# Chapter 2 flutter apprentice book error **URL:** \ **Category:** Flutter\ **Tags:** android, flutter\ **Created:** [December 11, 2023, 4:04pm UTC](https://forums.kodeco.com/t/chapter-2-flutter-apprentice-book-error/200375 "2023-12-11T16:04:10Z")\ **Posts on this page:** 2\ **Page:** 1
**Author:** ![prosper005](https://s3.amazonaws.com/cdn.raywenderlich.com/community/forum-assets/noun-game-ghost-878668.png) [@prosper005](https://forums.kodeco.com/u/prosper005)\ **Post date:** [December 11, 2023, 4:04pm UTC](https://forums.kodeco.com/t/chapter-2-flutter-apprentice-book-error/200375/1 "2023-12-11T16:04:11Z")
I’m encountering an issue while building my Flutter application. When attempting to build the project, I’m getting the following warnings: warning: [options] source value 8 is obsolete and will be removed in a future release warning: [options] target value 8 is obsolete and will be removed in a future release warning: [options] To suppress warnings about obsolete options, use -Xlint:-options. 3 warnings But more importantly, an error is preventing a successful build: ERROR:E:\NewApp\third\_app\build\path\_provider\_android\intermediates\runtime\_library\_classes\_jar\debug\classes.jar: D8: java.lang.NullPointerException: Cannot invoke “String.length()” because “” is null This error seems to be related to path\_provider\_android and occurs during the ‘:app:mergeDexDebug’ task. I’m using Flutter with a specific version of the Android Gradle Plugin (7.3.0). Do you have any suggestions on how to resolve this error and get the project to compile successfully? Thank you in advance for your assistance. > Blockquote ---
**Author:** ![robertomachorro](https://assets.chunter.kodeco.com/user_avatar/forums.kodeco.com/robertomachorro/32/111603_2.png) [@robertomachorro](https://forums.kodeco.com/u/robertomachorro)\ **Post date:** [December 13, 2023, 12:39am UTC](https://forums.kodeco.com/t/chapter-2-flutter-apprentice-book-error/200375/2 "2023-12-13T00:39:29Z")
It’s recommended you post questions on the official Forum topic for the book. As they are typically monitored by the authors or other folks that have the knowledge and are able to help. Follow the link: [Flutter Apprentice - Kodeco Forums](https://forums.kodeco.com/c/books/flutter-apprentice/68)