I have a tabhost in my first activity and Im calling another activity sometimes; to handle some details. I need to remember the last tab selected in my first activity when the second one returns. Problem is the first activity is getting destroyed and created again and onSaveInstanceState is not getting called. The only option which I can think of is to write the last tab selected to external memory and read it back, which seems a little extreme considering this is just one tag. Is there any other option? I cant avoid the second activity (I had tried to change that to another fragment--fragment calling another fragment-- but that didn't work so well for me)
Cheers
If you want to save small amounts of data in Android, you can always use SharedPreferences. Here is a good example on how to use it.
And there are some other storage options for Android listed here
Related
I have a form activity every Edittext open another activity when I change data and I get it in my activity I lose the others that I have changed them before . this is initial state and this is what I get by changing any data.
You need a consistent data model in which to store those values. If it's size isn't larger than 2MB you can make this model Parcelable and seriali. After that you must cache those values either in savedInstanceState, SharedPrefs, singleton (I do not recommend it), or local DB (i.e. sqlite). After doing so, whenever your activity is displayed you should check if you already have a saved value for that field and fill it with that.
you can fix this by letting it open another fragment instead of activity and make sure that you dont destroy the activity.
so overall view you gonna have 1 main activity and each edit text will replace fragment view
Bonjour Flora
An activity is not supposed to be persisted if not displayed. That means it could stay as you left in when returning from another activity but it also may not.
If the system needs to free memory it will destroy the activity and recreate it when the user gets back to it. This is the expected behaviour on Android.
So what you should do is store your data when the activity goes out (in onPause() method) and fill your edittexts when the activity goes back in (in onResume() method)
Pay also attention that you need to handle what they call configuration change (such as screen rotation) using onConfigurationChanged() that allows you to pass some information between the former configuration and the latter for reuse.
Finally you should build your layout according to Android's guidelines (material design) for your UI to look a bit more conventional ;)
Before I begin, I have read this, this and some more articles online. I am still unable to find a right way to do it.
So I have just one activity in my App, and 6 fragments. First one is a ListFragment which loads a list from a SQLite table. When user taps on a row in this list, I do 2 things:
1) Get an int from that row through a listener, and pass it back to the parent activity which stores it as a class variable using a simple setter method.
2) Replace this ListFragment with another simple Fragment. This new Fragment uses a simple getter() on that class variable to retrieve some information from a different table, and show all the details to the user.
So far so good. Now if I am on this details Fragment, and I change the screen orientation, the activity state is not reloaded (as I am checking if savedInstanceState is null in the onCreate()), but however, the class variables lose their value, and my app crashes.
Basically I am trying to pass data from the ListFragment to the details Fragment. I am doing it through the activity, which is causing a problem. As per Android Documentation:
All Fragment-to-Fragment communication is done through the associated
Activity. Two Fragments should never communicate directly.
There is no specific code which is giving me trouble, so didn't post any.
The onSaveInstanceState and onRestoreInstanceState is only used to save and restore per-instance state of an activity in case your activity is destroyed by OS (for example, to free the memory or in order to recreate it when the device orientation was changed). So you can save your variable in onSaveInstanceState and get them back using onRestoreInstanceState.
For your next question, I think this article will help you. Also answer by Gene for this question will help you.
In an app I'm making I have an Object to a class called Preferences in my MainMenu activity. I want to use this object in several pages. In the object is a class which contains an array with numbers. When I use it in another activity (Film) it changes one of the numbers in the object. Then I go back to the main menu and into a new activity (CurrentPrefs) in which I display the array of numbers on the screen. When I displayed the numbers they didn't contain the changes made in the Film file. So I started testing around with the variables a bit.
When I start the MainMenu, which is the start activity, it sets the object. Then when I enter film and check the object it still has the same name (object.toString()). I also checked to make sure that the values where changed correctly which they were.
Next I went back to MainMenu and checked again. The object still had the same name and the value were also like I changed them in Film.
Finally I entered the CurrentPrefs activity and there it goes wrong. The object suddenly has a different name and it also no longer contains the changes I made to it.
Why has the object changed and, more importantly, how can I make sure it doesn't change and stays the same everywhere?
There are any number of reasons why your object's values changed. Perhaps the previous Activity got destroyed and recreated without you realizing it.
You should check out Android's SharedPreference class. It is a way to store, edit, and retrieve preferences and have access to them in any Activity:
http://developer.android.com/reference/android/content/SharedPreferences.html
If you well know activity's lifecycle you can also understand why it happens. Probably some of your operation are delegated to onResume() method which is called whenever activity comes back from onPause() or immediately after onCreate(), while other operations reside in onCreate() called only when activity starts or after onDestroy(). I advise you to control this and trying to move all setText() in onResume() so that every updated object's variable will be read again.
I have 2 major activity in my project Connect+Details and Menu. After I switch between the first activity to the second everything goes well. the problem start in returning back from 'Menu' to 'Connect+Details'.
when I use the back key to switch between the second activity and go back to the first everything goes well.
problem start when I use this code:
Intent myIntent = new Intent(Menu.this, ConnectActivity.class);
startActivity(myIntent);
I do go back to 'Connect+Details' but every detail in that activity is lost.
my question is simple, how can i go back to previews activity and still have the details used in that activity.
Edit:
the same thing goes even when I am in the 4th, 5th activity so finish() didn't help me.
You probably want to either save your data in SharedPreferences or in a database then use the saved data to repopulate your Activity. You can use SharedPreferences to save a key/value pair when you leave your Connect Activity and this will persist even if your app is closed.
If there will be a lot of data stored then you may consider using an SQLite DB. This can be a little trickier to set up and use but may be worth it if you are storing a lot of data...especially if its for different users.
Both of these options will persist your data when you leave the Activity or the program. You could also use a static Array but one of the first two options will probably be better for you.
The Storage Options Docs has some decent examples to get you started, especially if you decide that Shared Preferences will work for you.
Edit
Unless something has changed, you can't store serializable objects in SharedPreferences. But Here is a SO link that discusses saving them to a file and reading from there. Maybe this will help you.
Don't use Intent to move from 'Menu' to 'Connect+Details' instead call finish(); from it
Only use intent in first class to move to second ie;'Connect+Details' to 'Menu'
Don't call finish() in Connect+Details
I am currently working on an app which takes a number of user entries. I want to have each EditText field on its own page, and instead of having a seperate activity for each entry, I wanted instead to call the same activity again. Is this possible, and if so, is it a feasible solution? Thanks.
It is possible but I don't think it is the way to go. Basically if the next input is a separate action then it deserves its own activity.
That is the way you are supposed to do it.
You could store the gathered values either in the Application class as a temporary storage or you can save it using SharedPreference. However if it is only temporary data I advice you to use the Application class rather than writing it to a file.
I would think that if your UI doesn't change (significantly) between views, then reusing your activity and displaying different data seems fine to me (I do this myself).
I keep an object on the Application class that contains a list of the sub-objects (Inputs in your case).
On the top level object, I keep the index of the current index.
This works very well, does not leak memory and is very fast to render as I swipe through my pages.