So I'm sure there's an easy answer for this one, but I haven't found it online. I'm using a fragment in Android that uses Play Services, and I want to throw any exceptions from using that fragment back to the activity that hosts it so that I can take the appropriate action depending on the activity. Where would I look to figure out how to do this?
Thank you.
You can define an interface to allows communication between Fragment and Activity.
Take a look at the Documentation
Related
Since the new upgrade I have no idea on how to navigate with fragments.
A lot of code from here is commented out. If I use the code that is left, it doesn't work. I get the activity not found exception. I use the same headers as written in demo example. What are the steps I need to follow to create a succesful fragment?
The new fragments are actually pretty straight forward. All you have to do is annotating your fragment classes with the MvxFragmentAttribute and then making sure that the type passed as the first argument of the MvxFragmentAttribute implements IMvxFragmentHost, so that it can handle the Open and Close methods used by the MvxFragmentsPresenter.
The new MvxFragmentsPresenter will handle whether or not the current top Activity is responsible for showing the requested fragment or not and, if it isn't, it'll start the proper activity in before showing the fragment.
Hope you guys can clarify something for me.
I've been using Android for about 6 months now and I'm still confused about the best way to communicate between Activity and Fragments. I've already read the the info on the android developer site.
Fragment to Activity
Right now I know with 100% absolute certainty that an interface is the best way to communicate from Fragment to Activity. I.e. creating an interface in your Fragment and letting your Activity implement it. This way you can call the method from your interface inside your Fragment and have it handled by the Activity (which implements the interface).
Activity to Fragment
Here's were I'm not sure. The android developer site says that in order to communicate with a Fragment you have to put your objects in a Bundle.
Bundle bundle = new Bundle();
bundle.putInt(SOME_IDENTIFIER, myInt);
Now I've been know to use a Singleton class every now and then when I have quite some functionality that I can separate. Say I have a Singleton called PersistenceService where I handle all of the persistence related stuff, e.g. saving something in the SharedPreferences. The PersistenceService will then hold methods like putMyString(String key, String myString) or putSomeObject(String key, SomeObject someObj). This way a class doesn't have to handle persistence itself but can just call the PersistenceService to do it.
Now say I have to update something in my Fragment, a TextView or something.
This is what I do:
String myString = PersistenceService.getInstance(getActivity()).getMyString(someKey);
textView.setText(myString);
I pass in a context (getActivity()) because I need it to get the SharedPreferences.
Now my actual question is:
Do I retrieve my data in the Activity and pass it to the desired Fragment through its Bundle? Or do I simply reference my Singleton right in my Fragment and access the data there directly.
I'm not stuck or anything, but I'd like to know what you guys would recommend.
Any advice, remarks, info etc. is greatly appreciated.
This is a very broad question, and as the pragmatic thinking and learning book says, the answer to most questions in software is "It all depends!".
And it really does, it really all depends, there's no hard rule in software, "always" and "never" are very powerful words that shouldn't be used in software, so, saying always go for "Bundle" info or Never go for a Singleton is a little bit stupid specifically in software, so, instead of telling you exactly what to use, ask your self what would fit better in your needs taking on count things like, scalability, extensibility manageability, etc. For example:
If you go for Bundle, you give some flexibility to your fragment, you are creating some kind of independent component ready to work with whatever information you provide, on the other hand, if you know that you need that fragment only in that place, and the information you will pass is somehow complex(can't be passed using a bundle), why complicating so much? Just go for the Singleton if it does the job simple and clean.
I hope my point is well explained here, there's no hard rules for one way or another, just be as diligent as possible and don't go one way or another just because of laziness or negligence, instead be analyst if it's worth going one way or another based on your needs, and always take on count that not because you went that way this time it will be true for ALL your scenarios.
Hope it Helps!
Regards!
I use bundle when I want send data from fragment to fragment (from fragment to activity by interface, from activity to fragment by bundle).
If data is used in all fragments singleton is the best way, sometime I use also a istance of data objcet in activity that I manipulate in fragment by public methods of activity but I don't think that this is a best pratic.
Please understand that 2 fragments can’t directly communicate with each other, They will need help of the activity under the context of which they are created. Using an interface :).
Implement the interface in a fragment
interface StartCommunication
Define the interface in the activity whose context fragment is using
public class MainActivity extends Activity implements
SendFragment.StartCommunication
I am new to Android Fragment and trying to learn Fragment to Activity communications.
What is the better approach(best practice) in Android for Fragment to Activity communication?
Lets say I have FragmentA and ActivityA.
After my screen popups FragmentA, I would like to perform somemethod(probably UI related) in ActivityA
Here are two(pattern) possible
Solutions:
In FragmentA getActivity and cast the Activity to ActivityA and then call somemethod.
In FragmentA create an interface callback and then implement that callback in ActivityA. Then on the callback, call somemethod.
