NDK so库的调用和编译

NDK动态库的调用分两种情况。

第一种是：so库和调用程序在同一个目录和源程序 通过同一个mk文件来编译；

另外一种情况是so是外部已经编译好了的，调用程序加载调用。

（博主：这两种其实是一样的，没有任何区别 -v-）

下面我们就来分析下面2种so的调用情况：

第一部分： 内部so调用

      A. 先看下工程的目录：

               

         jni目录下的文件通过编译最终会生成libtest.so和libtutorial.so两个库文件，供test01.java来使用。

     B. 然后看下具体的mk文件的写法以及java中的文件内容

test01.java （博主：类名还是开头大写比较规范哈）

/*
 * 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
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * 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.test;

import android.R.integer;
import android.app.Activity;
import android.widget.TextView;
import android.os.Bundle;


public class test01 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);
      
        int a = getinformation();
        String lls = a +"";
        tv.setText(lls);
        setContentView(tv);
    }

    /* A native method that is implemented by the
     * 'hello-jni' native library, which is packaged
     * with this application.
     */
    public native int  getinformation();
     /* 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("test");
    }
}

Android.mk

LOCAL_PATH := $(call my-dir)
#获取当前目录
include $(CLEAR_VARS)
#清除一些变量
LOCAL_MODULE    := tutorial
#要生成的库名
LOCAL_SRC_FILES := tutorial01.c tutorial02.c
#库对应的源文件
include $(BUILD_SHARED_LIBRARY)
#生成动态库libtutorial.so

include $(CLEAR_VARS)
#清除一些变量
LOCAL_MODULE    := test
#定义另外一个库的名
LOCAL_SRC_FILES := test01.c
#定义库对应的源文件
LOCAL_LDLIBS := -ldl -llog 
#libtest.so需要引用的库libdl.so:加载动态函数需要，liblog.so 日志打印需要，默认是system/lib目录下
include $(BUILD_SHARED_LIBRARY)
#生成共享库

 test01.c

#include 
#include 
#include 
#include 
#include 

#define  LOG_TAG    "libgl2jni"
#define  LOGI(...)  __android_log_print(ANDROID_LOG_INFO,LOG_TAG,__VA_ARGS__)
#define  LOGE(...)  __android_log_print(ANDROID_LOG_ERROR,LOG_TAG,__VA_ARGS__)
 //extern int getinformation();
jint Java_com_example_test_test01_getinformation(JNIEnv* env,jobject thiz)
{
	//getinformation();   ??thr .so file will load to the sdcard with the folder data/data/com.example.test/lib/

	void*  filehandle = dlopen("/data/data/com.example.test/lib/libtutorial.so", RTLD_LAZY );
	int ll = -1;
	if(filehandle)
	{
	    LOGI("open so success!");
		int( * getinformation ) (); 
		getinformation = dlsym(filehandle, "getinformation");
		if( getinformation )
		{
			LOGI("call function getinformation OK!");
			ll = getinformation();
		}
		else
		{
			ll = -3;
			LOGE("call function getinformation! ERROR!");
		}
		LOGI("return value=%d",ll);
		dlclose(filehandle);
		filehandle=0;
	}
	else
	{
		ll = -2;
		LOGE("open so ERROR!");
	}
    return ll;
}

tutorial01.c

#include 
#include "tutorial02.h"

int getinformation() 
{
	int c = getinformation2(191,81);
	return c;
}

 

 tutorial02.c

#include 

#include "tutorial02.h"

int getinformation2(int i,int j) 
{
	return (i+j);
}

 tutorial02.h

int getinformation2(int,int);

C: 编译：

    进入工程目录，执行  $NDK/ndk-build

（$NDK是引用一个环境变量，在你配置NDK时需要进行设置）

    输出结果：

/cygdrive/e/cygwin/android-ndk-r4
Compile thumb  : test <= /cygdrive/e/cygwin/android-ndk-r4/samples/testappso/jni/test01.c
SharedLibrary  : libtest.so
Install        : libtest.so => /cygdrive/e/cygwin/android-ndk-r4/samples/testappso/libs/armeabi
Compile thumb  : tutorial <= /cygdrive/e/cygwin/android-ndk-r4/samples/testappso/jni/tutorial01.c
Compile thumb  : tutorial <= /cygdrive/e/cygwin/android-ndk-r4/samples/testappso/jni/tutorial02.c
SharedLibrary  : libtutorial.so
Install        : libtutorial.so => /cygdrive/e/cygwin/android-ndk-r4/samples/testappso/libs/armeabi

