SwiftUI 打印视图

Question

我有一个使用 UIKit 和 Objective C 的旧 iOS 应用程序，我目前正在将其移植到 SwiftUI 和 Swift。一切都很顺利，我喜欢 Swift 和 SwiftUI。该应用程序几乎完成了，但该应用程序依赖于用户能够打印和/或将主视图保存为 PDF。我只是不知道如何在 swiftui 中访问视图以将其转换为 PDF。这是我现有/工作的 Objective-c 代码。

- (IBAction)actionPrint:(id)sender {
    // CREATE CLEAR BACKGROUND
    [legMain setBackgroundColor:[UIColor clearColor]];

    // SCROLL TO BASE POSITION
    [legMain scrollRectToVisible:CGRectMake(1, 1, 1, 1) animated:NO];

    // RESET ZOOM
    SnapPanel *myObject = [self fGetObject];
    myObject.zoom = [NSNumber numberWithDouble:1.0];
    [self fSave];

    // RECORD FRAME SIZE AND SET TO CONTENT SIZE
    double dWidth = legMain.frame.size.width;
    double dHeight = legMain.frame.size.height;
    [legMain setFrame:CGRectMake(legMain.frame.origin.x, legMain.frame.origin.y, legMain.contentSize.width, legMain.contentSize.height)];

    // GET VIEW AS NSDATA FOR PDF
    NSMutableData *pdfData = [NSMutableData data];
    CGRect pageSize = CGRectMake(0.0, 0.0, 8.5 * 72.0, 11.0 * 72.0);
    UIGraphicsBeginPDFContextToData(pdfData, pageSize, nil);
    CGContextRef pdfContext = UIGraphicsGetCurrentContext();

    // CREATE A SINGLE PAGE PDF
    UIGraphicsBeginPDFPage();
    [legMain.layer renderInContext:pdfContext];
    UIGraphicsEndPDFContext();

    // CREATE PRINT CONTROLLER
    UIPrintInteractionController *pc = [UIPrintInteractionController sharedPrintController];
    void (^completionHandler)(UIPrintInteractionController *, BOOL, NSError *) =
    ^(UIPrintInteractionController *pic, BOOL completed, NSError *error) {
        if (!completed && error){
            NSLog(@"Print error: %@", error);
        }
    };

    // SETUP PRINT CONTROLLER
    [pc setShowsNumberOfCopies:YES];
    [pc setShowsPageRange:YES];
    [pc setShowsPaperSelectionForLoadedPapers:YES];
    pc.printingItem = pdfData;

    // DISPLAY CONTROLLER DIALOG
    if (UI_USER_INTERFACE_IDIOM() == UIUserInterfaceIdiomPad) {
        [pc presentFromRect:texName.frame inView:viewMain.superview
                   animated:YES completionHandler:completionHandler];
    } else {
        [pc presentAnimated:YES completionHandler:completionHandler];
    }

    // RESET BACKGROUND COLOUR AND FRAME SIZE
    [legMain setBackgroundColor:[UIColor colorWithRed:.95 green:.95 blue:.95 alpha:1.0]];
    [legMain setFrame:CGRectMake(legMain.frame.origin.x, legMain.frame.origin.y, dWidth, dHeight)];
}

legMain 是我正在调整并最终转换为 PDF 的视图。我已经设法移植了大部分代码，直到我到达需要渲染视图的第 26 行。我什至不知道从哪里开始获取我的视图实例。

Answer 1

按照How to access own window within SwiftUI view? 中的描述访问托管窗口，您可以从任何 SwiftUI 视图中获取主要的UIView

let mainView = hostingWindow?.rootViewController.view

但对于打印，我可能会使用如下专用视图（以避免影响 UI 视图）

if let hostingController = hostingWindow?.rootController as UIHostingController {
    let printingView = UIHostingController(rootView: hostingController.rootView).view

    // ... do anything with printingView here, because it will have 
    //     a copy of SwiftUI rootView
}

更新：评论中的详细信息（在这种情况下不需要托管窗口）

VStack {
   PrintableView(arg: value) // << need to be made undependable, so all 
                             // parameters should be passed via arguments
}

然后在打印动作上可能是这样的

Button("Print") {
   let printingView = UIHostingController(rootView: PrintableView(arg: value)).view
   // do anything printing related with `printingView` here
}