FullScreen图像在UICollectionView中的应用

Question

我正在使用SDWebImage在UICollectionView中显示图像。我将productImageUrl和productId作为服务器响应。能够在Custom-cell中显示图像，现在我想要的是：

1)在另一个名为ProductDetailViewController的UIViewController上以大视图显示图像。(图像显示在ProductDetailViewController上，但我从ProductCollectionViewController传递图像url的方式不对，请查看代码，并建议更好的方法。)

2) On button click将调用服务器，并使用之前作为服务器响应获得的productId (如何将dictId传递给ProductDetailViewController，以便对服务器进行调用)。

3)获取only two key-value of an Object as response，所以可以在多个字典中解析多个值。但是如果响应包含多个值，那么什么将是the optimized way to parse the response。

这是我试过的密码。(很抱歉，长时间未优化的代码仍处于学习阶段)

ProductCollectionViewController.m

#import "ProductCollectionViewController.h"
#import "ProductCell.h"
#import "UIImageView+WebCache.h"
#import "ProductDetailViewController.h"

@interface ProductCollectionViewController ()

@property(strong, nonatomic) NSMutableArray *productList;

@end
@implementation ProductCollectionViewController

-(id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil
{
self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
if (self) {
}
return self;
}
static NSString * const reuseIdentifier = @"Cell";

-(void)viewDidLoad
{
[super viewDidLoad];
[self getProductList];
}

-(void)didReceiveMemoryWarning {
[super didReceiveMemoryWarning];
}
-(void)getProductList
{
 NSURL * url = [NSURL URLWithString:@"xxxx.yyyy.zzzz"];

NSMutableURLRequest * urlRequest = [NSMutableURLRequest requestWithURL:url];

NSURLSessionConfiguration *defaultConfigObject = [NSURLSessionConfiguration defaultSessionConfiguration];

NSURLSession *defaultSession = [NSURLSession sessionWithConfiguration: defaultConfigObject];

NSURLSessionDataTask * dataTask = [defaultSession dataTaskWithRequest:urlRequest completionHandler:^(NSData *data, NSURLResponse *response, NSError *error){
    if (!error)
    {
        NSDictionary *responseJson = [NSJSONSerialization JSONObjectWithData:data options:kNilOptions error:nil];

        NSArray *rsBody = responseJson[@"rsBody"];

        _productList = [NSMutableArray new];

        for(NSDictionary *dict in rsBody)
        {
            NSMutableDictionary *dictUrl=[[NSMutableDictionary alloc]init];
            NSMutableDictionary *dictProductId =[[NSMutableDictionary alloc]init];
            [dictUrl setValue:[dict valueForKey:@"productImageUrl"] forKey:@"url"];
             [dictId setValue:[dict valueForKey:@"productId"] forKey:@"id"];
            [_productList addObject:dictUrl];
            [_productList addObject:dictId];
         }
        NSLog(@"urls for image: %@",_productList );
        [self.collectionView reloadData];
    }}];
[dataTask resume];
}

#pragma mark <UICollectionViewDataSource>

-(NSInteger)numberOfSectionsInCollectionView:(UICollectionView *)collectionView {
return 1;
}

-(NSInteger)collectionView:(UICollectionView *)collectionView numberOfItemsInSection:(NSInteger)section
{
return _productList.count;

}

- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath {

ProductCell *cell = [collectionView dequeueReusableCellWithReuseIdentifier:@"Cell" forIndexPath:indexPath];

NSURL *imageUrl = [[_productList objectAtIndex:indexPath.row]valueForKey:@"url"];
[cell.productImageView sd_setImageWithURL:imageUrl placeholderImage:[UIImage imageNamed:@"placeholder.jpg"]];

NSString *id =[[_productList objectAtIndex:indexPath.row] valueForKey:@"id"];
cell.productPrice.text= id;

return cell;
}
- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender {
if ([segue.identifier isEqualToString:@"showProduct"]) {
    NSArray *indexPaths = [self.collectionView indexPathsForSelectedItems];
    ProductDetailViewController *destViewController = segue.destinationViewController;
    NSIndexPath *indexPath = [indexPaths objectAtIndex:0]
    destViewController.productName =[[_productList objectAtIndex:indexPath.row]valueForKey:@"url"];

    [self.collectionView deselectItemAtIndexPath:indexPath animated:NO];
}
}
@end

ProductDetailViewController.h

`#import <UIKit/UIKit.h>
@interface ProductDetailViewController : UIViewController
- (IBAction)buyButton:(id)sender;
- (IBAction)closeButton:(id)sender;
@property (weak, nonatomic) IBOutlet UIImageView *productImage;
@property (weak, nonatomic) NSString *productName;
@end`

ProductDetailViewController.m

- (void)viewDidLoad {
[super viewDidLoad];

self.productImage.image = [UIImage imageWithData:[NSData dataWithContentsOfURL:[NSURL URLWithString:self.productName]]];

 //code to get productId

}
- (IBAction)buyButton:(id)sender {
//code to make server call with productId.
}

JSON的服务器响应格式

{"rsBody":
 [{"productId":11,
"productImageUrl":"http:xxxx"},
{"productId":9,
"productImageUrl":"http:"xxxx"}]}

Answer 1

对于你的第一个问题，这句话

self.productImage.image = [UIImage imageWithData:[NSData dataWithContentsOfURL:[NSURL URLWithString:self.productName]]];

阻塞了主线程。这意味着应用程序将在更新屏幕或允许交互之前下载整个图像，这是不好的。

NSURL *url = [[NSURL alloc]initWithString:self.productName];
            dispatch_queue_t imageFetchQ = dispatch_queue_create("image fetcher", NULL);
            dispatch_async(imageFetchQ, ^{
                NSData *imageData = [[NSData alloc] initWithContentsOfURL:url];
                UIImage *image = [[UIImage alloc]initWithData:imageData];
                dispatch_async(dispatch_get_main_queue(), ^{
                    self.productImage.image=image;
                    }
                });

            }); 

试一试上面的块。它将在另一个线程上获取产品映像。

问题二:视图控制器之间的两个传输数据执行在prepareForSegue中所做的操作，设置目标视图控制器的公共属性。

问题三:最佳的方法是创建一个NSObject类，通过某种名为setupFromDictionary的方法将数据从字典中读取到该类的属性中。

这里有一个名为product的对象，它具有productID属性和productImageURL属性。这样，您就不会经常在某些字典中调用valueForKey或objectForKey。