Java JNI由淺入深(包括：Java和C++互傳ArrayList泛型對象參數)
我們知道Java是一個運行在虛擬機裏面的高級的編程語言，如果要調用系統的動態鏈接庫的話，就要先聲明native修飾的方法(類似接口裏面的方法)，再由C/C++程序來實現(類似實現接口裏的方法)。這樣Java調用這些native方法就相當於調用了C/C++裏面實現了的方法。通常我們把這種機制叫做JNI(Java NativeInterfac)，即Java 本地編程接口
Android也同理，要學會在Android上進行NDK開發，首先我們到打好java JNI的基礎。現在我們暫時把Android開發丟到一邊先，試試在Java之下編譯一個C動態鏈接庫，再用Java程序調用。
1)先來個最簡單的打印HelloWorld例子：
Java代碼(HelloJni.java)：
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1. import java.util.*;
2. public class HelloJni{
3.
4. static{
5. System.loadLibrary("hello");
6. }
7. public native static void sayHello();
8. public static void main(String [] args)
9. {
10. HelloJni.sayHello();
11. }
12. }
import java.util.*; public class HelloJni{ static{ System.loadLibrary("hello"); } public native static void sayHello(); public static void main(String [] args) { HelloJni.sayHello(); } }
生成頭文件(HelloJni.h)：
先javac HelloJni.java編譯你的Java源碼，再javah–jni HelloJni生成所需的頭文件
頭文件內容是這樣的：
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1. /* DO NOT EDIT THIS FILE - it is machine generated */
2. #include <jni.h>
3. /* Header for class HelloJni */
4. #ifndef _Included_HelloJni
5. #define _Included_HelloJni
6. #ifdef __cplusplus
7. extern "C" {
8. #endif
9. JNIEXPORT void JNICALL Java_HelloJni_sayHello (JNIEnv *, jclass);
10. #ifdef __cplusplus
11. }
12. #endif
13. #endif
/* DO NOT EDIT THIS FILE - it is machine generated */ #include <jni.h> /* Header for class HelloJni */ #ifndef _Included_HelloJni #define _Included_HelloJni #ifdef __cplusplus extern "C" { #endif JNIEXPORT void JNICALL Java_HelloJni_sayHello (JNIEnv *, jclass); #ifdef __cplusplus } #endif #endif
實現頭文件聲明的方法(HelloJni.cpp)
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1. #include "HelloJni.h"
2. JNIEXPORT void JNICALL Java_HelloJni_sayHello(JNIEnv *env, jclass cls)
3. {
4. printf("HelloWorld");
5. }
#include "HelloJni.h" JNIEXPORT void JNICALL Java_HelloJni_sayHello(JNIEnv *env, jclass cls) { printf("HelloWorld"); }
編譯命令: g++ -I$JAVA_HOME/include-I$JAVA_HOME/include/linux HelloJni.cpp -shared -o libhello.so
命令參數解析：-I 是指引入java虛擬機的庫的路徑，-shared 是指編譯成動態鏈接庫(共享庫) –o 輸出文件名(注意，在Linux平臺下的動態鏈接庫有一個命名格式：“lib+庫名+.so”在java代碼裏面loadLibrary的時候不要加lib前綴和.so後綴)
由於我這裏把這個動態鏈接庫編譯放在當前目錄下，所以還要設置環境變量LD_LIBRARY_PATH=該so動態鏈接庫所在的目錄，才能正常運行
#############################+++華麗的分割線+++###########################
2)好了，可以打印HelloWorld出來後，我們再深入一點點，傳入一個int的數，在C/C++代碼裏面加1後返回。
Java代碼(HelloJni.java)：
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1. public class HelloJni{
2. static{
3. System.loadLibrary("hello");
4. }
5. public static native void sayHello();
6. public native int getInt();
7. public native void setInt(int i);
8. public static void main(String args[]){
9. // HelloJni.sayHello();
10. HelloJni hello = new HelloJni();
11. hello.setInt(2);
12. System.out.println(hello.getInt());
13. }
14. }
public class HelloJni{ static{ System.loadLibrary("hello"); } public static native void sayHello(); public native int getInt(); public native void setInt(int i); public static void main(String args[]){ // HelloJni.sayHello(); HelloJni hello = new HelloJni(); hello.setInt(2); System.out.println(hello.getInt()); } }
生成頭文件(HelloJni.h)：
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1. /* DO NOT EDIT THIS FILE - it is machine generated */
2. #include <jni.h>
3. /* Header for class HelloJni */
4. #ifndef _Included_HelloJni
