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 !
JNI/NDK编程（二）——带参函数之模拟登录
JNI/NDK编程（三）——C 调用 Java 成员变量
JNI/NDK编程（四）——C 调用 Java 类中的函数/方法
三、编写代码
1.编写C++文件 login_lib.cpp
路径：NDKFifthDemo/app/src/main/cpp/login_lib.cpp
#include <jni.h>
#include "string.h"
#include <android/log.h>
#define LOG_TAG "jiat"
#define LOGD(...) __android_log_print(ANDROID_LOG_ERROR, LOG_TAG, __VA_ARGS__)
extern "C" JNIEXPORT jstring JNICALL
Java_com_tao_ndkfifthdemo_Java2CLogin_login(JNIEnv *env, jobject instance, jstring username, jstring password, jint authcode) {
const char *resultMessage;
if (authcode == 888) {
const char *cStr;
const char *pStr;
jboolean isCopy;
cStr = env->GetStringUTFChars(username, &isCopy);
LOGD("cStr = %s", cStr);
pStr = env->GetStringUTFChars(password, &isCopy);
LOGD("pStr = %s", pStr);
int reUsername = strcmp(cStr, "admin");
LOGD("reUsername = %d", reUsername);
int rePassword = strcmp(pStr, "1234");
LOGD("rePassword = %d", rePassword);
if (reUsername == 0 && rePassword == 0) {
LOGD("success login !");
resultMessage = "success login !";
} else {
LOGD("error username or error password");
resultMessage = "error username or error password";
}
} else {
LOGD("error authcode");
resultMessage = "error authcode";
}
return env->NewStringUTF(resultMessage);
}
2.编写Jave文件 Java2CLogin
路径：NDKFifthDemo/app/src/main/java/com.tao.ndkfifthdemo.Java2CLogin
package com.tao.ndkfifthdemo;
/**
* 作者： 麦典威
* 修改时间：2018/3/22 8:07
* 版权声明：www.ekwing.com
* 功能： ${TODO}
*/
public class Java2CLogin {
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：NDKFifthDemo/app/src/main/java/com.tao.ndkfifthdemo.MainActivity
package com.tao.ndkfifthdemo;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
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, "Java调用C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.ndkfifthdemo.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" />
</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}
log)
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 !
JNI/NDK编程（二）——带参函数之模拟登录
JNI/NDK编程（三）——C 调用 Java 成员变量
JNI/NDK编程（四）——C 调用 Java 类中的函数/方法
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