无法解析符号 R。[尝试了所有提到的解决方案]

Question

I am making an Android app. Due to some reasons, my current project files got all messed up. To solve this issue I created a new project in Android Studio and copied the files from the previous project to this new project.

I carefully copied all the layout, values, java files at their right location. I replaced the relavant content from the new manifest and gradle files with new content.

Everything looked perfect and then I got the "Cannot resolve symbol R" error.

I tried all the solutions like Invalidate Cache/Restart, Sync files with gradle, Rebuild Project, Clean Project etc. etc. etc.

Still couldn't fix it.

Can someone help?

Edit

Problem Details 1. I have correct package name everywhere (in AndroidManifest too) 2. I have proper and valid xml files 3. Even if I copied the files from other project the I've kept the project name and package names exactly the same. 4. I have only one app module.

Answer 1

尝试从每个 java 类中删除 .R 行。

Answer 2

You might have an error in one of your xml files, like a duplicated xml header. Check for every single one.

You can also update Android Studio as it now tells you the file and location of the error.

Answer 3

I strongly suggest you copy and paste your codes to individual right places if you want to move these to a new project. Copying folders and files to a newly created project would not work as there could be some lines that include your old folder paths

For example, your old project was in C://StudioProjects/YourProjectName so your codes should be in C://StudioProjects/YourProjectName/app/src/main/java/com/example/AppName but if you directly copy a file or folder to a newly created project, you could end up referencing the wrong path like C://StudioProjects/YourProjectName/app/src/main/java/com/example/NewAppName and this could blow your XML file which will lead to R cannot resolve symbol R.

Even though you put your folders in the same path, reference numbers changed in the new project.