[Android & JNI & ndk] describes each step in detail, allowing you to easily master Android JNI ndk

1. Development Environment Configuration

As we all know, it is difficult to start with everything. configuring a development environment is the most basic and necessary step for all development projects.

All software and development platforms used: win7 + netbeans + VMware + Ubuntu + ndk + Android SDK

First of all, in win7 platform to configure the development of Android environment, detailed reference blog: http://blog.csdn.net/tianshuai11/article/details/7367700

Then download the android-ndk-r7b's ndk Development Kit http://developer.android.com/sdk/ndk/index.html from Ubuntu systems in VMware to select the Linux version. Download and unzip to the/usr folder, then configure the environment variable: vi. bashrc Add: ndk =/usr/android-ndk-r7b export ndk --- at the end and then make the change take effect:Source
. Bashrc --- test at the terminal: Echo $ ndk to see whether the output is:/Usr/android-ndk-r7b if output indicates configuration successful

2. Coding

Before reading the following article, I hope you have some knowledge about JNI. If you're not very familiar with the example implementation in the 8-plus blog, http://blog.csdn.net/tianshuai11/article/details/7367881

1) create a project in netbeans: Project name: Hello; package name: tianshuai. Hello; Activity name: Hello; Target Platform: Android 2.3.3

2) Add the following code to the hello file:

Import android. app. activity; <br/> Import android. OS. bundle; <br/> Import android. widget. textview; </P> <p> public class Hello extends activity <br/> {<br/>/** called when the activity is first created. */<br/> @ override <br/> Public void oncreate (bundle savedinstancestate) <br/>{< br/> super. oncreate (savedinstancestate); <br/> setcontentview (R. layout. main); <br/> textview TV = (textview) findviewbyid (R. id. TV); <br/> // textview TV = new textview (this); <br/> // TV. settext ("Sss"); <br/> TV. settext (stringfromjni (); <br/>}< br/> Public native string stringfromjni (); <br/> static {<br/> system. loadlibrary ("hello"); <br/>}< br/>Make corresponding changes in Main. xml

3) Compile the C header file

Right-click-> Hello project-> Generate, and generate hello. Class in Hello \ bin \ Classes \ tianshuai \ hello

Then, in the DOS window of the terminal, CD to the \ Hello \ bin \ Classes Directory: Enter javah-classpath c: \ Users \ tianshuai \ Desktop \ Hello \ bin \ Classes-JNI tianshuai. hello. hello

The tianshuai_hello_hello.h file is generated in the classes Folder:

/* Do not edit this file-it is machine generated */<br/> # include <JNI. h> <br/>/* Header for class tianshuai_hello_hello */</P> <p> # ifndef _ delimiter <br/> # DEFINE _ included_tianshuai_hello_hello <br/> # ifdef _ _ cplusplus <br/> extern "C" {<br/> # endif <br/>/* <br/> * class: tianshuai_hello_hello <br/> * method: stringfromjni <br/> * Signature: () ljava/lang/string; <br/> */<br/> jniexport jstring jnicall java_tianshuai_hello_hello_stringfromjni <br/> (jnienv *, jobject ); </P> <p> # ifdef _ cplusplus <br/>}< br/> # endif <br/>

PS: Suppose you have configured the Java environment variable, see blog http://blog.csdn.net/tianshuai11/article/details/7367700

4) manually change the project

Create a JNI folder under the root directory of the hello project, and thenTianshuai_hello_hello.h
Copy the file

Add interface implementation file: tianshuai_hello_hello.c

# Include <string. h> <br/> # include <JNI. h> <br/> # include "tianshuai_hello_hello.h" <br/> jstring <br/> java_tianshuai_hello_hello_stringfromjni (jnienv * ENV, <br/> jobject thiz) <br/> {<br/> return (* env)-> newstringutf (ENV, "hello from JNI! "); <Br/>}< br/>Add and generate a processing file: Android. mkLocal_path: =$ (call my-DIR) </P> <p> include $ (clear_vars) </P> <p> local_module: = Hello <br/> local_src_files: = tianshuai_hello_hello.c </P> <p> include $ (build_shared_library) <br/>

5) save all the above projects and files and copy them to the Ubuntu Operating System Under VMware.

CD/Hello

./$ Ndk/ndk-build

The armeabi/libhello. So file is generated in/Hello/libs.

6) test:

Copy the changed project file in Linux to Windows, open it with netbeans, and run

Iii. Summary

1) objective: to call the source file that has been written in C through Java

2) Step 1. c files that are known to be written

2> compile Java code and call the c file of a specific function name

3> compile the written Java code into a. Class file and generate a. h file.

4> compile ndk. h.c and call Objective C through Java.

If you see the above results after a great deal of hard work, I believe that you will be able to see the results ......

The joy of programmers is here ......

I hope to leave a message on any suggestions and comments. I will actively listen to your comments and correct the omissions in the blog.