Question

iOS 10现在需要用户的权限才能访问媒体库。我们会在使用之前检查是否可以访问媒体库，如果没有，我们会再次使用[MPMediaLibrary requestAuthorization:向用户请求授权。

我希望这会显示相同的弹出窗口请求来访问我们在应用启动时获得的媒体库，但没有任何反应。它只是返回之前的MPMediaLibraryAuthorizationStatusDenied状态。

docs for requestAuthorization目前还不完整，所以我无法判断我是否只是错误地使用了这个，或者还有其他错误。

    if ( MPMediaLibrary.authorizationStatus == MPMediaLibraryAuthorizationStatusAuthorized)
    {
        // we already have access to the Media Library - use it here...
    }
    else
    {
        // We expect this to show a popup so the user can grant access, but does not work
        [MPMediaLibrary requestAuthorization:^(MPMediaLibraryAuthorizationStatus authorizationStatus)
         {
             if ( authorizationStatus == MPMediaLibraryAuthorizationStatusAuthorized )
             {
                 // success: the user authorized - use it here...
             }
             else
             {
                 // user did not authorize - tell user why here...
             }
         }];
    }

更新

显然无法使原始对话框重新出现（请参阅下面的评论）。我现在使用此代码至少将我带到设置中的正确位置，以便用户可以进行更改。（适用于iOS8及以上版本）

NSURL *url = [NSURL URLWithString:UIApplicationOpenSettingsURLString];
[[UIApplication sharedApplication] openURL:url];

Answer 1

MPMediaLibrary只会自动提示用户一次。如果您在用户授予或拒绝之前要求，则状态为MPMediaLibraryAuthorizationStatusNotDetermined。如果他们之前拒绝访问，您需要将用户发送到系统设置，以便他们可以为您的应用手动启用它。

以下代码就是我们如何做到的。

+ (void) validateMediaLibraryForMinimumIosAndAboveWithViewController:(UIViewController *)viewController
                                                        ifAuthorized:(void(^)())authorizedBlock
                                                     ifNotAuthorized:(void(^)())notAuthorizedBlock
{
    MPMediaLibraryAuthorizationStatus authorizationStatus = MPMediaLibrary.authorizationStatus;

    switch (authorizationStatus)
    {
        case MPMediaLibraryAuthorizationStatusAuthorized:
        {
            // We are already authorized - proceed
            if( authorizedBlock )
            {
                authorizedBlock();
            }
            break;
        }
        case MPMediaLibraryAuthorizationStatusNotDetermined:
        {
            // Not yet authorized - request it from the system
            [MPMediaLibrary requestAuthorization:^(MPMediaLibraryAuthorizationStatus authorizationStatus)
             {
                 if ( authorizationStatus == MPMediaLibraryAuthorizationStatusAuthorized )
                 {
                     if( authorizedBlock )
                     {
                         authorizedBlock();
                     }
                 }
                 else
                 {
                     PLog(@"The Media Library was not authorized by the user");
                     if( notAuthorizedBlock )
                     {
                         notAuthorizedBlock();
                     }
                 }
             }];
            break;
        }

        case MPMediaLibraryAuthorizationStatusRestricted:
        case MPMediaLibraryAuthorizationStatusDenied:
        {
            // user has previously denied access. Ask again with our own alert that is similar to the system alert
            // then take them to the System Settings so they can turn it on for the app
            NSString *titleString  = NSLocalizedStringWithDefaultValue(@"Media Library Privacy Alert Title",
                                                                       @"Localizable",
                                                                       [NSBundle mainBundle],
                                                                       @"Would Like to Access Apple Music And Your Media Library",
                                                                       @"Title for dialog requesting media library access");

            [self displayPermissionAlertFromViewController:viewController
                                                 withTitle:titleString];
            if( notAuthorizedBlock )
            {
                notAuthorizedBlock();
            }
            break;
        }
    }
}

+ (void)displayPermissionAlertFromViewController:(UIViewController *)viewController withTitle:(NSString *)title
{
    NSString* appName = [[NSProcessInfo processInfo] processName];

    NSString *titleString = [NSString stringWithFormat:@"\"%@\" %@",appName, title];

    NSString *cancelString = NSLocalizedStringWithDefaultValue(@"Don't Allow",
                                                               @"Localizable",
                                                               [NSBundle mainBundle],
                                                               @"Don't Allow",
                                                               @"Don't allow button");

    NSString *settingsString = NSLocalizedStringWithDefaultValue( @"Settings",
                                                                 @"Localizable",
                                                                 [NSBundle mainBundle],
                                                                 @"Settings",
                                                                 @"Settings button label");

    UIAlertController *alertController = [UIAlertController
                                          alertControllerWithTitle:titleString
                                          message:nil
                                          preferredStyle:UIAlertControllerStyleAlert];

    [alertController addAction:[UIAlertAction actionWithTitle:cancelString
                                                        style:UIAlertActionStyleDefault
                                                      handler:nil]];

    [alertController addAction:[UIAlertAction actionWithTitle:settingsString
                                                        style:UIAlertActionStyleDefault
                                                      handler:
                                ^(UIAlertAction * _Nonnull action)
                                {
                                    NSURL *url = [NSURL URLWithString:UIApplicationOpenSettingsURLString];
                                    [[UIApplication sharedApplication] openURL:url];
                                }]];

    [viewController presentViewController:alertController animated:true completion:nil];
}

以编程方式请求授权媒体库失败

1 个答案: