How to solve the problem that Android Studio cannot execute the main method of Java class

环境

android studio版本：3.6.1
gradle版本：5.6.4
gradle插件版本：3.6.1

错误提示

11:41:35 PM: Executing task 'TxtUtil.main()'...

Executing tasks: [TxtUtil.main()] in project /Users/tinytongtong/Documents/workspace/as/self/BlogDemo

FAILURE: Build failed with an exception.

* Where:
Initialization script '/private/var/folders/qw/8_p1t59142d0xntgn799rt1c0000gn/T/TxtUtil_main__.gradle' line: 20

* What went wrong:
A problem occurred configuring project ':app'.
> Could not create task ':app:TxtUtil.main()'.
   > SourceSet with name 'main' not found.

* 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

Deprecated Gradle features were used in this build, making it incompatible with Gradle 6.0.
Use '--warning-mode all' to show the individual deprecation warnings.
See https://docs.gradle.org/5.6.4/userguide/command_line_interface.html#sec:command_line_warnings

BUILD FAILED in 207ms
11:41:35 PM: Task execution finished 'TxtUtil.main()'.

解决方案：

方案一：暂时的替代方案

Run "XXX.main()" with Coverage

方案二：修改.idea/gradle.xml文件

Android Studio使用gradle作为构建工具，所以归根到底还是gradle配置的问题。我先找一个没问题的项目，再打开新创建的项目，对比着看他们的gradle配置。经过对比和尝试，发现.idea/gradle.xml文件内部不同，并且参照老项目进行修改是有效的。

老项目的.idea/gradle.xml：

<?xml version="1.0" encoding="UTF-8"?>
<project version="4">
 <component name="GradleMigrationSettings" migrationVersion="1" />
 <component name="GradleSettings">
 <option name="linkedExternalProjectsSettings">
 <GradleProjectSettings>
 <option name="delegatedBuild" value="false" />
 <option name="testRunner" value="PLATFORM" />
 <option name="distributionType" value="DEFAULT_WRAPPED" />
 <option name="externalProjectPath" value="$PROJECT_DIR$" />
 <option name="modules">
  <set>
  <option value="$PROJECT_DIR$" />
  <option value="$PROJECT_DIR$/app" />
  ...
  </set>
 </option>
 <option name="resolveModulePerSourceSet" value="false" />
 </GradleProjectSettings>
 </option>
 </component>
</project>

新项目的.idea/gradle.xml:

<?xml version="1.0" encoding="UTF-8"?>
<project version="4">
 <component name="GradleMigrationSettings" migrationVersion="1" />
 <component name="GradleSettings">
 <option name="linkedExternalProjectsSettings">
 <GradleProjectSettings>
 <option name="testRunner" value="PLATFORM" />
 <option name="distributionType" value="DEFAULT_WRAPPED" />
 <option name="externalProjectPath" value="$PROJECT_DIR$" />
 <option name="modules">
  <set>
  <option value="$PROJECT_DIR$" />
  <option value="$PROJECT_DIR$/app" />
  </set>
 </option>
 <option name="resolveModulePerSourceSet" value="false" />
 </GradleProjectSettings>
 </option>
 </component>
</project>

经过对比发现，新项目的<GradleProjectSettings>标签下少了<option name="delegatedBuild" value="false" />这行配置，然后给新项目添加这行配置，运行代码发现成功了。

根据配置的字面意思理解，这个设置的意思是不委托gradle进行构建。现实效果也是加了这行配置之后就是jvm执行Java类的main方法了，而不是gradle当做task来执行了。

知识点补充，参考方法

Android Studio 3.0 无法运行Java代码main() 方法的解决方案

Android Studio 升级到3.0 以后发现 运行Java 代码中的main()方法的时候grandle 就会报错的问题

解决方法 :

打开工程目录下的下图标注的文件:

打开文件后 在文件中添加

android.enableAapt2=false<br>

最后同步一下 OK!

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