Solve "Cannot Resolve Symbol R" Error Message
Solve “Cannot Resolve Symbol R” Error Message

Let’s face it. It’s quite frustrating to find an error in your Android application when testing especially after spending days and probably nights coding. Before testing, you were very sure that everything is ok but here you are; Android Studio is displaying the following error “cannot resolve symbol R.”
When faced with such an error, the majority of coders will probably start scratching their head looking for the source of the problem. Some will begin by removing certain components from the code. Others will try to undo the recent changes made to the code since the last successful test but alas! The problem still persists.

Understanding Cannot Resolve Symbol R Error

This is an error in Android Studio that contains vital data which helps to show reasons why the error occurred, what system component or application has problems plus more useful information. The error contains a numerical code which hosts data that manufacturers of a component or developers of an application can use to understand where and why the malfunction occurred. It is important to understand that the above error can occur in different locations when testing/running the application on Android Studio. As a result, it can be quite difficult to pinpoint a single source that prompted the error to occur.
Cause of the error
According to experts, there are several reasons which prompt the Android Studio to generate the Cannot Resolve Symbol R error. One of the sources of the above error is believed to be an incorrect or failed installation of software. It is quite common to install more add-ons or software in one’s PC which are designed to enhance one’s productivity. If the software is unable to meet the requirements of the user, it will be uninstalled. During uninstallation, the software may leave an invalid entry in your Windows registry. This maybe brought about by malware or virus attacks.
Another source believed to be the cause of the error is the improper shutdown of the system. If you are using a PC and your home or the electronics are not connected to an alternative power source, and a power failure occurs, then this could result in the above error.
On the other hand, you may allow a friend or family member to use your PC to complete an assignment or play games. Without your knowledge, the user may accidentally delete a vital system file or registry entry. This will also result in the occurrence of the error.
When using Android Studio, it is believed that the “Cannot Resolve Symbol R error” occurs when the IDE fails to correctly run a normal operation. In other words, the error occurs when Android Studio fails to generate the R.java file correctly.
It is important to understand that the error can occur at any moment. At one time, you may be testing the application and everything works fine. On another occasion, you may try to test the application and it fails to compile.
It is also quite common for Android Studio to flag all layout resources when it encounters the R.layout error. As a result, it can be quite difficult to pinpoint the source of the error.

How to solve “Cannot Resolve Symbol R Error” Error Message

There are several solutions that have been forwarded by experts and they have helped to eliminate the Cannot Resolve Symbol R error.
Solution One
An effective solution that has been tried by several developers is cleaning and rebuilding the project. How do you go about this? Well, from your Android Studio toolbar, simply select Build > Clean Project. Allow the IDE to run for a few seconds and once it has completed the operation, build the application/project by selecting Build > Rebuild Project.
Didn’t work on your first try? Repeating the procedure a few times may provide positive results. Remember, to perform the above operation in quick succession.
Solution Two
There are times when a developer opts to move files around. If the R.layout error occurs after moving files and directories, then the source of your error maybe a mismatch. This may happen between Android Studio’s cache and your current project layout. Here is the solution – File > Invalidate Caches/Restart > Invalidate and Restart. This should be performed on the Android Studio toolbar.
Solution Three
There are instances where a developer may fail to name a resource correctly or one may opt to name multiple resources with the same name. If some of your resources contain the same name or they have invalid characters, then the error will occur and affect your project. To resolve this, make sure you name or rename your resources with different names. Avoid using invalid characters too.
Final Word
With the solutions above, you are now set to remove the Cannot Resolve Symbol R error without worries. If you are encountering more errors, reach out to the Android community on Stack Overflow. They are always ready to help.
Good luck!

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