Android应用如何监听自己是否被卸载及卸载反馈功能的实现（第二版）

昨天发了一篇有关监听自己是否被卸载和卸载反馈功能实现的博客，地址如下：http://blog.csdn.net/myweishanli/article/details/39636699，发出去后收到几位热心网友的建议，在此特别感谢@cccode @泡泡糖 @Alexia(minmin) @0x00.pl ，你们的建议就是我前进的动力。

　　昨天的技术方案有一个硬伤，就是每1s就需要轮询目录是否存在，对资源消耗较大，第二版将会解决这一问题。思路是今天想到了一个Android自API1就有的一个类FileObserver，这个类用于监听某个文件的变化状态，如果是目录，这个类还可以监听其子目录及子目录文件的变化状态，通过阅读FileObserver源码，发现其实现利用了Linux内核中一个重要的机制inotify，它是一个内核用于通知用户空间程序文件系统变化的机制，详情可参考http://en.wikipedia.org/wiki/Inotify，里面对inotify有比较详细的说明。

　　使用inotify的好处就在于不需要每1s的轮询，这样就不会无谓地消耗系统资源，使用inotify时会用read()方法阻塞进程，直到收到IN_DELETE通知，此时进程重新被唤醒，执行反馈处理流程。

　　由于Activity代码和Android.mk文件和第一版并无实质性区别，这里就不贴代码了，直接贴出C端进程的实现代码吧。

核心——native方法头文件：

/* 头文件begin */#include <jni.h>#include <stdlib.h>#include <stdio.h>#include <string.h>#include <android/log.h>#include <unistd.h>#include <sys/inotify.h>#include <fcntl.h>/* 头文件end *//* 宏定义begin *///清0宏#define MEM_ZERO(pDest, destSize) memset(pDest, 0, destSize)//LOG宏定义#define LOG_INFO(tag, msg) __android_log_write(ANDROID_LOG_INFO, tag, msg)#define LOG_DEBUG(tag, msg) __android_log_write(ANDROID_LOG_DEBUG, tag, msg)#define LOG_WARN(tag, msg) __android_log_write(ANDROID_LOG_WARN, tag, msg)#define LOG_ERROR(tag, msg) __android_log_write(ANDROID_LOG_ERROR, tag, msg)/* 宏定义end */#ifndef _Included_main_activity_UninstalledObserverActivity#define _Included_main_activity_UninstalledObserverActivity#ifdef __cplusplusextern "C" {#endif#undef main_activity_UninstalledObserverActivity_MODE_PRIVATE#define main_activity_UninstalledObserverActivity_MODE_PRIVATE 0L#undef main_activity_UninstalledObserverActivity_MODE_WORLD_READABLE#define main_activity_UninstalledObserverActivity_MODE_WORLD_READABLE 1L#undef main_activity_UninstalledObserverActivity_MODE_WORLD_WRITEABLE#define main_activity_UninstalledObserverActivity_MODE_WORLD_WRITEABLE 2L#undef main_activity_UninstalledObserverActivity_MODE_APPEND#define main_activity_UninstalledObserverActivity_MODE_APPEND 32768L#undef main_activity_UninstalledObserverActivity_MODE_MULTI_PROCESS#define main_activity_UninstalledObserverActivity_MODE_MULTI_PROCESS 4L#undef main_activity_UninstalledObserverActivity_BIND_AUTO_CREATE#define main_activity_UninstalledObserverActivity_BIND_AUTO_CREATE 1L#undef main_activity_UninstalledObserverActivity_BIND_DEBUG_UNBIND#define main_activity_UninstalledObserverActivity_BIND_DEBUG_UNBIND 2L#undef main_activity_UninstalledObserverActivity_BIND_NOT_FOREGROUND#define main_activity_UninstalledObserverActivity_BIND_NOT_FOREGROUND 4L#undef main_activity_UninstalledObserverActivity_BIND_ABOVE_CLIENT#define main_activity_UninstalledObserverActivity_BIND_ABOVE_CLIENT 8L#undef main_activity_UninstalledObserverActivity_BIND_ALLOW_OOM_MANAGEMENT#define main_activity_UninstalledObserverActivity_BIND_ALLOW_OOM_MANAGEMENT 16L#undef main_activity_UninstalledObserverActivity_BIND_WAIVE_PRIORITY#define main_activity_UninstalledObserverActivity_BIND_WAIVE_PRIORITY 32L#undef main_activity_UninstalledObserverActivity_BIND_IMPORTANT#define main_activity_UninstalledObserverActivity_BIND_IMPORTANT 64L#undef main_activity_UninstalledObserverActivity_BIND_ADJUST_WITH_ACTIVITY#define main_activity_UninstalledObserverActivity_BIND_ADJUST_WITH_ACTIVITY 128L#undef main_activity_UninstalledObserverActivity_CONTEXT_INCLUDE_CODE#define main_activity_UninstalledObserverActivity_CONTEXT_INCLUDE_CODE 1L#undef main_activity_UninstalledObserverActivity_CONTEXT_IGNORE_SECURITY#define main_activity_UninstalledObserverActivity_CONTEXT_IGNORE_SECURITY 2L#undef main_activity_UninstalledObserverActivity_CONTEXT_RESTRICTED#define main_activity_UninstalledObserverActivity_CONTEXT_RESTRICTED 4L#undef main_activity_UninstalledObserverActivity_RESULT_CANCELED#define main_activity_UninstalledObserverActivity_RESULT_CANCELED 0L#undef main_activity_UninstalledObserverActivity_RESULT_OK#define main_activity_UninstalledObserverActivity_RESULT_OK -1L#undef main_activity_UninstalledObserverActivity_RESULT_FIRST_USER#define main_activity_UninstalledObserverActivity_RESULT_FIRST_USER 1L#undef main_activity_UninstalledObserverActivity_DEFAULT_KEYS_DISABLE#define main_activity_UninstalledObserverActivity_DEFAULT_KEYS_DISABLE 0L#undef main_activity_UninstalledObserverActivity_DEFAULT_KEYS_DIALER#define main_activity_UninstalledObserverActivity_DEFAULT_KEYS_DIALER 1L#undef main_activity_UninstalledObserverActivity_DEFAULT_KEYS_SHORTCUT#define main_activity_UninstalledObserverActivity_DEFAULT_KEYS_SHORTCUT 2L#undef main_activity_UninstalledObserverActivity_DEFAULT_KEYS_SEARCH_LOCAL#define main_activity_UninstalledObserverActivity_DEFAULT_KEYS_SEARCH_LOCAL 3L#undef main_activity_UninstalledObserverActivity_DEFAULT_KEYS_SEARCH_GLOBAL#define main_activity_UninstalledObserverActivity_DEFAULT_KEYS_SEARCH_GLOBAL 4L/* * Class:     main_activity_UninstalledObserverActivity * Method:    init * Signature: ()V */JNIEXPORT void JNICALL Java_main_activity_UninstalledObserverActivity_init(JNIEnv *, jobject);#ifdef __cplusplus}#endif#endif

