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Unity Engine

Java Native Interface APIs in Unity

Learn about the Java Native Interface APIs in Unity that you can use to call Java/Kotlin code from C# scripts.
Read time 2 minutesLast updated 7 days ago
Unity provides low-level and high-level Java Native Interface (JNI) APIs that allow you to interact with Java code from C# scripts.

Low-level API

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's primarily used by the high-level API, but they can be useful in certain situations.

High-level API

The high-level AndroidJavaObject, AndroidJavaClass, and AndroidJavaProxy classes 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.
Additionally, Unity provides the AndroidApplication class to simplify access to instances of 
currentActivity
, 
currentContext
, and 
currentConfiguration
for your application. This class also allows you to delegate code execution on the UI or main thread based on your application's requirement.
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:
  • Call a method.
  • Get the value of a field.
  • Set the value of a field.
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're setting. For methods that don't return a value, there's 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.

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