本文给大家汇总了几种IOS中实现异步加载图片的方法，十分的简单实用，有需要的小伙伴可以参考下。
比较原始的方法：
代码如下:
AsyncImageView.h:
#import
@interface AsyncImageView : UIView
{
NSURLConnection* connection;
NSMutableData* data;
}
- (void)loadImageFromURL:(NSURL*)url;
@end
AsyncImageView.m:
#import "AsyncImageView.h"
@implementation AsyncImageView
- (id)initWithFrame:(CGRect)frame
{
self = [super initWithFrame:frame];
if(self) {
// Initialization code
}
returnself;
}
- (void)loadImageFromURL:(NSURL*)url {
if(connection!=nil) { [connection release]; }
if(data!=nil) { [data release]; }
NSURLRequest* request = [NSURLRequest requestWithURL:url
cachePolicy:NSURLRequestUseProtocolCachePolicy
timeoutInterval:60.0];
connection = [[NSURLConnection alloc]
initWithRequest:request delegate:self];
}
- (void)connection:(NSURLConnection *)theConnection
didReceiveData:(NSData *)incrementalData {
if(data==nil) {
data =
[[NSMutableData alloc] initWithCapacity:2048];
}
[data appendData:incrementalData];
}
- (void)connectionDidFinishLoading:(NSURLConnection*)theConnection {
[connection release];
connection=nil;
if([[self subviews] count] > 0) {
[[[self subviews] objectAtIndex:0] removeFromSuperview];
}
UIImageView *imageView = [[[UIImageView alloc] initWithImage:[UIImage imageWithData:data]] autorelease];
imageView.contentMode = UIViewContentModeScaleAspectFit;
imageView.autoresizingMask = ( UIViewAutoresizingFlexibleWidth | UIViewAutoresizingFlexibleHeight );
[self addSubview:imageView];
imageView.frame = self.bounds;
[imageView setNeedsLayout];
[self setNeedsLayout];
[data release];
data=nil;
}
- (UIImage*) image {
UIImageView* iv = [[self subviews] objectAtIndex:0];
return[iv image];
}
- (void)dealloc {
[connection cancel];
[connection release];
[data release];
[super dealloc];
}
@end
方法二：
复制代码 代码如下:
@interface UIButton (AsyncImage)
//size by point
- (void)setImageFromURL:(NSString *)urlString adjustToSize:(CGSize)size completion:(void (^)(void))completion logo:(UIImage *)logoImage;
@end
@implementation UIButton (AsyncImage)
- (void)setImageFromURL:(NSString *)urlString adjustToSize:(CGSize)size completion:(void (^)(void))completion logo:(UIImage *)logoImage
{
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
UIImage *image = nil;
NSURL *url = [NSURL URLWithString:urlString];
NSData *data = [NSData dataWithContentsOfURL:url];
image = [UIImage imageWithData:data];
if (image) {
if (!CGSizeEqualToSize(size, CGSizeZero)) {
image = [UIImage imageWithCGImage:image.CGImage scale:[self scaleImage:image adjustToSize:size] orientation:image.imageOrientation];
}
if (logoImage) {
image = [self addLogoImage:logoImage toImage:image];
}
dispatch_async(dispatch_get_main_queue(), ^{
[self setImage:image forState:UIControlStateNormal];
completion();
});
}
else {
NSLog(@"async load error.");
}
});
}
// 缩放图片以适应按钮大小
- (CGFloat)scaleImage:(UIImage *)image adjustToSize:(CGSize)size
{
CGFloat xScale = size.width / image.size.width;
CGFloat yScale = size.height / image.size.height;
return 1.0 / MIN(xScale, yScale);
}
- (UIImage *)addLogoImage:(UIImage *)logo toImage:(UIImage *)img
{
//get image width and height
CGFloat scale = [UIScreen mainScreen].scale;
int w = scale * img.size.width;
int h = scale * img.size.height;
int logoWidth = logo.scale * logo.size.width;
int logoHeight = logo.scale * logo.size.height;
CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
//create a graphic context with CGBitmapContextCreate
CGContextRef context = CGBitmapContextCreate(NULL, w, h, 8, 4 * w, colorSpace, kCGImageAlphaPremultipliedFirst);
CGContextDrawImage(context, CGRectMake(0, 0, w, h), img.CGImage);
CGContextDrawImage(context, CGRectMake(w - logoWidth, 0, logoWidth, logoHeight), [logo CGImage]);
CGImageRef imageMasked = CGBitmapContextCreateImage(context);
CGContextRelease(context);
CGColorSpaceRelease(colorSpace);
return [UIImage imageWithCGImage:imageMasked scale:scale orientation:img.imageOrientation];
}
@end
方法三：
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1
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