android ndk 生成so

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java文件

Unzip.java

package com.android.xxx;import android.util.Log;class Unzip{    private static final String TAG = "Unzip";    public static boolean unzipSOFile() {    Log.d("ZLoader", "Unzip::unzipSOFile");return nativeUnzipSOFile();}public static void loadLibCompleted() {Log.d("ZLoader", "Unzip::loadLibCompleted");nativeLoadLibCompleted();}    private static native boolean nativeUnzipSOFile();    private static native void nativeLoadLibCompleted();}

c++文件, 使用mmm生成so文件

Unzip.cpp

#define LOG_TAG "Unzip"#include <stdio.h>#include <stdlib.h>#include <string.h>#include <errno.h>#include "zlib.h"#include <jni.h>#include <string.h>#include "base/logging.h"#include <android/log.h> namespace android {namespace {#define BUFFER_SIZE 16384#define NELEM(x) ((int) (sizeof(x) / sizeof((x)[0])))#define COMPILE_ASSERT(expr, err) static const char err[(expr) ? 1 : -1] = "";bool Compress(const char * DestName,const char *SrcName){    if (!DestName || !SrcName) {        __android_log_print(ANDROID_LOG_DEBUG, "Tag", "Parameters error: DestName=%p, SrcName=%p\n", DestName, SrcName);        return false;    }    FILE * fp_in = NULL;    int len = 0;    char buf[BUFFER_SIZE];    if (NULL == (fp_in = fopen(SrcName,"rb"))) {        __android_log_print(ANDROID_LOG_DEBUG, "Tag", "Can not open file: %s", SrcName);        return false;    }    /////////////////////////////////////////////    gzFile out = gzopen(DestName,"wb6f");    if (out == NULL) {        __android_log_print(ANDROID_LOG_DEBUG, "Tag", "Can not open file: %s", DestName);        return false;    }    bool re = true;    for (;;) {        len = fread(buf,1,sizeof(buf),fp_in);        if (ferror(fp_in)) {            re = false;            break;        }        if (len == 0) break;        if(gzwrite(out, buf, (unsigned)len) != len) {            re = false;        }    }    gzclose(out);    fclose(fp_in);    return re;}bool UnCompress(const char * DestName,const char *SrcName){    if (!DestName || !SrcName) {        __android_log_print(ANDROID_LOG_DEBUG, "Tag", "Parameters error: DestName=%p, SrcName=%p\n", DestName, SrcName);        return false;    }    FILE * fp_out = NULL;    bool re = true;    gzFile in;    unsigned int len = 0;    char buf[BUFFER_SIZE];    in = gzopen(SrcName,"rb");    if (in == NULL) {        __android_log_print(ANDROID_LOG_DEBUG, "Tag", "Open Src file error: %s", SrcName);        return false;    }    if (NULL == (fp_out = fopen(DestName,"wb"))) {        gzclose(in);        __android_log_print(ANDROID_LOG_DEBUG, "Tag", "Open Dest file error: %s(%s)", DestName, strerror(errno));        return false;    }    for (;;) {        len = gzread(in,buf,sizeof(buf));        if(len < 0) {            re = false;            break;        }        if(len == 0) break;        if(fwrite(buf,1,(unsigned)len,fp_out) != len) {            re = false;            break;        }    }    fclose(fp_out);    gzclose(in);    return re;}#ifdef UNZIP_TESTint main(void){    bool re = Compress("./a.so", "./b.so");    if (!re) {        printf("Compress error!\n");    } else {        printf("Compress success!\n");    }    re = UnCompress("./b.so", "./a.so");    if (!re) {        printf("Uncompress error!\n");    } else {        printf("Uncompress success!\n");    }    return 0;}#endifconst char originLibName[] = "/data/data/com.android.xxx/lib/liba.so";const char dstLibName[] = "/data/data/com.android.xxx/lib/libb.so";jboolean UnzipSOFile(JNIEnv*) {__android_log_print(ANDROID_LOG_DEBUG, "Tag", "UnzipSOfile!\n");    bool re = UnCompress(dstLibName, originLibName);    if (!re) {        __android_log_print(ANDROID_LOG_DEBUG, "Tag", "Unzip dynamic library error.");    }    return static_cast<jboolean>(re);}void LoadLibCompleted(JNIEnv*) {    remove(dstLibName);}const char kClassName[] = "com/android/xxx/Unzip";const JNINativeMethod kJniMethods[] = {    { "nativeUnzipSOFile", "()Z",        reinterpret_cast<void*>(UnzipSOFile) },    { "nativeLoadLibCompleted", "()V",        reinterpret_cast<void*>(LoadLibCompleted) }};}  // namespacevoid RegisterZLoader(JNIEnv* env) {    jclass clazz = env->FindClass(kClassName);    int res = env->RegisterNatives(clazz, kJniMethods, NELEM(kJniMethods));}}  // namespace android

jni_entry_point.cpp

#include <jni.h>#include <stdio.h>#include <android/log.h> namespace android {   void RegisterZLoader(JNIEnv* env);}  // namespace androidJNIEXPORT jint JNI_OnLoad(JavaVM* vm, void* reserved) {  __android_log_print(ANDROID_LOG_DEBUG, "Tag", "Unzip -> JNI_OnLoad\n");  JNIEnv* env = 0;  jint ret = vm->AttachCurrentThread(&env, 0);  android::RegisterZLoader(env);  return JNI_VERSION_1_4;}

