I am reading a book and it says like this
"Right now, fragments are very new, so there are few well-established
patterns to follow"
But I do not know where to read more about the design patterns for fragments at all.
I want to make an application with a lot of different screens and the app should be available for a tablet and for a phone, so the fragments will help me a lot here. But as I said this is big one and I am about to start designing it. So I really need good design. And before I start I want to see some design patterns guidelines for fragments in android.
I there something like best practices or something ?
I read a lot about fragments their usage and all those stuff, but I didn't find some well established design pattern for making app for phones and tablets.
I really need advanced chapter about this.
Thanks
You've probably read this but just in case, the Android Reference Document on Fragments quite nicely explains how to separate your UI and the Example right at the bottom of the page shows a reasonable way of how a UI using fragments can include more or less fragments given a change in orientation.
Related
I've developed an android phone app in which the navigation is mostly activities and starting activities for results. I've read that in order to make the tablet layout look like 2 screens of my phone app one next to the other I should have made it with fragments. Is there another way to migrate my functionality to the tablet app? Meaning to keep the start activity for result but just concatenate two activities on screen? (it may sound stupid, I know). Thanks
In order to keep the software design simple and modular, fragments come in really handy. You can use the same fragment's UI design + working code in multiple places without changing much functionality.
Since you have the code built and running in terms of activities, it won't take much time to migrate/port it to a Fragment since the life cycle methods are pretty similar. All you need to do is study the life cycle of a Fragment and move code chunks from the Activity to the Fragment class.
You can study all about Fragments here - http://developer.android.com/guide/components/fragments.html
or maybe a training session here will help you more -
http://developer.android.com/training/basics/fragments/index.html
You will learn a lot and once you have tried it you will be able to comprehend the advantages in a much better way. In future always make it a point to design in terms of Fragments to have a much modular design.
Along with that I think you will also need to learn to design layout for multiple screen sizes. This link over here will help you understand how to support multiple screen sizes -
http://developer.android.com/guide/practices/screens_support.html
If a tutorial to do this very quickly is what you seek then this should help -
http://www.101apps.co.za/index.php/articles/converting-android-activities-to-fragments.html
All the best :)
It very depends on your app GUI structure. Sometimes, you even not need to adapt your GUI for tablet (if you build interface dynamically basing on screen dimension). As rule, if you have two screens where one screen is advanced or logical extension of other then you can union it into one screen on tablets for better informativeness. Secondary way, as rule, based on fragments.
You can achieve it with help of Activity group but it is deprecated in Api level 13, for more details please visit http://developer.android.com/reference/android/app/ActivityGroup.html, but I will suggest to go with Fragment as Fragment having nearly similar life cycle like as Activity with extra methods and features. Please refer link for more details http://developer.android.com/guide/components/fragments.html
I have read the documentation and some other questions' threads about this topic and I don't really feel convinced; I don't see clearly the limits of use of this technique.
Fragments are now seen as a Best Practice; every Activity should be basically a support for one or more Fragments and not call a layout directly.
Fragments are created in order to:
allow the Activity to use many fragments, to change between them, to reuse these units... ==> the Fragment is totally dependent to the Context of an activity , so if I need something generic that I can reuse and handle in many Activities, I can create my own custom layouts or Views ... I will not care about this additional Complexity Developing Layer that fragments would add.
a better handling to different resolution ==> OK for tablets/phones in case of long process that we can show two (or more) fragments in the same Activity in Tablets, and one by one in phones. But why would I use fragments always ?
handling callbacks to navigate between Fragments (i.e: if the user is Logged-in I show a fragment else I show another fragment). ===> Just try to see how many bugs facebook SDK Log-in have because of this, to understand that it is really (?) ...
considering that an Android Application is based on Activities... Adding another life cycles in the Activity would be better to design an Application... I mean the modules, the scenarios, the data management and the connectivity would be better designed, in that way. ===> This is an answer of someone who's used to see the Android SDK and Android Framework with a Fragments vision. I don't think it's wrong, but I am not sure it will give good results... And it is really abstract...
