Android應用如何監聽本身是否被卸載及卸載反饋功能的實現(第三版)

  兩個月前發了兩篇有關監聽本身是否被卸載和卸載反饋功能實現的博客,第二版的地址以下:http://www.cnblogs.com/zealotrouge/p/3159772.html,感謝@whiletrue_童鞋發現了個人代碼在4.2.2系統上沒法實現卸載反饋,通過調試,有了問題的解決方案,可是因爲發完博客後即處於閉關開發階段,沒時間打理博客,因此解決方案遲遲沒有與你們見面,最近空閒下來,將解決思路及方案發出來給你們看看還有沒有問題。html

  調試發現,監聽依然沒有問題,畢竟是Linux Kernel中的接口,Framework層再怎麼改也改不到那兒去,那麼問題出在哪呢?阻塞結束後,經過調用exec函數發出am命令調起瀏覽器訪問網頁,在API16(Android 4.1.x)的設備上尚可正常訪問網頁,而API17(Android 4.2.x)的設備上連瀏覽器也不能調起。java

  經過分析log,發現了一條線索,以下面的log的所示:android

W/ActivityManager( 387): Permission Denial: startActivity asks to run as user -2 but is calling from user 0; this requires android.permission.INTERACT_ACROSS_USERS_FULL

  log中直接給出提示,須要加一個權限INTERACT_ACROSS_USERS_FULL,這個權限時API17新引入的,目的在於容許不一樣用戶的應用之間能夠產生交互。但是加上去以後發現,還不是沒法調起瀏覽器,並且log依然提示須要權限INTERACT_ACROSS_USERS_FULL,非常奇怪,因而繼續分析。瀏覽器

  首先說明一下Linux中的pid和uid,以及android擴展的userSerialNumber。pid是Process的標識,用於系統對進程的控制,從API層面看就是用於Process.killProcess()和Process.sendSignal();uid在Linux系統中是用來標識用戶的,而在android將uid視爲app的標識id,用於"sandbox"安全模型,即用於app權限控制;而對於API17引入的多用戶支持(目前只支持平板),uid已經被佔用,只好新引入userSerialNumber來標識用戶。安全

  回到剛纔的問題,log中告知startActivity時運行用戶標識爲-2,而調用倒是由用戶標識0發起,致使拒絕執行。用這句話搜索,發如今Google開發者網站中有相關的issue,連接以下:https://code.google.com/p/android/issues/detail?id=39801(打不開能夠把https改成http)。結合官方的回答,問題緣由以下:因爲被卸載,C端進程監聽到目錄被刪除,當即執行am命令,此時將會默認以USER_CURRENT的身份執行,因爲API17中ActivityManagerService.handleIncomingUser()會校驗userSerialNumber,發現用戶標識不匹配,致使權限校驗失敗——這也說明了權限的影響範圍僅限於Java端的進程,對於fork()出來的C端進程來講,並不繼承父進程在Android中聲明的權限。app

  解決方案:增長處理分支,若API>=17,將userSerialNumber傳遞給C端進程,而後在am命令中帶上參數--user userSerialNumber便可。ide

