[英]NSOperationQueue Issue
我有一個代碼在ios 6中用作圖像下載器,但是當我在使用ios 5的不同應用程序中使用相同的代碼時,它給我錯誤NSInvalidArgumentException', reason: '-[NSNull length]: unrecognized selector sent to instance
聽到的是我正在使用的代碼
[self.imageDownloadingQueue addOperationWithBlock:^{
NSURL *imageUrl = [NSURL URLWithString:ImageURL];
NSData *imageData = [NSData dataWithContentsOfURL:imageUrl];
UIImage *images = nil;
if (imageData)
images = [UIImage imageWithData:imageData];
if (images){
[self.imageCache setObject:images forKey:ImageURL];
[[NSOperationQueue mainQueue] addOperationWithBlock:^{
// make sure the cell is still visible
imageV.image = images;
}];
}
}];
誰能告訴我我在做什么錯,因為此代碼在單獨下載圖像時對我有很大幫助。 謝謝
PS我正在使用的整個功能
-(void) setScrollView:(UIScrollView *)scrollview :(NSArray *)contentArray{
int x = 0;
int i = 0;
NSString *ImageURL=@"http://www.online-image-editor.com/styles/2013/images/example_image.png";
for(NSDictionary *str in contentArray){
UIImageView *imageV = [[UIImageView alloc ] initWithFrame:CGRectMake(x, 0, 200,125)];
@try {
ImageURL = [str objectForKey:@"image"];
}
@catch (NSException * e) {
NSLog(@"Exception: %@", [e description]);
}
imageV.userInteractionEnabled = YES;
ImageTapGesture *singleTap = [[ImageTapGesture alloc] initWithTarget:self action:@selector(tapDetectedMain:)];
singleTap.newItem = str;
singleTap.currentItem = i ;
singleTap.numberOfTapsRequired = 1;
[imageV addGestureRecognizer:singleTap];
UILabel *title = [[UILabel alloc] initWithFrame:CGRectMake(x,125,200,20)];
[title setFont:[UIFont systemFontOfSize:11]];
title.numberOfLines = 2;
title.autoresizingMask = UIViewAutoresizingFlexibleHeight;
[title setBackgroundColor:[UIColor blackColor]];
[title setTextColor:[UIColor whiteColor]];
title.text = [NSString stringWithFormat:@" %@",[str objectForKey:@"title"]];
x += title.frame.size.width+2;
UIImage *cachedImage = [self.imageCache objectForKey:ImageURL];
if (cachedImage){
imageV.image = cachedImage;
}
else{
imageV.image = [UIImage imageNamed:@"vdo.png"];
[self.imageDownloadingQueue addOperationWithBlock:^{
NSURL *imageUrl = [NSURL URLWithString:ImageURL];
NSData *imageData = [NSData dataWithContentsOfURL:imageUrl];
UIImage *images = nil;
if (imageData)
images = [UIImage imageWithData:imageData];
if (images){
[self.imageCache setObject:images forKey:ImageURL];
[[NSOperationQueue mainQueue] addOperationWithBlock:^{
// make sure the cell is still visible
imageV.image = images;
}];
}
}];
}
[scrollview addSubview:imageV];
[scrollview addSubview:title];
}
scrollview.contentSize = CGSizeMake(x, scrollview.frame.size.height);
i++;
}
您絕對應該檢查要發送給操作的ImageURL
。 看來,這個ImageURL
是[NSNull null]
。 如果它是局部變量,是否聲明為__block NSString *ImageUrl
?
請嘗試以下代碼:
[self.imageDownloadingQueue addOperationWithBlock:^{
NSURL *imageUrl ;
if((ImageURL!=nil)&&(![ImageURL isKindOfClass:[NSNull class]]))
{
imageUrl= [NSURL URLWithString:ImageURL];
}
NSData *imageData;
if((imageUrl!=nil)&&(![imageUrl isKindOfClass:[NSNull class]]))
{
imageData = [NSData dataWithContentsOfURL:imageUrl];
}
UIImage *images = nil;
if((imageData!=nil)&&(![imageData isKindOfClass:[NSNull class]]))
images = [UIImage imageWithData:imageData];
if((images!=nil)&&(![images isKindOfClass:[NSNull class]]))
{
[self.imageCache setObject:images forKey:ImageURL];
[[NSOperationQueue mainQueue] addOperationWithBlock:^{
// make sure the cell is still visible
imageV.image = images;
}];
}
}];
希望這會幫助你。
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