本篇是承接的基础上进行的 #####1.编写Books实体类 /** * @author jayqiu * @describe * @date 2017/3/30 17:21 / public class Books { private String title; private String author; private String subject; private int book_id; public String getTitle() { return title; } public void setTitle(String title) { this.title = title; } public String getAuthor() { return author; } public void setAuthor(String author) { this.author = author; } public String getSubject() { return subject; } public void setSubject(String subject) { this.subject = subject; } public int getBook_id() { return book_id; } public void setBook_id(int book_id) { this.book_id = book_id; } } #####2.编写MyNdk.java /* * @author jayqiu * @describe * @date 2017/3/30 13:52 */ public class MyNdk { static { System.loadLibrary("MyNdk"); } public native int getAdd(int a,int b); public native Books getBooks(Books books); }

#####3.MyNdk.c生成Java_com_threehalf_mynewjni_MyNdk_getBooks 方法 JNIEXPORT jobject JNICALL Java_com_threehalf_mynewjni_MyNdk_getBooks(JNIEnv *env, jobject instance, jobject books) { jclass objectClass = (*env)->FindClass(env, "com/threehalf/mynewjni/Books");// java 实体类对应的位置 jfieldID title = (*env)->GetFieldID(env,objectClass, "title", "Ljava/lang/String;");//book title jfieldID book_id =(*env)->GetFieldID(env,objectClass, "book_id", "I");//book id

(*env)->SetObjectField(env,books, title, (*env)->NewStringUTF(env,"C 语言"));//设置booktitle    (*env)->SetIntField(env,books, book_id, 10);// 设置 book id    return  books;}复制代码

#####4.MainActivity public class MainActivity extends AppCompatActivity {

@Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        TextView textView = (TextView) findViewById(R.id.tv_name);        // textView.setText(new MyNdk().getAdd(10,20)+"");        Books books = new Books();        books = (Books) new MyNdk().getBooks(books);        textView.setText("ID:"+books.getBook_id() + "书名：" + books.getTitle());    }}复制代码

#####5.运行结果

#####6.GetFieldID Java基础类型对应的符号