objective-c - QLPreviewController 仅显示单个文件

Question

我正在使用 QLPreviewController 来显示一组文件。但是，它只显示第一个，我似乎无法滑动或执行任何操作来显示第二个。我究竟做错了什么？我必须手动设置吗？如果是这样 - 我将如何去做？

这是来 self 的 AppDelegate.m:

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
    // normal viewcontroller init here 

    [self showPreview] ;

    return YES;
}

NSArray* documents ;
QLPreviewController* preview ;

- (void) showPreview
{
    documents = [[NSArray alloc] initWithObjects: @"photo" , @"photo2" , nil ] ;

    preview = [[QLPreviewController alloc] init];
    preview.dataSource = self;
    preview.delegate = self;

    preview.view.frame = [[UIScreen mainScreen] bounds];
    //save a reference to the preview controller in an ivar
    //  self.previewController = preview;
    //refresh the preview controller
    [preview reloadData];
    [[preview view] setNeedsLayout];
    [[preview view] setNeedsDisplay];
    [preview refreshCurrentPreviewItem];
    preview.view.userInteractionEnabled = YES;

    //add it  
    [self.viewController.view addSubview:preview.view];
}

我还在同一个 AppDelegate.m 文件中声明了两个回调函数:

- (id <QLPreviewItem>) previewController: (QLPreviewController *) controller previewItemAtIndex: (NSInteger) index
{
    NSString* filename = [documents objectAtIndex:index] ;      //  @"photo" ; 
    NSURL* returnURL = [NSURL fileURLWithPath:[[NSBundle mainBundle] pathForResource: filename ofType:@"jpg" ]] ;

    return returnURL ;
}

- (NSInteger) numberOfPreviewItemsInPreviewController: (QLPreviewController *) controller
{
    return [documents count];
}

Answer 1

您的显示方式有误。QLPreviewController 是一个 UIViewController，这意味着您基本上有两种显示它的方式:

1. 将其插入您的 UINavigationController。
2. 以模态方式显示它(可以使用或不使用 UINavigationController 来完成 - 取决于您是否需要导航栏)。

如果您选择选项 2，您将获得“免费”导航箭头以在项目之间切换。对于选项 1，您需要自己创建箭头。

以下内容摘自 QLPreviewController文档:

If there is more than one item in the list, a modally-presented (that is, full-screen) controller displays navigation arrows to let the user switch among the items. For a Quick Look preview controller pushed using a navigation controller, you can provide buttons in the navigation bar for moving through the navigation list.