====> Why would I complicate my life, coding more, in using them always? else, why is it a best practice if it's just a tool for some cases? what are these cases?
I am sorry if I wrote too much, and thanks for your time. I hope I will get your attention, because I really need ideas and experiences about this topic.
Best regards, Ahmed
You shouldn't always use fragments. Fragments have their uses, such as when you want to page in and out parts of the screen or when you want to drastically change the UI in different orientations. When they make sense, use them. When they don't, skip them. I find they make sense in maybe about 10-20% of apps- I rarely see the need.
If there's a certain positive aspect apart from the simpler reuse of logic through different layouts, it's the ability of Fragments to be kept alive by the system at orientation change, aka while an Activity is reconstructed from zero, a Fragment can retain its instance, and therefore using them is more stable than an Activity. Also, switching between Fragments is quicker.
Personally, if I don't need to mess around with different orientations and layout sizes, I still prefer using Fragments and a singular container Activity around it, for stability and seamless switching between the different screens.
Its quite a general question and not directly related to a specific programming problem. But in my opinion good software is based on good design and therefore a good understanding and best practices. So your question is a good one for stackoverflow.
So, what about fragments. It took me a while to understand why you could or even should use them. As #pskink said, you can easily live without them. But if you are planning to rollout your software on different devices, you should definately think about fragments.
The screen resolution and density is not the only problem. Think about a smartphone. The screen is much smaller, so you can not present your app the same way as you can on a tablet. For instance a master detail flow. Left side, a list of elements and when you click one element, you will see details of that element on the right side. Easy to do on a tablet. But on a smartphone you would put the master-view into one fragment and the detail-view into another one.
You got two options to realize that scenario. Either programm different activities for smartphone and tablet but because they are actually doing the same logic, it's better practice to put the logic into fragments and reuse those fragments in two layouts (phone/tablet).
When designing an Android app, the question often pops up :
Is it better to design a given UI component as a view or as a fragment ?
Which criteria can be used to choose the 2 ?
In which situation, in which case do you prefer one to the other ?
Note 1:
I know the format of this question may not been suitable for this stack site but I think the question is relevant for the community.
Note 2:
With this question, I am not really looking for a definitive answer (though I could be wrong), but I am looking for a collective reflection, experience sharing on that matter.
To answer you and get out of some of the nitpicking in comments:
*Views are onscreen elements. Think of them as windows. In a MVC pattern, they're the V.
*Fragments are controllers in a MVC pattern. They typically own a bunch of views, and are used to define how the user interacts with those views in the program.
*Activities are controllers in a MVC pattern. They can contain any number (including 0) of views or fragments. Fragments are used to break up an activity into separate pieces if there's a big enough subset of easily separated functionality.
In an Android app, I have two screens* the user sees, one for preparing a query and the other for displaying the results. The right UI here is to have the query preparation in one screen, and then see the result on the second screen. Since this app is aimed at phone users, there's no need to display the two at once.
The traditional Android way is to use two activities, a QueryPreparationActivity and a DisplayResultActivity, and switch between the two. However, I've been hearing more and more about how the Android UI is switching to fragments. I can implement the two screens as two fragments and have the activity switch them, but is it worth the trouble? I will essentially be reproducing the Activity management code Android already has.
Is there a reason to use two fragments here?
*I'm using the term screen, because it isn't necessarily an activity...
Personally, I always develop using Fragments.
But the best reason I can give you for using Fragments is when you develop for handset and tablet devices you get a lot of reusability.
I know you already mentioned that there is no need to show both screens at once. But say later you were to develop the same "screen" for a tablet device and realize that the preparation screen is too barren and want to have both queryprep and display result show at the same time, you would have to write a totally new 3rd activity.
If you used fragments, you would reuse your 1 activity and 2 fragments, and that activity should be coded smart enough to determine the size of the screen and show the proper layout.
Code Reusability & Flexibility are the buzz words here.
If you have any questions please leave a comment and I will expand my answer. If you like my answer, please upvote and accept.
