Android MediaScanner.cpp 原始碼解析

標籤：android   原始碼   mediascan   

1. 簡介

實現對檔案夾的遞迴掃描
libmedia – libmedia.so
frameworks\av\media\libmedia\MediaScanner.cpp

2. 對檔案的掃描

由JNI調用processDirectory，然後由doProcessDirectory和doProcessDirectoryEntry實現對檔案夾的遞迴掃描。

2.1 doProcessDirectory

迴圈掃描該檔案夾內的所有項

MediaScanResult MediaScanner::doProcessDirectory(        char *path, int pathRemaining, MediaScannerClient &client, bool noMedia) {    char* fileSpot = path + strlen(path);    struct dirent* entry;    .....    // Treat all files as non-media in directories that contain a  ".nomedia" file    .....    //Skip .nomedia file    DIR* dir = opendir(path);    MediaScanResult result = MEDIA_SCAN_RESULT_OK;    while ((entry = readdir(dir))) {        if (doProcessDirectoryEntry(path, pathRemaining, client, noMedia, entry, fileSpot)                == MEDIA_SCAN_RESULT_ERROR) {            result = MEDIA_SCAN_RESULT_ERROR;            break;        }    }    closedir(dir);    return result;}

2.2 doProcessDirectoryEntry

判斷該項目是檔案、檔案夾還是需要跳過的項。
if 檔案夾
doProcessDirectory
else if 檔案
通過JNI調用java層scanFile
else if skip
skip this file or folder

MediaScanResult MediaScanner::doProcessDirectoryEntry(        char *path, int pathRemaining, MediaScannerClient &client, bool noMedia,        struct dirent* entry, char* fileSpot) {    struct stat statbuf;    const char* name = entry->d_name;    ........    int type = entry->d_type;    if (type == DT_UNKNOWN) {        if (stat(path, &statbuf) == 0) {            if (S_ISREG(statbuf.st_mode)) {            //檔案                type = DT_REG;            } else if (S_ISDIR(statbuf.st_mode)) {            //檔案夾                type = DT_DIR;            }        }    }    if (type == DT_DIR) {        bool childNoMedia = noMedia;        // set noMedia flag on directories with a name that starts with ‘.‘        // for example, the Mac ".Trashes" directory        if (name[0] == ‘.‘)            childNoMedia = true;        // report the directory to the client        if (stat(path, &statbuf) == 0) {            status_t status = client.scanFile(path, statbuf.st_mtime, 0,                    true /*isDirectory*/, childNoMedia);            if (status) {                return MEDIA_SCAN_RESULT_ERROR;            }        }        // and now process its contents        strcat(fileSpot, "/");        MediaScanResult result = doProcessDirectory(path, pathRemaining - nameLength - 1,                client, childNoMedia);        if (result == MEDIA_SCAN_RESULT_ERROR) {            return MEDIA_SCAN_RESULT_ERROR;        }    } else if (type == DT_REG) {        stat(path, &statbuf);        status_t status = client.scanFile(path, statbuf.st_mtime, statbuf.st_size,                false /*isDirectory*/, noMedia);        if (status) {            return MEDIA_SCAN_RESULT_ERROR;        }    }    return MEDIA_SCAN_RESULT_OK;}

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Android MediaScanner.cpp 原始碼解析