What is fragment write fragment life cycle in detail?įragments represent multiple screen inside one activity. Now, we have got the complete detailed explanation and answer for everyone, who is interested! The reason for that will become clear in the next section.This is a question our experts keep getting from time to time. #Fragment lifecycle android#However, there is one major difference form Activity’s onCreate(Bundle): you must not touch or do anything related to Android Views in Fragment’s onCreate(Bundle). Dependency injection and initialization of Fragment’s members takes place here. Therefore, just like with Activities, you’ll use onCreate(Bundle) method as a replacement for constructors. So, if you used constructor with arguments to instantiate the Fragments in the first place and passed dependencies into it, all of these dependencies will be set to null after save & restore. The re-creation mechanism uses reflective calls to Fragment’s no-arguments constructor. The bad news is that doing so will lead to serious bugs, so we can’t really do it.Īndroid will destroy and then re-create Fragments during so called save & restore flow. Remember that you don’t have access to Activity’s constructor so you can’t use it to inject dependencies into Activity? Well, the good news is that Fragment does have a public constructor, and we can even define additional ones. However, thinking about both lifecycles and the inter-dependencies between them is beyond what I’m capable of.īy satisfying this two goals I greatly reduce the complexity associated with Fragments thus making them more attractive. Each of them is extremely complex, but still manageable in isolation. Making Fragment independent of Activity’s lifecycle goes back to the diagram of their respective lifecycles. I’m also completely sure that doing so reduces risk of bugs, though that’s subjective. This means less effort during development, easier maintenance and quicker ramp-up of new team members. Developers will need to learn just one approach instead of two different ones. Let’s discuss each of these goals in more details.īy handling Fragment’s lifecycle similar to Activity’s lifecycle I greatly reduce the overall complexity of the application. Make Fragment’s lifecycle handling logic independent of Activity lifecycle.Make Fragment’s lifecycle handling logic as similar as possible to Activity’s logic.My approach to Fragment’s lifecycle aims to achieve two goals: If you haven’t, please do it now before you proceed with this post. Therefore, I’m going to assume that you already read that article about Activities. I already wrote an article about Activity’s lifecycle, and, in this post, I’ll draw many analogies between them. In some sense, Fragments are light-weight Activities. However, Fragment lifecycle have many similarities to Activity lifecycle. Basically, Fragments shouldn’t know anything about the Activity they’re hosted in. Activity LifecycleĪs you’ll see shortly, when I use Fragments, I try to decouple them from Activity lifecycle as much as possible. The main goals of this technique is to be pragmatic and keep the complexity of Fragments in Android applications at minimum. In this post I will describe my approach to handling of Fragment’s lifecycle. Many old bugs and inconsistencies were fixed and some nice features were added. This meant that Fragments once again gained a lot of focus and some love. In the recent years, Google decided to push the ecosystem in the direction of so-called single-Activity applications. These developers do have a point because it’s simply impossible to overstate the complexity of Fragment lifecycle. Not because they don’t understand their benefits, but because they clearly see Fragments’ drawbacks and limitations. #Fragment lifecycle professional#Many professional Android developers won’t use Fragments in their projects under any circumstances. For a long time now, they have been among the most controversial Android’s APIs. However, Fragments have had very troubled history. The idea of “organizing a single activity into separate, discrete pieces” was absolutely great. Currently supports adding and removing fragments, and performing basic lifecycle callbacks on them. That’s what she wrote in the original commit message:īasic implementation of an API for organizing a single activity into separate, discrete pieces. Fragments were introduced into Android in 2010 by Dianne Hackborn.
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