Flutter旧项目执行flutter run报错：java.lang.NullPointerException

问题详情 #

运行旧Flutter项目时，执行flutter run命令构建失败，抛出java.lang.NullPointerException且无额外错误信息。

flutter run报错日志 #

FAILURE: Build failed with an exception.

* Where:
Build file 'C:\Users\AbdoulayeB\OneDrive\Bureau\flutter\jellyflut\android\app\build.gradle' line: 30

* What went wrong:
A problem occurred evaluating project ':app'.
> java.lang.NullPointerException (no error message)

* 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 1m 13s
Running Gradle task 'assembleDebug'...                             74,6s
Error: Gradle task assembleDebug failed with exit code 1

执行./gradlew --info后的日志 #

> Configure project :app
Evaluating project ':app' using build file 'C:\Users\AbdoulayeB\OneDrive\Bureau\flutter\jellyflut\android\app\build.gradle'.
Using Kotlin Gradle Plugin gradle70 variant
Caching disabled for Kotlin DSL script compilation (Project/ScriptPlugin/stage1) because:
  Build cache is disabled
Skipping Kotlin DSL script compilation (Project/ScriptPlugin/stage1) as it is up-to-date.
Could not execute [class org.jetbrains.kotlin.gradle.plugin.statistics.KotlinBuildStatHandler.buildFinished]

FAILURE: Build failed with an exception.

* Where:
Build file 'C:\Users\AbdoulayeB\OneDrive\Bureau\flutter\jellyflut\android\app\build.gradle' line: 30

* What went wrong:
A problem occurred evaluating project ':app'.
> java.lang.NullPointerException (no error message)

* Try:
> Run with --stacktrace option to get the stack trace.
> Run with --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 15s
4 actionable tasks: 2 executed, 2 up-to-date
Watched directory hierarchies: [C:\dev_mobile\flutter\packages\flutter_tools\gradle]

解决建议 #

• 检查android/app/build.gradle第30行代码：空指针通常是引用了未初始化的变量或空对象调用方法，比如读取不存在的属性、插件配置里的空参数，确认该行代码的逻辑是否存在空引用问题。
• 升级Gradle与Kotlin版本：旧项目的Gradle或Kotlin插件版本可能和当前Flutter版本不兼容，尝试更新android/gradle/wrapper/gradle-wrapper.properties中的distributionUrl到稳定版本（如https\://services.gradle.org/distributions/gradle-7.5-bin.zip），同时更新android/build.gradle中buildscript的Kotlin版本到匹配Gradle的稳定版（如1.7.20）。
• 清理构建缓存：执行flutter clean，删除android/.gradle、android/app/build目录，再重新运行flutter run。
• 迁移项目路径：项目放在OneDrive目录下可能存在同步锁或权限问题，将项目复制到本地非同步目录（如C:\Users\AbdoulayeB\Documents\flutter\jellyflut）后重新构建。
• 获取详细栈追踪：执行./gradlew assembleDebug --stacktrace，查看完整的空指针调用栈，精准定位异常来源。

内容的提问来源于stack exchange，提问作者Abdoulaye