Which pattern is more common/perfer in Android development and why. Or do you have an even better way to communicate from fragment to activity in Android to share with me?
Any comments, opinions, and suggestions is highly appreciated and welcome. ^^ .
The second solution is the preferred one, because it allows your fragment to be more independent of its hosting activity.
If in the future you decide to put your fragment on a different activity, there are no changes needed on the fragment, and you will only need to implement the interface on your activity.
I'll add a third solution which is using an event bus (Otto for instance), which also works, although some might argue that it makes your code a little less readable.
First method will be a bad practice. Second method will work fine but your fragment is going to be tightly coupled with your activity.
There is one more better approach is to use some event bus library like otto
Using this you can communicate effectively with loose coupling in your activity & fragment.
Your second approach is more flexible. You might not see a huge benefit in one activity and one fragment case. If you have to use the same fragment in another activity, it will most likely break by casting your activity like that. That said, there is nothing wrong with the first approach, but it is just a little restricted.
First pattern is best when your fragment is used only by one activity.
Second approach is needed if you want your fragment to communicate with some other objects not the activity that hosts fragment. If you always want to communicate with hosting activity callback is not needed. Just create an interface and implement it on as many activities as needed. Then in your fragment cast activity returned by getActivity().
MyInterface myInteface = (MyInterface) getActivity();
myinterface.somemethod();
You can even check if activity implements needed interface(s) etc.
The interface approach works fine and is more flexible in so far as it doesn't tie your fragment to the activity directly. One thing you should also consider is how much work the activity might need to do, that is it may end up managing several fragments. This has a tendency to lead to 'fat fragments' as my question here asked when I started using them
The android developer tutorials recommend me using the host activities of fragments to pass around data and whatnot, so why is there a set/get target fragment method?
My application thus far contains a host activity, and a fragment, which has a button that launches a DialogFragment, in which there is a button that launches ANOTHER DialogFragment. Using setTargetFragment/getTargetFragment has made this whole ordeal somewhat confusing though, so I am thinking of reimplementing to let my main activity handle DialogFragment.show methods through my main fragment's custom interface.
Is this the right way of thinking? Or is there no harm in using setTargetFragment? Can anyone provide good and bad examples of using it?
Also, you may end up with exception of no target fragment found in fragment manager. This happens if after rotation (or other config change) your target fragment will not be readded to the fragment manager by the time when caller fragment will be adding.
Imagine you have some sort of Confirmation fragment which you add from MainFragment as so:
ConfirmationFragment frag = new ConfirmationFragment();
frag.setTargetFragment(this, 0);
getFragmentManager().beginFragmentTransaction().add(R.id.container, frag).commit();
Now on some confirmation button click you invoke a method from MainFragment by calling:
((MainFragment)this.getTargetFragment()).onUserSelectedGoodButton();
This is pretty and simple, but if you will rotate the screen and for some reason ConfirmationFragment will be added to FragmentManager before MainFragment, exception will be thrown, stating that target fragment is not found in the fragment manager
I don't think there is implicit harm in using setTargetFragment, however, I would only use it in very specific circumstances. For example, if the target fragment is only going to ever be used by the fragment (taking into account object reuse and designing your classes to be reusable when possible) and even then, sparingly.
By using them too much, you will end up with what you're seeing - confusing code that is hard to follow and maintain. On the outset, by marshaling everything through your activity you maintain a "flat" hierarchy that is simple to follow and maintain.
I think the decision to use setTargetFragment or not is a coding-style/philosophical one that, with wisdom and experience, it "feels" right or wrong. Maybe on your case, by evidence that you are questioning your older code, you are gaining that wisdom :)
I am working with ActivityGroup and I want to open an sub activity of the ActivityGroup on selection of another tab. Please anyone let me know if it is possible or not?
example - I have tab1 and I open a subActivity(say activity "A") in the same tab using ActivityGroup and now when I click on tab2 I should open the same Activity "A" with all its contents.
Thanks in Advance.
I really, strongly urge you to stop using ActivityGroup. This has been deprecated.
The fragment support library provides a much better way to do these things. The 3.2 version includes an example showing how to use it with the tab widget. See the "Fragment Tabs" example and the TabActivity documentation.
These can be used down to Android 1.6.
(There are also lots of demos there for other things you can do with fragments.)
This is how I thing it can be done :
open the sub-activity just as normally you do, create certain static variable to hold data between two opened activities, be it static bundle or strings, when ever you perform some action on activity ex: type some thing in edit text, save the content in those static variables, in the onResume of the activity, put those data from variables in views........
See if it works........
Try this code,
http://developer.android.com/resources/tutorials/views/hello-tabwidget.html
if not found helpful then please provide me some more details about flow and if possible then put your (xml/java) code. so i can clearly understand the problem.
Let me know it's useful for you or not by comment ?