[Android tutorial] Android JNI entry instance (Windows + cygwin + eclipse)

ArticleDirectory

• ① Create an android project and compile the testjni. Java class. The source code is as follows:
• ② Compile and generate the testjni. Class File
• ③ Compile and generate the com_testjni_testjni.h File
• ⑤ Create the Android. mk file (same directory as the. c file)
• 6 compile and generate the libtestjni. So file

[Android tutorial] Android JNI entry instance (Windows + cygwin + eclipse) Skyseraph Feb 20ty 2012 sztcl

Email: zgzhaobo@gmail.com QQ: 452728574

 

1 Basic Knowledge Point

① JNI: Java Native Interface
② Call JNI in Android:
Static // declared in the static areaCodeWill be executed before the oncreate Method
{
System. loadlibrary ("helloworld"); // load. The complete name is lib helloworld. So.
}
Private native string Hello (); // has the native keyword

2. Basic Steps for JNI Development

① Write. Java class
② Generate a. Class File
③ Generate a. h file
③ Check. h file
Jniexport and jnicall are JNI macros.
Note signature before the function: () ljava/lang/string; brackets in the meaning: indicates that the function parameter is null, ljava/lang/string indicates that the function return value is a string object of Java
④ Compile the. c/CPP File
⑤ Create an android. mk File(Same directory as the. c file)
⑥ Compile and generate the. So file

In addition:Borrow an image from the Refs-8, as shown below

3. Example: testjni ([cygwin] in windows, for the Linux environment, please refer to the article in refs) ① create an android project and compile the testjni. Java class. The source code is as follows:

 1  Package Com. testjni;
 2  
 3   Import Android. App. activity;
 4   Import Android. OS. Bundle;
 5   Import Android. util. log;
 6  
 7   Public   Class Testjni Extends Activity
 8 {
 9       /**  Called when the activity is first created.  */ 
 10 @ Override
 11       Public   Void Oncreate (bundle savedinstancestate)
 12 {
 13           Super . Oncreate (savedinstancestate );
 14 Setcontentview (R. layout. Main );
 15 Log. D ("hi", "android call JNI:" + outputjni ());
 16 }
 17      
 18       Private   Native String outputjni ();
 19      
 20       Static 
 21 {
22 System. loadlibrary ("testjni ");
 23 }
 24 }

② Compile and generate the testjni. Class File

Compilation Method:
Method 1: Click build project under android to generate the corresponding. Class file under the binfile of the project.
Method 2: Run cmd, locate the project directory, and run the javac command.

③ Compile and generate the com_testjni_testjni.h File

Compilation Method: As shown in. The first three red boxes are common errors. Please note!

④ Compile the. c file.

You can write it directly in Notepad. Of course, if your eclipse environment has been integrated with the C/C ++ Development Environment (For details, refer to [Android tutorial] to build the android ndk environment. ), Which can be directly written in eclipse

The Code is as follows. For the description, see the notes:

⑤ Create the Android. mk file (same directory as the. c file)

 

6 compile and generate the libtestjni. So file

Compilation Method:
Open cygwin (for cygwin installation, see [Android tutorial] to build the android ndk Environment). Run the following command:

Description:
I copied the project to the ndk configuration environment directory to run it. I can say that I can directly CD it to the current project directory, and then run it. I tried it n times and failed, my project is under D: \ My document (ndk is in c: \ Android \ android-ndk-r7)

The running result is as follows:

Refs/related

1 http://my.unix-center.net /~ Simon_fu /? P = 833
2 http://my.unix-center.net /~ Simon_fu /? P = 836
3 http://www.android123.com.cn/androidkaifa/679.html
4 http://doandroid.info/2012/03/18/jni_and_android_jni_details/
Http://blog.csdn.net/hellogv/article/details/6094127
Http://blog.csdn.net/redoffice/article/details/6654714
7 http://www.cnblogs.com/lilactutu/archive/2010/12/06/1897696.html
8 http://my.unix-center.net /~ Simon_fu /? P = 359