这可能是因为Android Studio的实例不止一个。

这些答案我都试过了，包括杀死java进程，在HOME_DIR和project dir中删除.gradle，重启Android Studio，甚至重启OS。

它开始正常工作后，我启动gradle同步。

Windows机器:

打开任务管理器(按Ctrl-Alt-Delete并检查进程)

如果你运行两个android studio实例，关闭一个(结束任务)

->关闭“OpenJDK Platform Binary”

-> Gradle同步现在AndroidStudio和它将工作

非常简单的解决方案:

不需要杀死Android Studio，只需杀死OpenJdkPlatform进程， 然后删除下面的.lock文件:

rootProject/.gradle/<version>/taskHistory

在我的案例中，罪魁祸首是限制性防火墙，反病毒系统的一部分。

根据https://discuss.gradle.org/t/timeout-waiting-to-lock-file-hash-cache/21961/2和https://github.com/elastic/elasticsearch/issues/50954#issuecomment-576772154, gradle-issue-8750, gradle服务器正在保留锁，并在其他gradle进程请求时释放它。通信通过本地主机上的UDP套接字进行。因此，如果有防火墙阻止这种通信，gradle保持文件锁和其他gradle进程不能继续。

尝试禁用AV /防火墙，看看问题是否消失。然后运行gradle，如下所示，以更好地了解发生了什么。

gradle --debug --no-daemon

调试日志显示锁的所有者，如果问题仍然存在，杀死锁的所有者。

2021-05-20T19:32:41.105+0200 [DEBUG] [org.gradle.cache.internal.DefaultFileLockManager] The file lock is held by a different Gradle process (pid: 67494, lockId: 628651820260732672). Pinged owner at port 58442
2021-05-20T19:32:42.330+0200 [DEBUG] [org.gradle.cache.internal.DefaultFileLockManager] The file lock is held by a different Gradle process (pid: 67494, lockId: 628651820260732672). Pinged owner at port 58442

然后kill -9 67494终止所有者并释放锁。

否则，一段时间后gradle会终止，并报错(在这里说明，这样很容易找到):

* What went wrong:
Gradle could not start your build.
 > Could not create service of type ResourceSnapshotterCacheService using GradleUserHomeServices.createResourceSnapshotterCacheService().
   > Timeout waiting to lock file hash cache (/Users/myusername/.gradle/caches/6.9/fileHashes). It is currently in use by another Gradle instance.
     Owner PID: 67494
     Our PID: 68313
     Owner Operation: 
     Our operation: 
     Lock file: /Users/myusername/.gradle/caches/6.9/fileHashes/fileHashes.lock

在@Sean Stayns的回答中引用了一个场景，以防它能帮助到任何人:如果你把你的项目保存在谷歌Drive文件夹中——不要这样做。只需将项目移动到本地驱动器即可解决此问题。

In the case we were trying to solve, were were also getting the "It is currently in use by another Gradle instance" error and nothing we tried here worked. The process ID was unknown as well. It didn't immediately occur to me to ask where the project was being saved, so in case anyone new to Android Dev is saving their projects to a Google Drive folder, just move over to your local drive. I would have just left this as a comment in @Sean Stayns's answer, but I can't comment. Hopefully it benefits someone.