Android Development – Benefits of Using Fragments in Android Projects

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I am learning Android programming and right now and i'm reading about fragments. I understand what fragments are, but either the tutorial is missing some steps or i'm missing something. So my question is when developing an Android UI, what are the benefits, if any, to using fragments as apposed to single page layouts? Are fragments more common than single page layouts or is it more based on the situation. Also, if fragments are more common, do you try to structure most situations so that fragments work?

Best Answer

Fragments aren't terribly useful on a phone. They were added to the API when people started wanting easier ways to take advantage of the extra real estate on a tablet.

Think of an app with a list down the left side. When you select an item on the list, it launches a new activity using the remainder of the screen space, and you want to be able to swipe to cycle between previously selected activities.

Without fragments, you require a class to manage the entire screen, keep a stack of which activities have been selected, keep track of which one is current, and manage all of their life cycles. If you use the same app on a phone, where the activity takes the entire screen, you don't need the manager class. With fragments, all the life cycle stuff is handled for you, essentially moving your manager class into the operating system. That makes tablet development easier and more standardized, and also makes sharing code between phones and tablets easier.

Write dumb code

^{"Often, the way to write fast code in Java applications is to write dumb code -- code that is straightforward, clean, and follows the most obvious object-oriented principles." -- Brian Goetz}

Don't get me wrong - there is a chance that particular object design may have substantial performance impact in some particular case on specific execution path in some application on some device - why not, everything is possible given the variety of Android devices. Know what? there is even a chance of it having an opposite impact on some other device, why not.

If (if) that happens, if (if) you'll somehow get a clear, solid, tested and proven justification of specific performance impact - then (then), go ahead, implement whatever tricks necessary to reach required performance, no matter how perverse they may be (BTDTGTTS). Until then, though, drop any baseless assumptions that just may come to your mind.

Until then... Just. Drop. It.

^{Developers love to optimize code and with good reason. It is so satisfying and fun. But knowing when to optimize is far more important. Unfortunately, developers generally have horrible intuition about where the performance problems in an application will actually be... Most performance tuning reminds me of the old joke about the guy who's looking for his keys in the kitchen even though he lost them in the street, because the light's better in the kitchen... (Brian Goetz)}

Java Android – Workaround for Multiple Inheritance

I am afraid you can-t implement your classsystem without codeduplication in android/java.

However you can minimize codeduplication if you combine special intermediate derived class with composite helper object. This is called the Decorator_pattern:

    class ActivityHelper {
        Activity owner;
        public ActivityHelper(Activity owner){/*...*/}
        onStart(/*...*/){/*...*/}   
    }

    public class MyTabActivityBase extends TabActivity {
        private ActivityHelper helper;
        public MyTabActivityBase(/*...*/) {
            this.helper = new ActivityHelper(this);
        }

        protected void onStart() {
            super.onStart();
            this.helper.onStart();
        }
        // the same for onStop, onSaveInstanceState, onRestoreInstanceState,...
    }

    Public class MySpecialTabActivity extends MyTabActivityBase  {
       // non helper logic goes here ....
    }

so every base class you create an intermediate baseclass that delegates its calls to the helper. The intermediate basesclasses are identical except the the baseclase where they inherit from.

Best Answer

Related Solutions

Object-Oriented Programming – Benefits for Android Development

Write dumb code

Java Android – Workaround for Multiple Inheritance

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