我touchesEnded在我的绘图应用程序中调用以下代码。但是，每次调用它时，内存使用量都会增加大约 2MB。最终它可能在 90-100MB 左右，如果用户快速绘制，应用程序将崩溃。
我在这里做错了什么？我怎样才能使这段代码快速但内存使用最少？
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH, 0), ^{
if(_pagessavedbg.count > selectedIndex)
self.topimage = [[UIImage alloc] initWithCGImage:[[_pagessavedbg objectAtIndex:selectedIndex] CGImage]];
else
self.topimage = [[UIImage alloc] initWithCGImage:[[UIImage imageNamed:@"BlankImage.png"] CGImage]];
UIImage *bottomimage = [notification.userInfo objectForKey:@"Image"];
NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
NSError *error2 = nil;
NSURL *documentsURL = [[NSFileManager defaultManager]
URLForDirectory:NSDocumentDirectory
inDomain:NSUserDomainMask
appropriateForURL:nil
create:YES
error:nil];
CGSize size = CGSizeMake(874, 732);
UIGraphicsBeginImageContextWithOptions(size, NO, 1);
[self.topimage drawInRect:CGRectMake(0, 0, size.width, size.height)];
[bottomimage drawInRect:CGRectMake(0, 0, size.width, size.height)];
UIImage *latest = UIGraphicsGetImageFromCurrentImageContext();
[activeView.layer renderInContext:UIGraphicsGetCurrentContext()];
UIImage *latest2 = UIGraphicsGetImageFromCurrentImageContext();
CGContextFlush(UIGraphicsGetCurrentContext());
UIGraphicsEndImageContext();
if(_pages.count > selectedIndex)
{
if([_pages objectAtIndex:selectedIndex])
[_pages replaceObjectAtIndex:selectedIndex withObject:latest];
}
if(_pages.count > selectedIndex)
{
if([_pagessavedbg objectAtIndex:selectedIndex])
[_pagessavedbg replaceObjectAtIndex:selectedIndex withObject:latest2];
else
[_pagessavedbg insertObject:latest2 atIndex:selectedIndex];
}
NSData *data = UIImageJPEGRepresentation(latest, 1.0);
NSError *error = nil;
NSDictionary *fileObjectMap = @{
@"ImageData" : data,
};
for (NSString *filename in fileObjectMap)
{
NSData *data = [NSPropertyListSerialization
dataWithPropertyList:fileObjectMap[filename]
format:NSPropertyListXMLFormat_v1_0
options:0
error:&error];
if (!data) {
NSLog(@"Failed to serialize array for filename %@ (contents %@) with error %@", filename, fileObjectMap[filename], error);
return;
}
NSURL *fileURL = [[documentsURL URLByAppendingPathComponent:filename]
URLByAppendingPathExtension:@"txt"];
if (![data writeToURL:fileURL options:NSDataWritingAtomic error:&error]) {
NSLog(@"Failed to write data to file URL %@ for filename %@ (data %@) with error %@", fileURL, filename, data, error);
return;
}
}
NSString *indexnotext = [defaults objectForKey:@"IndexNumber"];
myInt = [indexnotext intValue];
dispatch_async(dispatch_get_main_queue(), ^{
[self.sidebar reloadData];
[self.sidebar scrollRowAtIndexToVisible:_sidebar.selectedIndex];
});
if (!documentsURL) {
NSLog(@"Failed to get documents URL: %@", error2);
return;
}
NSMutableArray *imageDatas = [NSMutableArray arrayWithCapacity:self.pages.count];
for (UIImage *image in [_pages copy])
{
if(!image)
break;
else
[imageDatas addObject:UIImageJPEGRepresentation(image, 1.0)];
}
NSMutableArray *imageDatas2 = [NSMutableArray arrayWithCapacity:self.pagessavedbg.count];
for (UIImage *image2 in [self.pagessavedbg copy])
{
if(!image2)
break;
else
[imageDatas2 addObject:UIImageJPEGRepresentation(image2, 1.0)];
}
NSDictionary *fileObjectMap2 = @{
[NSString stringWithFormat:@"SavedPages%i", [_indexnumber intValue]] : imageDatas,
[NSString stringWithFormat:@"SavedPagesBG%i", [_indexnumber intValue]] : imageDatas2,
};
for (NSString *filename2 in fileObjectMap2)
{
self.data2 = [NSPropertyListSerialization
dataWithPropertyList:fileObjectMap2[filename2]
format:NSPropertyListXMLFormat_v1_0
options:0
error:&error2];
if (!self.data2) {
NSLog(@"Failed to serialize array for filename %@ (contents %@) with error %@", filename2, fileObjectMap2[filename2], error2);
return;
}
NSURL *fileURL2 = [[documentsURL URLByAppendingPathComponent:filename2]
URLByAppendingPathExtension:@"txt"];
if (![self.data2 writeToURL:fileURL2 options:NSDataWritingAtomic error:&error2]) {
NSLog(@"Failed to write data to file URL %@ for filename %@ (data %@) with error %@", fileURL2, filename2, self.data2, error2);
return;
}
}
});