Tag Archives: Sourceforge

Android MVC – Forward and Backward Navigation

This weekend’s changes to the Android MVC project include the following:

  • Reorganization of the Command classes. AbstractBaseCommand has been created for simple get/set. All methods except “execute” have been implemented. This class now forms the base for IdentityCommand as well as AbstractCommand.
  • Controller now has full support for forward as well as backward navigation.
  • Controller can now record the activity navigation. Uses ActivityStackInfo.
  • Controller now support forward navigation with few more options:
    1. Can optionally mark the command to not be recorded
    2. Can optionally reset the activity stack
  • Controller now has back method for backward navigation.
  • Controller, during forward navigation, manipulates the activity stack appropriately.
    • Missing part is handling failure scenario when receiving a response. When processing the response, if it is in “error” state, IMHO, the response must be handled by the same activity rather than launching a new one.
    • More so, the command must be removed from the top of the stack if there was an error.
  • The support for IMemento, IInitializable has been removed. Not required.
  • The initialize method, henceforth, has been removed from BaseActivity.
  • BaseActivity now has two methods preProcessData and processData called before onBeforeCreate and before onCreateContent respectively.
  • BaseActivity now handles the back button (using the v2.0 function onBackPressed) by calling the back method for navigation.
    • Developers using v1.6 can override the method onKeyPressed and look for the KeyEvent.KEYCODE_BACK and call the method back.

Sample case study (showcase) now comprises of the following:

  • SplashActivity that happens to be the main launcher activity.
  • Erstwhile MainActivity has been renamed to LoginActivity to reflect its purpose.
  • HomeActivitiy continues to be the same.
  • SplashActivity launches LoginActivity using IdentityCommand and sharing some data (using Tag)
  • LoginActivity launches HomeActivity upon successful login (sharing some data using Tag and passing some piece of data to LoginCommand using Data).

The code is, as usual, available on Sourceforge at http://android-mvc.git.sourceforge.net/git/gitweb.cgi?p=android-mvc/android-mvc;a=tree. Additionally, I’ve also pushed the codebase on Github at http://github.com/gvaish/Android-MVC.

Model View Controller (MVC) for Android

Finally, I have been able to find time to push the intial code for “Model View Controller” implementation on Android.

Quite a few people told me that MVC is inbuilt in Android, with the View being represented by the Activity but I failed to visualize or tangelize the Controller. Well, the Model can always be the backend data – the business entities.

The code is hosted on Sourceforge – https://sourceforge.net/projects/android-mvc/

If are you interested in the code, you can get it using Git at git://android-mvc.git.sourceforge.net/gitroot/android-mvc/android-mvc.

Or if you just want to browse the code before downloading it on your machine, you can visit http://android-mvc.git.sourceforge.net/.

The code, by any means, is not yet ready for production use since I know various pitfalls, specially for the scenarios when the “Command” fetches the data from the network or database or from anywhere that takes long time.

In these cases, the best practice would be to hive-off the execution in a separate thread (read: Non-UI Thread). When the response is ready, you would pass it to the main thread (read: UI Thread) using a Handler. This part is implemented in the Controller, however, there can be race conditions in the scenarios where in multiple commands get issued – specially in very interactive application. Well, the bigger question there can always be – should MVC be used in that specific scenario?

Additionally, since, currently, the progress is presented using another Activity, there is an extra house keeping that is being done and I know (by use of this approach in my application), it is bound to fail in near-extreme scenarios.

The fixes are available with me… and I should soon find time to push them. Besides, I also need to a create more powerful case-study! 😀

So… keep watching!

And yes… if you feel that the code has done any good to you, please do spread the word and “Share the Love” :)

Here are initial screenshots of a trivial case-study (scenario) of initial implementation…

[showtime bgcolor=’#fcd77f’ width=’480′ height=’640′]