5. #define _Included_HelloJni
6. #ifdef __cplusplus
7. extern "C" {
8. #endif
9. JNIEXPORT void JNICALL Java_HelloJni_sayHello (JNIEnv *, jclass);
10. JNIEXPORT jint JNICALL Java_HelloJni_getInt (JNIEnv *, jobject);
11. JNIEXPORT void JNICALL Java_HelloJni_setInt (JNIEnv *, jobject, jint);
12. #ifdef __cplusplus
13. }
14. #endif
15. #endif
/* DO NOT EDIT THIS FILE - it is machine generated */ #include <jni.h> /* Header for class HelloJni */ #ifndef _Included_HelloJni #define _Included_HelloJni #ifdef __cplusplus extern "C" { #endif JNIEXPORT void JNICALL Java_HelloJni_sayHello (JNIEnv *, jclass); JNIEXPORT jint JNICALL Java_HelloJni_getInt (JNIEnv *, jobject); JNIEXPORT void JNICALL Java_HelloJni_setInt (JNIEnv *, jobject, jint); #ifdef __cplusplus } #endif #endif
實現頭文件聲明的方法(HelloJni.cpp)
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1. #include "HelloJni.h"
2. int i=1;
3. JNIEXPORT void JNICALL Java_HelloJni_sayHello
4. (JNIEnv *env, jclass cls){
5. printf("HelloWorld/n");
6. }
7. JNIEXPORT jint JNICALL Java_HelloJni_getInt
8. (JNIEnv *env, jobject thiz){
9. return i;
10. }
11. JNIEXPORT void JNICALL Java_HelloJni_setInt
12. (JNIEnv *env, jobject thiz,jint ji){
13. i = ji+1;
14. }
#include "HelloJni.h" int i=1; JNIEXPORT void JNICALL Java_HelloJni_sayHello (JNIEnv *env, jclass cls){ printf("HelloWorld/n"); } JNIEXPORT jint JNICALL Java_HelloJni_getInt (JNIEnv *env, jobject thiz){ return i; } JNIEXPORT void JNICALL Java_HelloJni_setInt (JNIEnv *env, jobject thiz,jint ji){ i = ji+1; }
運行結果：打印2
3)只是傳入簡單的數據類型不爽，這次讓C/C++生成個Java對象返回
Java代碼：pojo實體類(User.java)
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1. public class User{
2. private long id;
3. private String userName;
4. private boolean isMan;
5. private int age;
6. public User(){}
7. public User(long id, String userName, boolean isMan, int age) {
8. super();
9. this.id = id;
10. this.userName = userName;
11. this.isMan = isMan;
12. this.age = age;
13. }
14. public long getId() {
15. return id;
16. }
17. public void setId(long id) {
18. this.id = id;
19. }
20. public String getUserName() {
21. return userName;
22. }
23. public void setUserName(String userName) {
24. this.userName = userName;
25. }
26. public boolean isMan() {
27. return isMan;
28. }
29. public void setMan(boolean isMan) {
30. this.isMan = isMan;
31. }
32. public int getAge() {
33. return age;
34. }
35. public void setAge(int age) {
36. this.age = age;
37. }
38. }
public class User{ private long id; private String userName; private boolean isMan; private int age; public User(){} public User(long id, String userName, boolean isMan, int age) { super(); this.id = id; this.userName = userName; this.isMan = isMan; this.age = age; } public long getId() { return id; } public void setId(long id) { this.id = id; } public String getUserName() { return userName; } public void setUserName(String userName) { this.userName = userName; } public boolean isMan() { return isMan; } public void setMan(boolean isMan) { this.isMan = isMan; } public int getAge() { return age; } public void setAge(int age) { this.age = age; } }
Java代碼(HelloJni.java)：
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1. public class HelloJni{
2. static{
3. System.loadLibrary("userbean");
4. }
5. public static native void sayHello();
6. public native int getInt();
7. public native void setInt(int i);
8. public native void setUser(String userName);
