NDK 生成动态链接库

程序员文章站 2022-06-25 18:45:42

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android NDK學習篇3之two-libs——使用（多個）靜態庫生成動態庫
2013年08月16日 ⁄ 綜合 ⁄ 共 4599字 ⁄ 字號小中大 ⁄ 評論關閉

還要以NDK提供的two-libs為例子，走一遍多個靜態庫（.a文件）生成動態庫（.so文件）的流程。

1、建立android工程，編寫java對應JNI層的本地接口：

package com.example.twolibs;

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

public class TwoLibs extends Activity
{
/* Called when the activity is first created. /
@Override
public void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);

    TextView  tv = new TextView(this);
    int       x  = 1000;
    int       y  = 42;

    // here, we dynamically load the library at runtime
    // before calling the native method.
    //

    int  z = add(x, y);

    tv.setText( "The sum of " + x + " and " + y + " is " + z );
    setContentView(tv);

}

public native int add(int  x, int  y);

static
{
    System.loadLibrary("twolib-second");
}

}
JNI文件夾下的準備預備文件如下，其中.o和.a文件都是用NDK編譯生成，具體操作見下：

Android.mk first.c first.o third.a third.h
first.a first.h second.c third.c third.o
2、編寫jni層中間層代碼second.c，在其中調用first.c中的first(int x,int y)函數及third.c中的test()函數，具體代碼如下：

first.h頭文件如下：

ifndef FIRST_H

define FIRST_H

extern int first(int x, int y);

endif /* FIRST_H */

first.c中c代碼：

include “first.h”

int first(int x, int y)
{
return x + y;
}

現在就用NDK的提供的C編譯器來編譯生成firs.a這個靜態庫，用於後續生成libtwolib-second.so動態庫的源文件。步驟跟linux下編譯生成靜態庫方法完全一樣.

第一步：找到NDK下自帶的gcc和ar，/android-ndk-r9e/toolchains/arm-linux-androideabi-4.6/prebuilt/linux-x86/bin/

第二步：用NDK的gcc編譯器來生成.a文件，如：

[email protected]:~/android/android-ndk-r9/samples/two-libs/jni$ ../../../toolchains/arm-linux-androideabi-4.6/prebuilt/linux-x86/bin/arm-linux-androideabi-gcc -o first.o -c first.c
第三步：用NDK的ar工具來生成.a文件，如：

[email protected]:~/android/android-ndk-r9/samples/two-libs/jni$ ../../../toolchains/arm-linux-androideabi-4.6/prebuilt/linux-x86/bin/arm-linux-androideabi-ar rcs first.a first.o
到此OK，生成了first.a靜態庫文件。類似步驟生成third.a庫。

third.h如：

ifndef THIRD_H

define THIRD_H

extern int third();

endif /* THIRD_H */

third.c中c代碼：

include “third.h”

int third()
{
return 10;
}
jni層中間層代碼second.c如下：

include “first.h”

include “third.h”

include

define LOG_TAG “log_from_second.c”

//日誌顯示的等級

define LOGD(…) android_log_print(ANDROID_LOG_DEBUG, LOG_TAG, __VA_ARGS)

define LOGI(…) android_log_print(ANDROID_LOG_INFO, LOG_TAG, __VA_ARGS)

jint
Java_com_example_twolibs_TwoLibs_add( JNIEnv* env,
jobject this,
jint x,
jint y )
{
int i = third();
LOGI(“the test result = %d”,i);
return first(x, y);
}
3、編寫Android.mk文件：如下兩種方式都可以，用於NDK編譯工具生成的兩個.a文件來生成最終的libtwolib-second.so 動態庫。

LOCAL_PATH:= $(call my-dir)

include $(CLEAR_VARS)

LOCAL_MODULE := libtwolib-second
LOCAL_SRC_FILES := second.c

LOCAL_LDFLAGS := first.a third.a
LOCAL_LDLIBS:=-L $(S Y S R O O T) / u s r / l i b - l l o g i n c l u d e$ (BUILD_SHARED_LIBRARY)
方式二：

LOCAL_PATH:= $(call my-dir)

include $(C L E A R_{V} A R S) L O C A L_{M} O D U L E := l i b t w o l i b - f i r s t L O C A L_{S} R C_{F} I L E S := f i r s t . a i n c l u d e$ (PREBUILT_STATIC_LIBRARY)

include $(CLEAR_VARS)

