使用照片框架将图像保存到照片库

Question

每次我尝试使用照片框架保存图像时，我的应用都会崩溃。

-(void)imagePickerController:(UIImagePickerController *)picker didFinishPickingMediaWithInfo:(NSDictionary *)info{

      _mChangeRequest = [PHAssetChangeRequest creationRequestForAssetFromImage:[info valueForKey:UIImagePickerControllerOriginalImage]];

      [[PHPhotoLibrary sharedPhotoLibrary] performChanges:^{

      _mChangeRequest = [PHAssetChangeRequest creationRequestForAssetFromImage:[info valueForKey:UIImagePickerControllerOriginalImage]];

      } completionHandler:^(BOOL success, NSError *error) {

          if (success) {

              PHObjectPlaceholder *assetPlaceholder = _mChangeRequest.placeholderForCreatedAsset;
          }
          else {

             NSLog(@"write error : %@",error);
          }
    }];
}

crash : NSInternalInconsistencyException', reason: 'This method can only be called from inside of -[PHPhotoLibrary performChanges:completionHandler:] or -[PHPhotoLibrary performChangesAndWait:error:]'

Answer 1

1. 删除第三行代码
2. 验证 _mChangeRequest 是 __block 变量
3. 编译运行

您将在照片应用中看到该图像

您可能会像这样更改代码...

- (void)imagePickerController:(UIImagePickerController *)picker
didFinishPickingMediaWithInfo:(NSDictionary *)info {
    __block PHAssetChangeRequest *_mChangeRequest = nil;
    [[PHPhotoLibrary sharedPhotoLibrary]
            performChanges:^{
                UIImage *image = [info valueForKey:UIImagePickerControllerOriginalImage];
                _mChangeRequest = [PHAssetChangeRequest creationRequestForAssetFromImage:image];
            }, completionHandler :^(BOOL success, NSError *error) {
        if (success) {
            PHObjectPlaceholder *assetPlaceholder = _mChangeRequest.placeholderForCreatedAsset;
        } else {
            NSLog(@"write error : %@", error);
        }
    }];
}

Answer 2

在 Swift 3 中，我这样做是为了将视频保存到库中。

if mediaType.isEqual(to: (kUTTypeMovie as NSString) as String) {
    if let videoURL = info[UIImagePickerControllerMediaURL] as? URL {
        PHPhotoLibrary.shared().performChanges({
            _ = PHAssetChangeRequest.creationRequestForAssetFromVideo(atFileURL: videoURL)
        }, completionHandler: { (success, error) in
            if success {
                print("ok")
                let videoData = NSData(contentsOf: videoURL)
                // use videoData here if needed...
                if let posterImage = self.firstFrame(videoURL: videoURL) {
                    self.imageView.image = posterImage
                }
                picker.dismiss(animated: true) { () -> Void in
                }
            } else {
                print(error?.localizedDescription)
            }
        })
    }
}

Answer 3

以下是如何使用UIImageWriteToSavedPhotosAlbum 函数将图像写入/保存到照片库的代码示例：

- (void)saveImage:(UIImage *)image {
    UIImageWriteToSavedPhotosAlbum(self.image, self, @selector(image:didFinishSavingWithError:contextInfo:), NULL);
}
- (void)image:(UIImage *)image didFinishSavingWithError:(NSError *)error contextInfo:(void *)contextInfo;
{
    if (!error) {
        // saved successfully

        PHFetchOptions *fetchOptions = [PHFetchOptions new];
        fetchOptions.sortDescriptors = @[[NSSortDescriptor sortDescriptorWithKey:@"creationDate" ascending:NO]];
        PHAsset *asset = [PHAsset fetchAssetsWithMediaType:PHAssetMediaTypeImage options:fetchOptions].firstObject;
        if (asset != nil) {
            // here you can use asset of your image
        }
    } else {
        NSLog(@"save image error: %@", error);
    }
}

不要忘记在您的 Info.plist 中添加一个键值对 Privacy - Camera Usage Description 以及使用说明。

Answer 4

您需要做的就是触发创建请求。正如错误所说，您只能在 performChanges 块内访问更改请求。

因此，要保存图像，您可以执行以下操作：

[[PHPhotoLibrary sharedPhotoLibrary] performChanges:^{
    [PHAssetChangeRequest creationRequestForAssetFromImage:[info valueForKey:UIImagePickerControllerOriginalImage]];
} completionHandler:^(BOOL success, NSError *error) {
    if (success) {
         NSLog(@"Success");
    }
    else {
        NSLog(@"write error : %@",error);
    }
}];

如果您需要对新创建资产的占位符进行操作，您可以在同一 performChanges 块内访问它：

PHAssetChangeRequest *changeRequest = [PHAssetChangeRequest creationRequestForAssetFromImage:[info valueForKey:UIImagePickerControllerOriginalImage]];
PHObjectPlaceholder *assetPlaceholder = changeRequest.placeholderForCreatedAsset;