1 / 26

Data access in native mobile apps

Data access in native mobile apps. http://www.flickr.com/photos/ourcage/8343799386/. Options for data storage / access. Storing data locally On the actual device Typically in Flash memory Storing data remotely On the server Typically in datastore. Pros and cons of local vs remote.

lizina
Télécharger la présentation

Data access in native mobile apps

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Data access in native mobile apps http://www.flickr.com/photos/ourcage/8343799386/

  2. Options for data storage / access • Storing data locally • On the actual device • Typically in Flash memory • Storing data remotely • On the server • Typically in datastore

  3. Pros and cons of local vs remote • Pros of local storage (vs remote) • Data are readily accessible for per-user computation • Data are accessible even without network • Cons of local storage (vs remote) • Data are not readily accessible for sharing with other people, or combining with others' data • Data can easily be stolen from devices

  4. Examples of situations to store locally • Storing user preferences • Storing username to reduce need for retyping • Storing records that are waiting to propagate back up to the server • Storing content in a local cache to improve performance • Storing rich content that is only needed locally

  5. Examples of reasons to store remotely • Storing data for plotting all users' data on a shared map or other visualization • Storing data for aggregate analysis of trends • Storing data from one user in order to show it to other users (e.g., photo sharing) • Storing information that needs to be analyzed with a computationally expensive algorithm • Storing data for long-term archiving

  6. Options for storing data locally • Property-value list • Every value is referenced by its property name • Files and blobs • Good for storing rich content • Structured data • Basically your own local database server

  7. Saving properties: key functions • Ti.App.Properties.setString(propName, propValue); • Ti.App.Properties.removeProperty(propName); • varallProperties = Ti.App.Properties.listProperties().sort(); for(vari = 0; i < allProperties.length; i++) { …

  8. Some caveats… • All app-defined properties will be loaded when the app starts up… • So don’t save hundreds and hundreds of properties, because that would slow startup. • System-defined properties will appear in the list of properties but cannot be edited reliably • System-defined properties might appear after execution begins (especially in simulator)

  9. Saving files: key functions • To list and read files: vardirPath = Ti.Filesystem.getApplicationDataDirectory(); vardirObject = Ti.Filesystem.getFile(dirPath); varallFiles = dirObject.getDirectoryListing(); for(vari = 1; i < allFiles.length; i++) { varfilename = allFiles[i]; varfileObject = Ti.Filesystem.getFile(dirPath, filename); varfileContent = fileObject.read(); // string or blob • To store: fileObject.write(filevalue, false); • To delete: fileObject.deleteFile();

  10. Other useful notes • One performance-related file will be automatically created by the emulator (Android) or simulator (iOS). • Other useful directories you can read/write: • Resources subdirectory (generally read-only) • External storage • Flash card • Android only • Check with isExternalStoragePresent first

  11. Structured data • Essentially a mini SqlLite database • Embedded database server • Limited data types: • NULL, INTEGER, REAL, TEXT, BLOB • But really you can put any kind of data into any column (except for INTEGER primary keys) - it will be coerced • Primary operators: • =, !=, <, >, <=, >=, IN, NOT IN, BETWEEN • ORDER BY and GROUP BY are generally reliable • Nice built-in functions http://www.sqlite.org/lang_corefunc.html

  12. Connecting to a database • First time you open() a database, it will be initialized. Use CREATE TABLE IF NOT EXISTS. Close connection after each operation (yes). // for example, let's make a table for storing preferences vardb = Ti.Database.open('mydb'); db.execute( 'CREATE TABLE IF NOT EXISTS proplist(pid '+ 'INTEGER PRIMARY KEY, pname TEXT, '+ 'pvalueTEXT)' );

  13. Retrieving all rows in a table var items = []; var db = Ti.Database.open('mydb'); var rs = db.execute('SELECT * from proplist'); while(rs.isValidRow()) { var item = { pid : rs.fieldByName('pid'), pname : rs.fieldByName('pname'), pvalue : rs.fieldByName('pvalue') }; items.push(item); rs.next(); } db.close();

  14. Insert, update, delete db.execute('INSERT INTO proplist'+ '(pname,pvalue) VALUES (?,?)', pname, pvalue); pid = db.lastInsertRowId; db.execute('UPDATE proplist SET pname=?, '+ 'pvalue=? WHERE pid=?', pname, pvalue, pid); db.execute('DELETE FROM proplist WHERE pid=?', pid);

  15. Important considerations • Security • Databases are not encrypted: if you store private data, be sure to encrypt it first (to be discussed later on) • Performance • Indexes are not created automatically except for primary key; to create a custom index, see http://www.sqlite.org/lang_createindex.html • Usability • For maximal usability, explore how to use platform-specific APIs so your app matches the usual look and feel of the platform

