Headless Fragments in Android

By Ali Muzaffar

Strategies for code reuse

Helper classesBase Activity

Helper classes/methods

Pro: Self contained. Helper classes either contain static methods related to certain

functionality such as Networking or are wholly dedicated to doing one thing.

Pro: Easy to modify without risk of breaking. If you want to change a static method, it's easy to see who all is

calling the method and what the impact may be, worst case is that you overload the current method or create a new method.

Con: Is not aware of the Activity lifecycle. Lot more code to handle lifecycle events. Risk of memory leaks.

Inherit from parent Activity Pro: Aware of lifecycle events. Pro: ContextWrapper, no need to pass around

context. Con: Very rigid implementation

All children get every feature, disabling features requires more code or flags and this make the code very non-intuitive to read.

Can't inherit from anything else like PreferenceActivity, ListActivity etc.

Hard to handle long running events across orientation changes.

The age old battle of Composition versus Inheritance Composition over inheritance (or Composite Reuse Principle)

in object-oriented programming is the principle that classes should achieve polymorphic behavior and code reuse by composition (containing other classes that implement the desired functionality), instead of through inheritance (being a subclass). - Kirk Knoernschild (2002). Java Design - Objects, UML, and Process: 1.1.5 Composite Reuse Principle (CRP).

"has a" versus "is a".

Ignore the internet, eachhas it's merits

Strategies for code reuse

Helper classesBase ActivityHeadless Fragment

FRAGMENTS, OFF WITH THEIR HEADS!!!

What are headless Fragments Headless Fragments are regular fragments that return null in

onCreateView() or do not override it.

They *often* have setRetainInstance() set to true in onCreate().

In every other way, they are just a Fragment. You get the convenience of a helper class and all the power of a Fragment (lifecycle and context awareness).

They use Composition to provide functionality to your Activity or Fragments.

Examples of how to create headless Fragments NetworkHelper

A headless Fragment to check for connectivity to the internet.

CameraMicPermissionHelper A headless Fragment that requests Android runtime permissions.

Read: Using headless Fragments to check network connectivity and request Android M Runtimer permissions on Medium or LinkedIn

How do I use a headless FragmentPretty much the same way as using a regular fragment. Since you retain instance, you want to check if an instance already exists and if not, create one and attach it.