Java端代碼以下:函數

 
  1 package main.activity;
  2 
  3 import java.lang.reflect.InvocationTargetException;
  4 import java.lang.reflect.Method;
  5 
  6 import pym.test.uninstalledobserver.R;
  7 import android.app.Activity;
  8 import android.os.Build;
  9 import android.os.Bundle;
 10 import android.util.Log;
 11 
 12 /**
 13  * @author pengyiming
 14  * @note 監聽此應用是否被卸載,若被卸載則彈出卸載反饋
 15  * @note 因爲API17加入多用戶支持,原有命令在4.2及更高版本上執行時缺乏userSerial參數,特此修改
 16  *
 17  */
 18 
 19 public class UninstalledObserverActivity extends Activity
 20 {
 21     /* 數據段begin */
 22     private static final String TAG = "UninstalledObserverActivity";
 23     
 24     // 監聽進程pid
 25     private int mObserverProcessPid = -1;
 26     /* 數據段end */
 27     
 28     /* static */
 29     // 初始化監聽進程
 30     private native int init(String userSerial);
 31     static
 32     {
 33         Log.d(TAG, "load lib --> uninstalled_observer");
 34         System.loadLibrary("uninstalled_observer");
 35     }
 36     /* static */
 37     
 38     /* 函數段begin */
 39     @Override
 40     public void onCreate(Bundle savedInstanceState)
 41     {
 42         super.onCreate(savedInstanceState);
 43         
 44         setContentView(R.layout.uninstalled_observer_layout);
 45         
 46         // API level小於17,不須要獲取userSerialNumber
 47         if (Build.VERSION.SDK_INT < 17)
 48         {
 49             mObserverProcessPid = init(null);
 50         }
 51         // 不然,須要獲取userSerialNumber
 52         else
 53         {
 54             mObserverProcessPid = init(getUserSerial());
 55         }
 56     }
 57     
 58     @Override
 59     protected void onDestroy()
 60     {
 61         super.onDestroy();
 62         
 63         // 示例代碼,用於結束監聽進程
 64 //        if (mObserverProcessPid > 0)
 65 //        {
 66 //            android.os.Process.killProcess(mObserverProcessPid);
 67 //        }
 68     }
 69     
 70     // 因爲targetSdkVersion低於17,只能經過反射獲取
 71     private String getUserSerial()
 72     {
 73         Object userManager = getSystemService("user");
 74         if (userManager == null)
 75         {
 76             Log.e(TAG, "userManager not exsit !!!");
 77             return null;
 78         }
 79         
 80         try
 81         {
 82             Method myUserHandleMethod = android.os.Process.class.getMethod("myUserHandle", (Class<?>[]) null);
 83             Object myUserHandle = myUserHandleMethod.invoke(android.os.Process.class, (Object[]) null);
 84             
 85             Method getSerialNumberForUser = userManager.getClass().getMethod("getSerialNumberForUser", myUserHandle.getClass());
 86             long userSerial = (Long) getSerialNumberForUser.invoke(userManager, myUserHandle);
 87             return String.valueOf(userSerial);
 88         }
 89         catch (NoSuchMethodException e)
 90         {
 91             Log.e(TAG, "", e);
 92         }
 93         catch (IllegalArgumentException e)
 94         {
 95             Log.e(TAG, "", e);
 96         }
 97         catch (IllegalAccessException e)
 98         {
 99             Log.e(TAG, "", e);
100         }
101         catch (InvocationTargetException e)
102         {
103             Log.e(TAG, "", e);
104         }
105         
106         return null;
107     }
108     /* 函數段end */
109 }
 

