Android - Fragments or custom views? Which should I be using?

Question

I am trying to create a layout in an activity that will look different in landscape and portrait, however it will contain the same sections, just in different places on the screen.

Most examples I find on fragments is always the list and detail, which is not what I'm looking at.

In my example I have, amongst others,

• a scrolling image section (carousel)
• a page title with some brief details
• a carousel of thumbnails
• two buttons
• full details of the page

Now in the landscape layout, the image section will always be on the left side with down the right side, the page title, carousel of thumbs, two buttons and full details. In the Portrait the title will appear at top, with image carousel beneath, then thumbs, then buttons etc.

The way it works in my head, is that each section should be a fragment, and then depending on the layout file in the respective res/layout folder corresponding to land/port, the fragments are arranged accordingly. But I'm also thinking is each section a whole fragment? Or could it be a separate view that get's loaded in, but just in a different order depending on the screen orientation.

I hope that made sense?

Does anyone have any good tutorials that explain exactly when you should and shouldn't use fragments. All the usual suspects just list the list/detail example, which is not applicable in my case.

tl;dr Can I use fragments as modules/blocks in various layouts or should I just create other layouts and display them inside the main layouts.

Answer 1

Fragments can be used to have split screen and to store previous state unlike views. It is difficult to manage back button with views

Answer 2

If you just want to change how the screen is laid out, the answer is neither. You can define orientation-specific resources (either a separate layout file for each orientation or different dimensions/constraints for each orientation) and the system will just provide you with the correct resource set for the current orientation.

That said, it sounds like you may be describing a modified version of master/detail flow. If this is the case, fragments are a good way to go since the landscape view is actually several separate screens in the portrait version of the app, so each section needs it's own state and lifecycle, which fragments provide.

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Now, I know you said you wanted an example beyond a list and detail view, so here's some more details on when to use fragments:

Fragment, like activities, have state and lifecycle. Custom views do not have lifecycle and are completely dependent on the activity or fragment containing them.

You might use a custom view when you have a widget on screen that is used in multiple places and is just like any other view – bound to the activity when the layout is inflated and controlled from there. It's a way to either reduce duplicating combinations of views in your layout or to draw a custom view that doesn't exist yet.

Fragments are good when you need some state or lifecycle for a section of the app that might get used in multiple places or shouldn't be logically connected to the activity it is contained in. If you use the new Navigation Component, you actually just define one activity and then each screen in the navigation tree is a fragment that gets swapped out as the user navigates around the app. Here each child component on the screen (each "screen" that the user navigates to) has it's own lifecycle, business logic, etc, so mixing the code for all of that in the activity wouldn't make sense.

So the question comes down to what you are trying to build, and this may be a case where the best way to learn the difference is to try each option out as bit. The differences become more clear with practice using them. As a general rule of thumb, personally, I only really use custom views when I am trying to make a new view that doesn't exist elsewhere. If what I'm trying to do is simply a matter of laying out existing views in a new way, the answer is probably some trick in the layout file or layout code inside the activity. If I'm trying to make a stand-alone piece of the app that does stuff, especially if it also appears in multiple places in the app, I'll probably be building a fragment.