本文源码：https://github.com/jt1024/JNIBasicForAndroid
环境
1.Android Studio 3.0
2.gradle-4.1-all
3.android sdk 26
一、在Android Studio 新建安卓工程
二、基本配置
参照:
JNI/NDK编程（一）——无参函数之Hello world !或JNI/NDK编程（二）——带参函数之模拟登录
三、编写代码
1.编写C++文件 login_lib.cpp
路径：NDKThirdDemo/app/src/main/cpp/login_lib.cpp
#include <jni.h>
#include "string.h"
extern "C" JNIEXPORT jstring JNICALL
Java_com_tao_ndkthirddemo_Java2CLogin_login(JNIEnv *env, jobject instance, jstring username, jstring password, jint authcode) {
jclass jclazz;
//1.加载java类得到class对象
jclazz = env->FindClass("com/tao/ndkthirddemo/Java2CLogin");
//2.获取java类成员变量
//2.1 获取java类成员变量ID
jfieldID codeErrorID = env->GetFieldID(jclazz, "codeError", "Ljava/lang/String;");
jfieldID usernameOrPasswordErrorID = env->GetFieldID(jclazz, "usernameOrPasswordError", "Ljava/lang/String;");
jfieldID loginSuccessErrorID = env->GetStaticFieldID(jclazz, "loginSuccess", "Ljava/lang/String;");
//2.2 通过成员变量ID获取java类成员变量
jstring jcodeError = (jstring) env->GetObjectField(instance, codeErrorID);
jstring jusernameOrPasswordError = (jstring) env->GetObjectField(instance, usernameOrPasswordErrorID);
jstring jloginSuccess = (jstring) env->GetStaticObjectField(jclazz, loginSuccessErrorID);
//return jloginSuccess;
//3.验证
if (authcode == 888) {
const char *cStr;
const char *pStr;
jboolean isCopy;
cStr = env->GetStringUTFChars(username, &isCopy);
pStr = env->GetStringUTFChars(password, &isCopy);
int reUsername = strcmp(cStr, "admin");
int rePassword = strcmp(pStr, "1234");
if (reUsername == 0 && rePassword == 0) {
return jloginSuccess;
} else {
return jusernameOrPasswordError;
}
} else {
return jcodeError;
}
}
2.编写Jave文件 Java2CLogin
路径：NDKThirdDemo/app/src/main/java/com.tao.ndkthirddemo.Java2CLogin
package com.tao.ndkthirddemo;
/**
* 作者： 麦典威
* 修改时间：2018/3/15 8:07
* 版权声明：www.ekwing.com
* 功能： ${TODO}
*/
public class Java2CLogin {
private String codeError = "验证码错误！";
private String usernameOrPasswordError = "用户名或密码错误！";
private static String loginSuccess = "登录成功！";
static {
System.loadLibrary("login_lib");
}
/**
* 带参数的 native 函数
*
* @param username 用户名
* @param password 密码
* @param authcode 验证码
* @return
*/
public native String login(String username, String password, int authcode);
}
3.编写Activity文件 MainActivity
路径：NDKThirdDemo/app/src/main/java/com.tao.ndkthirddemo.MainActivity
package com.tao.ndkthirddemo;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;
public class MainActivity extends AppCompatActivity {
private static final String TAG = "MainActivity";
private EditText edtUsername, edtPassword, edtAuthcode;
private Button btnLogin;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
initView();
}
private void initView() {
edtUsername = findViewById(R.id.edt_username);
edtPassword = findViewById(R.id.edt_password);
edtAuthcode = findViewById(R.id.edt_authcode);
btnLogin = findViewById(R.id.btn_login);
btnLogin.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
String username = edtUsername.getText().toString().trim();
String password = edtPassword.getText().toString().trim();
String authcodeStr = edtAuthcode.getText().toString().trim();
int authcode = Integer.parseInt(authcodeStr.equals("") ? "0" : authcodeStr);
String result = new Java2CLogin().login(username, password, authcode);
Log.e(TAG, "C 调用 Java 成员变量获取的结果是：" + result);
Toast.makeText(MainActivity.this, result, Toast.LENGTH_LONG).show();
}
});
}
}
4.编写 activity_main.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
tools:context="com.tao.ndkthirddemo.MainActivity">
<EditText
android:id="@+id/edt_username"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:hint="请输入用户名(admin)" />
<EditText
android:id="@+id/edt_password"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:hint="请输入密码(1234)" />
<EditText
android:id="@+id/edt_authcode"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:hint="请输入验证码(888)" />
<Button
android:id="@+id/btn_login"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="center_horizontal"
android:text="登录——C 调用 Java 成员变量" />
</LinearLayout>
5.编写CMakeLists.txt文件，以后如果编写其他jni类，只需替换里面的“login_lib”
# For more information about using CMake with Android Studio, read the
# documentation: https://d.android.com/studio/projects/add-native-code.html
# Sets the minimum version of CMake required to build the native library.
cmake_minimum_required(VERSION 3.4.1)
# Creates and names a library, sets it as either STATIC
# or SHARED, and provides the relative paths to its source code.
# You can define multiple libraries, and CMake builds them for you.
# Gradle automatically packages shared libraries with your APK.
add_library( # Sets the name of the library.
login_lib
# Sets the library as a shared library.
SHARED
# Provides a relative path to your source file(s).
src/main/cpp/login_lib.cpp )
# Searches for a specified prebuilt library and stores the path as a
# variable. Because CMake includes system libraries in the search path by
# default, you only need to specify the name of the public NDK library
# you want to add. CMake verifies that the library exists before
# completing its build.
find_library( # Sets the name of the path variable.
log-lib
# Specifies the name of the NDK library that
# you want CMake to locate.
log )
# Specifies libraries CMake should link to your target library. You
# can link multiple libraries, such as libraries you define in this
# build script, prebuilt third-party libraries, or system libraries.
target_link_libraries( # Specifies the target library.
login_lib
# Links the target library to the log library
# included in the NDK.
${log-lib} )
四、编译
点击build——>Rebuild Project 或 Make Progject
参照:
JNI/NDK编程（一）——无参函数之Hello world !或JNI/NDK编程（二）——带参函数之模拟登录
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