JNI使用类签名及字段签名获取字段值

原创

编程汇也 2025-01-21 11:43:49 ©著作权

文章标签 java android JNI 字段类对象 文章分类 Python 后端开发

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1.获取逻辑:

JNI使用类签名及字段签名获取字段值_字段

2.获取逻辑实现代码:

extern "C"
JNIEXPORT void JNICALL
Java_com_example_jnibasetypedemo_MainActivity_getAnimalsNameFromJNI(JNIEnv *env, jobject thiz,
                                                               jobjectArray animals) {
    jobject animalObj;
    int len = env->GetArrayLength(animals);//获取数组长度
    jclass animalClass = env->FindClass("com/example/jnibasetypedemo/Animal");//获取类对象
    //获取类字段
    jfieldID animalClassNameFiels = env->GetFieldID(animalClass, //类对象
                                   "name", //字段名
                                   "Ljava/lang/String;");//字段签名
    jstring _jni_string;
    const char *cplusplus_string;
    //遍历数组
    for (int i = 0; i < len; ++i) {
        animalObj = env->GetObjectArrayElement(animals, i);//取得元素
        //取类对象字段
        _jni_string = (jstring) (env->GetObjectField(animalObj, //类对象
                                              animalClassNameFiels));//类对字段对象
        //jstring转char*
        cplusplus_string = env->GetStringUTFChars(_jni_string, NULL);
        if (cplusplus_string == NULL) {
            continue;
        }
        LOGD("===>Animal类字段name值:%s", cplusplus_string);
        //释放内存
        env->ReleaseStringUTFChars(_jni_string, cplusplus_string);
    }
}

3.java实现:

声明JNI原生方法

JNI使用类签名及字段签名获取字段值_JNI_02

创建Animal类：

package com.example.jnibasetypedemo;

public class Animal{

    public String name;

    public Animal(String name) {
         = name;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
         = name;
    }

    public Animal() {
    }
}

调用原生方法并输入Animal类数组

Animal[] animals = new Animal[30];
        for (int i = 0; i < 30; i++) {
            Animal ani = new Animal();
            ani.setName("animal name"+(i+1));
            animals[i]=ani;
        }
        getAnimalsNameFromJNI(animals);

4.完整源码地址：

https:///tonyimax/JniBaseTypeDemo.git

5. 输出:

2025-01-12 13:29:51.211 29675-29675 JNI_LOG                 com.example.jnibasetypedemo          D  ===>Animal类字段name值:animal name1
2025-01-12 13:29:51.211 29675-29675 JNI_LOG                 com.example.jnibasetypedemo          D  ===>Animal类字段name值:animal name2
2025-01-12 13:29:51.211 29675-29675 JNI_LOG                 com.example.jnibasetypedemo          D  ===>Animal类字段name值:animal name3
2025-01-12 13:29:51.211 29675-29675 JNI_LOG                 com.example.jnibasetypedemo          D  ===>Animal类字段name值:animal name4
2025-01-12 13:29:51.211 29675-29675 JNI_LOG                 com.example.jnibasetypedemo          D  ===>Animal类字段name值:animal name5
2025-01-12 13:29:51.211 29675-29675 JNI_LOG                 com.example.jnibasetypedemo          D  ===>Animal类字段name值:animal name6
2025-01-12 13:29:51.212 29675-29675 JNI_LOG                 com.example.jnibasetypedemo          D  ===>Animal类字段name值:animal name7
2025-01-12 13:29:51.212 29675-29675 JNI_LOG                 com.example.jnibasetypedemo          D  ===>Animal类字段name值:animal name8
2025-01-12 13:29:51.212 29675-29675 JNI_LOG                 com.example.jnibasetypedemo          D  ===>Animal类字段name值:animal name9
2025-01-12 13:29:51.212 29675-29675 JNI_LOG                 com.example.jnibasetypedemo          D  ===>Animal类字段name值:animal name10
2025-01-12 13:29:51.212 29675-29675 JNI_LOG                 com.example.jnibasetypedemo          D  ===>Animal类字段name值:animal name11
2025-01-12 13:29:51.212 29675-29675 JNI_LOG                 com.example.jnibasetypedemo          D  ===>Animal类字段name值:animal name12
2025-01-12 13:29:51.212 29675-29675 JNI_LOG                 com.example.jnibasetypedemo          D  ===>Animal类字段name值:animal name13
2025-01-12 13:29:51.212 29675-29675 JNI_LOG                 com.example.jnibasetypedemo          D  ===>Animal类字段name值:animal name14
2025-01-12 13:29:51.212 29675-29675 JNI_LOG                 com.example.jnibasetypedemo          D  ===>Animal类字段name值:animal name15
2025-01-12 13:29:51.212 29675-29675 JNI_LOG                 com.example.jnibasetypedemo          D  ===>Animal类字段name值:animal name16
2025-01-12 13:29:51.212 29675-29675 JNI_LOG                 com.example.jnibasetypedemo          D  ===>Animal类字段name值:animal name17
2025-01-12 13:29:51.212 29675-29675 JNI_LOG                 com.example.jnibasetypedemo          D  ===>Animal类字段name值:animal name18
2025-01-12 13:29:51.212 29675-29675 JNI_LOG                 com.example.jnibasetypedemo          D  ===>Animal类字段name值:animal name19
2025-01-12 13:29:51.212 29675-29675 JNI_LOG                 com.example.jnibasetypedemo          D  ===>Animal类字段name值:animal name20
2025-01-12 13:29:51.212 29675-29675 JNI_LOG                 com.example.jnibasetypedemo          D  ===>Animal类字段name值:animal name21
2025-01-12 13:29:51.212 29675-29675 JNI_LOG                 com.example.jnibasetypedemo          D  ===>Animal类字段name值:animal name22
2025-01-12 13:29:51.213 29675-29675 JNI_LOG                 com.example.jnibasetypedemo          D  ===>Animal类字段name值:animal name23
2025-01-12 13:29:51.213 29675-29675 JNI_LOG                 com.example.jnibasetypedemo          D  ===>Animal类字段name值:animal name24
2025-01-12 13:29:51.213 29675-29675 JNI_LOG                 com.example.jnibasetypedemo          D  ===>Animal类字段name值:animal name25
2025-01-12 13:29:51.213 29675-29675 JNI_LOG                 com.example.jnibasetypedemo          D  ===>Animal类字段name值:animal name26
2025-01-12 13:29:51.213 29675-29675 JNI_LOG                 com.example.jnibasetypedemo          D  ===>Animal类字段name值:animal name27
2025-01-12 13:29:51.213 29675-29675 JNI_LOG                 com.example.jnibasetypedemo          D  ===>Animal类字段name值:animal name28
2025-01-12 13:29:51.213 29675-29675 JNI_LOG                 com.example.jnibasetypedemo          D  ===>Animal类字段name值:animal name29
2025-01-12 13:29:51.213 29675-29675 JNI_LOG                 com.example.jnibasetypedemo          D  ===>Animal类字段name值:animal name30