The method of compiling Java class Library and JNI Dynamic Library of Android system from source code _android

Using source code to compile the Java class Library of Android system
1. Writing Java projects and android.mk files

  ├──android.mk
  └──src
   └──com
     └──lhw
       └──framework
           └──led

Led.java file

Package com.lhw.framework.led; 
 
/** 
 * LED Operation Library 
 * @author Micky Liu 
/public class LEDs {public 
   
  Boolean turnon () {return 
    tru e; 
  }   
   
  public Boolean turnoff () {return 
    true; 
  }   

ANDROID.MK file

Local_path: = $ (call My-dir) 
 
local_src_files   : = $ (call All-java-files-under, SRC) 
local_module    : = framework_led 
local_module_tags  : = framework_led 
 
local_java_libraries    : = 
local_static _java_libraries: = 
 
include $ (build_java_library) 

2, compile

   Mmm/home/administrator/workspace/android_test/framework_led

Compilation results:

   Install:out/target/product/generic/system/framework/framework_led.jar    

using source code to compile the Android system JNI Dynamic Library
1, code and ANDROID.MK writing

├──jni
│  ├──android.mk
│  └──led.c

Led.c

#include <jni.h> 
#include <stdio.h> 
 
jboolean java_com_lhw_led_led_turnon (jnienv *env, Jclass Thiz) 
{return 
  jni_true; 
} 
 
Jboolean Java_com_lhw_led_led_trunoff (jnienv *env, Jclass thiz) 
{return 
  jni_true; 
} 

Note: The method name rule is: Java_ Package Name _ Class Name _ Method name, you can use the Javah command to generate the required. h header file According to the Java file. Of course, a better approach is to implement dynamic registration through Jni_onload and androidruntime::registernativemethods, so that you don't have to ignore the method name rules. Here is just a simple example, followed by an example to implement dynamic registration.

Android.mk

Local_path: = $ (call My-dir) 
 
local_src_files: = led.c 
local_module  : = Led_jni    local_module_tags : = Led_jni 
 
local_prelink_module  : = False 
local_shared_libraries: = libc 
 
include $ (build_shared_ LIBRARY) 

2, compile

  Mmm/home/administrator/workspace/android_test/jni

Compilation results:

  Install:out/target/product/generic/system/lib/led_jni.so