Android Java代码与JNI交互 JNI访问Java类方法 (七)-Toy模板网

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🔥 Android Studio 版本 🔥

🔥 创建包含JNI的类 JNIAccessMethod.java 🔥

package com.cmake.ndk1.jni;

import com.cmake.ndk1.model.Animal;

public class JNIAccessMethod {
    static {
        System.loadLibrary("access-method-lib");
    }

    public native void accessInstanceMethod(Animal animal);

    public native void accessStaticMethod(Animal animal);
}

🔥 Java方法对应Native层方法名称 🔥

 * ｜Java                   ｜JNI                   ｜
 * ｜String fun()           ｜()Ljva/lang/String;   ｜
 * ｜long f(int i,Class c); ｜(ILjava/lang/Class;)J ｜
 * ｜String(byte[] bytes);  ｜([B)V                 ｜

🔥 配置动态库名称 🔥

add_library(
        #动态库名称 access-method-lib
        access-method-lib

        SHARED

        jni/jni_access_method.cpp
)

🔥 生成可关联的库链接 🔥

为了让Java能够调用 access-method-lib 库中的函数，您需要使用 CMake 构建脚本中的 target_link_libraries() 命令来关联 access-method-lib 库
target_link_libraries( # Specifies the target library.
        ndk1
        person-lib
        dynamic-lib
        basic-type-lib
        string-lib
        reference-type-lib
        access-field-lib
        access-method-lib
        # Links the target library to the log library
        # included in the NDK. )
)

🔥 提供给 jni 调用的日志库链接 🔥

target_link_libraries( # Specifies the target library.
        access-method-lib
        # Links the target library to the log library
        # included in the NDK.
        ${log-lib})

🔥 Native层实现 JNIAccessMethod 类下面的JNI接口 🔥

实现调用 callInstanceMethod() 函数

extern "C"
JNIEXPORT void JNICALL
Java_com_cmake_ndk1_jni_JNIAccessMethod_accessInstanceMethod(JNIEnv *env,jobject instance, jobject animal) {
    jclass cls = env->GetObjectClass(animal);
    //查找Animal对象中的callInstanceMethod()函数，函数需要传递的参数是int类型对应I，
    //返回返回为void对应V
    jmethodID mid = env->GetMethodID(cls,"callInstanceMethod","(I)V");

    env->CallVoidMethod(animal,mid,2);
}

实现调用Animal中 callStaticMethod() 函数并传递字符串参数

extern "C"
JNIEXPORT void JNICALL
Java_com_cmake_ndk1_jni_JNIAccessMethod_accessStaticMethod(JNIEnv *env,jobject instance, jobject animal) {
    jclass cls = env->GetObjectClass(animal);
    //查找Animal对象中的callStaticMethod()函数，函数需要传递的参数是int类型对应I，
    //返回返回为void对应V
    jmethodID mid = env->GetStaticMethodID(cls,"callStaticMethod",
                                     "(Ljava/lang/String;)Ljava/lang/String;");

    //构造一个调用callStaticMethod()函数需要传递的参数
    jstring  parJString=env->NewStringUTF("jstrinig");
    env->CallStaticObjectMethod(cls,mid,parJString);
}

实现调用Animal中 callStaticMethod() 函数并传递集合和集合长度到参数

extern "C"
JNIEXPORT void JNICALL
Java_com_cmake_ndk1_jni_JNIAccessMethod_accessStaticMethod(JNIEnv *env,jobject instance, jobject animal) {
    jclass cls = env->GetObjectClass(animal);
    //查找Animal对象中的callStaticMethod()函数，函数需要传递的参数是int类型对应I，
    //返回返回为void对应V
    jmethodID mid = env->GetStaticMethodID(cls,"callStaticMethod",
                                     "(Ljava/lang/String;)Ljava/lang/String;");

    //构造一个调用callStaticMethod()函数需要传递的参数
    jstring  parJString=env->NewStringUTF("jstrinig");
    env->CallStaticObjectMethod(cls,mid,parJString);

    mid = env->GetStaticMethodID(cls,"callStaticMethod",
                                 "([Ljava/lang/String;I)Ljava/lang/String;");
    //在Native构建Java的字符串数组
    jclass strClass = env->FindClass("java/lang/String");
    int size=2;
    jobjectArray strArray = env->NewObjectArray(size,strClass, nullptr);
    jstring strItem;
    //循环添加字符串到strArray集合中
    for (int i = 0; i < size; ++i) {
        strItem = env->NewStringUTF("string in native");
        env->SetObjectArrayElement(strArray,i,strItem);
    }
    //调用静态方法
    env->CallStaticObjectMethod(cls,mid,strArray,size);
}

🔥 调用Native层函数操作Animal 中的函数 🔥

package com.cmake.ndk1;

import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.TextView;

import androidx.annotation.Nullable;
import androidx.appcompat.app.AppCompatActivity;

import com.cmake.ndk1.jni.JNIAccessField;
import com.cmake.ndk1.jni.JNIAccessMethod;
import com.cmake.ndk1.model.Animal;

public class MainActivity7 extends AppCompatActivity {


    @Override
    protected void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        JNIAccessMethod jniAccessMethod=new JNIAccessMethod();
        Animal animal=new Animal("animal");

        final TextView textView=findViewById(R.id.sample_text);
        textView.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                jniAccessMethod.accessInstanceMethod(animal);
                jniAccessMethod.accessStaticMethod(animal);
            }
        });
    }
}

D/Animal: call instance method and num is 2
D/Animal: call static method with jstrinig
D/Animal: call static method with string array
D/Animal: str in array is string in native
D/Animal: str in array is string in native