I am noob in Android. Suppose I have two Activity in my android app.
Activity A and B, currently I am on Activity A then on click on one button I am now Activity B. Here From Activity B I want to update some view with updated data that is in Activity A. I got updated data in Activity B so Should I use here LocalBroadCastReceiver for this or anything ?? so that When I press back then app should show me updated data in Activity A
Should we use our custom callback here to update the UI view data of Activity A from Activity B ??
No, you shouldn't use BroadcastReceiver for that. The method depends on the size of data you want to transfer from Activity B to Activity A. If it's quite small, you can start Activity B with startActivityForResult and then get data back at the onActivityResult method (in Activity B you should use setResult once you are done). If the size of data is quite big, it's better to use DB for storing it instead of keeping it in memory.
okay , there are multiple ways to do it :-
you can use a static variable to store you data that too of application level ( might not be a good approach ) check the value of vairable in onResume() and set it to the view.
you can use sharedpreferences if your data is not that large , store the data in Activity B and fetch it on onResume() method of activity A.
as #nikis has told you
if your data is too large store it in db.
I dont think broadcastreceiver fits right in your scenario !!
Related
I have got 2 activities - "A" contains fragment with a list of conversations, "B" represents a conversation (shows it's messages), in B I can also send a new message.
I would like to be able to update A's list of conversations every time a message is sent in B, so when I click android's back button, A activity's view is updated.
The core of the problem for me, is that I'm not starting A through an Intent when I click the android's back button, so I don't know how to get this effect.
Thank you for your help!
When A is on the backstack, there's no guarantee that an instance of A even exists in memory. The answer to the question of how to manipulate A from B is don't.
Some correct ways of doing it:
If your model (the list of conversations) is Parcelable or Serializable, you can pass it between activities via Intent. You can pass it back from B to A if you start B for result and retrieve it from the Intent returned to A's onActivityResult.
Make the model persistent, like in a database or SharedPreferences file.
Put the model in a bound Service. This would be faster than having each activity load it from persistent storage, but you may still need to make it persistent so you don't lose it when the Service shuts down.
I have application in which I have three activities. First and second activity have listview. I need selected values from the first and second activity in order to display some data in the third activity. Which is the best way to do this? Is it better to pass Intent from first to second activity, then from second to third activity or to use SharedPrefenreces?
This depends on what you need. If you need the data to be persistent in the event that your app is destroyed, then you will probably want to save the data in SharedPreferences (will also depend on what type of data since SharedPrefs aren't limited to what they can store) or a DB.
If you aren't worried about it being persistent then passing the data through Intent.putExtra() is fine. You can also create a Bundle and pass the Bundle through the Intent and add the data as you go.
You also have the option of creating a separate class which implements Serializable. Then you can create and pass the class Object through your Intents. Here is a post about doing that
Yes this can be achieved in many ways using:
Intents
Shared Preferences
Sqlite
Sqlite: You can use Sqlite to store data if the data is huge in first and second activity and retrieve the data in the third
activity (But if data is less this is not a feasible solution)
Shared Preferences: Here the data you have saved in the shared-Preferences is done in a xml file, so even if the app is
stopped the data is retained. This is helpful to save the password
and login details etc
Intents: My opinion Passing data with intents is much better option in your case because size of the data passed between your
first, second to third activity is less.
Finalizing :: Just put the data in bundle in first activity. Next get the data(Bundle) in second activity and add the data in second activity in addition to the data in the bundle received from first activity and pass that final bundle from second activity to the third activity.
In my opinion, it would be easiest to create an ArrayManager class, in which your variables are static. This way you can create methods to select and resize your arrays in the ArrayManager class. The only case in which this is bad is if you must hold references to Views, Contexts, or Activities (this will create a memory leak). In that case, codeMagic's solution is ideal.
In your case, if you need to pass same data from first activity to second activity then third activity & your data is small then I suggest use Shared Preferences.
If data passed from first activity to second activity is not same data of second activity to third activity then simply use intent.
There is a tricks. If your second activity always need data from first activity to operate then when you want to go back third activity to second activity then you will get stuck because from third activity you can not get first activity result. In that case saving data i mean Shared Preferences or Sqlite is best.
All above those scenario you need to find your own what is best to use for your app.
i have an application with many Actvities , i need to call each of those activities with paramaters to retrieve data from database or a file , but if i call an activity a second time i dont want that the activity retrieve data again cos it can be boring for users .
Example :
i have main activity with menu that can call 3 activities : A,B and C
each one of them need parameters to access database
in each activity i have a link to navigate between them , i need to
call back the activities then from stack so no need that they access
database again.
Any suggestions are greatly appreciated.
If you are not finishing your activities, data will persist. You dont have to do anything additional.
Otherwise you can extend Application class and save your data into some data structure there, which you can retrieve any time later.
Hi i am new to Android application development.In my Application i have two activity Activity1 and Activity2.From activity1 i call Activity2 as Intent.I want to access activity1 from this Activity(activity2) without going to first activity is there any posible way?Pls guide me
The only thing which make sence is passing data from Activity 1 to Activity 2. To do it just pass some data through the intent:
intent.putExtra("key", "Your data here");
in second activity:
String data = getIntent().getExtra("key");
If this is not the case, then your task is wrong somewhere. When activity gone background, there is no sence to interact with it.
No, there isn't. Activity1 might even have been shut down.
If you want to pass DATA between the two activities, that's of course doable. Either by passing data on with the intent, by using http://developer.android.com/reference/android/content/SharedPreferences.html or any other storage you can access from both activities.
If from your second activity wants to change something on the previous one, then, instead of using
startActivity(...);
you should use
startActivityForResult(...);
Maybe this link can help.
So you have the scenario where you start activity B from activity A and you want to change some parameters when activity B is done ( your changes can't be propagated in real time because you can't be sure what is the state of activity A ). So the best way to implement this is to use activity result - for more info about it check Android: Capturing the return of an activity
I have an Activity which is an OpenGL view. I also have an xml layout to use for preferences. Until now, to show the preference menu, I just brought it to front by setContentView(). And the same to get back to the OpenGL view.
But is this a case where I should give the preference menu its own Activity?
I guess this would make a few things much easier. For example, the back button would just work, opposed to now where I have to code it or it will just exits the application.
And if this is a good idea, how do I pass data both ways? I have a class that store all preferences. Can I send it to the Activity and back again? Or is the best way to store the preferences in a sqlite database and then use it for passing data?
I find it easier to segregate menus and such into separate activities (unless you are using dialogs etc..) As far as storing data you can do it a number of ways:
Database
StoredPreferences
Intent extras with putExtra/Bundle
Creating an application subclass and storing preferences there
Each have their merit. 4 is pretty easy as you just have to state the application class name in your manifest then call: MyAppClass app = (MyAppClass)getApplicationContext(); and you can then use any variables in MyAppClass via app. 2 is also straightforward.
You already pointed out the main difference: history management.
You can pass data to Activity via Intents putExtra()/getExtra():
Create an Intend and add custom data via Intent.putExtra(..)
Start the new Activity: startActivityForResult(intent).
Inside new Activity you can get extra data with intent.getXyzExtra() (where xyz is type).
When new Activity is done just call setResult(int, resultIntent). Again you can add extra data as described in 1.
Call finish() to end the activity.
In original Activity method onActivityResult will be called. Again extract data from Intent as described in 3.