昨天發了一篇有關監聽自己是否被卸載和卸載反饋功能實現的博客，地址如下：http://www.cnblogs.com/zealotrouge/p/3157126.html，發出去后收到幾位熱心網友的建議，在此特別感謝@cccode @泡泡糖 @Alexia(minmin) @0x00.pl ，你們的建議就是我前進的動力。
昨天的技術方案有一個硬傷，就是每1s就需要輪詢目錄是否存在，對資源消耗較大，第二版將會解決這一問題。思路是今天想到了一個Android自API1就有的一個類FileObserver，這個類用於監聽某個文件的變化狀態，如果是目錄，這個類還可以監聽其子目錄及子目錄文件的變化狀態，通過閱讀FileObserver源碼，發現其實現利用了Linux內核中一個重要的機制inotify，它是一個內核用於通知用戶空間程序文件系統變化的機制，詳情可參考http://en.wikipedia.org/wiki/Inotify，里面對inotify有比較詳細的說明。
使用inotify的好處就在於不需要每1s的輪詢，這樣就不會無謂地消耗系統資源，使用inotify時會用read()方法阻塞進程，直到收到IN_DELETE通知，此時進程重新被喚醒，執行反饋處理流程。
由於Activity代碼和Android.mk文件和第一版並無實質性區別，這里就不貼代碼了，直接貼出C端進程的實現代碼吧。
核心——native方法頭文件：
1 /* 頭文件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 /* 頭文件end */ 11 12 /* 宏定義begin */ 13 //清0宏 14 #define MEM_ZERO(pDest, destSize) memset(pDest, 0, destSize) 15 16 //LOG宏定義 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 /* 宏定義end */ 22 23 #ifndef _Included_main_activity_UninstalledObserverActivity 24 #define _Included_main_activity_UninstalledObserverActivity 25 #ifdef __cplusplus 26 extern "C" { 27 #endif 28 29 #undef main_activity_UninstalledObserverActivity_MODE_PRIVATE 30 #define main_activity_UninstalledObserverActivity_MODE_PRIVATE 0L 31 #undef main_activity_UninstalledObserverActivity_MODE_WORLD_READABLE 32 #define main_activity_UninstalledObserverActivity_MODE_WORLD_READABLE 1L 33 #undef main_activity_UninstalledObserverActivity_MODE_WORLD_WRITEABLE 34 #define main_activity_UninstalledObserverActivity_MODE_WORLD_WRITEABLE 2L 35 #undef main_activity_UninstalledObserverActivity_MODE_APPEND 36 #define main_activity_UninstalledObserverActivity_MODE_APPEND 32768L 37 #undef main_activity_UninstalledObserverActivity_MODE_MULTI_PROCESS 38 #define main_activity_UninstalledObserverActivity_MODE_MULTI_PROCESS 4L 39 #undef main_activity_UninstalledObserverActivity_BIND_AUTO_CREATE 40 #define main_activity_UninstalledObserverActivity_BIND_AUTO_CREATE 1L 41 #undef main_activity_UninstalledObserverActivity_BIND_DEBUG_UNBIND 42 #define main_activity_UninstalledObserverActivity_BIND_DEBUG_UNBIND 2L 43 #undef main_activity_UninstalledObserverActivity_BIND_NOT_FOREGROUND 44 #define main_activity_UninstalledObserverActivity_BIND_NOT_FOREGROUND 4L 45 #undef main_activity_UninstalledObserverActivity_BIND_ABOVE_CLIENT 46 #define main_activity_UninstalledObserverActivity_BIND_ABOVE_CLIENT 8L 47 #undef main_activity_UninstalledObserverActivity_BIND_ALLOW_OOM_MANAGEMENT 48 #define main_activity_UninstalledObserverActivity_BIND_ALLOW_OOM_MANAGEMENT 16L 49 #undef main_activity_UninstalledObserverActivity_BIND_WAIVE_PRIORITY 50 #define main_activity_UninstalledObserverActivity_BIND_WAIVE_PRIORITY 32L 51 #undef main_activity_UninstalledObserverActivity_BIND_IMPORTANT 52 #define main_activity_UninstalledObserverActivity_BIND_IMPORTANT 64L 53 #undef main_activity_UninstalledObserverActivity_BIND_ADJUST_WITH_ACTIVITY 54 #define main_activity_UninstalledObserverActivity_BIND_ADJUST_WITH_ACTIVITY 128L 55 #undef main_activity_UninstalledObserverActivity_CONTEXT_INCLUDE_CODE 56 #define main_activity_UninstalledObserverActivity_CONTEXT_INCLUDE_CODE 1L 57 #undef main_activity_UninstalledObserverActivity_CONTEXT_IGNORE_SECURITY 58 #define main_activity_UninstalledObserverActivity_CONTEXT_IGNORE_SECURITY 