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://www.cnblogs.com/zealotrouge/p/3157126.html，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：

 

 1 /* 头文件begin */ 2 #include <jni.h> 3 #include <stdlib.h> 4 #include <stdio.h> 5 #include <string.h> 6 #include <android/log.h> 7 #include <unistd.h> 8 #include <sys/inotify.h> 9 #include <fcntl.h>10 /* 头文件end */11 12 /* 宏定义begin */13 //清0宏14 #define MEM_ZERO(pDest, destSize) memset(pDest, 0, destSize)15 16 //LOG宏定义17 #define LOG_INFO(tag, msg) __android_log_write(ANDROID_LOG_INFO, tag, msg)18 #define LOG_DEBUG(tag, msg) __android_log_write(ANDROID_LOG_DEBUG, tag, msg)19 #define LOG_WARN(tag, msg) __android_log_write(ANDROID_LOG_WARN, tag, msg)20 #define LOG_ERROR(tag, msg) __android_log_write(ANDROID_LOG_ERROR, tag, msg)21 /* 宏定义end */22 23 #ifndef _Included_main_activity_UninstalledObserverActivity24 #define _Included_main_activity_UninstalledObserverActivity25 #ifdef __cplusplus26 extern "C" {27 #endif28 29 #undef main_activity_UninstalledObserverActivity_MODE_PRIVATE30 #define main_activity_UninstalledObserverActivity_MODE_PRIVATE 0L31 #undef main_activity_UninstalledObserverActivity_MODE_WORLD_READABLE32 #define main_activity_UninstalledObserverActivity_MODE_WORLD_READABLE 1L33 #undef main_activity_UninstalledObserverActivity_MODE_WORLD_WRITEABLE34 #define main_activity_UninstalledObserverActivity_MODE_WORLD_WRITEABLE 2L35 #undef main_activity_UninstalledObserverActivity_MODE_APPEND36 #define main_activity_UninstalledObserverActivity_MODE_APPEND 32768L37 #undef main_activity_UninstalledObserverActivity_MODE_MULTI_PROCESS38 #define main_activity_UninstalledObserverActivity_MODE_MULTI_PROCESS 4L39 #undef main_activity_UninstalledObserverActivity_BIND_AUTO_CREATE40 #define main_activity_UninstalledObserverActivity_BIND_AUTO_CREATE 1L41 #undef main_activity_UninstalledObserverActivity_BIND_DEBUG_UNBIND42 #define main_activity_UninstalledObserverActivity_BIND_DEBUG_UNBIND 2L43 #undef main_activity_UninstalledObserverActivity_BIND_NOT_FOREGROUND44 #define main_activity_UninstalledObserverActivity_BIND_NOT_FOREGROUND 4L45 #undef main_activity_UninstalledObserverActivity_BIND_ABOVE_CLIENT46 #define main_activity_UninstalledObserverActivity_BIND_ABOVE_CLIENT 8L47 #undef main_activity_UninstalledObserverActivity_BIND_ALLOW_OOM_MANAGEMENT48 #define main_activity_UninstalledObserverActivity_BIND_ALLOW_OOM_MANAGEMENT 16L49 #undef main_activity_UninstalledObserverActivity_BIND_WAIVE_PRIORITY50 #define main_activity_UninstalledObserverActivity_BIND_WAIVE_PRIORITY 32L51 #undef main_activity_UninstalledObserverActivity_BIND_IMPORTANT52 #define main_activity_UninstalledObserverActivity_BIND_IMPORTANT 64L53 #undef main_activity_UninstalledObserverActivity_BIND_ADJUST_WITH_ACTIVITY54 #define main_activity_UninstalledObserverActivity_BIND_ADJUST_WITH_ACTIVITY 128L55 #undef main_activity_UninstalledObserverActivity_CONTEXT_INCLUDE_CODE56 #define main_activity_UninstalledObserverActivity_CONTEXT_INCLUDE_CODE 1L57 #undef main_activity_UninstalledObserverActivity_CONTEXT_IGNORE_SECURITY58 #define main_activity_UninstalledObserverActivity_CONTEXT_IGNORE_SECURITY 2L59 #undef main_activity_UninstalledObserverActivity_CONTEXT_RESTRICTED60 #define main_activity_UninstalledObserverActivity_CONTEXT_RESTRICTED 4L61 #undef main_activity_UninstalledObserverActivity_RESULT_CANCELED62 #define main_activity_UninstalledObserverActivity_RESULT_CANCELED 0L63 #undef main_activity_UninstalledObserverActivity_RESULT_OK64 #define main_activity_UninstalledObserverActivity_RESULT_OK -1L65 #undef main_activity_UninstalledObserverActivity_RESULT_FIRST_USER66 #define main_activity_UninstalledObserverActivity_RESULT_FIRST_USER 1L67 #undef main_activity_UninstalledObserverActivity_DEFAULT_KEYS_DISABLE68 #define main_activity_UninstalledObserverActivity_DEFAULT_KEYS_DISABLE 0L69 #undef main_activity_UninstalledObserverActivity_DEFAULT_KEYS_DIALER70 #define main_activity_UninstalledObserverActivity_DEFAULT_KEYS_DIALER 1L71 #undef main_activity_UninstalledObserverActivity_DEFAULT_KEYS_SHORTCUT72 #define main_activity_UninstalledObserverActivity_DEFAULT_KEYS_SHORTCUT 2L73 #undef main_activity_UninstalledObserverActivity_DEFAULT_KEYS_SEARCH_LOCAL74 #define main_activity_UninstalledObserverActivity_DEFAULT_KEYS_SEARCH_LOCAL 3L75 #undef main_activity_UninstalledObserverActivity_DEFAULT_KEYS_SEARCH_GLOBAL76 #define main_activity_UninstalledObserverActivity_DEFAULT_KEYS_SEARCH_GLOBAL 4L77 78 /*79  * Class:     main_activity_UninstalledObserverActivity80  * Method:    init81  * Signature: ()V82  */83 JNIEXPORT void JNICALL Java_main_activity_UninstalledObserverActivity_init(JNIEnv *, jobject);84 85 #ifdef __cplusplus86 }87 #endif88 #endif

