AIR 3 Native Extensions for Android – Can I/How to include 3rd party libraries?

AIR 3 Native Extensions for Android – 3rd Party Libraries

Adobe AIR 3 introduced Native Extensions (ANE), allowing developers to access native device capabilities from ActionScript. While ANEs are powerful, they can also present challenges when integrating with 3rd party libraries. This article explores how to include 3rd party libraries in your AIR 3 Android projects using Native Extensions.

Understanding the Challenges

Integrating 3rd party libraries within an ANE introduces complexities.

Library Compatibility

• Language Compatibility: Most 3rd party libraries are written in Java, while ANEs are developed using C/C++. You’ll need a mechanism to bridge this language gap.
• API Design: ANE APIs should be designed for ActionScript consumption. This might require adapting the library’s native API structure.
• Dependencies: 3rd party libraries might rely on other libraries (dependencies) that you need to incorporate within your ANE.

Approaches to Integrating 3rd Party Libraries

1. Static Linking

In this method, the 3rd party library is directly incorporated into your ANE’s native code. This is suitable for small, static libraries.

Steps

• Include Library: Copy the library’s source code or pre-compiled binaries into your ANE project.
• Build ANE: Compile your ANE, ensuring the library is linked during the build process.
• API Wrapping: Create ActionScript classes that expose the library’s functionality through an API.

2. Dynamic Linking via JNI

JNI (Java Native Interface) offers a mechanism to call Java methods from your native code. This approach allows you to load the 3rd party library at runtime.

Steps

• JNI Interface: Create JNI interfaces to bridge your C/C++ ANE code with the Java library.
• Load Library: Use the JNI System.loadLibrary() method to load the 3rd party library during runtime.
• Call Methods: Invoke the library’s methods through JNI calls.

3. Hybrid Approach

Combine static linking for essential library parts with dynamic linking for specific components using JNI. This offers a balanced approach for complex libraries.

Example: Integrating a JSON Library

Let’s consider integrating a JSON library (e.g., Gson) into an AIR 3 Android ANE:

ANE Structure (Example)

// ANE native code (C++)
#include 

// Define JNI methods to access Gson
JNIEXPORT jstring JNICALL Java_com_example_ANE_JsonUtil_parseJson(JNIEnv *env, jobject thiz, jstring jsonString) {
  // ...
  return (*env)->NewStringUTF(env, parsedResult); // Return parsed JSON data
}

ActionScript Code (Example)

// ActionScript code
import com.example.ANE.JsonUtil;

public class Main {
  public function Main() {
    var jsonData = JsonUtil.parseJson("{\"name\":\"John\",\"age\":30}");
    trace(jsonData); // Output: {"name":"John","age":30}
  }
}

Considerations

• Security: Be mindful of potential security risks when working with 3rd party libraries. Carefully vet their code.
• Performance: Dynamic linking can introduce runtime overhead, especially for heavy libraries.
• Maintenance: Keeping your ANE and the 3rd party library updated is crucial for stability and compatibility.

Conclusion

Integrating 3rd party libraries into your AIR 3 Android Native Extensions can expand the capabilities of your apps. By understanding the challenges and adopting appropriate methods like static linking, dynamic linking, or hybrid approaches, you can leverage external libraries to create robust and feature-rich AIR applications.