  16. Integrating remote content into native mobile apps • User opens mobile app • App calls up the server, sends URL • Server figures out how to handle request • Maybe just sends a file back • Maybe calls some custom code (JSP or servlet) • Server sends HTML/XML/JSON to app • App interprets data • User interacts with app and is happy

  17. Big picture: Note similarity to AJAX in mobile web!! AppUI AppJS Server Servlet Data store UI event URL Request Query, etc Data HTML/XML/JSON HTML/XML/JSON updates

  18. Very simple example: just get html varurl = "http://www.google.com/"; var client = Ti.Network.createHTTPClient({ // function called when the response data is available onload : function(e) { alert('success:'+this.responseText); }, // function called when an error occurs, including a timeout onerror : function(e) { alert('error'+e.error); }, timeout : 5000 /* in milliseconds */ }); client.open("GET", url); client.send(); Ti.UI.createWindow().open(); Make a servlet that returns some HTML Hit the URL

  19. Debugging iOS apps locally on a Mac iOS apps in simulator often can’t access GAE. Here’s a hideous workaround. • Open Terminal (spotlight > Terminal) • Map 127.0.0.1 to a fake hostname vi /etc/hosts arrow key down to the end of the document, type letter “a” to append add the line: 127.0.0.1 www.cs496.com to save, type: escape :w! escape :q • Download Burp (or another proxy) proxy from http://portswigger.net/burp/downloadfree.html • Unzip Burp proxy, move files some place safe • Set Burp as your Mac’s proxy (Apple Symbol in top left corner > System preferences > Advanced > Proxies; check both Web Proxy and Secure Web Proxy, set the ip address to 127.0.0.1 and port to 8080) • Go to Terminal and start up Burp cd wherever you saved those Burp files java -jar -Xmx2g burpsuite_v1.4.01.jar • Now that Burp is running, go to your regular browser and try to hit http://www.cs496.com:8888/_ah/admin • By default, Burp will block access. Go to the Burp window, proxy tab, and click “Intercept” button to turn intercept off. Now the hostname should nicely map to your GAE admin console • In your Titanium code, you should now be able to successfully retrieve data from GAE through the fake hostname.

  20. Debugging Android apps in emulator • Very simple: use 10.0.2.2 in your app to refer to your own computer from the emulator • NOTE: The instruction above is about the emulator. Accessing your computer from a physical device still requires accessing your computer through your computer's real IP.

  21. Example: Getting HTML from GAE running locally (iOS) <%= (1+1) %> varurl = "http://10.0.2.2:8888/test1.jsp"; var client = Ti.Network.createHTTPClient({ // function called when the response data is available onload : function(e) { alert('success:'+this.responseText); }, // function called when an error occurs, including a timeout onerror : function(e) { alert('error'+e.error); }, timeout : 5000 /* in milliseconds */ }); client.open("GET", url); client.send(); Ti.UI.createWindow().open(); Make a servlet that returns some HTML In iOS app, create an http client, with specified “onload” and “onerror” handlers. Open, send request.

  22. Getting fancier: posting datajust like a browser would Make a servlet that returns some HTML In app, create an http client, with specified “onload” and “onerror” handlers. Open, send POST request with parameters. you sent me a total of <%= Integer.parseInt(request.getParameter("a")) + Integer.parseInt(request.getParameter("b")) %> varurl = "http://10.0.2.2:8888/test2.jsp"; var client = Ti.Network.createHTTPClient({ // function called when the response data is available onload : function(e) { alert('success:'+this.responseText); }, // function called when an error occurs, including a timeout onerror : function(e) { alert('error'+e.error); }, timeout : 5000 /* in milliseconds */ }); client.open("POST", url); // use GET for idempotent, POST for non-idempotent operations client.send({a:1,b:2}); Ti.UI.createWindow().open();

  23. Now you have some options… … for what your servlet does with the data… • Use it for some computations • Store it in the datastore • Forward it to another server (e.g., webservice)

  24. And some options for what to send back… • HTML • Pros: No need to write a separate servlet • Cons: Very inefficient to send and parse HTML • XML • Pros: Compatible with many other systems • Cons: Moderately inefficient to send and parse • JSON • Pros: Highly efficient to send and parse • Cons: More work for you, in many cases

  25. JS for reading XML in Titanium … onload : function(e) { var xml = this.responseXML; varels = xml.getElementsByTagName("myelement"); var sum = 0; for (var i = 0; i < els.length; i++) { var vl = parseFloat(els.item(i).getAttribute("cnt")); if (!isNaN(vl) && vl > 0) sum += vl; } alert("the sum is "+sum); }, …

  26. JS for reading JSON in Titanium … onload : function(e) { Ti.API.info("Received text: " + this.responseText); varjson = null; try { json= JSON.parse(this.responseText); alert('success'+json); } catch (err) { alert('unable to parse json:'+this.responseText); } }, …

More Related