这里是从谷歌驱动器下载文件的步骤。它适用于文件和谷歌文档。
第 1 步：
获取文件列表并将其存储到带有相关文件下载链接url的数组或字典中：
- (void)loadDriveFiles {
fileFetchStatusFailure = NO;
//for more info about fetching the files check this link
//https://developers.google.com/drive/v2/reference/children/list
GTLQueryDrive *query2 = [GTLQueryDrive queryForChildrenListWithFolderId:[parentIdList lastObject]];
query2.maxResults = 1000;
// queryTicket can be used to track the status of the request.
[self.driveService executeQuery:query2
completionHandler:^(GTLServiceTicket *ticket,
GTLDriveChildList *children, NSError *error) {
GTLBatchQuery *batchQuery = [GTLBatchQuery batchQuery];
//incase there is no files under this folder then we can avoid the fetching process
if (!children.items.count) {
[self.driveFiles removeAllObjects];
[fileNames removeAllObjects];
[self performSelectorOnMainThread:@selector(reloadTableDataFromMainThread) withObject:nil waitUntilDone:NO];
return ;
}
if (error == nil) {
int totalChildren = children.items.count;
count = 0;
[self.driveFiles removeAllObjects];
[fileNames removeAllObjects]; //http://stackoverflow.com/questions/14603432/listing-all-files-from-specified-folders-in-google-drive-through-ios-google-driv/14610713#14610713
for (GTLDriveChildReference *child in children) {
GTLQuery *query = [GTLQueryDrive queryForFilesGetWithFileId:child.identifier];
query.completionBlock = ^(GTLServiceTicket *ticket, GTLDriveFile *file, NSError *error) {
//increment count inside this call is very important. Becasue the execute query call is asynchronous
count ++;
NSLog(@"Google Drive: retrieving children info: %d", count);
if (error == nil) {
if (file != nil) { //checking the file resource is available or not
//only add the file info if that file was not in trash
if (file.labels.trashed.intValue != 1 )
[self addFileMetaDataInfo:file numberOfChilderns:totalChildren];
}
//the process passed all the files then we need to sort the retrieved files
if (count == totalChildren) {
NSLog(@"Google Drive: processed all children, now stopping HUDView - 1");
[self performSelectorOnMainThread:@selector(reloadTableDataFromMainThread) withObject:nil waitUntilDone:NO];
}
} else {
//the file resource was not found
NSLog(@"Google Drive: error occurred while retrieving file info: %@", error);
if (count == totalChildren) {
NSLog(@"Google Drive: processed all children, now stopping HUDView - 2");
[self performSelectorOnMainThread:@selector(reloadTableDataFromMainThread)
withObject:nil waitUntilDone:NO];
}
}
};
//add the query into batch query. Since we no need to iterate the google server for each child.
[batchQuery addQuery:query];
}
//finally execute the batch query. Since the file retrieve process is much faster because it will get all file metadata info at once
[self.driveService executeQuery:batchQuery
completionHandler:^(GTLServiceTicket *ticket,
GTLDriveFile *file,
NSError *error) {
}];
NSLog(@"\nGoogle Drive: file count in the folder: %d", children.items.count);
} else {
NSLog(@"Google Drive: error occurred while retrieving children list from parent folder: %@", error);
}
}];
}
第 2 步：
添加文件元数据信息
-(void)addFileMetaDataInfo:(GTLDriveFile*)file numberOfChilderns:(int)totalChildren
{
NSString *fileName = @"";
NSString *downloadURL = @"";
BOOL isFolder = NO;
if (file.originalFilename.length)
fileName = file.originalFilename;
else
fileName = file.title;
if ([file.mimeType isEqualToString:@"application/vnd.google-apps.folder"]) {
isFolder = YES;
} else {
//the file download url not exists for native google docs. Sicne we can set the import file mime type
//here we set the mime as pdf. Since we can download the file content in the form of pdf
if (!file.downloadUrl) {
GTLDriveFileExportLinks *fileExportLinks;
NSString *exportFormat = @"application/pdf";
fileExportLinks = [file exportLinks];
downloadURL = [fileExportLinks JSONValueForKey:exportFormat];
} else {
downloadURL = file.downloadUrl;
}
}
if (![fileNames containsObject:fileName]) {
[fileNames addObject:fileName];
NSArray *fileInfoArray = [NSArray arrayWithObjects:file.identifier, file.mimeType, downloadURL,
[NSNumber numberWithBool:isFolder], nil];
NSDictionary *dict = [NSDictionary dictionaryWithObject:fileInfoArray forKey:fileName];
[self.driveFiles addObject:dict];
}
}
第 3 步：
根据表格行上的文件选择下载文件
NSString *downloadUrl = [[[[self.driveFiles objectAtIndex:selectedFileIdx] allValues] objectAtIndex:0]
objectAtIndex:download_url_link];
NSLog(@"\n\ngoogle drive file download url link = %@", downloadUrl);
GTMHTTPFetcher *fetcher =
[self.driveService.fetcherService fetcherWithURLString:downloadUrl];
//async call to download the file data
[fetcher beginFetchWithCompletionHandler:^(NSData *data, NSError *error) {
if (error == nil) {
NSLog(@"\nfile %@ downloaded successfully from google drive", self.selectedFileName);
//saving the downloaded data into temporary location
[data writeToFile:<path> atomically:YES];
} else {
NSLog(@"An error occurred: %@", error);
}
}];