核心——native方法頭文件:網站

 
 1 /* 頭文件begin */
 2 #include <jni.h>
 3 #include <stdlib.h>
 4 #include <stdio.h>
 5 #include <string.h>
 6 #include <unistd.h>
 7 #include <fcntl.h>
 8 #include <sys/inotify.h>
 9 #include <sys/stat.h>
10 
11 #include <android/log.h>
12 /* 頭文件end */
13 
14 /* 宏定義begin */
15 //清0宏
16 #define MEM_ZERO(pDest, destSize) memset(pDest, 0, destSize)
17 
18 //LOG宏定義
19 #define LOG_INFO(tag, msg) __android_log_write(ANDROID_LOG_INFO, tag, msg)
20 #define LOG_DEBUG(tag, msg) __android_log_write(ANDROID_LOG_DEBUG, tag, msg)
21 #define LOG_WARN(tag, msg) __android_log_write(ANDROID_LOG_WARN, tag, msg)
22 #define LOG_ERROR(tag, msg) __android_log_write(ANDROID_LOG_ERROR, tag, msg)
23 /* 宏定義end */
24 
25 #ifndef _Included_main_activity_UninstalledObserverActivity
26 #define _Included_main_activity_UninstalledObserverActivity
27 #ifdef __cplusplus
28 extern "C" {
29 #endif
30 
31 #undef main_activity_UninstalledObserverActivity_MODE_PRIVATE
32 #define main_activity_UninstalledObserverActivity_MODE_PRIVATE 0L
33 #undef main_activity_UninstalledObserverActivity_MODE_WORLD_READABLE
34 #define main_activity_UninstalledObserverActivity_MODE_WORLD_READABLE 1L
35 #undef main_activity_UninstalledObserverActivity_MODE_WORLD_WRITEABLE
36 #define main_activity_UninstalledObserverActivity_MODE_WORLD_WRITEABLE 2L
37 #undef main_activity_UninstalledObserverActivity_MODE_APPEND
38 #define main_activity_UninstalledObserverActivity_MODE_APPEND 32768L
39 #undef main_activity_UninstalledObserverActivity_MODE_MULTI_PROCESS
40 #define main_activity_UninstalledObserverActivity_MODE_MULTI_PROCESS 4L
41 #undef main_activity_UninstalledObserverActivity_BIND_AUTO_CREATE
42 #define main_activity_UninstalledObserverActivity_BIND_AUTO_CREATE 1L
43 #undef main_activity_UninstalledObserverActivity_BIND_DEBUG_UNBIND
44 #define main_activity_UninstalledObserverActivity_BIND_DEBUG_UNBIND 2L
45 #undef main_activity_UninstalledObserverActivity_BIND_NOT_FOREGROUND
46 #define main_activity_UninstalledObserverActivity_BIND_NOT_FOREGROUND 4L
47 #undef main_activity_UninstalledObserverActivity_BIND_ABOVE_CLIENT
48 #define main_activity_UninstalledObserverActivity_BIND_ABOVE_CLIENT 8L
49 #undef main_activity_UninstalledObserverActivity_BIND_ALLOW_OOM_MANAGEMENT
50 #define main_activity_UninstalledObserverActivity_BIND_ALLOW_OOM_MANAGEMENT 16L
51 #undef main_activity_UninstalledObserverActivity_BIND_WAIVE_PRIORITY
52 #define main_activity_UninstalledObserverActivity_BIND_WAIVE_PRIORITY 32L
53 #undef main_activity_UninstalledObserverActivity_BIND_IMPORTANT
54 #define main_activity_UninstalledObserverActivity_BIND_IMPORTANT 64L
55 #undef main_activity_UninstalledObserverActivity_BIND_ADJUST_WITH_ACTIVITY
56 #define main_activity_UninstalledObserverActivity_BIND_ADJUST_WITH_ACTIVITY 128L
57 #undef main_activity_UninstalledObserverActivity_CONTEXT_INCLUDE_CODE
58 #define main_activity_UninstalledObserverActivity_CONTEXT_INCLUDE_CODE 1L
59 #undef main_activity_UninstalledObserverActivity_CONTEXT_IGNORE_SECURITY
60 #define main_activity_UninstalledObserverActivity_CONTEXT_IGNORE_SECURITY 2L
61 #undef main_activity_UninstalledObserverActivity_CONTEXT_RESTRICTED
62 #define main_activity_UninstalledObserverActivity_CONTEXT_RESTRICTED 4L
63 #undef main_activity_UninstalledObserverActivity_RESULT_CANCELED
64 #define main_activity_UninstalledObserverActivity_RESULT_CANCELED 0L
65 #undef main_activity_UninstalledObserverActivity_RESULT_OK
66 #define main_activity_UninstalledObserverActivity_RESULT_OK -1L
67 #undef main_activity_UninstalledObserverActivity_RESULT_FIRST_USER
68 #define main_activity_UninstalledObserverActivity_RESULT_FIRST_USER 1L
69 #undef main_activity_UninstalledObserverActivity_DEFAULT_KEYS_DISABLE
70 #define main_activity_UninstalledObserverActivity_DEFAULT_KEYS_DISABLE 0L
71 #undef main_activity_UninstalledObserverActivity_DEFAULT_KEYS_DIALER
72 #define main_activity_UninstalledObserverActivity_DEFAULT_KEYS_DIALER 1L
73 #undef main_activity_UninstalledObserverActivity_DEFAULT_KEYS_SHORTCUT
74 #define main_activity_UninstalledObserverActivity_DEFAULT_KEYS_SHORTCUT 2L
75 #undef main_activity_UninstalledObserverActivity_DEFAULT_KEYS_SEARCH_LOCAL
76 #define main_activity_UninstalledObserverActivity_DEFAULT_KEYS_SEARCH_LOCAL 3L
77 #undef main_activity_UninstalledObserverActivity_DEFAULT_KEYS_SEARCH_GLOBAL
78 #define main_activity_UninstalledObserverActivity_DEFAULT_KEYS_SEARCH_GLOBAL 4L
79 
80 /*
81  * Class:     main_activity_UninstalledObserverActivity
82  * Method:    init
83  * Signature: (Ljava/lang/String;)V
84  */
85 JNIEXPORT int JNICALL Java_main_activity_UninstalledObserverActivity_init(JNIEnv *, jobject, jstring);
86 
87 #ifdef __cplusplus
88 }
89 #endif
90 #endif
 