D：在重新刷新工程，你就可以在lib下面看到生成的so了，点击加载运行

 

第二部分：调用通过自己编写make方式生成的so

      我们还是引用上面的工程，不过把libtutorial.so 拿出来，通过自己写makefile来编译成so，这里请大家注意了，调用外部的so时候，不能够直接用在linux下生产的so来调用，必须通过ndk提供的gcc来编译，否则会因为平台的不同无法调用。

     A. 废话不多说，看makefile怎么写！我的ndk是1.6版本的.

         新建一个文件夹，把 tutorial01.c  tutorial02.c  tutorial02.h 文件拷贝过去，然后编写makefile文件

CC = /cygdrive/e/cygwin/android-ndk-r4/build/prebuilt/windows/arm-eabi-4.4.0/bin/arm-eabi-gcc-4.4.0

CFLAGS  = -g -O2 -fPIC -I/cygdrive/e/cygwin/android-ndk-r4/build/platforms/android-5/arch-arm/usr/include
SDFLAGS = -nostdlib -Wl,-T,armelf.xsc -Wl,-shared,-Bsymbolic -Wl,-soname,$@ -lc
CRT_OBJS= -L/cygdrive/e/cygwin/android-ndk-r4/build/platforms/android-5/arch-arm/usr/lib -lz -lm  -ldl
# source files:
SRCS= tutorial01.c tutorial02.c tutorial02.h

all: libtutorial.so

libtutorial.so: tutorial01.o tutorial02.o
        $(CC) $(SDFLAGS) -o $@ tutorial01.o tutorial02.o  $(CRT_OBJS)

tutorial01.o: tutorial02.h
tutorial02.o: tutorial02.h

clean:
        rm -f libtutorial.so *.o

在执行make的时候需要注意一下几点：

1.  指定程序需要的头文件目录 通过-I指定/cygdrive/e/cygwin/android-ndk-r4/build/platforms/android-5/arch-arm/usr/include NDK提供的一些基本c语言库的头文件

2.  指定库路径-L/cygdrive/e/cygwin/android-ndk-r4/build/platforms/android-5/arch-arm/usr/lib 里面有libz.so,libm.so,libdl.so等库的路径

3.   拷贝交叉编译文件armelf.xsc到android-ndk-r4/build/prebuilt/windows/arm-eabi-4.4.0/lib/gcc/arm-eabi/4.4.0下，armelf.xsc在目录./build/prebuilt/linux-x86/arm-eabi-4.4.0/arm-eabi/lib/ldscripts下

4.   拷贝libc.so到./build/prebuilt/linux-x86/arm-eabi-4.4.0/lib/gcc/arm-eabi/4.4.0目录下，libc.so位于./build/platforms/android-5/arch-arm/usr/lib库

完成上面的工作你就可以放心make了，成功后生成libtutorial.so文件

 

CC = /cygdrive/e/cygwin/android-ndk-r4/build/prebuilt/windows/arm-eabi-4.4.0/bin/arm-eabi-gcc-4.4.0

CFLAGS  = -g -O2 -fPIC -I/cygdrive/e/cygwin/android-ndk-r4/build/platforms/android-5/arch-arm/usr/include
SDFLAGS = -nostdlib -Wl,-T,armelf.xsc -Wl,-shared,-Bsymbolic -Wl,-soname,$@ -lc
CRT_OBJS= -L/cygdrive/e/cygwin/android-ndk-r4/build/platforms/android-5/arch-arm/usr/lib -lz -lm  -ldl

