title: Flutter Dependency problem with advance_pdf_viewer and firebase_storage
body: <p>Can't able to complie the app when advance_pdf_viewer and firebase_storage package is used.
  At first it works fine but later its version changed and i dont know the exact version which matches.</p>
  <p>Publicspec.yaml file</p>
  <pre><code>  cupertino_icons: ^1.0.3
    flutter_svg: ^0.22.0 # help us to use SVG in our app
    provider: ^5.0.0 # for State management
    getwidget: ^2.0.2
    shared_preferences: ^2.0.5
    firebase_auth: ^1.0.1
    firebase_core: ^1.0.2
    cloud_firestore: ^1.0.3
    firebase_storage: ^8.0.1
    advance_pdf_viewer:
    date_time_picker: ^2.0.0
    file_picker:
    intl: ^0.17.0
    path: ^1.8.0
    http:
  </code></pre>
  <p>Error message</p>
  <pre><code>Running &quot;flutter pub get&quot; in appT...
  Launching lib/main.dart on SDKPhone in debug mode...
  Running Gradle task 'assembleDebug'...
  Picked up _JAVA_OPTIONS: -Dawt.useSystemAAFontSettings=on -Dswing.aatext=true
  ../../flutter/.pub-cache/hosted/pub.dartlang.org/advance_pdf_viewer-2.0.0/lib/src/document.dart:64:14: Error: The class 'File' is abstract and can't be instantiated.
        file = File(&quot;${dir.path}/file.pdf&quot;);
               ^^^^
  ../../flutter/.pub-cache/hosted/pub.dartlang.org/advance_pdf_viewer-2.0.0/lib/src/document.dart:72:26: Error: Non-nullable variable 'file' must be assigned before it can be used.
      document._filePath = file.path;
                           ^^^^
  ../../flutter/.pub-cache/hosted/pub.dartlang.org/advance_pdf_viewer-2.0.0/lib/src/document.dart:75:58: Error: Non-nullable variable 'file' must be assigned before it can be used.
            .invokeMethod('getNumberOfPages', {'filePath': file.path});
                                                           ^^^^
  
  
  FAILURE: Build failed with an exception.
  
  * Where:
  Script '/home/flutter/packages/flutter_tools/gradle/flutter.gradle' line: 1035
  
  * What went wrong:
  Execution failed for task ':app:compileFlutterBuildDebug'.
  &gt; Process 'command '/home/flutter/bin/flutter'' finished with non-zero exit value 1
  
  * Try:
  Run with --stacktrace option to get the stack trace. Run with --info or --debug option to get more log output. Run with --scan to get full insights.
  
  * Get more help at https://help.gradle.org
  
  BUILD FAILED in 48s
  Exception: Gradle task assembleDebug failed with exit code 1
  </code></pre>