核心——native方法實現:ui

 
  1 /* 頭文件begin */
  2 #include "main_activity_UninstalledObserverActivity.h"
  3 /* 頭文件end */
  4 
  5 #ifdef __cplusplus
  6 extern "C"
  7 {
  8 #endif
  9 
 10 /* 內全局變量begin */
 11 static char TAG[] = "UninstalledObserverActivity.init";
 12 static jboolean isCopy = JNI_TRUE;
 13 
 14 static const char APP_DIR[] = "/data/data/pym.test.uninstalledobserver";
 15 static const char APP_FILES_DIR[] = "/data/data/pym.test.uninstalledobserver/files";
 16 static const char APP_OBSERVED_FILE[] = "/data/data/pym.test.uninstalledobserver/files/observedFile";
 17 static const char APP_LOCK_FILE[] = "/data/data/pym.test.uninstalledobserver/files/lockFile";
 18 /* 內全局變量 */
 19 
 20 /*
 21  * Class:     main_activity_UninstalledObserverActivity
 22  * Method:    init
 23  * Signature: ()V
 24  * return: 子進程pid
 25  */
 26 JNIEXPORT int JNICALL Java_main_activity_UninstalledObserverActivity_init(JNIEnv *env, jobject obj, jstring userSerial)
 27 {
 28     jstring tag = (*env)->NewStringUTF(env, TAG);
 29 
 30     LOG_DEBUG((*env)->GetStringUTFChars(env, tag, &isCopy)
 31             , (*env)->GetStringUTFChars(env, (*env)->NewStringUTF(env, "init observer"), &isCopy));
 32 
 33     // fork子進程,以執行輪詢任務
 34     pid_t pid = fork();
 35     if (pid < 0)
 36     {
 37         LOG_ERROR((*env)->GetStringUTFChars(env, tag, &isCopy)
 38                 , (*env)->GetStringUTFChars(env, (*env)->NewStringUTF(env, "fork failed !!!"), &isCopy));
 39 
 40         exit(1);
 41     }
 42     else if (pid == 0)
 43     {
 44         // 若監聽文件所在文件夾不存在,建立
 45         FILE *p_filesDir = fopen(APP_FILES_DIR, "r");
 46         if (p_filesDir == NULL)
 47         {
 48             int filesDirRet = mkdir(APP_FILES_DIR, S_IRWXU | S_IRWXG | S_IXOTH);
 49             if (filesDirRet == -1)
 50             {
 51                 LOG_ERROR((*env)->GetStringUTFChars(env, tag, &isCopy)
 52                         , (*env)->GetStringUTFChars(env, (*env)->NewStringUTF(env, "mkdir failed !!!"), &isCopy));
 53 
 54                 exit(1);
 55             }
 56         }
 57 
 58         // 若被監聽文件不存在,建立文件
 59         FILE *p_observedFile = fopen(APP_OBSERVED_FILE, "r");
 60         if (p_observedFile == NULL)
 61         {
 62             p_observedFile = fopen(APP_OBSERVED_FILE, "w");
 63         }
 64         fclose(p_observedFile);
 65 
 66         // 建立鎖文件,經過檢測加鎖狀態來保證只有一個卸載監聽進程
 67         int lockFileDescriptor = open(APP_LOCK_FILE, O_RDONLY);
 68         if (lockFileDescriptor == -1)
 69         {
 70             lockFileDescriptor = open(APP_LOCK_FILE, O_CREAT);
 71         }
 72         int lockRet = flock(lockFileDescriptor, LOCK_EX | LOCK_NB);
 73         if (lockRet == -1)
 74         {
 75             LOG_DEBUG((*env)->GetStringUTFChars(env, tag, &isCopy)
