我正在尝试在Android Studio中生成一个已签名的应用程序，但收到以下错误。.idea 文件夹缺少模块.xml文件，但在我看来，这应该由 Android Studio 自动生成。我是 Android Studio 的新手，为什么缺少 .idea/modules.xml 文件？我该如何生成它？
Internal error: (java.io.FileNotFoundException) /home/will/git/mtdapp/.idea/modules.xml (No such file or directory)
java.io.FileNotFoundException: /home/will/git/mtdapp/.idea/modules.xml (No such file or directory)
at java.io.FileInputStream.open(Native Method)
at java.io.FileInputStream.<init>(FileInputStream.java:140)
at com.intellij.openapi.util.JDOMUtil.loadDocument(JDOMUtil.java:340)
at org.jetbrains.jps.model.serialization.JpsLoaderBase.loadRootElement(JpsLoaderBase.java:69)
at org.jetbrains.jps.model.serialization.JpsLoaderBase.loadRootElement(JpsLoaderBase.java:40)
at org.jetbrains.jps.model.serialization.JpsProjectLoader.loadFromDirectory(JpsProjectLoader.java:123)
at org.jetbrains.jps.model.serialization.JpsProjectLoader.loadProject(JpsProjectLoader.java:99)
at org.jetbrains.jps.model.serialization.impl.JpsSerializationManagerImpl.loadModel(JpsSerializationManagerImpl.java:41)
at org.jetbrains.jps.cmdline.JpsModelLoaderImpl.loadModel(JpsModelLoaderImpl.java:45)
at org.jetbrains.jps.cmdline.BuildRunner.load(BuildRunner.java:71)
at org.jetbrains.jps.cmdline.BuildSession.runBuild(BuildSession.java:198)
at org.jetbrains.jps.cmdline.BuildSession.run(BuildSession.java:113)
at org.jetbrains.jps.cmdline.BuildMain$MyMessageHandler$1.run(BuildMain.java:133)
at org.jetbrains.jps.service.impl.SharedThreadPoolImpl$1.run(SharedThreadPoolImpl.java:41)
at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:471)
at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:334)
at java.util.concurrent.FutureTask.run(FutureTask.java:166)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1146)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
at java.lang.Thread.run(Thread.java:701)
关闭 Android Studio，删除 .iml 和 .idea 目录，然后重新导入项目。