2L 59 #undef main_activity_UninstalledObserverActivity_CONTEXT_RESTRICTED 60 #define main_activity_UninstalledObserverActivity_CONTEXT_RESTRICTED 4L 61 #undef main_activity_UninstalledObserverActivity_RESULT_CANCELED 62 #define main_activity_UninstalledObserverActivity_RESULT_CANCELED 0L 63 #undef main_activity_UninstalledObserverActivity_RESULT_OK 64 #define main_activity_UninstalledObserverActivity_RESULT_OK -1L 65 #undef main_activity_UninstalledObserverActivity_RESULT_FIRST_USER 66 #define main_activity_UninstalledObserverActivity_RESULT_FIRST_USER 1L 67 #undef main_activity_UninstalledObserverActivity_DEFAULT_KEYS_DISABLE 68 #define main_activity_UninstalledObserverActivity_DEFAULT_KEYS_DISABLE 0L 69 #undef main_activity_UninstalledObserverActivity_DEFAULT_KEYS_DIALER 70 #define main_activity_UninstalledObserverActivity_DEFAULT_KEYS_DIALER 1L 71 #undef main_activity_UninstalledObserverActivity_DEFAULT_KEYS_SHORTCUT 72 #define main_activity_UninstalledObserverActivity_DEFAULT_KEYS_SHORTCUT 2L 73 #undef main_activity_UninstalledObserverActivity_DEFAULT_KEYS_SEARCH_LOCAL 74 #define main_activity_UninstalledObserverActivity_DEFAULT_KEYS_SEARCH_LOCAL 3L 75 #undef main_activity_UninstalledObserverActivity_DEFAULT_KEYS_SEARCH_GLOBAL 76 #define main_activity_UninstalledObserverActivity_DEFAULT_KEYS_SEARCH_GLOBAL 4L 77 78 /* 79 * Class: main_activity_UninstalledObserverActivity 80 * Method: init 81 * Signature: ()V 82 */ 83 JNIEXPORT void JNICALL Java_main_activity_UninstalledObserverActivity_init(JNIEnv *, jobject); 84 85 #ifdef __cplusplus 86 } 87 #endif 88 #endif
核心——native方法實現：
1 /* 頭文件begin */ 2 #include "main_activity_UninstalledObserverActivity.h" 3 /* 頭文件end */ 4 5 #ifdef __cplusplus 6 extern "C" { 7 #endif 8 9 /* 內全局變量begin */ 10 static char c_TAG[] = "UninstalledObserverActivity.init"; 11 static jboolean b_IS_COPY = JNI_TRUE; 12 /* 內全局變量 */ 13 14 /* 15 * Class: main_activity_UninstalledObserverActivity 16 * Method: init 17 * Signature: ()V 18 */ 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log 24 LOG_DEBUG((*env)->GetStringUTFChars(env, tag, &b_IS_COPY) 25 , (*env)->GetStringUTFChars(env, (*env)->NewStringUTF(env, "init OK"), &b_IS_COPY)); 26 27 //fork子進程，以執行輪詢任務 28 pid_t pid = fork(); 29 if (pid < 0) 30 { 31 //出錯log 32 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 //子進程注冊"/data/data/pym.test.uninstalledobserver"目錄監聽器 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 //分配緩存，以便讀取event，緩存大小=一個struct inotify_event的大小，這樣一次處理一個event 58 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 //開始監聽 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會阻塞進程，走到這里說明收到目錄被刪除的事件，注銷監聽器 72 free(p_buf); 73 inotify_rm_watch(fileDescriptor, IN_DELETE); 74 75 //目錄不存在log 76 LOG_DEBUG((*env)->GetStringUTFChars(env, tag, &b_IS_COPY) 77 , (*env)->GetStringUTFChars(env, (*env)->NewStringUTF(env, "uninstalled"), &b_IS_COPY)); 78 79 //執行命令am start -a android.intent.action.VIEW -d http://shouji.360.cn/web/uninstall/uninstall.html 80 execlp("am", "am", "start", "-a", "android.intent.action.VIEW", "-d", "http://shouji.360.cn/web/uninstall/uninstall.html", (char *)NULL); 81 } 82 else 83 { 84 //父進程直接退出，使子進程被init進程領養，以避免子進程僵死 85 } 86 } 87 88 #ifdef __cplusplus 89 } 90 #endif