To call Java code from C# scriptsA piece of code that allows you to create your own Components, trigger game events, modify Component properties over time and respond to user input in any way you like. More info
See in Glossary, Unity provides C# APIs that communicate with the Android Java Native Interface (JNI) through C++. Unity provides both a low level and a high level APIA system for building multiplayer capabilities for Unity games. It is built on top of the lower level transport real-time communication layer, and handles many of the common tasks that are required for multiplayer games. More info
See in Glossary that you can use to interact with Java code using JNI.
The low-level AndroidJNI class wraps JNI calls and provides static methods that directly map to JNI methods. The AndroidJNIHelper API provides helper functionality that is primarily used by the high-level API, but they can be useful in certain situations.
The high-level AndroidJavaObject, AndroidJavaClass, and AndroidJavaProxy APIs automate a lot of tasks required for JNI calls. They also use caching to make calls to Java faster. The combination of AndroidJavaObject and AndroidJavaClass is built on top of AndroidJNI and AndroidJNIHelper, but they also contain additional functionality such as static methods that you can use to access static members of Java classes.
Instances of AndroidJavaObject and AndroidJavaClass have a one-to-one mapping to an instance of java.lang.Object and java.lang.Class respectively. They provide three types of interactions with Java/Kotlin code:
Each interaction also has a static version:
When you get the value of a field or call a method that returns a value, you use generics to specify the return type. When you set the value of a field, you also use generics to specify the type of the field that you are setting. For methods that don’t return a value, there is a regular, non-generic, version of Call.
Important: You must access any non-primitive type as an AndroidJavaObject. The only exception is a string which you access directly, even though they don’t represent a primitive type in Java.
This section contains code samples that show how to use the high-level AndroidJavaObject and AndroidJavaClass APIs.
The following code sample creates an instance of java.lang.String initialized with a string, and retrieves the hash value for that string.
using UnityEngine;
public class JavaExamples
{
public static int GetJavaStringHashCode(string text)
{
using (AndroidJavaObject jo = new AndroidJavaObject("java.lang.String", text))
{
int hash = jo.Call<int>("hashCode");
return hash;
}
}
}
This example:
AndroidJavaObject that represents a java.lang.String. The AndroidJavaObject constructor takes at least one parameter, which is the name of the class to construct an instance of. Any parameters after the class name are for the constructor call on the object, in this case the text parameter from GetJavaStringHashCode.int generic type parameter for Call because hashCode() returns the hash code as an integer.
Note: You can’t use dotted notation to instantiate a nested Java class. You must use the $ separator to instantiate inner classes. For example, Use android.view.ViewGroup$LayoutParams or android/view/ViewGroup$LayoutParams, where the LayoutParams class is nested in the ViewGroup class.
The following code sample shows how to get the cache directory for the current application in C# without using plug-insA set of code created outside of Unity that creates functionality in Unity. There are two kinds of plug-ins you can use in Unity: Managed plug-ins (managed .NET assemblies created with tools like Visual Studio) and Native plug-ins (platform-specific native code libraries).