LOCAL_MODULE := libtwolib-third
LOCAL_SRC_FILES := third.a

include $(PREBUILT_STATIC_LIBRARY)

include $(CLEAR_VARS)

LOCAL_MODULE := libtwolib-second
LOCAL_SRC_FILES := second.c

LOCAL_STATIC_LIBRARIES := libtwolib-first libtwolib-third
LOCAL_LDLIBS:=-L $(S Y S R O O T) / u s r / l i b - l l o g i n c l u d e$ (BUILD_SHARED_LIBRARY)
4、生成動態庫

[email protected]:~/android/android-ndk-r9/samples/two-libs/jni$ /home/thinker/android/android-ndk-r8e/ndk-build
/home/thinker/android/android-ndk-r8e/build/core/add-application.mk:128: Android NDK: WARNING: APP_PLATFORM android-14 is larger than android:minSdkVersion 3 in /home/thinker/android/android-ndk-r9/samples/two-libs/AndroidManifest.xml
Compile thumb : twolib-second <= second.c
SharedLibrary : libtwolib-second.so
Install : libtwolib-second.so => libs/armeabi/libtwolib-second.so
運行查看打印信息，一切OK。

參考網址：

http://blog.csdn.net/wjr2012/article/details/6887559

附：

可以直接編寫Android.mk文件來生成兩個.a文件，如下：

LOCAL_PATH:= $(call my-dir)

include $(C L E A R_{V} A R S) L O C A L_{M} O D U L E := l i b t w o l i b - f i r s t L O C A L_{S} R C_{F} I L E S := f i r s t . c i n c l u d e$ (BUILD_STATIC_LIBRARY)

include $(CLEAR_VARS)

LOCAL_MODULE := libtwolib-third
LOCAL_SRC_FILES := third.c

include $(BUILD_STATIC_LIBRARY)

include $(CLEAR_VARS)

LOCAL_MODULE := libtwolib-second
LOCAL_SRC_FILES := second.c

LOCAL_STATIC_LIBRARIES := libtwolib-first libtwolib-third
LOCAL_LDLIBS:=-L $(S Y S R O O T) / u s r / l i b - l l o g i n c l u d e$ (BUILD_SHARED_LIBRARY)
編譯：

[email protected]:~/android/android-ndk-r9/samples/two-libs/jni$ ../../../../android-ndk-r8e/ndk-build
/home/thinker/android/android-ndk-r8e/build/core/add-application.mk:128: Android NDK: WARNING: APP_PLATFORM android-14 is larger than android:minSdkVersion 3 in /home/thinker/android/android-ndk-r9/samples/two-libs/AndroidManifest.xml
Compile thumb : twolib-second <= second.c
Compile thumb : twolib-first <= first.c
StaticLibrary : libtwolib-first.a
Compile thumb : twolib-third <= third.c
StaticLibrary : libtwolib-third.a
SharedLibrary : libtwolib-second.so
Install : libtwolib-second.so => libs/armeabi/libtwolib-second.so
生成的.a文件在工程/obj/local/armeabi目錄下：

[email protected]:~/android/android-ndk-r9/samples/two-libs/obj/local/armeabi$ ls
libtwolib-first.a libtwolib-second.so libtwolib-third.a objs

NDK 生成动态链接库

ifndef FIRST_H

define FIRST_H

endif /* FIRST_H */

include “first.h”

ifndef THIRD_H

define THIRD_H

endif /* THIRD_H */

include “third.h”

include “first.h”

include “third.h”

include

include

include

define LOG_TAG “log_from_second.c”

define LOGD(…) android_log_print(ANDROID_LOG_DEBUG, LOG_TAG, __VA_ARGS)

define LOGI(…) android_log_print(ANDROID_LOG_INFO, LOG_TAG, __VA_ARGS)

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NDK 生成动态链接库

ifndef FIRST_H

define FIRST_H

endif /* FIRST_H */

include “first.h”

ifndef THIRD_H

define THIRD_H

endif /* THIRD_H */

include “third.h”

include “first.h”

include “third.h”

include

include

include

define LOG_TAG “log_from_second.c”

define LOGD(…) android_log_print(ANDROID_LOG_DEBUG, LOG_TAG, __VA_ARGS)

define LOGI(…) android_log_print(ANDROID_LOG_INFO, LOG_TAG, __VA_ARGS)

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