The custom class selection dialog is shown when you add an action, a screen or a form component from your custom code.
The custom class selector shows all classes that implement the appropriate interface, depending on the context:
com.install4j.api.actions.InstallAction
for actions in the installation mode.
com.install4j.api.actions.UninstallAction
for actions in the uninstallation mode.
com.install4j.api.screens.InstallerScreen
for screens in the installation mode.
com.install4j.api.screens.UninstallerScreen
for screens in the uninstallation mode.
com.install4j.api.formcomponents.FormComponent
for form components.
Note that you usually do not implement these interface directly but rather extend one of the abstract classes in the respective packages.
Please see the API description for a detailed explanation of these base classes.