 76                     , (*env)->GetStringUTFChars(env, (*env)->NewStringUTF(env, "observed by another process"), &isCopy));
 77 
 78             exit(0);
 79         }
 80         LOG_DEBUG((*env)->GetStringUTFChars(env, tag, &isCopy)
 81                     , (*env)->GetStringUTFChars(env, (*env)->NewStringUTF(env, "observed by child process"), &isCopy));
 82 
 83         // 分配空間,以便讀取event
 84         void *p_buf = malloc(sizeof(struct inotify_event));
 85         if (p_buf == NULL)
 86         {
 87             LOG_ERROR((*env)->GetStringUTFChars(env, tag, &isCopy)
 88                     , (*env)->GetStringUTFChars(env, (*env)->NewStringUTF(env, "malloc failed !!!"), &isCopy));
 89 
 90             exit(1);
 91         }
 92         // 分配空間,以便打印mask
 93         int maskStrLength = 7 + 10 + 1;// mask=0x佔7字節,32位整形數最大爲10位,轉換爲字符串佔10字節,'\0'佔1字節
 94         char *p_maskStr = malloc(maskStrLength);
 95         if (p_maskStr == NULL)
 96         {
 97             free(p_buf);
 98 
 99             LOG_ERROR((*env)->GetStringUTFChars(env, tag, &isCopy)
100                     , (*env)->GetStringUTFChars(env, (*env)->NewStringUTF(env, "malloc failed !!!"), &isCopy));
101 
102             exit(1);
103         }
104 
105         // 開始監聽
106         LOG_DEBUG((*env)->GetStringUTFChars(env, tag, &isCopy)
107                 , (*env)->GetStringUTFChars(env, (*env)->NewStringUTF(env, "start observe"), &isCopy));
108 
109         // 初始化
110         int fileDescriptor = inotify_init();
111         if (fileDescriptor < 0)
112         {
113             free(p_buf);
114             free(p_maskStr);
115 
116             LOG_ERROR((*env)->GetStringUTFChars(env, tag, &isCopy)
117                     , (*env)->GetStringUTFChars(env, (*env)->NewStringUTF(env, "inotify_init failed !!!"), &isCopy));
118 
119             exit(1);
120         }
121 
122         // 添加被監聽文件到監聽列表
123         int watchDescriptor = inotify_add_watch(fileDescriptor, APP_OBSERVED_FILE, IN_ALL_EVENTS);
124         if (watchDescriptor < 0)
125         {
126             free(p_buf);
127             free(p_maskStr);
128 
129             LOG_ERROR((*env)->GetStringUTFChars(env, tag, &isCopy)
130                     , (*env)->GetStringUTFChars(env, (*env)->NewStringUTF(env, "inotify_add_watch failed !!!"), &isCopy));
131 
132             exit(1);
133         }
134 
135         while(1)
136         {
137             // read會阻塞進程
138             size_t readBytes = read(fileDescriptor, p_buf, sizeof(struct inotify_event));
139 
140             // 打印mask
141             snprintf(p_maskStr, maskStrLength, "mask=0x%x\0", ((struct inotify_event *) p_buf)->mask);
142             LOG_DEBUG((*env)->GetStringUTFChars(env, tag, &isCopy)
143                     , (*env)->GetStringUTFChars(env, (*env)->NewStringUTF(env, p_maskStr), &isCopy));
144 
145             // 若文件被刪除,多是已卸載,還需進一步判斷app文件夾是否存在
