IOS探索之从拍照中获取图像对应的ALAsset

打开相机

//先设定sourceType为相机，然后判断相机是否可用（ipod）没相机，不可用将sourceType设定为相片库
UIImagePickerControllerSourceType sourceType = UIImagePickerControllerSourceTypeCamera;
//    if (![UIImagePickerController isSourceTypeAvailable: UIImagePickerControllerSourceTypeCamera]) {
//        sourceType = UIImagePickerControllerSourceTypePhotoLibrary;
//    }
//sourceType = UIImagePickerControllerSourceTypeCamera; //照相机
//sourceType = UIImagePickerControllerSourceTypePhotoLibrary; //图片库
//sourceType = UIImagePickerControllerSourceTypeSavedPhotosAlbum; //保存的相片
UIImagePickerController *picker = [[UIImagePickerController alloc] init];//初始化
picker.delegate = self;
picker.allowsEditing = YES;//设置可编辑
picker.sourceType = sourceType;
[self presentModalViewController:picker animated:YES];//进入照相界面
[picker release];

看一下UIImagePickerControllerDelegate结构的声明

@protocol UIImagePickerControllerDelegate<NSObject>
@optional
// The picker does not dismiss itself; the client dismisses it in these callbacks.
// The delegate will receive one or the other, but not both, depending whether the user
// confirms or cancels.
- (void)imagePickerController:(UIImagePickerController *)picker didFinishPickingImage:(UIImage *)image editingInfo:(NSDictionary *)editingInfo NS_DEPRECATED_IOS(2_0, 3_0);
- (void)imagePickerController:(UIImagePickerController *)picker didFinishPickingMediaWithInfo:(NSDictionary *)info;
- (void)imagePickerControllerDidCancel:(UIImagePickerController *)picker;

@end

其中

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

便是我们拍照完成之后的一个通知，其中的info携带了有关图片的一些信息，下面代码便是从这个info中抽取有用的信息得到我们需要的图像对应的ALAsset对象指针，

- (void)saveImageToPhotos:(UIImage*)savedImage
{
if(nil == _library)
_library = [[ALAssetsLibrary alloc] init];
__weak __typeof__(self) weakSelf = self;
[_library writeImageToSavedPhotosAlbum:[savedImage CGImage] orientation:(ALAssetOrientation)[savedImage imageOrientation] completionBlock:^(NSURL *assetURL, NSError *error){
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_BACKGROUND, 0),^{
[weakSelf.library assetForURL:assetURL resultBlock:^(ALAsset *asset){//这里的asset便是我们所需要的图像对应的ALAsset了
dispatch_async(dispatch_get_main_queue(),^{
//以下代码纯属个人业务代码，可以不需要关心
NSMutableDictionary *mediaInfo = [[NSMutableDictionary alloc] init];
NSMutableArray* assets = [NSMutableArray array];
[assets addObject:asset];
[mediaInfo setObject:assets forKey:kMultiMediaData];
[mediaInfo setObject:[NSNumber numberWithInt:EFilterTypePhotos
] forKey:kMultiMediaFilter];

if (self.mediaReViewViewController) {
[self.mediaReViewViewController addPhotoInfo:mediaInfo];
}

[[YYViewControllerCenter currentVisiableRootViewController] dismissViewControllerAnimated:NO completion:^{}];
});
}failureBlock:^(NSError *error) {
//                [[YYViewControllerCenter currentVisiableRootViewController] dismissViewControllerAnimated:NO completion:^{}];
}];
});
}];
}

上面assetForURL消息中的resultBlock函数块参数便是回调回来的ALAsset对象指针了。