> For the complete documentation index, see [llms.txt](https://apertus.gitbook.io/vr/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://apertus.gitbook.io/vr/installation/android-install/how-to-use.md). # How to use ### Overview The wrapper classes are placed in the `org.apertusvr` package. For each ApertusVR entity type there's a corresponding Java wrapper class. Also there are a wrapper classes for the manager classes (e.g. `ape::EventManager`, `ape::SceneManager`)and `ape::Event` and there are several supporting classes (e.g. `apeColor`, `apeVector3`). To be able to cast the interfaces, we ha a builder Java interface (`apeBuilder`) too. ### Event connection Just like using the C++ interface, the user can connect to various events (fired by ApertusVR) from Java code. To do that, we need to implement the `apeEventCallback` function: ```java class MyEventCallback implements apeEventCallback { @Override public void onEvent(apeEvent event) { // do sth with event } } ``` We also have to create an instance of the `MyEventCallback` class, e.g. ```java MyEventCallback eventCallback = new MyEventCallback(); ``` After instantiation, the connection works simply with the usage of `apeManager`'s `connectEvent(...)` function. E.g., to be able to listen `NODE` events, just type: ```java apeEventManager.connectEvent(apeEvent.Group.NODE, eventCallback); ``` To get an insight of what actually happens here, let us discuss the details! When the user connects an event, the `apeEventManager` (which is a static class) puts this `eventCallback` into a map: ```java private static Map> mEventMap ``` The app developer also creates a `FrameCallback` class, which implements Android's built in `Choreographer.FrameCallback`. Like in the following code block: ```java class FrameCallback implements Choreographer.FrameCallback { @Override public void doFrame(long frameTimeNanos) { choreographer.postFrameCallback(this); if (apeSystem.isRunning()) { ApertusJNI.processEventDoubleQueue(); } } } ``` This will parse all the events fired in the C++ side, during the last frame. The ApertusJNI member function called `processEventDoubleQueue()` is a JNI-function, which calls back to Java with `apeEventManager`'s `fireEvent()` function, which will call the `onEvent(apeEvent)` function of our `apeEventCallback` implementation, if its instance is connected to the event's group (so the implementation object can be found under the `apeEvent.Group.NODE` key in the map). ![](/files/-MEXN73sQQwihBMzTxz9) ### Entity wrappers As it was written before, for each entity class in ApertusVR we have a corresponding Java class. The member functions and the class hierarchies on the Java side are the same, as they are on the C++ side. Therefore the API does not differ much, but there are tiny differences between the two. We will go through everything you need, to use ApertusVR entities from Java. #### Getting access to entities In C++, knowing the entity's name, we ask the `ape::ISceneManager` to give us a weak pointer. Then we use the `lock()` function to access it. After calling `lock()`, we can also cast the resulted `shared_ptr` to the proper type (`ape::Entity::Type`), if we know what the entity's type should be.\ When using ApertusVR from Java, we just use the interface's constructor to get access to an entity, then we check with the `isValid()` function, that we can actually lock it in C++. E.g. assume, that we want to access an `apeFileGeometry` entity we know about, with the name of `"FooBar"`, and our goal is to query its `OwnerID`. The procedure goes something like on the following code example: ```java String fooBarName = "FooBar"; apeFileGeometry fooBarGeometry = new apeFileGeometry(fooBarName); if (fooBarGeometry.isValid()) { String ownerID = fooBarGeometry.getOwnerID(); } ``` The following figure summarizes the procedure executed in the background: ![](/files/-MEbRleCQjR-y7O8W5lU) This is the way in 90% of the cases. However, what if we don't know already the type of the entity, and only its name is given. In this case, we can use the `apeSceneManager` interface: ```java String fooBarName = "FooBar"; apeEntity fooBarEntity = apeSceneManager.getEntity(fooBarName); if (fooBarEntity != null && fooBarEntity.isValid()) { apeEntity.Type fooBarType = fooBarEntity.getType(); if (fooBarType == apeEntity.Type.GEOMETRY_FILE) { apeFileGeometry fooBarGeometry = new apeFileGeometry(fooBarName); // ... } } ``` #### Creating an entity The next question is, how can we create entities in Java? Easy. Just use the `apeSceneManager` interface!: ```java String fooBarName = "FooBar"; apeEntity.Type fooBarType = apeEntity.Type.GEOMETRY_FILE; boolean fooBarIsReplicate = false; String fooBarOwner = "FooBarOwner"; apeEntity fooBarEntity = apeSceneManager.createEntity( fooBarName, fooBarType, fooBarIsReplicate, fooBarOwner); ``` Okay, then how do we cast it to our needs? We wanted `apeFileGeometry` interface, not `apeEntity`.\ This is where the `apeBuilder` interface come in! The `apeEntity` abstract class has a member function called `cast`: ```java public apeType cast(apeBuilder builder) ``` Providing a proper builder class (which implements the `apeBuilder` interface), we can cast our `apeEntity` to any given type extended from it. In the example, we just type: ```java apeFileGeometry fooBarGeometry = Objects.requireNonNull( apeSceneManager.createEntity( fooBarName, fooBarType, fooBarIsReplicate, fooBarOwner)) .cast(new apeFileGeometry.FileGeometryBuilder()); ``` Or an alternative way is to instance an other `apeFileGeometry` entity with the `apeEntity`'s name you got from `apeSceneManager` (like you saw it in the former sub-subsection). #### Deleting entities Deleting an entity in Java is the same as in C++, an example is presented below: ```java String entityName = "FooBar"; apeSceneManager.deleteEntity(entityName); ``` --- # Agent Instructions This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com. ## Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter: ``` GET https://apertus.gitbook.io/vr/installation/android-install/how-to-use.md?ask= ``` The question should be specific, self-contained, and written in natural language. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.