Bootstrap

JNI(四) 反射调用Android API

1. 字段描述符

JNI字段描述符是一种对函数返回值和参数的编码。这种编码叫做JNI字段描述符（JavaNative Interface FieldDescriptors)。

JNI方法描述符，主要就是在括号里放置参数，在括号后面放置返回类型，如下：

（参数描述符）返回类型

  • 一个数组int[]，就需要表示为这样"[I"。
  • 如果多个数组double[][][]就需要表示为这样 “[[[D”。也就是说每一个方括号开始，就表示一个数组维数。多个方框后面，就是数组的类型。
  • 如果以一个L开头的描述符，就是类描述符，它后紧跟着类的字符串，然后分号“；”结束。比如"Ljava/lang/String;"就是表示类型String；
  • "[Ljava/lang/Object;"就是表示Object[]。
  • 不需要返回参数类型时，使用”V”来表示。
    "([B)V"就是表示void String(byte[] bytes);
  • "()Ljava/lang/String;"表示String f();
  • "(ILjava/lang/Class;)J"表示long f(int i, Class c);
Java 类型符号
BooleanZ
ByteB
CharC
ShortS
IntI
LongJ
FloatF
DoubleD
VoidV
objects对象以"L"开头，以";“结尾，中间是用”/" 隔开的包及类名。比如：Ljava/lang/String;如果是嵌套类，则用 来 表 示 嵌 套 。 例 如 " ( L j a v a / l a n g / S t r i n g ; L a n d r o i d / o s / F i l e U t i l s 来表示嵌套。例如 "(Ljava/lang/String;Landroid/os/FileUtils 来表示嵌套。例如"(Ljava/lang/String;Landroid/os/FileUtilsFileStatus;)Z"

2. 常用方法

2.1 获取Application上下文
jobject getApplication(JNIEnv *env) {
    jobject application = NULL;
    jclass activity_thread_clz = env->FindClass("android/app/ActivityThread");
    if (activity_thread_clz != NULL) {
        jmethodID get_Application = env->GetStaticMethodID(activity_thread_clz,
                                                           "currentActivityThread",
                                                           "()Landroid/app/ActivityThread;");
        if (get_Application != NULL) {
            jobject currentActivityThread = env->CallStaticObjectMethod(activity_thread_clz,
                                                                        get_Application);
            jmethodID getal = env->GetMethodID(activity_thread_clz, "getApplication",
                                               "()Landroid/app/Application;");
            application = env->CallObjectMethod(currentActivityThread, getal);
        }
        return application;
    }
    return application;
}
2.2 获取包名
jstring getPackageName(JNIEnv *env) {
    jobject context = getApplication(env);
    if (context == NULL) {
        LOGD("context is null!");
        return NULL;
    }
    jclass activity = env->GetObjectClass(context);
    jmethodID methodId_pack = env->GetMethodID(activity, "getPackageName", "()Ljava/lang/String;");
    jstring name_str = static_cast<jstring >( env->CallObjectMethod(context, methodId_pack));
    return name_str;
}
2.3 获取签名
char *getSha1(JNIEnv *env, jobject context_object) {
    //上下文对象
    jclass context_class = env->GetObjectClass(context_object);

    //反射获取PackageManager
    jmethodID methodId = env->GetMethodID(context_class, "getPackageManager",
                                          "()Landroid/content/pm/PackageManager;");
    jobject package_manager = env->CallObjectMethod(context_object, methodId);
    if (package_manager == NULL) {
        LOGD("package_manager is NULL!!!");
        return NULL;
    }

    //反射获取包名
    methodId = env->GetMethodID(context_class, "getPackageName", "()Ljava/lang/String;");
    jstring package_name = (jstring) env->CallObjectMethod(context_object, methodId);
    if (package_name == NULL) {
        LOGD("package_name is NULL!!!");
        return NULL;
    }
    env->DeleteLocalRef(context_class);

    //获取PackageInfo对象
    jclass pack_manager_class = env->GetObjectClass(package_manager);
    methodId = env->GetMethodID(pack_manager_class, "getPackageInfo",
                                "(Ljava/lang/String;I)Landroid/content/pm/PackageInfo;");
    env->DeleteLocalRef(pack_manager_class);
    jobject package_info = env->CallObjectMethod(package_manager, methodId, package_name, 0x40);
    if (package_info == NULL) {
        LOGD("getPackageInfo() is NULL!!!");
        return NULL;
    }
    env->DeleteLocalRef(package_manager);

    //获取签名信息
    jclass package_info_class = env->GetObjectClass(package_info);
    jfieldID fieldId = env->GetFieldID(package_info_class, "signatures",
                                       "[Landroid/content/pm/Signature;");
    env->DeleteLocalRef(package_info_class);
    jobjectArray signature_object_array = (jobjectArray) env->GetObjectField(package_info, fieldId);
    if (signature_object_array == NULL) {
        LOGD("signature is NULL!!!");
        return NULL;
    }
    jobject signature_object = env->GetObjectArrayElement(signature_object_array, 0);
    env->DeleteLocalRef(package_info);

