“无法解析符号R”在Android Studio

In every instance in all of my classes where I reference R.id.something, the R is in red and it says "cannot resolve symbol R". Also every time there is R.layout.something it is underlined in red and says "cannot resolve method setContentView(?)". The project always builds fine. It is annoying to see this all the time. I have read many other questions on here about something similar but most involved importing projects from Eclipse. I am using what I believe to be the most recent version of Android Studio and the project was created with Android Studio and worked without any "cannot resolve R" problems. I would like to know what causes this if anyone knows.

当前回答

以上答案都不能解决我的问题。所以我添加了我的解决方案，以防有人遇到类似的问题。在我的构建中。我有gradle依赖，

compile 'com.android.support:appcompat-v7:22+'

我的compilesdk版本是编译esdkversion 21，所以android工作室不高兴。我简单地更新了我的compilesdkversion到23，并进行了同步。

我还将依赖项更新为

compile 'com.android.support:appcompat-v7:23.1.1'

匹配我的支持库在工具—> Android—> SDK管理器—> SDK工具选项卡—> Android支持库—>版本。现在一切都好了。快乐编码:)

2015-12-18 09:23:43

其他回答

同样的问题。当我在我的可绘制文件夹中添加了一些图像并试图访问它们时开始。此外，添加的图像有大写字母的扩展名。这似乎使构建崩溃，因为即使我重命名它们，消息也是一样的，R是不可访问的。我所做的是，在.iml文件中，我寻找了excludeFolder并删除了它们(如下图所示):

  <excludeFolder url="file://$MODULE_DIR$/build/apk" />
  <excludeFolder url="file://$MODULE_DIR$/build/assets" />
  <excludeFolder url="file://$MODULE_DIR$/build/bundles" />
  <excludeFolder url="file://$MODULE_DIR$/build/classes" />
  <excludeFolder url="file://$MODULE_DIR$/build/dependency-cache" />
  <excludeFolder url="file://$MODULE_DIR$/build/incremental" />
  <excludeFolder url="file://$MODULE_DIR$/build/libs" />
  <excludeFolder url="file://$MODULE_DIR$/build/manifests" />
  <excludeFolder url="file://$MODULE_DIR$/build/res" />
  <excludeFolder url="file://$MODULE_DIR$/build/symbols" />
  <excludeFolder url="file://$MODULE_DIR$/build/tmp" />

在那之后，我重建了项目，R神奇地重新出现了。

2014-03-21 10:07:13

考虑以下IDE功能:

用gradle文件同步项目 Build ->清洁项目 Build ->重建项目 File ->使缓存失效

我的简单解决方案是:

Check that there is no error line in the dependencies of the build.gradle of the app or in all the resource files in the /res directory; where some common errors are when the attribute values are left without references when using: "@string/.." "@style/.." Make sure you are not getting an error of the type Android resource linking failed when the project is rebuilt. Open the file that contains the line with the error Cannot resolve symbol 'R' Scrolling to the last line of the class with said error line Click on a position to the right of the closing key } of the class

通过这种方式，IDE警告对话框将执行r类的导入。

2018-11-14 00:04:42

看看Gradle控制台。在我的例子中，我包含了一个文件扩展名错误的资源。

AAPT: libpng error: Not a PNG file
:app:mergeDebugResources FAILED

FAILURE: Build failed with an exception.

在重命名文件和同步项目与Gradle文件之后，一切都很好。

2017-06-12 11:27:43

//有时由于不完全同步会产生问题

//所以只要按照步骤，它会做你的工作肯定

Click on Build->Clean Project and that will perform a gradle clean

2017-05-20 06:20:54

我正面临一个错误“无法解析符号R” java文件中的R显示为红色。我已经解出来了。

不保存任何大写字母的图像像ABC.png。首先删除映像或重命名它。清洁项目重建项目

2018-09-27 11:34:59

“无法解析符号R”在Android Studio

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