Scala项目不会在Eclipse中编译; “找不到主类”。 [英] Scala project won't compile in Eclipse; "Could not find the main class."

问题描述

我已经从/ update-current（这是Scala 2.8 final）安装了Eclipse 3.5.2和今天的Scala插件。我可以编译和运行由实现main（）的单个单例对象组成的Scala项目。

但是，如果一个项目包含更多的类，我收到找不到主类错误。

我已经尝试搜索解决方案，我发现：

Eclipse正在寻找Main $类，而不是Main类

*在调试配置下，我的主要类被正确地标识为mypackage.Main

*我的插件是最新的，推荐我的Eclipse版本

*清理，重启等等帮助。

同样的项目将使用scalac进行编译。

感谢任何有关如何解决这个问题的想法。 p>

编辑：MatthieuF建议我应该发布代码。

此代码段会产生错误。这不是最惯用的代码，但是我用这种方法来测试我的环境。我试过它作为单个文件和单独的文件。它可以与scalac一起工作。

  import swing._ 
 
 class HelloFrame extends Frame {
 title =First program
 contents = new Label（Hello，world！）
} 
 
对象Hello {
 val frame = new HelloFrame 
 def main（args：Array [String]）：Unit = {
 frame.visible = true 
} 
} 
  

但是，如果我在Hello中嵌套HelloFrame的定义，它可以工作。这个代码段完美运行：

  import swing._ 
 
对象你好{
 
 class HelloFrame extends Frame {
 title =First program
 contents = new Label（Hello，world！）
} 
 
 val frame = new HelloFrame 
 
 def main（args：Array [String]）：Unit = {
 frame.visible = true 
} 
} 
  

解决方案

对我来说，问题是有一个构建错误（见问题选项卡）防止编译;哎呀！您看到错误的原因是，尽管编译失败步骤，运行宏仍在继续，并尝试运行它期望的类文件;它们不存在，因为存在构建错误阻止编译，所以它说它找不到Main（没有编译）。

构建完成时问题消失成功地，即错误是固定的。

我猜，理论上来说，您的构建可能还没有成功完成，没有列在问题中。

I have installed Eclipse 3.5.2 and today's Scala plugin from /update-current (that's Scala 2.8 final.) I can compile and run Scala projects consisting of a single singleton object that implements main().

But, if a project contains more classes, I receive the "Could not find the main class" error.

I have tried searching for the solution and I discovered:

Eclipse is correctly looking for the Main$ class, not the Main class
* under Debug Configurations, my main class is correctly identified as mypackage.Main
* my plugin is up to date and recommended for my version of Eclipse
* cleaning, restarting etc. doesn't help.

The same project will compile with scalac.

Thanks for any ideas on how to solve this.

EDIT: MatthieuF suggested I should post the code.

This snippet produces an error. It's not the most idiomatic code, but I wrote it that way to test my environment. I tried it as a single file and as separate files. It DOES work with scalac.

import swing._

class HelloFrame extends Frame {
        title = "First program"
        contents = new Label("Hello, world!")
}

object Hello {
  val frame = new HelloFrame    
  def main(args : Array[String]) : Unit = {
        frame.visible = true
   }
}

BUT, if I nest the definition of HelloFrame within Hello, it works. This snippet runs perfectly:

import swing._

object Hello {

    class HelloFrame extends Frame {
        title = "First program"
        contents = new Label("Hello, world!")
    }

    val frame = new HelloFrame

    def main(args : Array[String]) : Unit = {
        frame.visible = true
    }
}

解决方案

For me, the problem was that there was a build error (see Problems tab) which was preventing compilation; oops! The reason you see the error is that the run macro proceeds despite the failed compilation step, and attempts to run class files it expects to be there; they don't exist because there was a build error preventing compilation, so it says it can't find Main (not compiled).

Problem goes away when build can complete successfully, i.e. errors are fixed.

I guess, theoretically, there may be more complicated reasons your build is not completing successfully that are not listed in Problems.

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