Android NDK で C++ から java の呼び出し

概要

Visual Studio 2017の**OpenGLES アプリケーション(Android, iOS)**で、C++からJavaを呼び出すメモ

環境

• Visual Studio 2017
• Visual C++ > クロスプラットフォーム > OpenGLES アプリケーション(Android, iOS)
• android-21

内容

既存クラスの場合

auto env = state->activity->env;
auto vm = state->activity->vm;

vm->AttachCurrentThread(&env, NULL);

jstring str = env->NewStringUTF("abc");

jclass     cls = env->FindClass("java/lang/String");
jmethodID  mid = env->GetMethodID(cls, "toCharArray", "()[C");
jcharArray ary = (jcharArray)env->CallObjectMethod(str, mid);

vm->DetachCurrentThread();

ユーザークラスの場合

[プロジェクト名].Packagingプロジェクトのsrcフォルダ以下にjavaのソースを追加

Test.java

package com.test;

public class Test
{
    public boolean test()
    {
        return true;
    }
}

AndroidManifest.xmlのapplication:android:hasCodeをtrueに

AndroidManifest.xml

<application android:label="@string/app_name" android:hasCode="true">

NativeActivity:getClassLoaderを使って呼び出す

https://stackoverflow.com/questions/14586821/android-flurry-integration-with-ndk-app
http://archive.is/QzA8#selection-471.0-507.81

auto env = state->activity->env;
auto vm = state->activity->vm;

vm->AttachCurrentThread(&env, NULL);

jclass activityClass = env->FindClass("android/app/NativeActivity");
jmethodID getClassLoader = env->GetMethodID(activityClass,"getClassLoader", "()Ljava/lang/ClassLoader;");
jobject classLoaderInstance = env->CallObjectMethod(state->activity->clazz, getClassLoader);
jclass classLoader = env->FindClass("java/lang/ClassLoader");
jmethodID findClass = env->GetMethodID(classLoader, "findClass", "(Ljava/lang/String;)Ljava/lang/Class;");
jstring strClassName = env->NewStringUTF("com/test/Test");
jclass classIWant = (jclass)env->CallObjectMethod(classLoaderInstance, findClass, strClassName);
jmethodID testMethod = env->GetStaticMethodID(classIWant, "test", "()Z");
jboolean retValue = env->CallStaticBooleanMethod(classIWant, testMethod);

vm->DetachCurrentThread();