# source files:
SRCS= test01.c


all: libtest.so

libtest.so: test01.o
        $(CC) $(SDFLAGS) -o $@ test01.o  $(CRT_OBJS)

test01.o: test01.c


clean:
        rm -f libtest.so *.o

B. 生成so文件后，在工程目录下建立目录libs/armeabi,然后把so拷贝进去，在打开工程，刷新加载，一切搞定

C.  一些小技巧：

    a. 查看so是不是编译成ARM模式下的so （博主：这个挺好用的）

         $ file libtest.so
         libtest.so: ELF 32-bit LSB shared object, ARM, version 1 (SYSV), dynamically linked, not stripped

    b.  如果别人提供了你一个so，查看提供了那些方法，更详细的用法，查看nm命令（博主：这个也挺好用的）

$ nm libtutorial.so |grep T
00001344 a _GLOBAL_OFFSET_TABLE_
000002a8 T getinformation
000002b4 T getinformation2

D.  下面提供一个大工程的编译的makefile，吧opencore --omx下的testapp独立编译成so，编译通过，未加载库，给大家参考。

cc=/home/zhangweia/android/android-ndk-r4b/build/prebuilt/linux-x86/arm-eabi-4.4.0/bin/arm-eabi-gcc-4.4.0

CFLAGS = -g -O2 -fPIC -DANDROID -I./include -I/home/zhangweia/android/android-ndk-r4b/build/platforms/android-5/arch-arm/usr/include

CFLAGS += -I$(SDK)/out/target/product/generic/obj/include/libpv \
        -I$(opencore)/codecs_v2/common/include \
        -I$(opencore)/pvmi/pvmf/include \
        -I$(opencore)/nodes/common/include \
        -I$(opencore)/extern_libs_v2/khronos/openmax/include \
        -I$(opencore)/build_config/opencore_dynamic \
        -I$(opencore)/android/drm/oma1/src \
        -I$(opencore)/engines/author/include \
        -I$(opencore)/oscl/oscl/config/shared \
        -I$(opencore)/oscl/oscl/config/android \
        -I$(opencore)/engines/common/include \
        -I$(opencore)/extern_libs_v2/khronos/openmax/include \
        -I$(opencore)/android \

#SDFLAGS = -nostdlib -Wl,-T,armelf.xsc -Wl,-shared,-Bsymbolic -Wl,-soname,$@ -lc
SDFLAGS = -nostdlib -Wl,-T,armelf.xsc -Wl,-Bsymbolic -Wl,-soname,$@ -lc

CRT_OBJS=-L/home/zhangweia/android/android-ndk-r4b/build/platforms/android-5/arch-arm/usr/lib -lz -lm  -ldl

