Complete example of getting started with JNI

MainActivity: [java] package c. c; import android. OS. bundle; import android. view. view; import android. view. view. onClickListener; import android. widget. button; import android. widget. toast; import android. app. activity;/*** HelloWorld example of JNI * 1 download and install cygwin. important reference: * http://www.cnblogs.com/playing/archive/2011/07/14/2106727.html * pay attention to make component installation, this step does not, but with binutils, gcc, gcc-mingw, gdb * is similar to * 2. Check whether cygwin is correctly installed * enter cygwin and enter cd $ NDKROOT through the command line, if a line related to ndk * configuration in bash_profile is output, the installation is successful. * Note that the input command here is cd $ NDKROOT, so the * Name configured in the bash_profile file should also be NDKROOT. that is, the two are consistent. * 3 compile * 3.1 to enter cygwin, then cd, then space, and then drag the android project to the completion path. * For example, run $ cd/cygdrive/d/workplace/JNITest * 3.2 and then run $ NDKROOT/ndk-build-B. so file ** write a small example of HelloWorld related to JNI, reference: * http://blog.csdn.net/zhangjie201412/article/details/7297899 * Notes: * 1 JNI function name format * Java _ complete Activity path _ method name * For example: * jstring java_c_mainactivity_getstring (JNIEnv * env, jobject jobj) * This issue is also mentioned on the above URL. Pay special attention to * 2 using System. when loadLibrary () is loaded into the native library * the parameter is. the name of the c file, for example, * System. loadLibrary ("HelloWorld") */public class MainActivity extends Activity {private Button mButton; @ Override public void onCreate (Bundle savedInstanceState) {super. onCreate (savedInstanceState); setContentView (R. layout. main); init ();} private void init () {mButton = (Button) findViewById (R. id. button); mButton. setOnClickListener (new OnClickListener () {public void onClick (View v) {String result = getString (); Toast. makeText (MainActivity. this, result, Toast. LENGTH_LONG ). show () ;}) ;}// declare the JNI function public native String getString (); // load the static {System. loadLibrary ("HelloWorld") ;}} HelloWorld. c: [cpp] // HelloWorld. c # include <string. h> # include <jni. h> jstring java_c_mainactivity_getstring (JNIEnv * env, jobject jobj) {return (* env)-> NewStringUTF (env, "HelloWorld, JNI is good");} Android. mk is as follows: [java] LOCAL_PATH: = $ (call my-dir) include $ (CLEAR_VARS) LOCAL_MODULE: = HelloWorld LOCAL_SRC_FILES: = HelloWorld. c LOCAL_LDLIBS + =-llog-ldl include $ (BUILD_SHARED_LIBRARY) Application. mk. mk is as follows: [java] APP_STL: = gnustl_static APP_CPPFLAGS: =-frtti-fexceptions APP_ABI: = armeabi-v7a main. xml is as follows: [html] <RelativeLayout xmlns: android = "http://schemas.android.com/apk/res/android" xmlns: tools = "http://schemas.android.com/tools" android: layout_width = "match_parent" android: layout_height = "match_parent"> <Button android: id = "@ + id/button" android: layout_width = "wrap_content" android: layout_height = "wrap_content" android: layout_centerHorizontal = "true" android: layout_centerVertical = "true" android: text = "hello JNI"/> </RelativeLayout>