9. public native User getUser();
10. public static void main(String args[]){
11. // HelloJni.sayHello();
12. HelloJni hello = new HelloJni();
13. // hello.setInt(2);
14. // System.out.println(hello.getInt());
15. hello.setUser("LiangYaotian");
16. User user = hello.getUser();
17. System.out.println("user from c/c++");
18. System.out.println("name:"+user.getUserName());
19. System.out.println("isMan?:"+user.isMan());
20. System.out.println("age:"+user.getAge());
21. }
22. }
public class HelloJni{ static{ System.loadLibrary("userbean"); } public static native void sayHello(); public native int getInt(); public native void setInt(int i); public native void setUser(String userName); public native User getUser(); public static void main(String args[]){ // HelloJni.sayHello(); HelloJni hello = new HelloJni(); // hello.setInt(2); // System.out.println(hello.getInt()); hello.setUser("LiangYaotian"); User user = hello.getUser(); System.out.println("user from c/c++"); System.out.println("name:"+user.getUserName()); System.out.println("isMan?:"+user.isMan()); System.out.println("age:"+user.getAge()); } }
生成頭文件(HelloJni.h)：
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1. #include <jni.h>
2. /* Header for class HelloJni */
3. #ifndef _Included_HelloJni
4. #define _Included_HelloJni
5. #ifdef __cplusplus
6. extern "C" {
7. #endif
8. JNIEXPORT void JNICALL Java_HelloJni_sayHello (JNIEnv *, jclass);
9. JNIEXPORT jint JNICALL Java_HelloJni_getInt (JNIEnv *, jobject);
10. JNIEXPORT void JNICALL Java_HelloJni_setInt (JNIEnv *, jobject, jint);
11. JNIEXPORT void JNICALL Java_HelloJni_setUser (JNIEnv *, jobject, jstring);
12. JNIEXPORT jobject JNICALL Java_HelloJni_getUser (JNIEnv *, jobject);
13. #ifdef __cplusplus
14. }
15. #endif
16. #endif
#include <jni.h> /* Header for class HelloJni */ #ifndef _Included_HelloJni #define _Included_HelloJni #ifdef __cplusplus extern "C" { #endif JNIEXPORT void JNICALL Java_HelloJni_sayHello (JNIEnv *, jclass); JNIEXPORT jint JNICALL Java_HelloJni_getInt (JNIEnv *, jobject); JNIEXPORT void JNICALL Java_HelloJni_setInt (JNIEnv *, jobject, jint); JNIEXPORT void JNICALL Java_HelloJni_setUser (JNIEnv *, jobject, jstring); JNIEXPORT jobject JNICALL Java_HelloJni_getUser (JNIEnv *, jobject); #ifdef __cplusplus } #endif #endif
實現頭文件聲明的方法(HelloJni.cpp)
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1. #include <iostream>
2. #include <stdio.h>
3. using namespace std;
4. int i=1;
5. jobject user;
6. JNIEXPORT void JNICALL Java_HelloJni_sayHello
7. (JNIEnv *env, jclass cls){
8. printf("HelloWorld/n");
9. }
10. JNIEXPORT jint JNICALL Java_HelloJni_getInt
11. (JNIEnv *env, jobject thiz){
12. return i;
13. }
14. JNIEXPORT void JNICALL Java_HelloJni_setInt
15. (JNIEnv *env, jobject thiz,jint ji){
16. i = ji+1;
17. }
18. JNIEXPORT void JNICALL Java_HelloJni_setUser
19. (JNIEnv *env, jobject thiz, jstring name){
20. jclass userClass = env->FindClass("User");
21. jmethodID userMethod = env->GetMethodID(userClass,"<init>","()V");
22. jfieldID mId = env->GetFieldID(userClass,"id","J");
23. jfieldID mUserName = env->GetFieldID(userClass,"userName","Ljava/lang/String;");
24. jfieldID mIsMan = env->GetFieldID(userClass,"isMan","Z");
25. jfieldID mAge = env->GetFieldID(userClass,"age","I");
26. jobject userObject = env->NewObject(userClass,userMethod);
27. env->SetObjectField(userObject,mUserName,name);
