Android, is an awesome mobile development platform. I have worked on iOS, Brew, Symbian and Android platforms but I can tell you one thing, the kind of productivity you get while developing apps for Android platform is higher than any other mobile platform.
Android does a lot of things automatically for you. One of them is screen orientation change. Android platform detects that the screen orientation has changed and adapts the GUI accordingly. How does Android platform achieve this?
What happens when Android detects that the screen orientation has changed?
Android *destroys* the current activity and *recreates* the same activity all over again.
Yes, you read it right! And I will say it again,
It *destroys* the current activity and *recreates* the same activity all over again.
Why does it do that?
Normally, in the portrait mode the screen has more hight than the width. In landscape mode the scene is reversed. The screen has more width than the height. This means that if we go by the default behavior, user might see lot of blank spaces on the right side in the landscape mode.
|Screen in Portrait mode|
|Screen in landscape mode|
Have a look at the images of an activity in Portrait and Landscape mode. In Portrait mode the screen looks decent, but in landscape mode the screen looks ugly. There is too much gap between the logo image on the left corner and "some screen" button on the right hand corner. Moreover, the text box with the hint "Enter Zip or City, State" looks is way to long in the landscape mode.
Android has provided us a way to get around this problem. We as developers can provide different layouts for landscape and portrait modes.
The layouts that should be used for landscape mode should be placed in a directory called layout-land
|Landscape layout XML|
Lets say we updated the layout for the landscape mode so that the icon, button, text box and the Search button appear all in one line. The updated screen would look like
|Updated screen in landscape layout|
As you can see in the updated screenshot, the layout in the landscape mode looks much better now.
Using different layouts for landscape and portrait mode enables us to effectively use the space.
Because of this reason, when screen orientation changes, Android destroys the current activity and recreates the activity all over again by choosing the correct layouts and configuration.
This behavior lets you declare resources like layout's and drawable's based on the orientation, screen size, locale, etc.
This architectural choice, helps Android adapt the GUI easily and effectively when screen orientation changes.
Think over this approach for a moment, do you think there are any problems with this approach?
What are the problems with this approach?
What if your activity performs some expensive operation when activity is created?
As show in the above code when SomeActivity is created we creating an instance of SomeExpensiveObject class. To indicate that creating the instance of this class is expensive, I have added a sleep of 5 seconds in the constructor of SomeExpensiveObject class.
Think about the user experience, when user changes screen orientation while viewing SomeActivity.
- User has waited 5 seconds for the activity to load completely
- He/She changes the screen orientation
- Current activity is destroyed
- New activity is re-created
- User has to wait for 5 more seconds for the activity to be loaded completely with the new screen orientation.
How do we solve this problem?
In the next post I will show how effectively we can handle this problem. Android provides not just one but two elegant solutions to the above problem. All that and more in the next post. Stay tuned!