1. Access to known folders, using pickers, writing to and reading from files, caching files for future access George Georgiev Telerik Software Academy academy.telerik.com Technical Trainer itgeorge.net

2. 2  Store Apps File Access  Capabilities, Prompting for Access  Accessing "Known Folders"  Documents, pictures, etc.  Pickers  Folder Picker  File Open Picker  Reading and writing to a file  File Save Picker  Storing Files in the Access Cache

3. Restrictions, Capabilities, Prompting for Access

4. 4  Store Apps don't have typical access to files  Only to the per-app virtual file system  Several ways of accessing the file system  Through known folders  Documents, Pictures, Removable Storage, etc.  Need to add capabilities in app manifest  Through file/folder pickers  System-controlled dialogs/prompts to the user  Through other apps  Participating in file picker or share contracts

5.  WinRT Storage APIs  Provide file pickers & file picker contracts  Provide KnownFolders enumeration  Provide file input/output operations, file/folder creation, renaming, deleting, etc.  Other storage locations and options  Namespace – Windows.Storage 5

6. Adding capabilities, using the storage API

7. 7  Known folders are typical folders in Windows  Documents library, Music library, etc.  Apps can access them directly  If they define this capability in the app manifest  Adding known folders capabilities  Go to the manifest, under Capabilities  Pick the folder(s) needed for the app  Under declarations, add File Type Associations  Customize for files your app will access in the known folders

8.  After editing the manifest, use the storage API  E.g. Windows.Storage.KnownFolders.documentsLibrary  The API returns a StorageFolder object  Once you have a StorageFolder, you can:  Access file types declared in the manifest  Read, write, rename, delete, etc.  Create any file type  Open & create subfolders 8

9. Live Demo

10. Winows.Storage.Pickers

11. 11  Pickers are special views in Store Apps  Controlled and styled by the system  Limited customization options for apps  Button text, file display mode, visible files (by extension), suggestedStartLocation etc.  Asynchronously pick files/folders  Visualize picking UI for the user  App keeps running as if on-screen  On successful pick, app gets access to picked item  App can store the file for future access  Windows.Storage.Pickers

12. Introduction to pickers, picking a folder

13. 13  Folder pickers provide UI for picking folders  Result is received asynchronously  pickSingleFolderAsync() returns a promise  Result value is a StorageFolder  like when using Known Folders  Requires a FileTypeFilter to be set  Files listed to the user when navigating  List/array of strings (extensions, e.g. ".txt", "*")  Doesn't require any capability declarations  Except if using Known Folders for suggestedStartLocation

14. Live Demo

15. Opening existing files

16. 16  File Open pickers open existing files  Result is received asynchronously  pickSingleFileAsync()/pickMultipleFilesAsync() return a promise  Result value is a StorageFile  Read, write, rename, delete, copy, move, properties, thumbnail, etc.  Requires FileTypeFilter (same as in FolderPicker)  Doesn't require any capability declarations  Except if using Known Folders for suggestedStartLocation

17. Live Demo

18. Using Winows.Storage.FileIO

19. 19  Access to file contents happens through Windows.Storage.FileIO  Provides several read and write methods  Reading, writing & appending strings, bytes, etc.  Operations are asynchronous (return promises)  Read operation get content in success handler  Write operations could skip handling  Except for success/error notification Windows.Storage.FileIO.writeTextAsync(file, text).done(writeSuccessMessage, writeErrorMessage);.done(writeSuccessMessage, writeErrorMessage);Windows.Storage.FileIO.readTextAsync(file).done(function (text) {/*use text here*/}).done(function (text) {/*use text here*/})

20. Live Demo

21. Using transaction stream to ensure write integrity

22. 22  Some apps need stream operations over files  Streams are supported by FileIO  Stream writing can be interrupted by an error  Losing part of the data, corrupting files  For writes that need to be atomic use transactStream from WinRT  Works asynchronously  Ensures a full write or no write at all

23. Live Demo

24. Creating files from Apps

25. 25  File Save pickers create or overwrite files  Created file is received asynchronously  pickSaveFileAsync() returns a promise  Result value is a StorageFile  Requires FileTypeChoices (key-value pairs)  Key: the user-friendly file type (e.g. "Web Page")  Value: list of strings, possible filename extensions (e.g. [".htm", ".html"])  Doesn't require any capability declarations  Except if using Known Folders for suggestedStartLocation picker.fileTypeChoices.insert("Plain Text", [".txt"])

26. Live Demo

27. Creating files from Apps

28. 28  Apps access files through StorageFile objects  Folders through StorageFolder objects  Apps can't create such objects on their own  E.g. need a file picker to do it  Can't save the URI of a file and access it  Unless file is in AppData  WinRT supports an API which saves StorageFiles and persists them  Called futureAccessList  Key-value pairs (string token – StorageFile pairs)

29.  Using futureAccessList  Insert the StorageFile the app will need later  The file needs a unique string token (e.g. filename + timestamp)  The file can be accessed at any time (even after app has restarted) 29 var accessCache = Windows.Storage.AccessCache; var futureAccessList = accessCache. StorageApplicationPermissions.futureAccessList; StorageApplicationPermissions.futureAccessList; futureAccessList.addOrReplace(token, file); futureAccessList.getFileAsync(token).then(function(file){/*use file here*/});.then(function(file){/*use file here*/});

30. Live Demo

31. форум програмиране, форум уеб дизайн курсове и уроци по програмиране, уеб дизайн – безплатно програмиране за деца – безплатни курсове и уроци безплатен SEO курс - оптимизация за търсачки уроци по уеб дизайн, HTML, CSS, JavaScript, Photoshop уроци по програмиране и уеб дизайн за ученици ASP.NET MVC курс – HTML, SQL, C#,.NET, ASP.NET MVC безплатен курс "Разработка на софтуер в cloud среда" BG Coder - онлайн състезателна система - online judge курсове и уроци по програмиране, книги – безплатно от Наков безплатен курс "Качествен програмен код" алго академия – състезателно програмиране, състезания ASP.NET курс - уеб програмиране, бази данни, C#,.NET, ASP.NET курсове и уроци по програмиране – Телерик академия курс мобилни приложения с iPhone, Android, WP7, PhoneGap free C# book, безплатна книга C#, книга Java, книга C# Николай Костов - блог за програмиране http://academy.telerik.com

32. 1. Implement a simple Video Player app  The app should be able to open video files through file pickers  The opened files should be stored into an in-app playlist  The app should be able to play any file from the playlist  * after a file has finished playing, the next one should start  The app should be able to remove songs from the playlist  The app should be able to save the playlist through a file save picker  Save the file in any format you like (e.g. your own or a one of the built into Windows)  The app should be able to load a any playlist it saved through a file open picker and be able to play its files  * buttons for adding/removing songs should be in AppBar