加載系統圖片庫的實現

首先要實現UIImagePickerControllerDelegate代理

//從系統的圖片庫中添加圖片，會調用他得代理方法
- (IBAction)addPicture:(id)sender {
    imagePicker=[[UIImagePickerController alloc]init];
    imagePicker.sourceType=UIImagePickerControllerSourceTypePhotoLibrary;
    imagePicker.delegate=self;
    imagePicker.allowsEditing=YES;
    [self presentViewController:imagePicker animated:YES completion:nil];
}

- (IBAction)photograph:(id)sender {
    //先設定sourceType爲相機，然後判斷相機是否可用（ipod）沒相機，不可用將sourceType設定爲相片庫
    UIImagePickerControllerSourceType sourceType = UIImagePickerControllerSourceTypeCamera;
    if (![UIImagePickerController isSourceTypeAvailable: UIImagePickerControllerSourceTypeCamera]) {
        sourceType = UIImagePickerControllerSourceTypePhotoLibrary;
    }
    UIImagePickerController *picker = [[UIImagePickerController alloc] init];
    picker.delegate = self;
    picker.allowsEditing = YES;
    picker.sourceType = sourceType;
    [self presentViewController:picker animated:YES completion:nil];
    [picker release];
}

- (void)saveImage:(UIImage *)image {
    self.picImageView.image=image;
}
#pragma mark - UIImagePickerControllerDelegate
- (void)imagePickerController:(UIImagePickerController *)picker didFinishPickingMediaWithInfo:(NSDictionary *)info
{
    [picker dismissViewControllerAnimated:YES completion:nil];
    UIImage *image1 = [[info objectForKey:UIImagePickerControllerEditedImage]retain];
    [self performSelector:@selector(saveImage:)
               withObject:image1
               afterDelay:0.5];
    NSURL *imageURL = [info valueForKey:UIImagePickerControllerReferenceURL];
    ALAssetsLibraryAssetForURLResultBlock resultblock = ^(ALAsset *myasset)
    {
        ALAssetRepresentation *representation = [myasset defaultRepresentation];
        self.imageName = [representation filename];
    };
    ALAssetsLibrary* assetslibrary = [[[ALAssetsLibrary alloc] init] autorelease];
    [assetslibrary assetForURL:imageURL
                   resultBlock:resultblock
                  failureBlock:nil];
}

- (void)imagePickerControllerDidCancel:(UIImagePickerController *)picker
{
    [picker dismissViewControllerAnimated:YES completion:nil];
}