28. env->SetLongField(userObject,mId,1001);
29. env->SetBooleanField(userObject,mIsMan,1);
30. env->SetIntField(userObject,mAge,21);
31. user = userObject;
32. }
#include <iostream> #include <stdio.h> using namespace std; int i=1; jobject user; JNIEXPORT void JNICALL Java_HelloJni_sayHello (JNIEnv *env, jclass cls){ printf("HelloWorld/n"); } JNIEXPORT jint JNICALL Java_HelloJni_getInt (JNIEnv *env, jobject thiz){ return i; } JNIEXPORT void JNICALL Java_HelloJni_setInt (JNIEnv *env, jobject thiz,jint ji){ i = ji+1; } JNIEXPORT void JNICALL Java_HelloJni_setUser (JNIEnv *env, jobject thiz, jstring name){ jclass userClass = env->FindClass("User"); jmethodID userMethod = env->GetMethodID(userClass,"<init>","()V"); jfieldID mId = env->GetFieldID(userClass,"id","J"); jfieldID mUserName = env->GetFieldID(userClass,"userName","Ljava/lang/String;"); jfieldID mIsMan = env->GetFieldID(userClass,"isMan","Z"); jfieldID mAge = env->GetFieldID(userClass,"age","I"); jobject userObject = env->NewObject(userClass,userMethod); env->SetObjectField(userObject,mUserName,name); env->SetLongField(userObject,mId,1001); env->SetBooleanField(userObject,mIsMan,1); env->SetIntField(userObject,mAge,21); user = userObject; }
4)有些同學可能會說：“返回個Java對象算什麼啊，C/C++和Java之間互傳複雜對象纔好玩呢！”正所謂“不怕做不到，就怕想不到”，我們接着重構一下上面那個例子!
這次我們傳包含有User對象的List到C/C++程序裏面
Java代碼(User.java)
同上。
Java代碼(HelloJni.java)
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1. import java.util.*;
2. public class HelloJni{
3. static{
4. System.loadLibrary("userbean");
5. }
6. public native int get();
7. public native void set(int i);
8. public native void setUser(String userName);
9. public native User getUser();
10. public native void setUserList(ArrayList<User> userList);
11. public native ArrayList<User> getUserList();
12. public static void main(String [] args)
13. {
14. HelloJni hello = new HelloJni();
15. // hello.set(2);
16. // System.out.println(hello.get());
17. /*
18. hello.setUser("LiangYaotian");
19. User user = hello.getUser();
20. System.out.println("user from c/c++");
21. System.out.println("name:"+user.getUserName());
22. System.out.println("isMan?:"+user.isMan());
23. System.out.println("age:"+user.getAge());
24. */
25. ArrayList<User> userList = new ArrayList<User>();
26. for(int i=0;i<10;i++){
27. User u = new User((long)(1000+i),"LiangYaotian"+i,true,21);
28. userList.add(u);
29. }
30. hello.setUserList(userList);
31. userList = null;
32. userList = hello.getUserList();
33. System.out.println("ArrayList<User> construct from C++,then Java print it.....");
34. for(User u : userList){
35. System.out.println("id:"+u.getId()+"; name:"+u.getUserName());
36. }
37. }
38. }
import java.util.*; public class HelloJni{ static{ System.loadLibrary("userbean"); } public native int get(); public native void set(int i); public native void setUser(String userName); public native User getUser(); public native void setUserList(ArrayList<User> userList); public native ArrayList<User> getUserList(); public static void main(String [] args) { HelloJni hello = new HelloJni(); // hello.set(2); // System.out.println(hello.get()); /* hello.setUser("LiangYaotian"); User user = hello.getUser(); System.out.println("user from c/c++"); System.out.println("name:"+user.getUserName()); System.out.println("isMan?:"+user.isMan()); System.out.println("age:"+user.getAge()); */ ArrayList<User> userList = new ArrayList<User>(); for(int i=0;i<10;i++){ User u = new User((long)(1000+i),"LiangYaotian"+i,true,21); userList.add(u); } hello.setUserList(userList); userList = null; userList = hello.getUserList(); System.out.println("ArrayList<User> construct from C++,then Java print it....."); for(User u : userList){ System.out.println("id:"+u.getId()+"; name:"+u.getUserName()); } } }