#all : libomxde.so
OBJECT= omx_threadsafe_callbacks.o \
        omxdectest.o \
        omxdectestbase.o \
        omxtest_buffer_busy.o \
        omxtest_corrupt_nal.o \
        omxtest_dynamic_reconfig.o \
        omxtest_eos_missing.o \
        omxtest_extra_partialframes.o \
        omxtest_flush_eos.o \
        omxtest_flush_port.o \
        omxtest_get_role.o \
        omxtest_incomplete_nal.o \
        omxtest_missing_nal.o \
        omxtest_multiple_instance.o \
        omxtest_param_negotiation.o \
        omxtest_partialframes.o \
        omxtest_pause_resume.o \
        omxtest_portreconfig_transit_1.o \
        omxtest_portreconfig_transit_2.o \
        omxtest_portreconfig_transit_3.o \
        omxtest_reposition.o \
        omxtest_usebuffer.o \
        omxtest_without_marker.o
#libomxde.so : $(OBJECT)
omxde : $(OBJECT)
        $(cc) $(SDFLAGS) -o $@ $(CRT_OBJS)
omx_threadsafe_callbacks.o:src/omx_threadsafe_callbacks.cpp
        $(cc) $(CFLAGS) $(SDFLAGS) -c src/omx_threadsafe_callbacks.cpp
omxdectest.o:src/omxdectest.cpp
        $(cc) $(CFLAGS) $(SDFLAGS) -c src/omxdectest.cpp
omxdectestbase.o:src/omxdectestbase.cpp
        $(cc) $(CFLAGS) $(SDFLAGS) -c src/omxdectestbase.cpp
omxtest_corrupt_nal.o:src/omxtest_corrupt_nal.cpp
        $(cc) $(CFLAGS) $(SDFLAGS) -c src/omxtest_corrupt_nal.cpp
omxtest_buffer_busy.o:src/omxtest_buffer_busy.cpp
        $(cc) $(CFLAGS) $(SDFLAGS) -c src/omxtest_buffer_busy.cpp
omxtest_dynamic_reconfig.o:src/omxtest_dynamic_reconfig.cpp
        $(cc) $(CFLAGS) $(SDFLAGS) -c src/omxtest_dynamic_reconfig.cpp
omxtest_eos_missing.o:src/omxtest_eos_missing.cpp
        $(cc) $(CFLAGS) $(SDFLAGS) -c src/omxtest_eos_missing.cpp
omxtest_extra_partialframes.o:src/omxtest_extra_partialframes.cpp
        $(cc) $(CFLAGS) $(SDFLAGS) -c src/omxtest_extra_partialframes.cpp
omxtest_flush_eos.o:src/omxtest_flush_eos.cpp
        $(cc) $(CFLAGS) $(SDFLAGS) -c src/omxtest_flush_eos.cpp
omxtest_flush_port.o:src/omxtest_flush_port.cpp
        $(cc) $(CFLAGS) $(SDFLAGS) -c src/omxtest_flush_port.cpp
omxtest_get_role.o:src/omxtest_get_role.cpp
        $(cc) $(CFLAGS) $(SDFLAGS) -c src/omxtest_get_role.cpp
omxtest_incomplete_nal.o:src/omxtest_incomplete_nal.cpp
        $(cc) $(CFLAGS) $(SDFLAGS) -c src/omxtest_incomplete_nal.cpp
omxtest_missing_nal.o:src/omxtest_missing_nal.cpp
        $(cc) $(CFLAGS) $(SDFLAGS) -c src/omxtest_missing_nal.cpp
omxtest_multiple_instance.o:src/omxtest_multiple_instance.cpp
        $(cc) $(CFLAGS) $(SDFLAGS) -c src/omxtest_multiple_instance.cpp
omxtest_param_negotiation.o:src/omxtest_param_negotiation.cpp
        $(cc) $(CFLAGS) $(SDFLAGS) -c src/omxtest_param_negotiation.cpp
omxtest_partialframes.o:src/omxtest_partialframes.cpp
        $(cc) $(CFLAGS) $(SDFLAGS) -c src/omxtest_partialframes.cpp
omxtest_pause_resume.o:src/omxtest_pause_resume.cpp
        $(cc) $(CFLAGS) $(SDFLAGS) -c src/omxtest_pause_resume.cpp
omxtest_portreconfig_transit_1.o:src/omxtest_portreconfig_transit_1.cpp
        $(cc) $(CFLAGS) $(SDFLAGS) -c src/omxtest_portreconfig_transit_1.cpp
omxtest_portreconfig_transit_2.o:src/omxtest_portreconfig_transit_2.cpp
        $(cc) $(CFLAGS) $(SDFLAGS) -c src/omxtest_portreconfig_transit_1.cpp
omxtest_portreconfig_transit_3.o:src/omxtest_portreconfig_transit_3.cpp
        $(cc) $(CFLAGS) $(SDFLAGS) -c src/omxtest_portreconfig_transit_1.cpp
omxtest_reposition.o:src/omxtest_reposition.cpp
        $(cc) $(CFLAGS) $(SDFLAGS) -c src/omxtest_reposition.cpp
omxtest_usebuffer.o:src/omxtest_usebuffer.cpp
        $(cc) $(CFLAGS) $(SDFLAGS) -c src/omxtest_usebuffer.cpp
omxtest_without_marker.o:src/omxtest_without_marker.cpp
        $(cc) $(CFLAGS) $(SDFLAGS) -c src/omxtest_without_marker.cpp
clean:
        rm -rf *.o