安卓学习日记——NDK开发

NDK下载地址：https://developer.android.google.cn/ndk/downloads/index.html
解压完之后配置Path
activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity" >

    <EditText
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:inputType="number"
        android:ems="10"
        android:id="@+id/editText"
        android:layout_alignParentTop="true"
        android:layout_alignParentLeft="true"
        android:layout_alignParentStart="true"
        android:layout_alignParentRight="true"
        android:layout_alignParentEnd="true" />

    <EditText
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:inputType="number"
        android:ems="10"
        android:id="@+id/editText1"
        android:layout_below="@+id/editText"
        android:layout_alignParentLeft="true"
        android:layout_alignParentStart="true"
        android:layout_alignRight="@+id/editText"
        android:layout_alignEnd="@+id/editText" />

    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="加法运算"
        android:onClick="addClick"
        android:id="@+id/button"
        android:layout_below="@+id/editText1"
        android:layout_centerHorizontal="true" />

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="结果："
        android:id="@+id/textView"
        android:layout_below="@+id/button"
        android:layout_centerHorizontal="true" />
</RelativeLayout>

MainActivity

package com.example.ndk;

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

public class MainActivity extends AppCompatActivity {
    private EditText editText_num1,editText_num2;
    private TextView textView_result;
    //加载动态链接库
    static
    {
        System.loadLibrary("hello");
    }
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        editText_num1= (EditText) findViewById(R.id.editText);
        editText_num2= (EditText) findViewById(R.id.editText1);
        textView_result= (TextView) findViewById(R.id.textView);
    }
    //声明一个本地方法，该方法由C或c++实现
    public native int add(int num1,int num2);
    public void addClick(View v){
        String num1=editText_num1.getText().toString();
        String num2=editText_num2.getText().toString();
//调用本地方法
        int result= add(Integer.parseInt(num1),Integer.parseInt(num2));
        textView_result.setText("结果："+result);
    }
}

com_example_ndk_MainActivity.h

/* DO NOT EDIT THIS FILE - it is machine generated */
#include <jni.h>
/* Header for class com_example_ndk_MainActivity */

#ifndef _Included_com_example_ndk_MainActivity
#define _Included_com_example_ndk_MainActivity
#ifdef __cplusplus
extern "C" {
#endif
/*
 * Class:     com_example_ndk_MainActivity
 * Method:    add
 * Signature: (II)I
 */
JNIEXPORT jint JNICALL Java_com_example_ndk_MainActivity_add
  (JNIEnv *, jobject, jint, jint);

#ifdef __cplusplus
}
#endif
#endif

hello.c

#include "com_example_ndk_MainActivity.h"
JNIEXPORT jint JNICALL Java_com_example_ndk_MainActivity_add
  (JNIEnv * env, jobject obj, jint num1, jint num2){

    return num1+num2;
  }

Android.mk

LOCAL_PATH := $(call my-dir)
include $(CLEAR_VARS)
LOCAL_MODULE:= hello
LOCAL_SRC_FILES := hello.c
include $(BUILD_SHARED_LIBRARY)

效果