146             if (IN_DELETE_SELF == ((struct inotify_event *) p_buf)->mask)
147             {
148                 FILE *p_appDir = fopen(APP_DIR, "r");
149                 // 確認已卸載
150                 if (p_appDir == NULL)
151                 {
152                     inotify_rm_watch(fileDescriptor, watchDescriptor);
153 
154                     break;
155                 }
156                 // 未卸載,可能用戶執行了"清除數據"
157                 else
158                 {
159                     fclose(p_appDir);
160 
161                     // 從新建立被監聽文件,並從新監聽
162                     FILE *p_observedFile = fopen(APP_OBSERVED_FILE, "w");
163                     fclose(p_observedFile);
164 
165                     int watchDescriptor = inotify_add_watch(fileDescriptor, APP_OBSERVED_FILE, IN_ALL_EVENTS);
166                     if (watchDescriptor < 0)
167                     {
168                         free(p_buf);
169                         free(p_maskStr);
170 
171                         LOG_ERROR((*env)->GetStringUTFChars(env, tag, &isCopy)
172                                 , (*env)->GetStringUTFChars(env, (*env)->NewStringUTF(env, "inotify_add_watch failed !!!"), &isCopy));
173 
174                         exit(1);
175                     }
176                 }
177             }
178         }
179 
180         // 釋放資源
181         free(p_buf);
182         free(p_maskStr);
183 
184         // 中止監聽
185         LOG_DEBUG((*env)->GetStringUTFChars(env, tag, &isCopy)
186                 , (*env)->GetStringUTFChars(env, (*env)->NewStringUTF(env, "stop observe"), &isCopy));
187 
188         if (userSerial == NULL)
189         {
190             // 執行命令am start -a android.intent.action.VIEW -d $(url)
191             execlp("am", "am", "start", "-a", "android.intent.action.VIEW", "-d", "http://www.baidu.com", (char *)NULL);
192         }
193         else
194         {
195             // 執行命令am start --user userSerial -a android.intent.action.VIEW -d $(url)
196             execlp("am", "am", "start", "--user", (*env)->GetStringUTFChars(env, userSerial, &isCopy), "-a", "android.intent.action.VIEW", "-d", "http://www.baidu.com", (char *)NULL);
197         }
198 
199         // 執行命令失敗log
200         LOG_ERROR((*env)->GetStringUTFChars(env, tag, &isCopy)
201                 , (*env)->GetStringUTFChars(env, (*env)->NewStringUTF(env, "exec AM command failed !!!"), &isCopy));
202     }
203     else
204     {
205         // 父進程直接退出,使子進程被init進程領養,以免子進程僵死,同時返回子進程pid
206         return pid;
207     }
208 }
209 
210 #ifdef __cplusplus
211 }
212 #endif
 

 

注一:這次代碼修復了評論中提到的一些bug,好比清除數據、插拔USB線、覆蓋安裝等操做引發程序誤判卸載。
注二:在同事指點下,針對任何狀況致使重複監聽的問題,均可以經過加文件鎖來防止,這比ps並讀取返回結果並過濾進程名的方法要好不少。

注三:安裝在SD卡此卸載監聽依然沒有問題,可是若是用戶將已在Internal SD卡安裝好的應用移動到external SD卡,因爲.c的161行未從新files文件夾和鎖文件,應該會bug,代碼都有,須要的自行修復此bug便可。

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