android NDK学习篇3之two-libs——使用(多个)静态库生成动态库
16lz
2022-04-09
还要以NDK提供的two-libs为例子,走一遍多个静态库(.a文件)生成动态库(.so文件)的流程。
1、建立android工程,编写java对应JNI层的本地接口:
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文件夹下的准备预备文件如下,其中.o和.a文件都是用NDK编译生成,具体操作见下:
Android.mk first.c first.o third.a third.hfirst.a first.h second.c third.c third.o
2、编写jni层中间层代码second.c,在其中调用first.c中的first(int x,int y)函数及third.c中的test()函数,具体代码如下:
first.h头文件如下:
#ifndef FIRST_H#define FIRST_Hextern int first(int x, int y);#endif /* FIRST_H */
first.c中c代码:
#include "first.h"int first(int x, int y){ return x + y;}
现在就用NDK的提供的C编译器来编译生成firs.a这个静态库,用于后续生成libtwolib-second.so动态库的源文件。步骤跟linux下编译生成静态库方法完全一样.
第一步:找到NDK下自带的gcc和ar,/android-ndk-r9e/toolchains/arm-linux-androideabi-4.6/prebuilt/linux-x86/bin/
第二步:用NDK的gcc编译器来生成.a文件,如:
thinker@fans:~/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工具来生成.a文件,如:
thinker@fans:~/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静态库文件。类似步骤生成third.a库。
third.h如:
#ifndef THIRD_H#define THIRD_Hextern int third();#endif /* THIRD_H */
third.c中c代码:
#include "third.h"int third(){return 10;}
jni层中间层代码second.c如下:
#include "first.h"#include "third.h"#include #include #include //修改日志tag中的值 #define LOG_TAG "log_from_second.c"//日志显示的等级 #define LOGD(...) __android_log_print(ANDROID_LOG_DEBUG, LOG_TAG, __VA_ARGS__) #define LOGI(...) __android_log_print(ANDROID_LOG_INFO, LOG_TAG, __VA_ARGS__) jintJava_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、编写Android.mk文件:如下两种方式都可以,用于NDK编译工具生成的两个.a文件来生成最终的libtwolib-second.so 动态库。
LOCAL_PATH:= $(call my-dir)include $(CLEAR_VARS)LOCAL_MODULE := libtwolib-secondLOCAL_SRC_FILES := second.cLOCAL_LDFLAGS := first.a third.aLOCAL_LDLIBS:=-L$(SYSROOT)/usr/lib -lloginclude $(BUILD_SHARED_LIBRARY)
方式二:
LOCAL_PATH:= $(call my-dir)include $(CLEAR_VARS)LOCAL_MODULE := libtwolib-firstLOCAL_SRC_FILES := first.ainclude $(PREBUILT_STATIC_LIBRARY)include $(CLEAR_VARS)LOCAL_MODULE := libtwolib-thirdLOCAL_SRC_FILES := third.ainclude $(PREBUILT_STATIC_LIBRARY)include $(CLEAR_VARS)LOCAL_MODULE := libtwolib-secondLOCAL_SRC_FILES := second.cLOCAL_STATIC_LIBRARIES := libtwolib-first libtwolib-thirdLOCAL_LDLIBS:=-L$(SYSROOT)/usr/lib -lloginclude $(BUILD_SHARED_LIBRARY)
4、生成动态库 thinker@fans:~/android/android-ndk-r9/samples/two-libs/jni$ /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.cSharedLibrary : libtwolib-second.soInstall : libtwolib-second.so => libs/armeabi/libtwolib-second.so
运行查看打印信息,一切OK。
参考网址:
http://blog.csdn.net/wjr2012/article/details/6887559
附:
可以直接编写Android.mk文件来生成两个.a文件,如下:
LOCAL_PATH:= $(call my-dir)include $(CLEAR_VARS)LOCAL_MODULE := libtwolib-firstLOCAL_SRC_FILES := first.cinclude $(BUILD_STATIC_LIBRARY)include $(CLEAR_VARS)LOCAL_MODULE := libtwolib-thirdLOCAL_SRC_FILES := third.cinclude $(BUILD_STATIC_LIBRARY)include $(CLEAR_VARS)LOCAL_MODULE := libtwolib-secondLOCAL_SRC_FILES := second.cLOCAL_STATIC_LIBRARIES := libtwolib-first libtwolib-thirdLOCAL_LDLIBS:=-L$(SYSROOT)/usr/lib -lloginclude $(BUILD_SHARED_LIBRARY)
编译:
thinker@fans:~/android/android-ndk-r9/samples/two-libs/jni$ ../../../../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.cCompile thumb : twolib-first <= first.cStaticLibrary : libtwolib-first.aCompile thumb : twolib-third <= third.cStaticLibrary : libtwolib-third.aSharedLibrary : libtwolib-second.soInstall : libtwolib-second.so => libs/armeabi/libtwolib-second.so
生成的.a文件在工程/obj/local/armeabi目录下:
thinker@fans:~/android/android-ndk-r9/samples/two-libs/obj/local/armeabi$ lslibtwolib-first.a libtwolib-second.so libtwolib-third.a objs
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