JNI由浅入深_6_简单对象的应用

一、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();

}

二、Person类对象

有两个构造函数，主要是为了在jni中经过不一样的构造函数来建立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;
	}

	@Override
	public String toString() {
		return "Person [name=" + name + ", age=" + age + "]";
	}

}

三、jni操做实现

JNI中，构造函数能够和实例方法同样被调用，调用方式也类似。传入“<init>”做为方法名，“V”做为返回类型。你能够经过向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.改为/
	jfieldID m_fid_name = (*env)->GetFieldID(env,m_cls, "name", "Ljava/lang/String;");
	//基本类型，I表示Java中的int
	jfieldID 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"); //得到ArrayList类引用

	jmethodID list_costruct = (*env)->GetMethodID(env, list_cls, "<init>","()V"); //得到得构造函数Id
	jobject list_obj = (*env)->NewObject(env, list_cls, list_costruct); //建立一个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"); //得到Person类引用
	//得到该类型的构造函数  函数名为 <init> 返回类型必须为 void 即 V
	jmethodID 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");
		//经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;
}