NDK笔记--C++调用java

Posted 2022-11-11 ljt2724960661

     这一节主要了解从C/C++调用java的过程，一般是用在android与Native交互的场景中，在调用过程中，一般需要C/C++层持有Java的对象，然后调用相关方法，如下

Java:

static 
        System.loadLibrary("ndkplay");
    

package com.sky.ndkplay;
public class Employee 

    public String name;
    public int age;

    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 "Employee" +
                "name='" + name + '\\'' +
                ", age=" + age +
                '';
    

public class MainActivity extends AppCompatActivity 

    // Used to load the 'ndkplay' library on application startup.
    static 
        System.loadLibrary("ndkplay");
    
    private ActivityMainBinding binding;
    @Override
    protected void onCreate(Bundle savedInstanceState) 
        super.onCreate(savedInstanceState);

        binding = ActivityMainBinding.inflate(getLayoutInflater());
        setContentView(binding.getRoot());

    

    public native void insertObject();
    public void  showEmployeeInfo(View view) 
        insertObject();
    

extern "C"
JNIEXPORT void JNICALL
Java_com_sky_ndkplay_MainActivity_insertObject(JNIEnv *env
,jobject instance) 
    jclass employee_class = env->FindClass("com/sky/ndkplay/Employee");
    jobject employee_obj = env->AllocObject(employee_class);
    jmethodID setName = env->GetMethodID(employee_class,"setName","(Ljava/lang/String;)V");
    jmethodID setAge = env->GetMethodID(employee_class,"setAge","(I)V");

    jstring strRes = env->NewStringUTF("lisi");
    env->CallVoidMethod(employee_obj,setName,strRes);
    env->CallVoidMethod(employee_obj,setAge,100);