我尝试使用以下代码在我的 iPad 应用程序上制作后台所有视图的拇指:
NSString *path = [self.page previewPathForOrientation:currentOrientation];
dispatch_async( dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_LOW, 0), ^{
@autoreleasepool {
UIGraphicsBeginImageContextWithOptions(self.previewView.bounds.size, NO, 0.0);
[self.previewView.layer renderInContext:UIGraphicsGetCurrentContext()];
UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
self.previewView = nil;
float scale = [UIScreen mainScreen].scale;
CGRect previewRect = currentOrientation == Landscape ? [[OrientationLandscape singleton] frameForPreviewImage] : [[OrientationPortrait singleton] frameForPreviewImage];
CGSize previewSize = CGSizeMake(previewRect.size.width * scale, previewRect.size.height * scale);
UIImage *scaledImage = [image scaleImageToSize:previewSize];
CGImageDestinationRef imageDestination = CGImageDestinationCreateWithURL((__bridge CFURLRef)[[NSURL alloc] initFileURLWithPath:path], (__bridge CFStringRef)@"public.png", 1, NULL);
CGImageDestinationAddImage(imageDestination, [scaledImage CGImage], NULL);
CGImageDestinationFinalize(imageDestination);
CFRelease(imageDestination);
NSFileManager *fileMngr = [[NSFileManager alloc] init];
if(![fileMngr fileExistsAtPath:path])
{
ZAssert(0, @"could not save preview file");
}
dispatch_async(dispatch_get_main_queue(), ^{
rendered++;
//DLog(@"rendered %d items", rendered);
[GetController addSkipBackupAttributeToItemAtPath:path];
[self.page setPreviewRenderedForOrientation:currentOrientation];
contentsCount = 0;
currentContentIndex = 0;
//[self prepareOtherOrientation];
if(self.journal == nil && (![self.page previewRenderedForOrientation:Landscape] || ![self.page previewRenderedForOrientation:Portrait])){
[self appendPage:self.page];
}
DLog(@"rendered page %@ in orientation %d", self.page, currentOrientation);
self.page = nil;
[self retry];
});
}
});
retry 函数使用 NSTimer 再次启动相同的函数,经过短暂的延迟并使用不同的页面。使用分配工具,堆不断增长。过了一会儿,在应用程序崩溃后不久,我收到了内存警告。
当我删除所有调度调用时,一切正常,但这当然不是我想要的。另外,当我将重试方法的延迟增加到 5 秒时,问题也消失了,所以当事情快速连续处理时,似乎内存没有释放。
我绝对确保这种方法一次不会运行超过一次......有什么想法吗?