C頭文件(HelloJni.h)
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1. #include <jni.h>
2. /* Header for class HelloJni */
3. #ifndef _Included_HelloJni
4. #define _Included_HelloJni
5. #ifdef __cplusplus
6. extern "C" {
7. #endif
8. JNIEXPORT void JNICALL Java_HelloJni_sayHello (JNIEnv *, jclass);
9. JNIEXPORT jint JNICALL Java_HelloJni_getInt (JNIEnv *, jobject);
10. JNIEXPORT void JNICALL Java_HelloJni_setInt (JNIEnv *, jobject, jint);
11. JNIEXPORT void JNICALL Java_HelloJni_setUser (JNIEnv *, jobject, jstring);
12. JNIEXPORT jobject JNICALL Java_HelloJni_getUser (JNIEnv *, jobject);
#include <jni.h> /* Header for class HelloJni */ #ifndef _Included_HelloJni #define _Included_HelloJni #ifdef __cplusplus extern "C" { #endif JNIEXPORT void JNICALL Java_HelloJni_sayHello (JNIEnv *, jclass); JNIEXPORT jint JNICALL Java_HelloJni_getInt (JNIEnv *, jobject); JNIEXPORT void JNICALL Java_HelloJni_setInt (JNIEnv *, jobject, jint); JNIEXPORT void JNICALL Java_HelloJni_setUser (JNIEnv *, jobject, jstring); JNIEXPORT jobject JNICALL Java_HelloJni_getUser (JNIEnv *, jobject);
頭文件的實現(HelloJni.cpp)
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1. #include "HelloJni.h"
2. int i=1;
3. jobject user;
4. JNIEXPORT jint JNICALL Java_HelloJni_get
5. (JNIEnv *env, jobject jthiz){
6. printf("HelloWorld/n");
7. }
8. JNIEXPORT void JNICALL Java_HelloJni_set
9. (JNIEnv *env, jobject jthiz, jint ji){
10. i = ji+1;
11. }
12. JNIEXPORT void JNICALL Java_HelloJni_setUser
13. (JNIEnv *env, jobject jthiz, jstring name){
14. jclass userClass = env->FindClass("User");
15. jmethodID userMethod = env->GetMethodID(userClass,"<init>","()V");
16. jfieldID mId = env->GetFieldID(userClass,"id","J");
17. jfieldID mUserName = env->GetFieldID(userClass,"userName","Ljava/lang/String;");
18. jfieldID mIsMan = env->GetFieldID(userClass,"isMan","Z");
19. jfieldID mAge = env->GetFieldID(userClass,"age","I");
20. jobject userObject = env->NewObject(userClass,userMethod);
21. env->SetObjectField(userObject,mUserName,name);
22. env->SetLongField(userObject,mId,1001);
23. env->SetBooleanField(userObject,mIsMan,1);
24. env->SetIntField(userObject,mAge,21);
25. user = userObject;
26. }
27. JNIEXPORT jobject JNICALL Java_HelloJni_getUser
28. (JNIEnv *env, jobject jthiz){
29. return user;
30. }
31. JNIEXPORT void JNICALL Java_HelloJni_setUserList
32. (JNIEnv *env, jobject jthiz, jobject userList){
33. int i;
34. //class ArrayList
35. jclass cls_arraylist = env->GetObjectClass(userList);
36. //method in class ArrayList
37. jmethodID arraylist_get = env->GetMethodID(cls_arraylist,"get","(I)Ljava/lang/Object;");
38. jmethodID arraylist_size = env->GetMethodID(cls_arraylist,"size","()I");
39. jint len = env->CallIntMethod(userList,arraylist_size);
40. printf("get java ArrayList<User> object by C++ , then print it...../n");
41. for(i=0;i<len;i++){
42. jobject obj_user = env->CallObjectMethod(userList,arraylist_get,i);
43. jclass cls_user = env->GetObjectClass(obj_user);
