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
在最新版本的Android Studio中,至少对我来说,如下作品:
“工具”->“Android”->“同步项目与Gradle文件”
在最新的Android Studio 3.1.3(2018年7月)中,“同步项目与Gradle文件”在主菜单栏中可用。
其他回答
最近,当我更新一个项目的很多库时,我就遇到了这种情况。没有找到R,但是我可以很好地构建和运行项目。它没有崩溃。IDE只是在所有地方显示红色。
我试过
Check for damaged/improper XMLs and images, none found Check for invalid resource file names (e.g. capitalized), none found Downgrade some libraries because maybe it was a resource conflict, not resolved Lowered compileSdkVersion and targetSdkVersion because, in the past, I encountered resource issues due to this. In this project however, that was not the case. Clean, didn't help Rebuild project, didn't help Invalidate caches/Restart multiple times, didn't help Adjusted idea.max.intellisense.filesize to a very high value, didn't help Did a Lint run, no errors found
最后,我发现降级我的Gradle构建工具(从3.3.1到3.2.1)解决了这个问题。这是我唯一要做的改变。其余内容已更新。现在,我所有的库都更新了,没有问题。
buildscript {
repositories {
google()
jcenter()
}
dependencies {
//classpath 'com.android.tools.build:gradle:3.3.1'
classpath 'com.android.tools.build:gradle:3.2.1'
classpath 'com.google.gms:google-services:4.2.0'
// NOTE: Do not place your application dependencies here; they belong
// in the individual module build.gradle files
}
}
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。
GL
对我来说,问题是我升级到一个似乎有一些bug的Gradle版本。3.4.0-alpha02是我更新到的,发现这是“无法解析符号R”错误的罪魁祸首。我恢复到3.3.0-alpha10(即类路径'com.android.tools.build:gradle:3.3.0-alpha10'),它解决了这个问题。
这显然不是一个持久的解决方案,因为我迟早需要升级,但截至2018年11月3日,3.4.0-alpha02是最新版本,它阻碍了我的开发,因为它不允许我通过单击R引用在IDE中跳跃。
我今天升级了gradle版本和gradle插件版本的最新版本,它为我工作。
之后,同步项目与gradle文件。
对我来说,重要的是说Android Studio在一开始就会给学习带来麻烦,但就像这里有解决方案清洁项目可以解决这个问题,总是检查包装的名称,不要试图混乱的逻辑,我喜欢软件,但有时我试着思考如果方式是正确的或不正确,我也喜欢Linux,但对我来说,Android Studio重写所有软件也许这不会发生。总之,祝你好运!!!!
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