    //签名信息转换成sha1值
    jclass signature_class = env->GetObjectClass(signature_object);
    methodId = env->GetMethodID(signature_class, "toByteArray", "()[B");
    env->DeleteLocalRef(signature_class);
    jbyteArray signature_byte = (jbyteArray) env->CallObjectMethod(signature_object, methodId);
    jclass byte_array_input_class = env->FindClass("java/io/ByteArrayInputStream");
    methodId = env->GetMethodID(byte_array_input_class, "<init>", "([B)V");
    jobject byte_array_input = env->NewObject(byte_array_input_class, methodId, signature_byte);
    jclass certificate_factory_class = env->FindClass("java/security/cert/CertificateFactory");
    methodId = env->GetStaticMethodID(certificate_factory_class, "getInstance",
                                      "(Ljava/lang/String;)Ljava/security/cert/CertificateFactory;");
    jstring x_509_jstring = env->NewStringUTF("X.509");
    jobject cert_factory = env->CallStaticObjectMethod(certificate_factory_class, methodId,
                                                       x_509_jstring);
    methodId = env->GetMethodID(certificate_factory_class, "generateCertificate",
                                ("(Ljava/io/InputStream;)Ljava/security/cert/Certificate;"));
    jobject x509_cert = env->CallObjectMethod(cert_factory, methodId, byte_array_input);
    env->DeleteLocalRef(certificate_factory_class);
    jclass x509_cert_class = env->GetObjectClass(x509_cert);
    methodId = env->GetMethodID(x509_cert_class, "getEncoded", "()[B");
    jbyteArray cert_byte = (jbyteArray) env->CallObjectMethod(x509_cert, methodId);
    env->DeleteLocalRef(x509_cert_class);
    jclass message_digest_class = env->FindClass("java/security/MessageDigest");
    methodId = env->GetStaticMethodID(message_digest_class, "getInstance",
                                      "(Ljava/lang/String;)Ljava/security/MessageDigest;");
    jstring sha1_jstring = env->NewStringUTF("SHA1");
    jobject sha1_digest = env->CallStaticObjectMethod(message_digest_class, methodId, sha1_jstring);
    methodId = env->GetMethodID(message_digest_class, "digest", "([B)[B");
    jbyteArray sha1_byte = (jbyteArray) env->CallObjectMethod(sha1_digest, methodId, cert_byte);
    env->DeleteLocalRef(message_digest_class);

    //转换成char
    jsize array_size = env->GetArrayLength(sha1_byte);
    jbyte *sha1 = env->GetByteArrayElements(sha1_byte, NULL);
    char *hex_sha = new char[array_size * 2 + 1];
    for (int i = 0; i < array_size; ++i) {
        hex_sha[2 * i] = hexcode[((unsigned char) sha1[i]) / 16];
        hex_sha[2 * i + 1] = hexcode[((unsigned char) sha1[i]) % 16];
    }
    hex_sha[array_size * 2] = '\0';

    LOGD("hex_sha %s ", hex_sha);
    return hex_sha;
}
2.4 获取meta-data
jstring getMetaData(JNIEnv *env, jobject context_object, jstring name) {
    jstring package_name = getPackageName(env);

    jclass context_class = env->GetObjectClass(context_object);
    jmethodID methodId = env->GetMethodID(context_class, "getPackageManager",
                                          "()Landroid/content/pm/PackageManager;");
    jobject package_manager = env->CallObjectMethod(context_object, methodId);

    jclass package_manager_class = env->GetObjectClass(package_manager);
    methodId = env->GetMethodID(package_manager_class, "getApplicationInfo",
                                "(Ljava/lang/String;I)Landroid/content/pm/ApplicationInfo;");
    jfieldID fieldId = env->GetStaticFieldID(package_manager_class, "GET_META_DATA", "I");
    jint flags = env->GetStaticIntField(package_manager_class, fieldId);
    jobject application_info = env->CallObjectMethod(package_manager, methodId, package_name,
                                                     flags);
    jclass application_info_class = env->GetObjectClass(application_info);
    fieldId = env->GetFieldID(application_info_class, "metaData", "Landroid/os/Bundle;");

    jobject metaData = env->GetObjectField(application_info, fieldId);
    if (metaData == NULL) {
        LOGE(name + "不能为空，请在Manifest中配置metadata!");
        return env->NewStringUTF("");
    }
    jclass bundle_class = env->GetObjectClass(metaData);
    methodId = env->GetMethodID(bundle_class, "getString",
                                "(Ljava/lang/String;)Ljava/lang/String;");
    jstring value = (jstring) env->CallObjectMethod(metaData, methodId, name);
    if (value == NULL) {
        LOGE(name + "不能为空，请在Manifest中配置metadata!");
        return env->NewStringUTF("");
    }
    return value;
}

悦读

道可道，非常道；名可名，非常名。 无名，天地之始，有名，万物之母。 故常无欲，以观其妙，常有欲，以观其徼。 此两者，同出而异名，同谓之玄，玄之又玄，众妙之门。

最新收录
jqueryeasyui 事件方法onChange(),onSelect()
什么是组合设计模式？组合模式实战代码
在 ssh ， telnet 终端中文显示乱码解决办法
丹摩 | 基于PyTorch的CIFAR-10图像分类实现
kotlin---使用注释处理的 Android 框架
树莓派和鲁班猫跑视差图算法时间
Dlib格式与Opencv之间的转化
springboot毕设 直播购物平台 程序+论文
浅拷贝、深拷贝以及Memberwise Copy 和 Bitwise Copy
vue 登录页面背景 - 动态粒子特效包括vue3使用 (Vue-Particles)
;