TechWeekend Pune 7, on Mobile Application Development was held on Saturday, 19th Feb. These are the live-tweets, collected here for your benefit. Remember, they are live-tweets that were being typed while the event was happening, so they’re not necessarily as coherent and as well-organized as a regular article.

Windows Phone 7 by Mayur Tendulkar

The first talk was by Mayur Tendulkar talking about Windows Phone 7

• This talk is a basic overview of Windows Phone 7. Important now, because Nokia has now thrown its weight behind it.
• “If windows is not behaving well, you format your drive and start again. MSFT did same with its Mobile OS. Win Phone 7 is completely new”
• Mobile phone world suffers from large number of devices of different resolutions that behave differently. This is not true of Win Mobile 7. Windows Phone 7 insists on a standardized hardware & screen configuration. So your Win Phone 7 will always look and behave the same.
  • WinPhone7 screen config: 480×800 or 320×480. No other sizes allowed. S-LCD/AMOLED capacitive touchscreen. 4-point multi-touch
  • WinPhone7 will always have these sensors: A-GPS, proximity sensor, accelerometer, compass, light.
  • All WinPhone7 devices must have these three buttons: Start, Back, Search. (As usual, to shutdown, you press Start 🙂
• App Development for WinPhone7: regular apps using Silverlight, and game apps using XNA.
  • “Silverlight is just like Flash”. Modern app UI framework. Apparently has 500,000 developers spanning windows, web (and now mobile)
  • Visit the Tata Nano site or the Hard Rock Cafe New York site to see some cool uses of Silverlight
  • The XNA framework for game development is mature and widely accepted – because it was in XBox 360, Windows and Zune.
• WinPhone7 developers get all the goodness of Visual Studio for developing mobile apps with Visual Studio 2010 Express for WP.
• Other developer tools: Silverlight Dev Kit. XNA Game Studio 4.0. Expression Blend 4.0. Also VB for WinPhone7.
• All these development tools for WinPhone7 are free.

This was followed by a walk through of building a WinPhone7 app using Visual Studio 2010 and Silverlight.

Some interesting audience Q&A:

• Q: What languages are supported for WinPhone7 development? A: At this point, only Visual Basic and C#
• Q: Does WinPhone7 support multi-tasking. A: No. Some standard system services can run in the background; but apps don’t multitask.

Cross-Platform Mobile Application Development by Rohit Ghatol

Next up: Rohit Ghatol talking about cross-platform mobile app development using phonegap, titanium etc.

• Two ways of developing cross-platform apps. 1. Develop html5 apps for webkit. 2. Use a translator that translates your app to native code.
• For now, all major mobile platforms have a webkit based browser (except WinPhone7). So writing an app targeting webkit is “cross-platform”
• Q: Will a webkit based app work with WinPhone7? A: No. But Mango release of WinPhone7 will support html5, so you should be close.
• Translating common codebase to different native apps – Titanium. Write in JavaScript, and translate to Native.
• PhoneGap = HTML5 + CSS3 + JavaScript + special ability to make calls to access phone sensors etc.
  • Note: HTML5/CSS3 development for mobile apps works because all phone browsers are much more advanced on this issue than desktop browsers
  • Features supported by phonegap: accelerometer, camera, compass, contacts, file io, geolocation, audio recording, sound, vibration, storage. Note: not all these features are supported on all mobile phone platforms
  • PhoneGap prerequisites: Need to be a html/javascript expert. Also, it doesn’t help you with UI, you need to be able to develop that
  • So with PhoneGap app development, you’ll probably be doing UIs by using JQueryUI or something like that.
  • Note: PhoneGap ultimately creates a native app that users install. Not just a website that they visit in the browser.
• At this point, Rohit, showed actual PhoneGap code for a mobile app – to write an app that shows a google map of my current location.
• Big challenge of PhoneGap is that you need to bring your own UI development framework. This is an advantage also! – PhoneGap allows you to have same UI framework for website as well as your mobile app.
• Rohit’s suggestions for UI framework – 1. GWT 2. jQueryMobile
• With Titanium, you write apps in Javascript. This is interpreted by MozillaRhino on Android, and by Webkit JavascriptCore on iOS
  • You have two different directories for images – one for Android, & one for iPhone, because they handle images differently.
  • iPhone requires just one size of images. Android allows different images for different screen sizes/resolutions/orientations.
  • Titanium problem – layout is absolute. For people used to the great layout capabilities of Android, this is a big step down
  • Titanium uses native UI (iPhone and Android), where are PhoneGap uses non-native (html/css) UI. Former gives better experience…
• PhoneGap/Titanium both use Javascript Interpretation, so both can’t do multi-threaded apps
• Building your own webkit based cross-platform framework makes sense if you want to overcome limitations of phonegap/titanium.
• This won’t be as clean as phonegap/titanium, but might be good for your specific case. Steal phonegap/titanium code if required!
• Comparison of PhoneGap vs Titanium. Titanium more proprietary, limited UI, …
  html5/css3/javascript is the future; but not there yet. Until then, write to webkit specs…

Android Performance Tuning by Anand Hariharan

Next speaker was Anand Hariharan talking about Android Performance tuning.

• For app performance: first focus on what the user wants, don’t just improve performance for the sake of improving performance. Optimize only after measuring performance, and having specific performance goals. A lot of performance tuning, is really about managing user perception. When doing something that will take time, keep user engaged.
• Don’t optimize everything for performance – you don’t have the time. Focus on the most important user visible features and fix those. In mobile world – reduce features and use the time saved on fixing performance.
• Manage user perception better: e.g. Apple’s use of loading a bitmap image of app at beginning to give impression that app has loaded. At app startup time, load a bitmap that looks like your app without the latest data. Gives impression that app load is fast.
• Performance tips: All platforms have a “recommended best practices” doc. Read that – many developers dont 🙂 e.g. Android best practice: for tasks that take time, use a background service (not an activity).
• Anand talking about how to avoid an “Application Not Responding” (ANR) dialog for your app
  • An android app is single-threaded. So don’t do io (network or disk) synchronously. Use an async mechanism.
• Keep activities small. Don’t overload activities. Use different activities to do different things.
• Use the minimum number of views. Do not use a deeply nested view hierarchy. Your view hierarchy shouldn’t be more than 3 levels deep. If you’re views are getting complicated, consider writing custom views.
• Track memory allocations. Garbage collection happening during user activity causes slowdowns.
• Close your cursors. Otherwise garbage collector cannot reclaim memory. Then you get GC cycles, and slowdowns.
• use onRetainNonConfigurationInstance() to retain large amounts of data between device orientation changes (landscape to portrait)
• Use SoftReferences to cache data so that the garbage collector can reclaim the memory when required.
• Avoid database writes as far as possible. Writes take 5ms to 200ms. And full SD card has slower writes.
• Avoid using data from mutiple tables in a single list (AdapterView). First copy data from multiple tables to a single table and show that. e.g. in Email app, subject and body came from different tables. This really slowed down the inbox view (which shows first line of body).
• Tools to help with android app optimization: Fix your views using: hierarchyviewer, layoutopt. Check flow & times using: traceview. Use zipalign to optimize your apk (improves app load time).
• Above all, you must understand what you’re optimizing and why. Measure, measure, measure.