 

核心——native方法实现：

/* 头文件begin */#include "main_activity_UninstalledObserverActivity.h"/* 头文件end */#ifdef __cplusplusextern "C" {#endif/* 内全局变量begin */static char c_TAG[] = "UninstalledObserverActivity.init";static jboolean b_IS_COPY = JNI_TRUE;/* 内全局变量 *//* * Class:     main_activity_UninstalledObserverActivity * Method:    init * Signature: ()V */JNIEXPORT void JNICALL Java_main_activity_UninstalledObserverActivity_init(JNIEnv *env, jobject obj){    jstring tag = (*env)->NewStringUTF(env, c_TAG);    //初始化log    LOG_DEBUG((*env)->GetStringUTFChars(env, tag, &b_IS_COPY)            , (*env)->GetStringUTFChars(env, (*env)->NewStringUTF(env, "init OK"), &b_IS_COPY));    //fork子进程，以执行轮询任务    pid_t pid = fork();    if (pid < 0)    {        //出错log        LOG_ERROR((*env)->GetStringUTFChars(env, tag, &b_IS_COPY)                , (*env)->GetStringUTFChars(env, (*env)->NewStringUTF(env, "fork failed !!!"), &b_IS_COPY));    }    else if (pid == 0)    {        //子进程注册"/data/data/pym.test.uninstalledobserver"目录监听器        int fileDescriptor = inotify_init();        if (fileDescriptor < 0)        {            LOG_DEBUG((*env)->GetStringUTFChars(env, tag, &b_IS_COPY)                    , (*env)->GetStringUTFChars(env, (*env)->NewStringUTF(env, "inotify_init failed !!!"), &b_IS_COPY));             exit(1);        }        int watchDescriptor;        watchDescriptor = inotify_add_watch(fileDescriptor, "/data/data/pym.test.uninstalledobserver", IN_DELETE);        if (watchDescriptor < 0)        {            LOG_DEBUG((*env)->GetStringUTFChars(env, tag, &b_IS_COPY)                    , (*env)->GetStringUTFChars(env, (*env)->NewStringUTF(env, "inotify_add_watch failed !!!"), &b_IS_COPY));            exit(1);        }        //分配缓存，以便读取event，缓存大小=一个struct inotify_event的大小，这样一次处理一个event        void *p_buf = malloc(sizeof(struct inotify_event));        if (p_buf == NULL)        {            LOG_DEBUG((*env)->GetStringUTFChars(env, tag, &b_IS_COPY)                    , (*env)->GetStringUTFChars(env, (*env)->NewStringUTF(env, "malloc failed !!!"), &b_IS_COPY));            exit(1);        }        //开始监听        LOG_DEBUG((*env)->GetStringUTFChars(env, tag, &b_IS_COPY)                    , (*env)->GetStringUTFChars(env, (*env)->NewStringUTF(env, "start observer"), &b_IS_COPY));        size_t readBytes = read(fileDescriptor, p_buf, sizeof(struct inotify_event));        //read会阻塞进程，走到这里说明收到目录被删除的事件，注销监听器        free(p_buf);        inotify_rm_watch(fileDescriptor, IN_DELETE);        //目录不存在log        LOG_DEBUG((*env)->GetStringUTFChars(env, tag, &b_IS_COPY)                    , (*env)->GetStringUTFChars(env, (*env)->NewStringUTF(env, "uninstalled"), &b_IS_COPY));        //执行命令am start -a android.intent.action.VIEW -d http://shouji.360.cn/web/uninstall/uninstall.html        execlp("am", "am", "start", "-a", "android.intent.action.VIEW", "-d", "http://shouji.360.cn/web/uninstall/uninstall.html", (char *)NULL);    }    else    {        //父进程直接退出，使子进程被init进程领养，以避免子进程僵死    }}#ifdef __cplusplus}#endif