44. jmethodID user_getId = env->GetMethodID(cls_user,"getId","()J");
45. jmethodID user_getUserName = env->GetMethodID(cls_user,"getUserName","()Ljava/lang/String;");
46. jmethodID user_isMan = env->GetMethodID(cls_user,"isMan","()Z");
47. jmethodID user_getAge = env->GetMethodID(cls_user,"getAge","()I");
48. jstring name = (jstring)env->CallObjectMethod(obj_user,user_getUserName);
49. jboolean b = true;
50. const char *namePtr = env->GetStringUTFChars(name,&b);
51. jlong id = env->CallLongMethod(obj_user,user_getId);
52. jboolean sex = env->CallBooleanMethod(obj_user,user_isMan);
53. jint age = env->CallIntMethod(obj_user,user_getAge);
54. printf("Id:%d; ",id);
55. printf("Name:%s; ",namePtr);
56. printf("isMan? %d; ",sex);
57. printf("Age:%d /n ",age);
58. }
59. }
60. JNIEXPORT jobject JNICALL Java_HelloJni_getUserList
61. (JNIEnv *env, jobject jthiz){
62. //ArrayList Object
63. jclass cls_ArrayList = env->FindClass("java/util/ArrayList");
64. jmethodID construct = env->GetMethodID(cls_ArrayList,"<init>","()V");
65. jobject obj_ArrayList = env->NewObject(cls_ArrayList,construct,"");
66. jmethodID arrayList_add = env->GetMethodID(cls_ArrayList,"add","(Ljava/lang/Object;)Z");
67. //User Object
68. jclass cls_user = env->FindClass("User");
69. //none argument construct function
70. jmethodID construct_user = env->GetMethodID(cls_user,"<init>","()V");
71. //new a object
72. jobject obj_user = env->NewObject(cls_user,construct_user,"");
73. //get method id
74. /*
75. jmethodID user_setId = env->GetMethodID(cls_user,"setId","(J)V");
76. jmethodID user_setUserName = env->GetMethodID(cls_user,"setUserName","(Ljava/lang/String;)V");
77. jmethodID user_setMan = env->GetMethodID(cls_user,"setMan","(Z)V");
78. jmethodID user_setAge = env->GetMethodID(cls_user,"setAge","(I)V");
79. */
80. int i;
81. for(i=0;i<10;i++){
82. //new a object
83. jobject obj_user = env->NewObject(cls_user,construct_user,"");
84. //get field id
85. jfieldID user_id = env->GetFieldID(cls_user,"id","J");
86. jfieldID user_name = env->GetFieldID(cls_user,"userName","Ljava/lang/String;");
87. jfieldID user_isMan = env->GetFieldID(cls_user,"isMan","Z");
88. jfieldID user_age = env->GetFieldID(cls_user,"age","I");
89. env->SetLongField(obj_user,user_id,i);
90. env->SetObjectField(obj_user,user_name,env->NewStringUTF("LiangYaoTian"));
91. env->SetBooleanField(obj_user,user_isMan,1);
92. env->SetIntField(obj_user,user_age,21);
93. env->CallObjectMethod(obj_ArrayList,arrayList_add,obj_user);
94. }
95. return obj_ArrayList;
96. }
#include "HelloJni.h" int i=1; jobject user; JNIEXPORT jint JNICALL Java_HelloJni_get (JNIEnv *env, jobject jthiz){ printf("HelloWorld/n"); } JNIEXPORT void JNICALL Java_HelloJni_set (JNIEnv *env, jobject jthiz, jint ji){ i = ji+1; } JNIEXPORT void JNICALL Java_HelloJni_setUser (JNIEnv *env, jobject jthiz, jstring name){ jclass userClass = env->FindClass("User"); jmethodID userMethod = env->GetMethodID(userClass,"<init>","()V"); jfieldID mId = env->GetFieldID(userClass,"id","J"); jfieldID mUserName = env->GetFieldID(userClass,"userName","Ljava/lang/String;"); jfieldID mIsMan = env->GetFieldID(userClass,"isMan","Z"); jfieldID mAge = env->GetFieldID(userClass,"age","I"); jobject userObject = env->NewObject(userClass,userMethod); env->SetObjectField(userObject,mUserName,name); env->SetLongField(userObject,mId,1001); env->SetBooleanField(userObject,mIsMan,1); env->SetIntField(userObject,mAge,21); user = userObject; } JNIEXPORT jobject JNICALL Java_HelloJni_getUser (JNIEnv *env, jobject jthiz){ return user; } JNIEXPORT void JNICALL Java_HelloJni_setUserList (JNIEnv *env, jobject jthiz, jobject userList){ int i; //class ArrayList jclass cls_arraylist = env->GetObjectClass(userList); //method in class ArrayList jmethodID arraylist_get = env->GetMethodID(cls_arraylist,"get","(I)Ljava/lang/Object;"); jmethodID arraylist_size = env->GetMethodID(cls_arraylist,"size","()I"); jint len = env->CallIntMethod(userList,arraylist_size); printf("get java ArrayList<User> object by C++ , then print it...../n"); for(i=0;i<len;i++){ jobject obj_user = env->CallObjectMethod(userList,arraylist_get,i); jclass cls_user = env->GetObjectClass(obj_user); jmethodID user_getId = env->GetMethodID(cls_user,"getId","()J"); jmethodID user_getUserName = env->GetMethodID(cls_user,"getUserName","()Ljava/lang/String;"); jmethodID user_isMan = env->GetMethodID(cls_user,"isMan","()Z"); jmethodID user_getAge = env->GetMethodID(cls_user,"getAge","()I"); jstring name = (jstring)env->CallObjectMethod(obj_user,user_getUserName); jboolean b = true; const char *namePtr = env->GetStringUTFChars(name,&b); jlong id = env->CallLongMethod(obj_user,user_getId); jboolean sex = env->CallBooleanMethod(obj_user,user_isMan); jint age = env->CallIntMethod(obj_user,user_getAge); printf("Id:%d; ",id); printf("Name:%s; ",namePtr); printf("isMan? %d; ",sex); printf("Age:%d /n ",age); } } JNIEXPORT jobject JNICALL Java_HelloJni_getUserList (JNIEnv *env, jobject jthiz){ //ArrayList Object jclass cls_ArrayList = env->FindClass("java/util/ArrayList"); jmethodID construct = env->GetMethodID(cls_ArrayList,"<init>","()V"); jobject obj_ArrayList = env->NewObject(cls_ArrayList,construct,""); jmethodID arrayList_add = env->GetMethodID(cls_ArrayList,"add","(Ljava/lang/Object;)Z"); //User Object jclass cls_user = env->FindClass("User"); //none argument construct function jmethodID construct_user = env->GetMethodID(cls_user,"<init>","()V"); //new a object jobject obj_user = env->NewObject(cls_user,construct_user,""); //get method id /* jmethodID user_setId = env->GetMethodID(cls_user,"setId","(J)V"); jmethodID user_setUserName = env->GetMethodID(cls_user,"setUserName","(Ljava/lang/String;)V"); jmethodID user_setMan = env->GetMethodID(cls_user,"setMan","(Z)V"); jmethodID user_setAge = env->GetMethodID(cls_user,"setAge","(I)V"); */ int i; for(i=0;i<10;i++){ //new a object jobject obj_user = env->NewObject(cls_user,construct_user,""); //get field id jfieldID user_id = env->GetFieldID(cls_user,"id","J"); jfieldID user_name = env->GetFieldID(cls_user,"userName","Ljava/lang/String;"); jfieldID user_isMan = env->GetFieldID(cls_user,"isMan","Z"); jfieldID user_age = env->GetFieldID(cls_user,"age","I"); env->SetLongField(obj_user,user_id,i); env->SetObjectField(obj_user,user_name,env->NewStringUTF("LiangYaoTian")); env->SetBooleanField(obj_user,user_isMan,1); env->SetIntField(obj_user,user_age,21); env->CallObjectMethod(obj_ArrayList,arrayList_add,obj_user); } return obj_ArrayList; }
運行結果：
theEnd.jpg
源碼：E-Mail我：[email protected]
原創作品，轉載需註明出處...http://blog.csdn.net/u_xtian/archive/2010/11/25/6033963.aspx
Java JNI由淺入深(包括：Java和C++互傳ArrayList泛型對象參數)
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