# Maximum Open Projects Sample [![JetBrains IntelliJ Platform SDK Docs](https://jb.gg/badges/docs.svg)][docs] *Reference: [Plugin Services in IntelliJ SDK Docs][docs:plugin_services]* ## Quickstart Maximum Open Projects Sample implements a `StartupActivity` extension point to run on project open as well as a `ProjectManagerListener` for tracking projects being closed. Both use `ProjectCountingService` application-level [light service][docs:plugin_services:light_services]. It provides methods to increase and decrease the counter of currently opened projects in the IDE. When opening more projects than the maximum allowed (3), a message dialog is shown. ### Extension Points | Name | Implementation | Extension Point Class | |------------------------------------|---------------------------------------------------------------|-----------------------| | `com.intellij.postStartupActivity` | [ProjectOpenStartupActivity][file:ProjectOpenStartupActivity] | `StartupActivity` | ### Application Listeners | Name | Implementation | Listener Class | |----------|-------------------------------------------------------|--------------------------| | listener | [ProjectOpenCloseListener][file:ProjectCloseListener] | `ProjectManagerListener` | *Reference: [Plugin Listeners in IntelliJ SDK Docs][docs:listeners]* [docs]: https://plugins.jetbrains.com/docs/intellij/ [docs:plugin_services]: https://plugins.jetbrains.com/docs/intellij/plugin-services.html [docs:plugin_services:light_services]: https://plugins.jetbrains.com/docs/intellij/plugin-services.html#light-services [docs:listeners]: https://plugins.jetbrains.com/docs/intellij/plugin-listeners.html [file:ProjectOpenStartupActivity]: ./src/main/kotlin/org/intellij/sdk/maxOpenProjects/ProjectOpenStartupActivity.kt [file:ProjectCountingService]: ./src/main/java/org/intellij/sdk/maxOpenProjects/ProjectCountingService.java [file:ProjectCloseListener]: ./src/main/java/org/intellij/sdk/maxOpenProjects/ProjectCloseListener.java