Android MediaScanner.cpp 源代码解析

1. 简介

实现对文件夹的递归扫描 libmedia – libmedia.so frameworks\av\media\libmedia\MediaScanner.cpp

2. 对文件的扫描

由JNI调用processDirectory，，然后由doProcessDirectory和doProcessDirectoryEntry实现对文件夹的递归扫描。

2.1 doProcessDirectory

循环扫描该文件夹内的所有项

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 fileDIR* 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

判断该项目是文件、文件夹还是需要跳过的项。 if 文件夹 doProcessDirectory else if 文件 通过JNI调用java层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)) {//文件type = DT_REG;} else if (S_ISDIR(statbuf.st_mode)) {//文件夹type = DT_DIR;}}}if (type == DT_DIR) {bool childNoMedia = noMedia;(name[0] == ‘.’)childNoMedia = true;// report the directory to the clientif (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 contentsstrcat(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;}

背着背包的路上，看过许多人，