Fragments were introduced encapsulate UI elements and related behaviour into a single, reusable module. Before fragments you had to re-write the much of the same code that 2 or more activities had in common especially if you couldn't find a good approach to abstract the UI/control code into a super class. This was further complicated by the limitations that activities only call setContentView once. So sharing some code between activities wasn't all that nice.
Now, to answer your question, it all depends on you. If you think that further down the road you could use the QueryPreparation or DisplayResult ui as a module (layout and logic behind it) then go for the fragment implementation. It could be a different layout for landscape view on phone or if you decide to support smaller tablets like the nexus 7. If you are sure that it will never happen then stick with activities. Personally, I use fragments everywhere and they are a sure way to "future proof" your implementation for reuse down the road.
In short Fragments were introduced to accommodate the emergence of tablet/large screen devices and allow developers to create applications that will run across a wide range of screen sizes with very little change to code.
More can be read here at the Android Blog. That blog also details some of the finer technical details for the reasons for the move toward Fragments. Also introduced at Goolge IO 2012 were DialogFragments which you should consider using instead of Dialogs. Another blog post here describes them.
You're better off getting used to using Fragments and DialogFragments from the get go as this is the way Android is moving. Only use individual Activities if you really really need to do a quick-and-dirty app for say testing purposes. Fragments, in my opinion, do require a bit more code-work to incorporate and to initially get your head round but it's worth the effort.
I will try to keep this short, but I need some advice.
I work on a team that is developing applications for android, iphone, and wp7 in parallel.
We have a design team that comes up with a single design for all three platforms.
The latest application’s design is more marketing than productivity. The original POC for this app was done on the iphone. The design is very animation centric and most state changes are seamless (things will animate on and off the screen during state transitions).
If I keep developing against this design it means I will have to have everything in a single activity. So far, this has been a major headache. To my knowledge, dividing your application into activities is almost required. I could try to dynamically load and unload views as I change states but this doesn’t seem right.
I see where the design team is coming from where they want all these state changes to be seamless, but I don’t think this is right for android.
I would like to know what makes most sense. Should the design change to incorporate multiple activities or would it be worth trying to make this work.
We have a design team that comes up with a single design for all three platforms.
That's akin to coming up with a single floor plan to be applied to apartments, single family homes, and warehouses. The designers, or management, need to have their heads examined.
The latest application’s design is more marketing than productivity.
Did I mention that the designers, or management, need to have their heads examined?
If I keep developing against this design it means I will have to have everything in a single activity.
If I am interpreting your requirements correctly, that is probably accurate. While you can arrange for animations between activities, it is more of a "slide the old off, slide the new on", and I suspect that your requirements exceed that.
To my knowledge, dividing your application into activities is almost required.
It is certainly Android's intended development model for ordinary apps. However, games and the like may not follow this pattern, and you don't have to either.
I could try to dynamically load and unload views as I change states but this doesn’t seem right.
Depending on how many states there are, you might just hang onto all of them, recycling as you go.
I am surprised no one mentioned fragments which can be used instead of activities at many places.
Fragments can be seamlessly animated in and out or an activity.
You might want to take a look at subclassing ActivityGroup for your top-level activity. That can host multiple sub-activities. TabActivity, the only stock subclass of ActivityGroup, is perhaps not what you need because it includes a tab widget, but you can use it as inspiration for what you do need.
What specific headaches are you having with a single-activity architecture? Perhaps there are ways to make that less painful.
In general, if you are aiming to have native apps with a native look and feel, it is not reasonable to have a single UI design for all three platforms. The UI guidelines and user expectations for the systems are different, and those differences should be reflected in the UI designs.
If you really want to have a single UI for all platforms, just create a web app instead.
I'm not sure exactly what you mean by an "animation centric" design with seamless state changes. If you use multiple Activities, Android will animate between them in a way that Android users will expect. If you explain what exactly you are trying to accomplish, we can help you figure out if it makes sense in Android, and if so how to accomplish it.