iOS 编程：文档预览，更改“完成”按钮

Question

我正在使用 UIDocumentInteractionController 类来预览文档。是否可以将关闭预览的完成按钮更改为另一个按钮？例如，我想设置一个不同的标题：“关闭”而不是“完成”。

Answer 1

我使用 QLPreviewController 而不是 UIDocumentInteractionController，并且能够更改“完成”按钮（QLPreviewController 也由 UIDocumentInteractionController 调用）。呈现 QLPreviewController 后，我发现他的导航控制器作为索引 0 处的子视图控制器，然后我替换了左栏按钮项。使用数据源委托向 QLPreviewController 提供您的 url。

另请参阅此链接

在我的 viewcontroller.h 中：

#import <UIKit/UIKit.h>
#import <QuickLook/QuickLook.h>

@interface MyViewController : UIViewController<QLPreviewControllerDataSource>
{    
    // Video preview
    QLPreviewController *_qlPreviewController;
    NSURL *_currentUrl;
}

在我的 viewcontroller.m 中：

#import "MyViewController.h"

@implementation MyViewController

/*
    ........
*/

-(void)showDocument
{
    _currentUrl = [NSURL fileURLWithPath:@"path to your document here"];
    _qlPreviewController = [[QLPreviewController alloc] init];
    _qlPreviewController.dataSource = self;
    [self presentViewController:_qlPreviewController animated:true completion:^(void){
        if ([self->_qlPreviewController.childViewControllers count] > 0) {
            UINavigationController *nav = (UINavigationController*) self->_qlPreviewController.childViewControllers[0];
            UIBarButtonItem *origDoneButton = nav.navigationBar.items[0].leftBarButtonItem;
            nav.navigationBar.items[0].leftBarButtonItem = [[UIBarButtonItem alloc] initWithTitle:@"MyTitle" style:UIBarButtonItemStyleDone target:origDoneButton.target action:origDoneButton.action];
        }
    }];

}


#pragma mark - QLPreviewControllerDatasource

-(NSInteger)numberOfPreviewItemsInPreviewController:(QLPreviewController *)controller {
    return 1;
}

-(id<QLPreviewItem>)previewController:(QLPreviewController *)controller previewItemAtIndex:(NSInteger)index {
    return _currentUrl;
}


@end

Answer 2

用“完成”按钮更改“完成”按钮 示例：

我读到您可以从最后一个对象获取导航项并更改左侧或右侧按钮。

要更改完成按钮，您需要等待控制器 UIDocumentInteractionController 视图完成显示。遗憾的是没有方法可以知道这一点，但是有：

• (void)documentInteractionControllerWillBeginPreview:(UIDocumentInteractionController *)controller

这会告诉您它何时开始。

我所做的：添加一个计时器，当控制器准备好时，然后获取导航栏项目按钮并将其替换为新按钮。

1) 在 .h 中添加此委托和计时器

.. UIViewController <UIDocumentInteractionControllerDelegate>
@property (nonatomic, strong) NSTimer *timer;

2) 在 .m 中

#import "UIView+BK.h"

- (void)documentInteractionControllerWillBeginPreview:(UIDocumentInteractionController *)controller{
        //Start timer
        _timer = [NSTimer scheduledTimerWithTimeInterval:.05
                                                  target:self
                                                selector:@selector(checkNavigationBar)
                                                userInfo:_timer
                                                 repeats:YES]; //YES TO CYCLE
    }

- (void) checkNavigationBar
    {
        //get the last view open (the UIDocumentInteractionController View)
        UIView *lastWindow = [[[[UIApplication sharedApplication] keyWindow ] subviews] lastObject];

        //Find the controller the view belongs too. 
        UIViewController *controller = [lastWindow findViewController];

        if (controller) {
            //find navigation bar using a category
            UINavigationBar *bar = [controller.view navigationBarFromView];

            //get the navigationItem
            UINavigationItem *item = bar.topItem;

            //get the done button
            UIBarButtonItem *doneButton = item.leftBarButtonItem ;

            //Creates the new button
            UIBarButtonItem *newDoneButton = [[UIBarButtonItem alloc ]
                                            initWithTitle:@"Finished"
                                            style:UIBarButtonItemStylePlain
                                            target:doneButton.target
                                            action:doneButton.action];

            //change done button
            item.leftBarButtonItem = newDoneButton;

            //Stop timer
            [_timer invalidate];
            _timer = nil;
        }
    }

3) 您需要此类别

标头类别：

导入

@interface UIView (BK)

- (UIViewController *)findViewController;

- (UINavigationBar *)navigationBarFromView;
@end

实现类别：

#import "UIView+BK.h"

@implementation UIView (BK)
- (UIViewController *)findViewController {
    Class vcc = [UIViewController class];    // Called here to avoid calling it iteratively unnecessarily.
    UIResponder *responder = self;
    while ((responder = [responder nextResponder])) if ([responder isKindOfClass: vcc]) return (UIViewController *)responder;
    return nil;
}

- (UINavigationBar *)navigationBarFromView {

    for (UIView *subview in self.subviews) {
        if ([subview isKindOfClass:[UINavigationBar  class]]) {
            return (UINavigationBar *)subview;
        }

        UIView *result = [subview navigationBarFromView];
        if (result) {
            return (UINavigationBar *)result;
        }

    }
    return nil;
}
@end