之前之前用R4，現在一下就跳到用R7了，Android4.0出來過後，應該有不少熱機友敢望資療吧，OK，在網上偶爾浏覽的時候，看到有很多初學者希望了解在ANDROID中NDK應用的開發，不知道它是怎麼開發與運行的，今天我就簡單來圖解一個HelloWorld的簡單實列吧，以好供初學者做給力的參考，OK，不廢話了，直入正題吧：
首先，我們得配置環境，當然這是在你本來就有SDK開發環境的情況下，請去官方下個NDK吧：http://www.android.com.,最新版本為android-ndk-r7-linux-x86.tar.bz2，即R7，我一直用的是LINUX，所以我下的是LINUX版本，如果你是WINDOWS或者MAC的話，你自己看著辦吧，OK，下下來後，解壓在你自己認為可以放的地方就行了，看目錄：，以上為解壓後的R7目錄,先別急新建項目開發，先配置NDK環境:打開終端，輸入命令:sudo vim ~/.baserc,打開後根據下面圖，填入下下來的NDK目錄路徑:
在圖中可以看到有這行：export NDK_HOME=/home/development/android/android-ndk-r7/
即為NDK所需配置的環境路徑。保存後，輸入: source ~/.baserc 來使其配置立即生效，OK後，咋們來新創建一個項目，為jni_demo,下面我需要看當前那個目錄截圖，你會發現目錄中有一個sample目錄，裡面就是其本身已有的列子，在這裡我得提醒各位，不敢你遇到任何新的語言，先看它的Hello World列子，不要急於誤打誤撞的敲代碼，先看清楚它的列子的運行效果，OK，在這裡我們就以hello-jni這個列子來驗證吧，打開這個目錄:
可看到有四個目錄，一個是JNI為C～比源碼處，一個是APP的RES，一個SRC為JAVA源代碼，再一個就是測試目錄，另外兩個文件就不在這裡說了，我們新建了項目後，需要寫JNI代碼與JAVA代碼，所以在這裡，我就直接把這裡的jni裡面的代碼拷貝到我的項目中去，記得在自己的項目中需要新建一個jni文件,其拷貝的兩個文件分別是:Android.mk與hello-jni.c,其Android.mk文件內容是:
# Copyright (C) 2009 The Android Open Source Project
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
#
LOCAL_PATH := $(call my-dir)
include $(CLEAR_VARS)
LOCAL_MODULE := hello-jni
LOCAL_SRC_FILES := hello-jni.c
include $(BUILD_SHARED_LIBRARY)
hello-jni.c文件的內容為:
/*
* Copyright (C) 2009 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*
*/
#include <string.h>
#include <jni.h>
/* This is a trivial JNI example where we use a native method
* to return a new VM String. See the corresponding Java source
* file located at:
*
* apps/samples/hello-jni/project/src/com/example/HelloJni/HelloJni.java
*/
jstring
Java_com_jsd_jni_demo_JsdJniActivity_getJniDatas( JNIEnv* env,
jobject thiz )
{
return (*env)->NewStringUTF(env, "This is for Datas from JNI !");
}
注意觀察紅色字體，其為項目目錄路徑地址，根據自己實際項目目錄來定，
好了，在新建ACTIVITY類中：
package com.jsd.jni.demo;
import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.TextView;
/**
*
* @author jankey
*
*/
public class JsdJniActivity extends Activity {
private Button mJniDemo = null;
private TextView mGetJni = null;
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
findById();
}
private void findById(){
mJniDemo = (Button) findViewById(R.id.jniDemo);
mGetJni = (TextView) findViewById(R.id.getJni);
mJniDemo.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
mGetJni.setText(getJniDatas());
}
});
}
/**
* A native method that is implemented by the
* 'hello-jni' native library, which is packaged
* with this application.
* @return
*/
public native String getJniDatas();
/**
*This is another native method declaration that is *not*
* implemented by 'hello-jni'. This is simply to show that
* you can declare as many native methods in your Java code
* as you want, their implementation is searched in the
* currently loaded native libraries only the first time
* you call them.
*
* Trying to call this function will result in a
* java.lang.UnsatisfiedLinkError exception !
* @return
*/
public native String unimplementedGetJniDatas();
/**
* this is used to load the 'hello-jni' library on application
* startup. The library has already been unpacked into
* /data/data/com.example.HelloJni/lib/libhello-jni.so at
* installation time by the package manager.
*/
static{
System.loadLibrary("hello-jni");
}
}
上面有注釋，其native方法為JNI需要調用與執行的方法，
在布局裡就添加了一個按鈕與一個文本，使用按鈕單點後來獲得文本顯示的字符為JNI所得來的數據,其實這個過程很簡單，基本就是NDK裡面本身的列子般過來運行一樣，等這都完了，先不要急於運行，你需要先把C文件進行編譯後才能執行運行APP，在命令行進入其目錄的JNI目錄,使用ndk-build命令來構建編譯：
你會看到：jankey@jankey-ThinkPad-Edge:~/workspace/jni_demo/jni$ ndk-build
Compile thumb : hello-jni <= hello-jni.c
SharedLibrary : libhello-jni.so
Install : libhello-jni.so => libs/armeabi/libhello-jni.so，生成了兩個文件目錄：
即兩個.so為後綴的文件，在這裡基本就沒什麼問題了，這樣就建立了C與JAVA通信的一個過程，OK，使用CTRI+F11開始運行其APP：
，先我們可以單擊來獲取JNI返回回來的數據了:
這就把數據給調出來了，如果你是初學者，你還等什麼呢，趕快動手吧，希望這能給在入門裡做最給裡的參考，謝謝。
