我试图弄清楚为什么我的应用程序使用大量内存,然后在多次内存警告后崩溃。Instrument VM Tracker 显示它使用 ~30Mb 作为脏内存。分配显示 10-15 Mb 不是那么多。一旦应用程序处理显示大量图像(缩略图),我就认为图像是我应该看的。我不使用标准的 UIImage imageNamed 方法,而是使用 imageWithData 并进行缓存。当系统发送内存警告时,我会清理缓存存储。为了确保我创建的图像在不再需要时被销毁,我将 UIImage 子类化并覆盖了 imageWithData、release 和 dealloc 方法。我可以看到 imageWithData 被调用,但 release 和 dealloc 从未被调用。我就是这样做的:
BaseUIimage.h
@interface BaseUIimage : UIImage
@end
BaseUIimage.m
#import "BaseUIimage.h"
@implementation BaseUIimage
+ (id)imageWithData:(NSData *)data {
NSLog(@"UIImage imageWithData");
return [UIImage imageWithData:data];
}
- (id)retain {
NSLog(@"UIImage retain: %d", [self retainCount]);
return [super retain];
}
- (oneway void)release {
NSLog(@"UIImage release: %d", [self retainCount]);
[super release];
}
- (id)autorelease {
NSLog(@"UIImage autorelease: %d", [self retainCount]);
return [super autorelease];
}
- (void)dealloc {
NSLog(@"UIImage deallocated");
[super dealloc];
}
@end
我的缓存代码:
。H
#import "BaseUIimage.h"
@interface UIImageCached : BaseUIimage
// CACHE
+ (NSMutableDictionary*) cache;
+ (void) cleanCache;
+ (UIImageCached *)imageNamed:(NSString *)imageName;
+ (UIImageCached *)retinaImageNamed:(NSString *)imageName;
+ (UIImageCached *)imageFromPath:(NSString *)imagePath;
.m
#import "UIImageCached.h"
@implementation UIImageCached
static NSMutableDictionary *data;
+ (NSMutableDictionary*) cache {
if (data == nil)
data = [[NSMutableDictionary alloc] initWithCapacity:150];
return data;
}
+ (void) cleanCache {
NSLog(@"Cache cleaned images: %d", data.count);
for (BaseUIimage *image in data) {
NSLog(@"image rc: %d", [image retainCount]); // always prints rc = 1
}
[data removeAllObjects];
}
+ (UIImageCached *)imageFromPath:(NSString *)imagePath {
UIImageCached *image = (UIImageCached*)[self.cache objectForKey:imagePath];
if (image == nil) {
NSData *imageData = [[NSData alloc] initWithContentsOfFile:imagePath options:NSDataReadingMappedIfSafe error:nil];
image = (UIImageCached*)[UIImageCached imageWithData:imageData];
[imageData release];
if (image) {
[self.cache setObject:image forKey:imagePath];
//NSLog(@"new cached image: #%d", self.cache.count);
} else {
//NSLog(@"can't cache image: #%d", self.cache.count);
}
}
return image;
}
+ (UIImageCached *)imageNamed:(NSString *)imageName {
NSString *extension = [imageName pathExtension];
NSString *fileName = [imageName stringByDeletingPathExtension];
NSString *fileLocation = [[NSBundle mainBundle] pathForResource:fileName ofType:extension];
return [self imageFromPath:fileLocation];
}
+ (UIImageCached *)retinaImageNamed:(NSString *)imageName {
UIImageCached *image = (UIImageCached*)[self.cache objectForKey:imageName];
if (image == nil) {
NSString *extension = [imageName pathExtension];
NSString *fileName = [imageName stringByDeletingPathExtension];
float s = 1.0;
// retina filename support
if(!isIPAD && [[UIScreen mainScreen] respondsToSelector:@selector(scale)]) {
s = [[UIScreen mainScreen] scale];
if (s > 1)
fileName = NSTR2(@"%@%@", fileName, @"@2x");
}
NSString *fileLocation = [[NSBundle mainBundle] pathForResource:fileName ofType:extension];
NSData *imgData = [[NSData alloc] initWithContentsOfFile:fileLocation options:NSDataReadingMappedIfSafe error:nil];
BaseUIimage *tmpImage = [[BaseUIimage alloc] initWithData:imgData];
[imgData release];
image = (UIImageCached*)[UIImageCached imageWithCGImage:tmpImage.CGImage
scale:s
orientation:UIImageOrientationUp];
[tmpImage release];
if (image) {
[self.cache setObject:image forKey:imageName];
//NSLog(@"-- CACHE: new cached image: #%d", self.cache.count);
} else {
NSLog(@"-- CACHE: can't cache image: %@", fileLocation);
}
} else {
//NSLog(@"-- CACHE: read cached image");
}
return image;
}
@end
为什么从不调用 release 和 dealloc?这是否意味着我创建的 UIImage 实例没有被释放,这就是虚拟内存增长的原因?