如何在不同的语言/平台中获取Android ID

最近开发工作中需要使用到AndroidID,在Unity和native code中也需要使用，java获取很方便，Unity中也不难，最难的是在native code中获取。

获取android ID需要有一个上下文实例，也就是Context实例，看下面的java获取方式：

在java中获取

Android原生代码，这个是最简单的：

public static String GetAndroid(Context context){    final String androidId;    androidId = android.provider.Settings.Secure.getString(context.getContentResolver(), android.provider.Settings.Secure.ANDROID_ID);    return androidId; }

在Unity中获取

Unity获取androidID首先需要获取Unity环境中当前的activity，由activiy调用getContentResolver。

    private String GetAndroidID()    {        AndroidJavaClass up = new AndroidJavaClass ("com.unity3d.player.UnityPlayer");        AndroidJavaObject currentActivity = up.GetStatic<AndroidJavaObject> ("currentActivity");        AndroidJavaObject contentResolver = currentActivity.Call<AndroidJavaObject> ("getContentResolver");          AndroidJavaClass secure = new AndroidJavaClass ("android.provider.Settings$Secure");        string android_id = secure.CallStatic<string> ("getString", contentResolver, "android_id");        return android_id;    }

在C中获取

在C代码中只能通过JNI方式调用java来获取,代码看起来比较乱，有很多同java进行交互的部分。获取流程如下:

• 首先JVM加载native code所在动态库的时候（loadlibrary）会自动调用JNI_OnLoad，这时候会初始化一个全局的JavaJVM，一个进程只能有一个JavaJVM。

• 当前线程获取JNIEnv,调用AttachCurrentThread来获得。
• 通过JNI获取Java中的相关类，方法。获取Context（getGlobalContext）的方法研究了很长时间，网上搜了好多资料。
• 得到jstring类型的Android,转换成char *

• 最后返回。

#include <jni.h>#include <assert.h>#include "libavutil/avassert.h"#define JNI_CLASS_PATH     /JNI/CLASS/pathstatic JavaVM* g_jvm=NULL;static jobject getGlobalContext(JNIEnv *env){    jclass activityThread = (*env)->FindClass(env,"android/app/ActivityThread");    jmethodID currentActivityThread = (*env)->GetStaticMethodID(env,activityThread, "currentActivityThread", "()Landroid/app/ActivityThread;");    jobject at = (*env)->CallStaticObjectMethod(env,activityThread, currentActivityThread);    jmethodID getApplication = (*env)->GetMethodID(env,activityThread, "getApplication", "()Landroid/app/Application;");    jobject context = (*env)->CallObjectMethod(env,at, getApplication);    return context;}static jstring_getAndroidID(JNIEnv *env, jobject thiz){      jclass c_settings_secure = (*env)->FindClass(env, "android/provider/Settings$Secure");    jclass c_context = (*env)->FindClass(env,"android/content/Context");    if(c_settings_secure == NULL || c_context == NULL){        return NULL;    }    //Get the getContentResolver method    jmethodID m_get_content_resolver = (*env)->GetMethodID(env, c_context, "getContentResolver",                                                           "()Landroid/content/ContentResolver;");    if(m_get_content_resolver == NULL){        return NULL;    }    //Get the Settings.Secure.ANDROID_ID constant    jfieldID f_android_id = (*env)->GetStaticFieldID(env, c_settings_secure, "ANDROID_ID", "Ljava/lang/String;");    if(f_android_id == NULL){        return NULL;    }    jstring s_android_id = (*env)->GetStaticObjectField(env, c_settings_secure, f_android_id);      //create a ContentResolver instance context.getContentResolver()    jobject o_content_resolver = (*env)->CallObjectMethod(env, getGlobalContext(env), m_get_content_resolver);    if(o_content_resolver == NULL || s_android_id == NULL){        return NULL;    }    //get the method getString    jmethodID m_get_string = (*env)->GetStaticMethodID(env, c_settings_secure, "getString",                                                       "(Landroid/content/ContentResolver;Ljava/lang/String;)Ljava/lang/String;");    if(m_get_string == NULL){        return NULL;    }    //get the Android ID    jstring android_id = (*env)->CallStaticObjectMethod(env, c_settings_secure,                                                        m_get_string,                                                        o_content_resolver,                                                        s_android_id);    return android_id;}static  char* jstringTostr( jstring jstr){        JNIEnv* env = NULL;    if ((*g_jvm)->GetEnv(g_jvm, (void**) &env, JNI_VERSION_1_4) != JNI_OK) {        return -1;    }    assert(env != NULL);        char* pStr = NULL;    jclass     jstrObj   = (*env)->FindClass(env, "java/lang/String");    jstring    encode    = (*env)->NewStringUTF(env, "utf-8");    jmethodID  methodId  = (*env)->GetMethodID(env, jstrObj, "getBytes", "(Ljava/lang/String;)[B");    jbyteArray byteArray = (jbyteArray)(*env)->CallObjectMethod(env, jstr, methodId, encode);    jsize      strLen    = (*env)->GetArrayLength(env, byteArray);    jbyte      *jBuf     = (*env)->GetByteArrayElements(env, byteArray, JNI_FALSE);    if (jBuf > 0)    {        pStr = (char*)malloc(strLen + 1);        if (!pStr)        {            return NULL;        }        memcpy(pStr, jBuf, strLen);        pStr[strLen] = 0;    }       (*env)->ReleaseByteArrayElements(env, byteArray, jBuf, 0);    //av_log(NULL, AV_LOG_INFO, "the android is end%s
", pStr);    return pStr;}char * getAndroidID(){    JNIEnv* env = NULL;    if((*g_jvm)->AttachCurrentThread(g_jvm, &env, NULL) != JNI_OK)    {       return NULL;    }    jstring androidID = _getAndroidID(env,NULL);    return jstringTostr(androidID);}JNIEXPORT jint JNI_OnLoad(JavaVM *vm, void *reserved){    JNIEnv* env = NULL;    g_jvm = vm;    if ((*vm)->GetEnv(vm, (void**) &env, JNI_VERSION_1_4) != JNI_OK) {       return -1;    }    assert(env != NULL);    return JNI_VERSION_1_4;}