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Flutter – Why doesnt the StreamBuilder update the PDFView widget?

Im new to flutter and stuck at the following problem, hope someone can help:

I am trying to build an App where the Presenter opens a pdf file and the Viewer can join the Presentation. The viewer gets the PDF file, opens it, and gets constant updates on the currently opened page (from the Presenter).

I set up a firebaseauth, firebase realtime database and firebase storage, authenticating the user throug a login, uploading and downloading the pdf to storage and writing the currentPage into realtime database. This part is working fine.

I am currently stuck for days at my pdf viewer client part, where i wrapped a StreamBuilder around the PDF Widget from the flutter_pdfview package, expecting it to update the Page opened by the widget.The Stream listens to the database entry written from the presenter "page".

body: StreamBuilder(
          stream: _firestore
              .collection('pdfControl')
              .doc(loggedInUser.uid)
              .snapshots(),
          builder: (context, snapshot) {
            if (snapshot.hasData && snapshot.data != null) {
              print(snapshot.data?['page']);
              var page = snapshot.data!['page'];
              currentPage = page;
              print ('currentpage:  $currentPage');
              //_pdfController.setPage(page);

              return PDFView(

I did try to check if i get changes from the realtimedb snapshot.

`if (snapshot.hasData && snapshot.data != null) {
              print(snapshot.data?['page']);`

is working. The Output is 1, 2, 3, 2 etc

But the

`return PDFView(
                  filePath: widget.pdfPath,
                  autoSpacing: true,
                  enableSwipe: true,
                  pageSnap: true,
                  swipeHorizontal: true,
                  defaultPage: currentPage!,
                  onError: (error) {
                    print(error);
                  },
                  onPageError: (page, error) {
                    print('$page: ${error.toString()}');
                  },
                  onRender: (_pages) {
                    setState(() {
                      pages = _pages!;
                      isReady = true;
                      print ('currpage:  $currentPage');
                    });
                  },
                  onViewCreated: (PDFViewController vc)  {
                    setState(() {
                      _pdfController = vc;
                      _controller.complete(vc);
                      vc.setPage(currentPage);
                      print(page);
                      print(snapshot.data?['page']);
                    });

                  },
                  onPageChanged: (int? page, int? total) {
                    setState(() {
                      currentPage = page!;
                    });

                  });`

It is not swaping the page. when the snapshot.data?[‘page’] gets an update.

Why?

I thought the StreamBuilder would listen on the

stream: _firestore
              .collection('pdfControl')
              .doc(loggedInUser.uid)
              .snapshots(),

and rebuilds the widgets it is wrapped around on changes in the db collection?

`I/flutter (12485): currentpage:  3
E/FrameEvents(12485): updateAcquireFence: Did not find frame.
E/FrameEvents(12485): updateAcquireFence: Did not find frame.
I/flutter (12485): 3
I/flutter (12485): currentpage:  3
E/FrameEvents(12485): updateAcquireFence: Did not find frame.
I/chatty  (12485): uid=10123(com.example.screenshare_project) RenderThread identical 21 lines
E/FrameEvents(12485): updateAcquireFence: Did not find frame.
I/flutter (12485): 4
I/flutter (12485): currentpage:  4
I/flutter (12485): 4
I/flutter (12485): currentpage:  4
I/flutter (12485): 3
I/flutter (12485): currentpage:  3
I/flutter (12485): 3
I/flutter (12485): currentpage:  3`

this is my output

I really need some help here…can someone please explain this behavior to me? What am i doing wrong?

PS: The setState lines are my desperate attempt for another solution (not working)

Tags:

2

Answers


  1. Chosen as BEST ANSWER
    0

    I was able to solve it with implementing the suggestions from Dhafin Rayhan:

    (StreamBuilder to listener and nullable PDFViewController):

    PDFViewController? _pdfController;

@override
  void initState() {
    super.initState();
    getCurrentUser();

    _firestore
        .collection('pdfControl')
        .doc(loggedInUser.uid)
        .snapshots()
        .listen((snapshot) {
      var page = snapshot.data()?['page'];
      print(page);
      _pdfController?.setPage(page);
    });

@override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Center(
        child: PDFView(
          filePath: widget.pdfPath,
          autoSpacing: true,
          enableSwipe: true,
          pageSnap: true,
          swipeHorizontal: true,
          onError: (error) {
            print(error);
          },
          onPageError: (page, error) {
            print('$page: ${error.toString()}');
          },
          onRender: (page) {
            
          },
          onViewCreated: (PDFViewController vc) {
            _controller.complete(vc);
            _pdfController = vc;
            
          },
          onPageChanged: (int? page, int? total) {
            
          },
        ),
      ),
    );
  }

    Thanks a lot!


  2. 0

    defaultPage is only used at the time the PDF file is loaded, after that it won’t control what page is currently being displayed.

    Use the controller to change the page.

    _pdfController.setPage(page);

    Also you don’t need to wrap PDFView inside a StreamBuilder. Just listen to the stream with the listen method, and call that setPage method in the callback.

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