iOS UICollectionView 入门 07 点击cell放大图片

Posted 2020-07-04 phlsheji

这一节，我们实现通过点击图片将图片放大显示的功能。

首先我们创建一个名为FlickrPhotoViewConroller的类，这个类继承于UIViewController。

改动头文件内容例如以下：

#import <UIKit/UIKit.h>
@class FlickrPhoto;

@interface FlickrPhotoViewConroller : UIViewController
@property (nonatomic, strong) FlickrPhoto *flickrPhoto;
@end

声明outlet和action：

#import "FlickrPhotoViewConroller.h"
#import "Flickr.h"
#import "FlickrPhoto.h"

@interface FlickrPhotoViewConroller ()

@property (weak) IBOutlet UIImageView *imageView;
- (IBAction)done:(id)sender;

@end

打开storyboard，加入一个UIViewController到storyboard中，设置这个view的class为FlickrPhotoViewConroller。

从主view使用ctrl+drag创建一个到Flickr Photo view controller的modal segue。

选中这个segue。设置其identifier为ShowFlickrPhoto

加入一个toolbar和一个imageview到view中，改动toolbarbutton标题为Done，ctrl+drag连接button和FlickrPhotoViewController的done:方法。

再将imageView的outlet也连接上：

打开ViewController.m。加入下面代码到@interface区域中：

@property (nonatomic) BOOL sharing;

改动didSelectItemAtIndexPath方法：

    if (!self.sharing)
    {
        NSString *searchTerm = self.searchs[indexPath.section];
        FlickrPhoto *photo = self.searchResults[searchTerm][indexPath.row];
        [self performSegueWithIdentifier:@"ShowFlickrPhoto" sender:photo];
        [self.collectionView deselectItemAtIndexPath:indexPath animated:YES];
    }
    else
    {
        
    }

当用户点击某幅缩略图时，运行ShowFlickrPhoto segue。

#import "FlickrPhotoViewConroller.h"
- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender
{
    if ([segue.identifier isEqualToString:@"ShowFlickrPhoto"])
    {
        FlickrPhotoViewConroller *flickrPhotoViewController = segue.destinationViewController;
        flickrPhotoViewController.flickrPhoto = sender;
    }
}

实现viewWillAppear方法。显示大图片到view中：

-(void)viewDidAppear:(BOOL)animated { // 1
    if(self.flickrPhoto.largeImage)
    {
        self.imageView.image = self.flickrPhoto.largeImage;
    }
    else
    { // 2
        self.imageView.image = self.flickrPhoto.thumbnail;
        // 3
        [Flickr loadImageForPhoto:self.flickrPhoto thumbnail:NO completionBlock:^(UIImage *photoImage, NSError *error) {
            if(!error) { // 4
                dispatch_async(dispatch_get_main_queue(), ^{ self.imageView.image =
                    self.flickrPhoto.largeImage;
                });
            }
        }];
    }
}

实现done方法。通过点击Donebutton返回到主view：

- (void)done:(id)sender
{
    [self.presentingViewController dismissViewControllerAnimated:YES completion:^{}];
}

程序运行效果例如以下：