Android NDK JNI 开发指南-优快云博客

本文链接：https://blog.youkuaiyun.com/weixin_40511536/article/details/78295266

针对Android Studio工具

一、新建一个project，再新建一个java.class文件TestJni，如下图添加代码

package com.example.byc.testndk;

/**
 * Created by byc on 2017/10/19.
 */

public class TestJni {
    public native String getStringFromNative();
}

二、在MainActivity中添加调用native方法的代码

package com.example.byc.testndk;

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.widget.TextView;

public class MainActivity extends AppCompatActivity {

    private TestJni testJni;
    private TextView tv;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        tv = (TextView)findViewById(R.id.tv);
        testJni = new TestJni();
        tv.setText(testJni.getStringFromNative());
    }
}

三、build project 得到中间文件.class，路径：

app\build\intermediates\classes\debug

根据生成的.class文件，用javah生成.h文件，进入Terminal界面，默认路径是...app，进入...build\intermediates\classes\debug路径执行：

javah -jni com.example.byc.testndk.TestJni

执行完后会在此目录下生成.h文件

com_example_byc_testndk_TestJni.h

四、在main目录下新建一个jni目录，把第三步中的.h文件剪切里面，新建一个.c文件，代码如下：

#include "com_example_byc_testndk_TestJni.h"
/*
 * Class:     com_example_byc_testndk_TestJni
 * Method:    getStringFromNative
 * Signature: ()Ljava/lang/String;
 */

JNIEXPORT jstring JNICALL Java_com_example_byc_testndk_TestJni_getStringFromNative
  (JNIEnv *env, jobject obj){
     return (*env)->NewStringUTF(env,"This just a test for Android Studio NDK JNI developer!");
  }

五、在project structure-->SDK Location中设置NDK的路径，如下图，或是在local.properties中添加如下代码：

ndk.dir=C\:\\Users\\byc\\AppData\\Local\\Android\\Sdk\\ndk-bundle
sdk.dir=C\:\\Users\\byc\\AppData\\Local\\Android\\Sdk

六、module的build.gradle文件，在defaultConfig中添加：

defaultConfig {
        ...

        ndk{
            moduleName "TestJniLib"
            abiFilters "armeabi","armeabi-v7a","x86" //输出指定三种abi体系结构下的.so库
        }
    }

七、在MainActivity中添加显示代码即可。要添加库的引用

public class MainActivity extends AppCompatActivity {

    static{
        System.loadLibrary("TestJniLib");
    }
    private TestJni testJni;
    private TextView tv;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        tv = (TextView)findViewById(R.id.tv);
        testJni = new TestJni();
        tv.setText(testJni.getStringFromNative());
    }
}

遇到的问题：

一、java.io.IOException: Could not delete path ...build\intermediates\classes\debug

解决方案：因为上面操作时在Terminal界面路径还是上面报错的路径，退回到...app下即可

二、cannot resolve corresponding JNI function...