Between some versions of Delphi, e.g. Delphi 10.4.x and 11.0, there may have been changes to the Android libraries (specifically, which libraries) that Delphi is dependent on.

If you create an app with Delphi 10.4.2, open it with Delphi 11, then open the Project Manager and expand the Android platforms nodes, under Libraries you will see this:

The little red "x" marks on the libraries indicate that they are not present. As mentioned above, the Android libraries that Delphi depends on have been changed.

Similarly, for a project built for a later version of Delphi, e.g. Delphi 12, if you open it with an earlier version, e.g. Delphi 11, you will see the same issue.

When you run the application you may receive a message like:

Java type Jcontent_ContextCompat could not be found

This is because the required Android libraries have not been built into the app. With Delphi 11.1, the app will not compile because it attempts to merge the non-existent .dex files

The process is rather simple:

1. Right-click the Libraries node, and click Revert System Files to Default

2. Do this for both Android 32-bit and Android 64-bit
3. Save the project
4. Do a Clean (right-click the project and click Clean)
5. Do a Build (right-click the project and click Build)

If the app still crashes on startup, and you have a service with the application, it may be due to changes in the Delphi service code. In which case, follow these steps:

1. In the root of the source folder for the service, delete the .template.java files. This will cause Delphi to recreate them when you:
2. Rebuild the project