第一个JNI应用

1:创建一个firstjni.java文件

在中端执行

D:\Users\caron_wy\FirstJNI\app\src\main\java\wuyu\jni\api>javac  firstjni.java

生成firstjni.class

D:\Users\caron_wy\FirstJNI\app\src\main\java>javah -jni wuyu.jni.api.firstjni

生成wuyu_jni_api_firstjni.h

创建jni文件夹.拷贝生成的.h文件到jni文件夹下,创建.c文件

#include 

//
// Created by caron_wy on 2019/2/25.
//
JNIEXPORT jint JNICALL Java_wuyu_jni_api_firstjni_add(JNIEnv *env, jobject thiz,jint a,jint b)
{
        return a+b;
}

创建CMakeLists.txt文件生成so文件

apply plugin: 'com.android.application'

android {
    compileSdkVersion 28
    defaultConfig {
        applicationId "browser.android.com.firstjni"
        minSdkVersion 26
        targetSdkVersion 28
        versionCode 1
        versionName "1.0"
        testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"

        externalNativeBuild {
            cmake {
                //abiFilters 'armeabi-v7a'
                cppFlags ""
                arguments "-DANDROID_STL=c++_shared"
            }
        }
    }
    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
        }
    }

    externalNativeBuild {
        cmake {
            path "CMakeLists.txt" //编译后so文件的名字
        }
    }
}

dependencies {
    implementation fileTree(dir: 'libs', include: ['*.jar'])
    implementation 'com.android.support:appcompat-v7:28.0.0'
    implementation 'com.android.support.constraint:constraint-layout:1.1.3'
    testImplementation 'junit:junit:4.12'
    androidTestImplementation 'com.android.support.test:runner:1.0.2'
    androidTestImplementation 'com.android.support.test.espresso:espresso-core:3.0.2'
}

测试

package browser.android.com.firstjni;

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import wuyu.jni.api.firstjni;

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Log.d("wuyu","jni =" + firstjni.add(100,33));
    }
}