Android.mk

LOCAL_PATH:= $(call my-dir)include $(CLEAR_VARS)TARGET_BUILD_APPS := falseLOCAL_ARM_MODE := arm LOCAL_MODULE := libUnzipLOCAL_MODULE_TAGS := optionalLOCAL_SRC_FILES:= \        jni_entry_point.cpp \        Unzip.cppLOCAL_C_INCLUDES:= \        $(SYSROOT_INC)/usr/include \        $(PWD)/ndk/sources/cxx-stl/stlport/stlport \        $(PWD)/external/chromium_org \        $(PWD)/external/chromium_org/third_party/zlib  LOCAL_C_INCLUDES_Release := \        $(LOCAL_C_INCLUDES)LOCAL_C_INCLUDES_Debug := \        $(LOCAL_C_INCLUDES)LOCAL_CFLAGS += -DAVOID_TABLESLOCAL_CPPFLAGS_Release := \    -fPIC \MY_CFLAGS_Release := \    -fPIC \LOCAL_LDFLAGS_Release := \    -fPIC \LOCAL_SHARED_LIBRARIES := libz liblogLOCAL_CFLAGS := $(MY_CFLAGS_$(GYP_CONFIGURATION)) $(MY_DEFS_$(GYP_CONFIGURATION))LOCAL_CPPFLAGS := $(LOCAL_CPPFLAGS_$(GYP_CONFIGURATION))LOCAL_LDFLAGS := $(LOCAL_LDFLAGS_$(GYP_CONFIGURATION))include $(BUILD_SHARED_LIBRARY)

注：

1.Android JNI 使用的数据结构JNINativeMethod

typedef struct {
    const char* name; // Java中函数的名字
    const char* signature; // 描述了函数的参数和返回值的字符串
    void* fnPtr; // C函数指针
} JNINativeMethod;

http://hi.baidu.com/leicejbgnndjrze/item/b87a4895e06a6c1c924f41f4

第二个参数

"()" 中的字符表示参数，后面的则代表返回值。例如"()V" 就表示void Func();

"(II)V" 表示 void Func(int, int);

在编译chromium（android4.4）时产生好多jni目录，里面有很多这样的例子

out/target/product/generic/obj/GYP/shared_intermediates/android_view/jni/

具体的每一个字符的对应关系如下

字符 Java类型 C类型

V      void            void
Z       jboolean     boolean
I        jint              int
J       jlong            long
D      jdouble       double
F      jfloat            float
B      jbyte            byte
C      jchar           char
S      jshort          short

数组则以"["开始，用两个字符表示

[I       jintArray      int[]
[F     jfloatArray    float[]
[B     jbyteArray    byte[]
[C    jcharArray    char[]
[S    jshortArray   short[]
[D    jdoubleArray double[]
[J     jlongArray     long[]
[Z    jbooleanArray boolean[]

上面的都是基本类型。如果Java函数的参数是class，则以"L"开头，以";"结尾中间是用"/" 隔开的包及类名。而其对应的C函数名的参数则为jobject. 一个例外是String类，其对应的类为jstring

Ljava/lang/String; String jstring
Ljava/net/Socket; Socket jobject

如果JAVA函数位于一个嵌入类，则用$作为类名间的分隔符。

例如 "(Ljava/lang/String;Landroid/os/FileUtils$FileStatus;)Z"

2. native log re-direct logcat

使用android/log.h，提供了4个函数

   int __android_log_write(int prio, const char *tag, const char *text);
   int __android_log_print(int prio, const char *tag, const char *fmt, ...) ;
   int __android_log_vprint(int prio, const char *tag, const char *fmt, va_list ap);
   void __android_log_assert(const char *cond, const char *tag, const char *fmt, ...) ;

其中参数prio的值有：

typedef enum android_LogPriority {
    ANDROID_LOG_UNKNOWN = 0,
    ANDROID_LOG_DEFAULT,    /* only for SetMinPriority() */
    ANDROID_LOG_VERBOSE,
    ANDROID_LOG_DEBUG,
    ANDROID_LOG_INFO,
    ANDROID_LOG_WARN,
    ANDROID_LOG_ERROR,
    ANDROID_LOG_FATAL,
    ANDROID_LOG_SILENT,     /* only for SetMinPriority(); must be last */
} android_LogPriority;

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