从照片库中选择多个图像

Question

I am going to ask that one question that perhaps has been already asked a million times.

I am making an app for iPad and want to give users the ability to multi-select images from their photo-library. I already have a working code for user to select one image at a time. (not what I need)

I have already downloaded and looked into ELC image picker sample code but that code is not compatible with iOS 5 or Xcode 4. ie it has ARC and compile problems left and right, its using release and dealloc all over the place.

I am just frustrated that apple hasn't already created a built in-api for us developers for this most commonly requested functionality in most of our iPhone/ipad apps. (not one but multi-select pics)

Is there any other sample code available? Trust me, I have been googling for a while.

Answer 1

Ok, I have this figured out. The problem with Assets Library is that it gives you all the GEO data of the image. What that means for your users using your app is that they will get a prompt saying that your app is trying to access their location. Infact all you are trying to do is let them choose multiple images from their photo-album. Most users will be turned off thinking its a piracy issue. The best approach is to use apples api of imagePickerController. I know it lets you choose one pic at a time but if you add the following code, it will let you choose multiple pictures.

The way I am doing is let the users keep selecting pictures they want, keep saving those files in the app documents directory, till they hit the done button. See here my sample code and hopefully it will save you the pain of going through Assets Library

-(IBAction)selectExitingPicture
{
    //Specially for fing iPAD
    UIImagePickerController *imagePicker = [[UIImagePickerController alloc] init];
    imagePicker.delegate = self;
    imagePicker.sourceType = UIImagePickerControllerSourceTypePhotoLibrary;
    imagePicker.mediaTypes = [NSArray arrayWithObject:(NSString *)kUTTypeImage];

    popoverController = [[UIPopoverController alloc] initWithContentViewController:imagePicker];
    [popoverController presentPopoverFromRect:CGRectMake(0.0, 0.0, 400.0, 300.0) 
                             inView:self.view
           permittedArrowDirections:UIPopoverArrowDirectionAny 
                           animated:YES];
}

//Done button on top
- (void)navigationController:(UINavigationController *)navigationController
      willShowViewController:(UIViewController *)viewController
                    animated:(BOOL)animated
{    
    //NSLog(@"Inside navigationController ...");


    if (!doneButton) 
    {
        doneButton = [[UIBarButtonItem alloc] initWithTitle:@"Done"
                                                      style:UIBarButtonItemStyleDone
                                                     target:self action:@selector(saveImagesDone:)];
    }

    viewController.navigationItem.rightBarButtonItem = doneButton;
}

- (IBAction)saveImagesDone:(id)sender
{
    //NSLog(@"saveImagesDone ...");

    [popoverController dismissPopoverAnimated:YES];
}


-(void)imagePickerController:(UIImagePickerController *)picker
      didFinishPickingImage : (UIImage *)image
                 editingInfo:(NSDictionary *)editingInfo
{


    //DONT DISMISS
    //[picker dismissModalViewControllerAnimated:YES];
    //[popoverController dismissPopoverAnimated:YES];

        IMAGE_COUNTER = IMAGE_COUNTER + 1;

        imageView.image = image;

        // Get the data for the image
        NSData* imageData = UIImageJPEGRepresentation(image, 1.0);


        // Give a name to the file
        NSString* incrementedImgStr = [NSString stringWithFormat: @"UserCustomPotraitPic%d.jpg", IMAGE_COUNTER];


        NSArray* paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
        NSString* documentsDirectory = [paths objectAtIndex:0];

        // Now we get the full path to the file
        NSString* fullPathToFile2 = [documentsDirectory stringByAppendingPathComponent:incrementedImgStr];

        // and then we write it out
        [imageData writeToFile:fullPathToFile2 atomically:NO];

}

//Now use this code to get to user selected pictures. Call it from wherever you want in your code

 NSArray* paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask ,YES);
        NSString* documentsPath = [paths objectAtIndex:0];
        NSString* dataFile = [documentsPath stringByAppendingPathComponent:@"UserCustomPotraitPic1.jpg"];

        NSData *potraitImgData = [NSData dataWithContentsOfFile:dataFile];
        backgroundImagePotrait = [UIImage imageWithData:potraitImgData];

Answer 2

Apple has provided api for this. It is called ALAssetsLibrary .

Using this you can select multiple images/ videos and other operations that you do using photo application on iOS device.

As in documentation Apple says:

Assets Library Framework

Introduced in iOS 4.0, the Assets Library framework (AssetsLibrary.framework) provides a query-based interface for retrieving photos and videos from the user's device. Using this framework, you can access the same assets that are normally managed by the Photos application, including items in the user's saved photos album and any photos and videos that were imported onto the device. You can also save new photos and videos back to the user's saved photos album.

Here are few links where you can learn more. Now to use it you can search for ALAssetsLibrary.

Assets Library Reference

http://www.fiveminutes.eu/accessing-photo-library-using-assets-library-framework-on-iphone/

Answer 3

Starting with iOS 14, multiple image selection is now supported in the new Photos picker. Here is sample code from Apple: Selecting Photos and Videos in iOS .

Answer 4

I use ALAssetsLibrary and rolled my own UI. The problem with UIImagePickerController is that it says you are supposed to dismiss the view controller in the didFinishPickingMediaWithInfo callback, so hacking multiple selection by not dismissing may run into problems. I know I did when I first tried it. I can't recall exactly what went wrong, but there were cases where UIImagePickerController simply stopped working if I didn't dismiss it like the docs say.