JNI由浅入深_6_简单对象的应用

1、声明native方法

public class ComplexObject {/** * 返回一个对象数组 * @param val * @return */public native Person[] receiverBeanArray(String val);/** * 获取对象 * @return */public native Person getPerson();/** * 获取对象的集合 * @return */public native ArrayList<Person> getPersonList();}

2、Person类对象

有两个构造函数，主要是为了在jni中通过不同的构造函数来创建Person对象。

public class Person {public String name;private int age;public Person() {super();}public Person(int age, String name) {super();this.age = age;this.name = name;}public String getName() {return name;}public void setName(String name) {this.name = name;}public int getAge() {return age;}public void setAge(int age) {this.age = age;}@Overridepublic String toString() {return "Person [name=" + name + ", age=" + age + "]";}}

3、jni操作实现

JNI中，构造函数可以和实例方法一样被调用，调用方式也相似。传入“<init>”作为方法名，“V”作为返回类型。你可以通过向JNI函数NewObject传入方法来调用构造函数。

/** * 拼接字符串 */char* strJoin(char *s1, char *s2) {char *result = malloc(strlen(s1) + strlen(s2) + 1);if (result == NULL)exit(1);strcpy(result, s1);strcat(result, s2);return result;}/** * 返回一个数组类型到Java */JNIEXPORT jobjectArray JNICALL Java_com_example_jniandroid_service_ComplexObject_receiverBeanArray  (JNIEnv * env, jobject obj , jstring string) {jclass objClass = (*env)->FindClass(env, "java/lang/Object");jobjectArray mails = (*env)->NewObjectArray(env, (jsize) ARRAY_LENGTH,objClass, 0);jclass personClass = (*env)->FindClass(env,"com/example/jniandroid/bean/Person");jfieldID field_name = (*env)->GetFieldID(env, personClass, "name","Ljava/lang/String;");jmethodID construction_id = (*env)->GetMethodID(env, personClass, "<init>","()V");jfieldID field_age = (*env)->GetFieldID(env,personClass, "age", "I");jclass mPerson = (*env)->NewObject(env, personClass, construction_id);int i = 0;//将jstring类型转成char*char* nameStr = (char*)(*env)->GetStringUTFChars(env,string, 0);//拼接字符串const char* name = strJoin(nameStr,"-join jni");LOGD("数组总和 =%s", name);for (; i < ARRAY_LENGTH; i++) {int age = 20+i;//将Java的字符串和c的字符串进行拼接后赋值给name属性(*env)->SetObjectField(env, mPerson, field_name, (*env)->NewStringUTF(env,name));(*env)->SetIntField(env,mPerson, field_age,age);(*env)->SetObjectArrayElement(env, mails, (jsize)i, mPerson);}return mails;}/** * 在jni中给Java对象设置值并返回 */JNIEXPORT jobject JNICALL Java_com_example_jniandroid_service_ComplexObject_getPerson  (JNIEnv * env, jclass obj) {//找到Person类jclass m_cls = (*env)->FindClass(env,"com/example/jniandroid/bean/Person");//无参数的构造方法jmethodID m_mid = (*env)->GetMethodID(env,m_cls, "<init>", "()V");//获取Java中复杂类型以L开始;结尾，中间是类型将.改成/jfieldID m_fid_name = (*env)->GetFieldID(env,m_cls, "name", "Ljava/lang/String;");//基本类型，I表示Java中的intjfieldID m_fid_age = (*env)->GetFieldID(env,m_cls, "age", "I");if(m_fid_name==NULL){printf("m_fid_name is null ");return;}if(m_fid_age==NULL){printf("m_fid_age is null ");return;}jobject m_obj = (*env)->NewObject(env,m_cls, m_mid);(*env)->SetObjectField(env,m_obj, m_fid_name, (*env)->NewStringUTF(env,"Set the name Person object in the JNI value"));(*env)->SetIntField(env,m_obj, m_fid_age,96);return m_obj;}/** * 返回ArrayList集合 */JNIEXPORT jobject JNICALL Java_com_example_jniandroid_service_ComplexObject_getPersonList(JNIEnv * env, jobject obj) {jclass list_cls = (*env)->FindClass(env, "java/util/ArrayList"); //获得ArrayList类引用jmethodID list_costruct = (*env)->GetMethodID(env, list_cls, "<init>","()V"); //获得得构造函数Idjobject list_obj = (*env)->NewObject(env, list_cls, list_costruct); //创建一个Arraylist集合对象//Arraylist类中的 add()方法ID，其方法原型为： boolean add(Object object) ,boolean类型对应的是Z;jmethodID list_add = (*env)->GetMethodID(env, list_cls, "add","(Ljava/lang/Object;)Z");jclass personClass = (*env)->FindClass(env,"com/example/jniandroid/bean/Person"); //获得Person类引用//获得该类型的构造函数  函数名为 <init> 返回类型必须为 void 即 VjmethodID person_costruct = (*env)->GetMethodID(env, personClass, "<init>","(ILjava/lang/String;)V");int i=0;for (; i < 5; i++) {jstring str = (*env)->NewStringUTF(env, "jni Native");//通过调用该对象的构造函数来new 一个 Student实例jobject person_obj = (*env)->NewObject(env, personClass,person_costruct, i, str); //构造一个对象//执行Arraylist类实例的add方法，添加一个Person对象(*env)->CallBooleanMethod(env,list_obj, list_add, person_obj);}return list_obj;}