No variants found for ‘:app’.

When the error message “no variants found for ‘:app'” is encountered, it typically means that the specified variant of the app is not available. This could occur due to various reasons, such as incorrect project configuration or missing files.

To resolve this issue, you can follow these steps:

1. Check the project configuration:
   
   Ensure that the project configuration is correct, including the build.gradle files and any other relevant configuration files. Make sure that the correct variant is specified and properly configured.
2. Ensure necessary files are in place:
   
   Verify that all the required files for the specified app variant are present. This could include resources, assets, or any other files that are specific to the variant.
3. Build the project:
   
   Clean and rebuild the project to ensure that all the necessary files are compiled correctly. This can be done using the build tools or IDE commands.
4. Check dependencies:
   
   Make sure that any dependencies or libraries used by the app variant are properly configured and up to date. This includes checking the version compatibility and resolving any conflicts.

Here’s an example scenario to illustrate the issue:

    
      // build.gradle

      android {
          ...
          buildTypes {
              debug {
                  ...
              }
              release {
                  ...
              }
          }
          flavorDimensions "version"
          productFlavors {
              free {
                  dimension "version"
              }
              paid {
                  dimension "version"
              }
          }
      }

      // mainActivity.java

      if (BuildConfig.FLAVOR.equals("pro")) {
          // Perform actions specific to the 'pro' variant
          ...
      } else if (BuildConfig.FLAVOR.equals("free")) {
          // Perform actions specific to the 'free' variant
          ...
      }
    
  

In this example, if the error message “no variants found for ‘:app'” is encountered, it could mean that either the specified variant (‘pro’ or ‘free’) is incorrect or the necessary configuration and files for those variants are missing.