Jni样例

package kaiqi.cn.demo001;

public class Key {
    public static native String hello();
    public static void init() {
        System.loadLibrary("hello");
    }
}

public class MainActivity extends AppCompatActivity {

    public static String KEY = "30001";

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        final EditText et = (EditText)findViewById(R.id.ets);//submit
        Button sub = (Button)findViewById(R.id.submit);//submit
        sub.setOnClickListener(new View.OnClickListener() {

            @Override
            public void onClick(View arg0) {
                if(KEY.equals(et.getText().toString().trim())){
                    Toast.makeText(MainActivity.this, "成功", Toast.LENGTH_SHORT).show();
                } else {
                    Toast.makeText(MainActivity.this, "失败", Toast.LENGTH_SHORT).show();
                }
            }
        });
        Key.init();
        KEY = Key.hello();
    }
}

Android.mk

LOCAL_PATH := $(call my-dir)

include $(CLEAR_VARS)
LOCAL_LDLIBS    := -lm -llog -landroid
LOCAL_MODULE    := hello
LOCAL_SRC_FILES := K.cpp

include $(BUILD_SHARED_LIBRARY)

K.cpp

#include <jni.h>
#include <stdio.h>
#include <string.h>
extern "C" jstring statTst(JNIEnv* env, jobject thiz);
//(void*) 指针
JNINativeMethod metheds[] = {
// java方法名,函数签名(参数列表)-返回值,java映射成C世界的方法
        { "hello", "()Ljava/lang/String;", (void*) statTst } };

jstring statTst(JNIEnv* env, jobject thiz) {
    return env->NewStringUTF("2000");
}

jint JNI_OnLoad(JavaVM* vm, void* reserved) {
    jint result = JNI_ERR;
    JNIEnv* env = NULL;
    if (vm->GetEnv((void**) &env, JNI_VERSION_1_4) != JNI_OK) {
        return result;
    }
    jclass clazz = env->FindClass("kaiqi/cn/demo001/Key");
    if (clazz == NULL) {
        return result;
    }
    if (env->RegisterNatives(clazz, metheds,
            sizeof(metheds) / sizeof(metheds[0])) < 0) {
        return result;
    }
    result = JNI_VERSION_1_4;
    return result;
}

apply plugin: 'com.android.application'

android {
    compileSdkVersion 27



    defaultConfig {
        applicationId "kaiqi.cn.demo001"
        minSdkVersion 16
        targetSdkVersion 27
        versionCode 1
        versionName "1.0"

//        externalNativeBuild {
//            //cmake {...}
//            cmake {
//            }
//        }

        ndk{
            moduleName "hello2" // 生成hello.so文件
            ldLibs "log"//实现__android_log_print
//            abiFilters "armeabi", "armeabi-v7a", "x86"  //输出指定三种abi体系结构下的so库。
            abiFilters "armeabi-v7a"  //输出指定三种abi体系结构下的so库。
//            abiFilters "x86"  //输出指定三种abi体系结构下的so库。
//            abiFilters "armeabi" //输出指定三种abi体系结构下的so库。
        }

        sourceSets{
            main {
                //jniLibs.srcDirs = ['src/main/libs']
                jni.srcDirs = []
                jniLibs.srcDir "src/main/libs"
            }
        }
    }
//    packagingOptions{
//        doNotStrip '*/mips/*.so'
//        doNotStrip '*/mips64/*.so'
//    }
//    externalNativeBuild {
//        ndkBuild {
//            path 'src/main/jni/*.cpp'
//        }
//    }

    externalNativeBuild {
        ndkBuild {
            //path file("src/main/jni/Android.mk")
            path "src/main/jni/Android.mk"
        }
    }
    lintOptions {
        checkReleaseBuilds false
        // Or, if you prefer, you can continue to check for errors in release builds,
        // but continue the build even when errors are found:
        abortOnError false
    }
    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
        }
       // sourceSets { main { jni .srcDirs= ['src/main/jni','src/main/jni/'] } }


    }

}

dependencies {
    implementation fileTree(dir: 'libs', include: ['*.jar'])

    implementation 'com.android.support:appcompat-v7:27.1.1'
}