终端切换到 <sdk>/tools/ 目录下执行 Android 命令就可以把AVD Manager 打开了。 可是，如果你没有添加 <sdk>/tools 到你的环境变量中时，输入 android 回车后终端只会提示你
android：找不到命令
而只要在android前加上 ./ 就可以解决问题：
./android
更简单的办法是将 <sdk>/tools 路径添加进 PATH 环境变量。可以添加进用户级环境变量，也可以添加到系统环境变量中。通过命令或编辑文件均可，在这里我只提供一个办法，打开终端，输入：
sudo gedit /etc/environment
回车，在PATH=”………………….”的双引号中追加上：
:<sdk>/tools:<sdk>/platform-tools
比如：
:/opt/android-sdk/tools:/opt/android-sdk/platform-tools
注意，:是分隔符。
重启一下或者 source /etc/environment(立即生效) 在终端输入 android 回车就会有反应了。
安装Android NDK echo 解压缩得到android-ndk-r6b目录，即可。 tar -jxvf android-ndk-r6b-linux-x86.tar.bz2也将其路径加入到source路径中
经过了上述步骤，在命令行下敲：
ndk-bulid
弹出如下的错误，而不是说ndk-build not found，就说明ndk环境已经安装成功了。
Android NDK: Could not find application project directory !
Android NDK: Please define the NDK_PROJECT_PATH variable to point to it.
/home/braincol/workspace/android/android-ndk-r5/build/core/build-local.mk:85: *** Android NDK: Aborting . Stop.
二、代码的编写
1.首先是写java代码
建立一个Android应用工程HelloJni，创建HelloJni.java文件：
HelloJni.java :
/*
* 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
*
*
*
* 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.
*/
package
com.example.hellojni;
import
android.app.Activity;
import
android.widget.TextView;
import
android.os.Bundle;
public
class
HelloJni extends
Activity
{
/** Called when the activity is first created. */
@Override
public
void
onCreate(Bundle savedInstanceState)
{
super
.onCreate(savedInstanceState);
/* Create a TextView and set its content.
* the text is retrieved by calling a native
* function.
*/
TextView tv = new
TextView(this
);
tv.setText( stringFromJNI() );
setContentView(tv);
}
/* A native method that is implemented by the
* 'hello-jni' native library, which is packaged
* with this application.
*/
public
native
String stringFromJNI();
/* 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 !
*/
public
native
String unimplementedStringFromJNI();
/* 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"
);
}
}
这段代码很简单，注释也很清晰，这里只提两点：:
static{
System.loadLibrary("hello-jni" );
}
表明程序开始运行的时候会加载hello-jni, static区声明的代码会先于onCreate方法执行。如果你的程序中有多个类，而且如果HelloJni这个类不是你应用程序的入口，那么 hello-jni（完整的名字是libhello-jni.so）这个库会在第一次使用HelloJni这个类的时候加载。
public native String stringFromJNI();
public native String unimplementedStringFromJNI();
可以看到这两个方法的声明中有 native 关键字， 这个关键字表示这两个方法是本地方法，也就是说这两个方法是通过本地代码（C/C++）实现的，在java代码中仅仅是声明。
用eclipse编译该工程，生成相应的.class文件，这步必须在下一步之前完成，因为生成.h文件需要用到相应的.class文件。