//1. NSData dataWithContentsOfURL
// [self.icon setImage:[UIImage imageWithData:[NSData dataWithContentsOfURL:tempUrl]]];
//2. dispath形式添加到異步處理
// [self imageDownLoadByUrlASYNC:tempUrl Complete:^(UIImage *image) {
// [self.icon setImage:image];
// }];
//3. 當前我所選用的方式 邊下載邊加載的方式 用的CGImageRef imageWithCGImage
_request = [[NSURLRequest alloc] initWithURL:tempUrl];
_conn = [[NSURLConnection alloc] initWithRequest:_request delegate:self];
_incrementallyImgSource = CGImageSourceCreateIncremental(NULL);
_recieveData = [[NSMutableData alloc] init];
_isLoadFinished = false;
self.icon.alpha = .5;
self.lblTitle.alpha = .5;
[self.lblTitle setText:appName];
第一種方式，是基本上很少有人用的 是最基礎的方式 這種方式有個問題 就是網絡不好的情況下會卡主線程，導致程序假死
第二種方式，請款這段實現代碼
//
//-(void)imageDownLoadByUrlASYNC:(NSURL *)url Complete:(complete)finished
//{
// //異步並列執行
// dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
// UIImage *image = nil;
// NSError *error;
// NSData *responseData = [NSData dataWithContentsOfURL:url options:NSDataReadingMappedIfSafe error:&error];
// image = [UIImage imageWithData:responseData];
// //跳回主隊列執行
// dispatch_async(dispatch_get_main_queue(), ^{
// //在主隊列中進行ui操作
// finished(image);
// });
//
// });
//}
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
NSError *error;
UIImage *image = nil;
SDWebImageManager *manager = [SDWebImageManager sharedManager];
BOOL existBool = [manager diskImageExistsForURL:url];//判斷是否有緩存
if (existBool) {
image = [[manager imageCache] imageFromDiskCacheForKey:url.absoluteString];
}else{
NSData *responseData = [NSData dataWithContentsOfURL:url options:NSDataReadingMappedIfSafe error:&error];
image = [UIImage imageWithData:responseData];
}
//跳回主隊列執行
dispatch_async(dispatch_get_main_queue(), ^{
//在主隊列中進行ui操作
__block CGFloat itemW = mWidth;
__block CGFloat itemH = 0;
NSLog(@"%f",image.size.width);
//根據image的比例來設置高度
if (image.size.width) {
itemH = image.size.height / image.size.width * itemW;
if (itemH >= itemW) {
if (itemH >= mHeight-64) {
NSLog(@"%f",[UIScreen mainScreen].bounds.size.width);
UIScrollView *sv = [[UIScrollView alloc]initWithFrame:CGRectMake(0, 64, itemW, mHeight-64)];
sv.contentSize = CGSizeMake(itemW, itemH);
sv.showsVerticalScrollIndicator = NO;
sv.userInteractionEnabled = YES;
[self.view addSubview:sv];
imageView.frame = CGRectMake(0, 0, itemW, itemH);
imageView.contentMode = UIViewContentModeScaleAspectFit;
[sv addSubview:imageView];
}else{
imageView.frame = CGRectMake(0, 64, itemW, itemH);
imageView.contentMode = UIViewContentModeScaleAspectFit;
[self.view addSubview:imageView];
}
}else{
imageView.frame = CGRectMake(0, 64, itemW, itemH);
imageView.contentMode = UIViewContentModeScaleAspectFit;
[self.view addSubview:imageView];
}
}else{
imageView.frame = CGRectMake(0, 64, mWidth, mHeight-64);
imageView.contentMode = UIViewContentModeScaleAspectFit;
[self.view addSubview:imageView];
}
[self.myView stopAnimating];
});
});
雖然情況跟第一種實現一樣，但是將執行代碼添加到對應的異步執行中 然后再成功下載之后 獲取到image之后 放到主線程執行回調 設置image
第三種方式 需要以下代碼 這是我百度到的方式
#pragma mark -- NSURLConnectionDataDelegate
-(void)connection:(NSURLConnection*)connection didReceiveResponse:(NSURLResponse*)response
{
_expectedLeght=response.expectedContentLength;
NSLog(@"expectedLength:%lld",_expectedLeght);
NSString*mimeType=response.MIMEType;
NSLog(@"MIMETYPE%@",mimeType);
NSArray*arr=[mimeType componentsSeparatedByString:@"/"];
if(arr.count<1||![[arr objectAtIndex:0] isEqual:@"image"])
{
NSLog(@"notaimageurl");
[connection cancel];
_conn=nil;
}
}
-(void)connection:(NSURLConnection*)connection didFailWithError:(NSError*)error
{
NSLog(@"Connection%@error,errorinfo:%@",connection,error);
}
-(void)connectionDidFinishLoading:(NSURLConnection*)connection
{
NSLog(@"ConnectionLoadingFinished!!!");
//ifdownloadimagedatanotcomplete,createfinalimage
if(!_isLoadFinished){
CGImageSourceUpdateData(_incrementallyImgSource,(CFDataRef)_recieveData,_isLoadFinished);
CGImageRef imageRef=CGImageSourceCreateImageAtIndex(_incrementallyImgSource,0,NULL);
UIImage * image=[UIImage imageWithCGImage:imageRef];
[self.icon setImage:image];
CGImageRelease(imageRef);
}
}
-(void)connection:(NSURLConnection*)connection didReceiveData:(NSData*)data
{
[_recieveData appendData:data];
_isLoadFinished=false;if(_expectedLeght==_recieveData.length){
_isLoadFinished=true;
}
CGImageSourceUpdateData(_incrementallyImgSource,(CFDataRef)_recieveData,_isLoadFinished);
CGImageRef imageRef=CGImageSourceCreateImageAtIndex(_incrementallyImgSource,0,NULL);
UIImage * image=[UIImage imageWithCGImage:imageRef];
[self.icon setImage:image];
CGImageRelease(imageRef);
}
這個方法經過我測試了 非常好用 但是不知道會不會有什么bug 只是剛使用 並且用戶體驗也會相應增加