如何保存相机拍摄的图片并在另一个ViewController中展示？

Hey there! Let's get your photo saving and collection view display working properly. I'll break this down into clear, actionable steps with code examples tailored to your existing implementation.

Step 1: Add Image Persistence Logic #

First, we need to save the selected/captured images to your app's Documents directory (so they persist between app launches) and keep track of their filenames. Add these methods to your ViewController.m:

// Helper method to save image to Documents directory
- (BOOL)saveImageToDocuments:(UIImage *)image withFileName:(NSString *)fileName {
    NSData *imageData = UIImageJPEGRepresentation(image, 0.8); // 0.8 balances quality and file size
    if (!imageData) return NO;
    
    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
    NSString *documentsDirectory = [paths firstObject];
    NSString *filePath = [documentsDirectory stringByAppendingPathComponent:fileName];
    
    return [imageData writeToFile:filePath atomically:YES];
}

// Helper method to get saved images filenames from UserDefaults
- (NSMutableArray *)savedImageFilenames {
    NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
    NSMutableArray *filenames = [[defaults objectForKey:@"SavedImageFilenames"] mutableCopy];
    if (!filenames) filenames = [NSMutableArray array];
    return filenames;
}

Now update your imagePickerController:didFinishPickingMediaWithInfo: method to save the image and update the filename list:

- (void)imagePickerController:(UIImagePickerController *)picker didFinishPickingMediaWithInfo:(NSDictionary *)info {
    UIImage *chosenImage = info[UIImagePickerControllerEditedImage];
    self.imageView.image = chosenImage;
    
    // Generate a unique filename using timestamp to avoid duplicates
    NSString *fileName = [NSString stringWithFormat:@"Photo_%f.jpg", [[NSDate date] timeIntervalSince1970]];
    
    // Save the image and update the saved filenames list
    if ([self saveImageToDocuments:chosenImage withFileName:fileName]) {
        NSMutableArray *savedFilenames = [self savedImageFilenames];
        [savedFilenames addObject:fileName];
        [[NSUserDefaults standardUserDefaults] setObject:savedFilenames forKey:@"SavedImageFilenames"];
        [[NSUserDefaults standardUserDefaults] synchronize];
    }
    
    [picker dismissViewControllerAnimated:YES completion:NULL];
}

Step 2: Create the Photo Collection View Controller #

Create a new UIViewController subclass named PhotoCollectionViewController (check "Also create XIB file" or use Storyboard based on your setup).

Configure the Collection View #

1. Add a UICollectionView to the view controller, set constraints to fill the entire view.
2. Set the collection view's dataSource and delegate to the view controller.
3. Create a UICollectionViewCell subclass (e.g., PhotoCell) with a UIImageView inside, set constraints for the image view to fill the cell.

Code for PhotoCollectionViewController.m #

#import "PhotoCollectionViewController.h"
#import "PhotoCell.h"

@interface PhotoCollectionViewController () <UICollectionViewDataSource, UICollectionViewDelegateFlowLayout>
@property (nonatomic, strong) NSMutableArray *imageFilenames;
@property (nonatomic, strong) NSString *documentsDirectory;
@end

@implementation PhotoCollectionViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    
    // Get path to Documents directory
    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
    self.documentsDirectory = [paths firstObject];
    
    // Load saved image filenames from UserDefaults
    NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
    self.imageFilenames = [[defaults objectForKey:@"SavedImageFilenames"] mutableCopy];
    if (!self.imageFilenames) self.imageFilenames = [NSMutableArray array];
    
    // Register the cell class (skip if using Storyboard/XIB with identifier)
    [self.collectionView registerClass:[PhotoCell class] forCellWithReuseIdentifier:@"PhotoCell"];
}

#pragma mark - UICollectionView DataSource
- (NSInteger)collectionView:(UICollectionView *)collectionView numberOfItemsInSection:(NSInteger)section {
    return self.imageFilenames.count;
}

- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath {
    PhotoCell *cell = [collectionView dequeueReusableCellWithReuseIdentifier:@"PhotoCell" forIndexPath:indexPath];
    
    // Load image from Documents directory
    NSString *fileName = self.imageFilenames[indexPath.row];
    NSString *filePath = [self.documentsDirectory stringByAppendingPathComponent:fileName];
    cell.imageView.image = [UIImage imageWithContentsOfFile:filePath];
    
    return cell;
}

#pragma mark - UICollectionView DelegateFlowLayout
- (CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout *)collectionViewLayout sizeForItemAtIndexPath:(NSIndexPath *)indexPath {
    // Show 3 columns with small spacing
    CGFloat width = (collectionView.bounds.size.width - 20) / 3;
    return CGSizeMake(width, width);
}

- (UIEdgeInsets)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout *)collectionViewLayout insetForSectionAtIndex:(NSInteger)section {
    return UIEdgeInsetsMake(10, 10, 10, 10);
}

@end

Code for PhotoCell.h #

#import <UIKit/UIKit.h>

@interface PhotoCell : UICollectionViewCell
@property (nonatomic, strong) UIImageView *imageView;
@end

Code for PhotoCell.m #

#import "PhotoCell.h"

@implementation PhotoCell

- (instancetype)initWithFrame:(CGRect)frame {
    self = [super initWithFrame:frame];
    if (self) {
        self.imageView = [[UIImageView alloc] initWithFrame:self.bounds];
        self.imageView.contentMode = UIViewContentModeScaleAspectFill;
        self.imageView.clipsToBounds = YES;
        [self.contentView addSubview:self.imageView];
    }
    return self;
}

@end

Step 3: Navigate to the Collection View Controller #

Add a button (or any trigger) in your original ViewController to push/present the PhotoCollectionViewController. For example, add this IBAction:

- (IBAction)showPhotoCollection:(UIButton *)sender {
    PhotoCollectionViewController *collectionVC = [[PhotoCollectionViewController alloc] init];
    [self.navigationController pushViewController:collectionVC animated:YES];
    // Use this instead if not using a navigation controller:
    // [self presentViewController:collectionVC animated:YES completion:nil];
}

Important Notes #

• Permissions: Don't forget to add required privacy permissions to your Info.plist:
  • NSCameraUsageDescription (explain why your app needs camera access)
  • NSPhotoLibraryUsageDescription (explain why your app needs photo library access)
• Image Quality: Adjust the compression value in UIImageJPEGRepresentation (0.0 to 1.0) based on your quality/storage needs.
• Scalability: For apps with many images, consider using Core Data instead of UserDefaults to store filenames for better performance and management.

内容的提问来源于stack exchange，提问作者Dhanush kumar Sivaji