 

核心——native方法实现：

 

 1 /* 头文件begin */ 2 #include "main_activity_UninstalledObserverActivity.h" 3 /* 头文件end */ 4  5 #ifdef __cplusplus 6 extern "C" { 7 #endif 8  9 /* 内全局变量begin */10 static char c_TAG[] = "UninstalledObserverActivity.init";11 static jboolean b_IS_COPY = JNI_TRUE;12 /* 内全局变量 */13 14 /*15  * Class:     main_activity_UninstalledObserverActivity16  * Method:    init17  * Signature: ()V18  */19 JNIEXPORT void JNICALL Java_main_activity_UninstalledObserverActivity_init(JNIEnv *env, jobject obj)20 {21     jstring tag = (*env)->NewStringUTF(env, c_TAG);22 23     //初始化log24     LOG_DEBUG((*env)->GetStringUTFChars(env, tag, &b_IS_COPY)25             , (*env)->GetStringUTFChars(env, (*env)->NewStringUTF(env, "init OK"), &b_IS_COPY));26 27     //fork子进程，以执行轮询任务28     pid_t pid = fork();29     if (pid < 0)30     {31         //出错log32         LOG_ERROR((*env)->GetStringUTFChars(env, tag, &b_IS_COPY)33                 , (*env)->GetStringUTFChars(env, (*env)->NewStringUTF(env, "fork failed !!!"), &b_IS_COPY));34     }35     else if (pid == 0)36     {37         //子进程注册"/data/data/pym.test.uninstalledobserver"目录监听器38         int fileDescriptor = inotify_init();39         if (fileDescriptor < 0)40         {41             LOG_DEBUG((*env)->GetStringUTFChars(env, tag, &b_IS_COPY)42                     , (*env)->GetStringUTFChars(env, (*env)->NewStringUTF(env, "inotify_init failed !!!"), &b_IS_COPY));43 44              exit(1);45         }46 47         int watchDescriptor;48         watchDescriptor = inotify_add_watch(fileDescriptor, "/data/data/pym.test.uninstalledobserver", IN_DELETE);49         if (watchDescriptor < 0)50         {51             LOG_DEBUG((*env)->GetStringUTFChars(env, tag, &b_IS_COPY)52                     , (*env)->GetStringUTFChars(env, (*env)->NewStringUTF(env, "inotify_add_watch failed !!!"), &b_IS_COPY));53 54             exit(1);55         }56 57         //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event58         void *p_buf = malloc(sizeof(struct inotify_event));59         if (p_buf == NULL)60         {61             LOG_DEBUG((*env)->GetStringUTFChars(env, tag, &b_IS_COPY)62                     , (*env)->GetStringUTFChars(env, (*env)->NewStringUTF(env, "malloc failed !!!"), &b_IS_COPY));63 64             exit(1);65         }66         //开始监听67         LOG_DEBUG((*env)->GetStringUTFChars(env, tag, &b_IS_COPY)68                     , (*env)->GetStringUTFChars(env, (*env)->NewStringUTF(env, "start observer"), &b_IS_COPY));69         size_t readBytes = read(fileDescriptor, p_buf, sizeof(struct inotify_event));70 71         //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72         free(p_buf);73         inotify_rm_watch(fileDescriptor, IN_DELETE);74 75         //目录不存在log76         LOG_DEBUG((*env)->GetStringUTFChars(env, tag, &b_IS_COPY)77                     , (*env)->GetStringUTFChars(env, (*env)->NewStringUTF(env, "uninstalled"), &b_IS_COPY));78 79         //执行命令am start -a android.intent.action.VIEW -d http://shouji.360.cn/web/uninstall/uninstall.html80         execlp("am", "am", "start", "-a", "android.intent.action.VIEW", "-d", "http://shouji.360.cn/web/uninstall/uninstall.html", (char *)NULL);81     }82     else83     {84         //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85     }86 }87 88 #ifdef __cplusplus89 }90 #endif