL:url
options:0
error:&error];
[data writeToFile:destFile options:NSDataWritingAtomic error:&error];
} else {
[manager createDirectoryAtPath:destFile withIntermediateDirectories:YES attributes:nil error:&error];
}
}
}
}
}
您可能需要重构此代码以使用
NSOperationQueue
。这解决了峰值内存问题,但也让您享受一定程度的并发性。由于iOS只允许4-5个并发请求,因此您希望将并发操作的最大数量限制在合理的数量,这样可以在尝试运行太多并发请求时降低网络超时风险。(此maxConcurrentOperationCount
功能是我建议使用操作队列的主要原因。)
无论如何,这可能看起来像:
-(void)loadImagesFromList:(NSArray *)theArray
sourceBundle:(NSString *)bundlePath
destBundle:(NSString *)localBundlePath
manager:(NSFileManager *)manager {
// initialize the progress and activity indicator
[[NSOperationQueue mainQueue] addOperationWithBlock:^{
// your UI update here
}];
int __block counter = 0;
float __block prog = 0;
float increment = 1.0 / [theArray count];
float stepSize = [theArray count] / 10;
NSOperationQueue *queue = [[NSOperationQueue alloc] init];
queue.maxConcurrentOperationCount = 4;
for (NSString *file in theArray)
{
[queue addOperationWithBlock:^{
if (stopFlag) {
NSLog(@"I see stopFlag = true, counter = %d, prog = %f", counter, prog);
return;
}
NSString *srcFile = [bundlePath stringByAppendingPathComponent:file];
NSString *destFile = [localBundlePath stringByAppendingPathComponent:file];
[[NSOperationQueue mainQueue] addOperationWithBlock:^{
counter += 1;
prog += increment;
if (counter == stepSize) {
self.progressIndictor.progress = prog;
counter = 0;
}
}];
// only download if file isn't already here
BOOL fileExists = [manager fileExistsAtPath:destFile]; // check if we already have it
if (!fileExists) {
NSError *error = nil;
// jpg or folder check
if ([[destFile pathExtension] isEqualToString:@"jpg"]) {
NSURL *url = [NSURL URLWithString:srcFile];
NSData *data = [NSData dataWithContentsOfURL:url
options:0
error:&error];
[data writeToFile:destFile options:NSDataWritingAtomic error:&error];
} else {
[manager createDirectoryAtPath:destFile withIntermediateDirectories:YES attributes:nil error:&error];
}
}
}];
}
}
我可能会建议进行其他改进(例如,实现取消逻辑,而不是查看stopFlag
),但我试图尽量减少代码更改。我只是利用了一个事实,即可以轻松地替换dispatch\u async
:
dispatch_async(dispatchQueue, ^{ ... });
使用NSOperationQueue
方法addOperationWithBlock
:
[operationQueue addOperationWithBlock:^{ ... }];
但是现在我们可以使用一个并发的
NSOperationQueue
,它的maxConcurrentOperationCount
值为4或5,您会突然享受到一种良好的、受限的并发度。您可能会发现这比按顺序下载文件要快得多。您的标题将其描述为“泄漏”,但我想知道您是否有理由将其描述为泄漏,而不仅仅是因为您有很多非常大的自动释放对象,在自动释放池耗尽之前不会释放这些对象。我下面的回答假设后者是真实的,但如果你有一些证据表明确实存在泄漏,请告诉我们,但我没有看到任何泄漏。主要的问题似乎是自动释放池没有足够频繁地排空。在阅读了你的答案后,我想你是对的。我假设对象正在被释放,所以不会增加。不应该使用[[NSData alloc]initWithContentsOfURL:…]
而不是[NSData dataWithContentsOfURL:…]
来解决这个问题吗?“完成后,您将该变量置为零“他不是nil
-ing任何东西;它只是超出了范围NewAcct,是的,如果他使用initWithContentsOfURL
使其成为非自动释放对象,这将大大减少对池的需要,但他确实有其他自动释放对象,并且通过使用手动池,就不必担心哪些是自动释放,哪些不是。但是你是对的,如果他对不使用自动释放对象非常谨慎,那么就不需要手动池。