Develop Reference

Grid View rotation handling

I have slight problem. I have gridView in main activity, and on device rotation the list will always start from the top. I fonud several solutions but non of them work for gridView. How can I maintain same gridView position on device rotation using onSavedInstanceState?
Thanks in advance. :)

You first need to understand the facts because of which this is happening. This is happening because whenever your device orientation changes your onDestroy() and onCreate() lifecycle methods are called. To survive your activity state using onSaveInstanceState, you need to save your grid view scroll position when onDestroy() is called and then retrieve it in your onCreate() method. You can do this using Bundle. The code will look something like this, onSaveInstanceState() will be called by android os before your activity get destroyed \n
#Override
onSaveInstanceState(Bundle bundle){
super.onSaveInstanceState(bundle);
bundle.putInt("SCROLL_VIEW_POSITION",scroll_position);
}
//And in your on Create
onCreate(Bundle saveInstanceState){
super.onCreate(saveInstanceState);
int scrollPosition = saveInstanceState.get("SCROLL_VIEW_POSITION",default_value);
}
Once you get your same scrollPosition before oreientation change you can use it to set scroll position of your grid view.

Notifying fragments in a viewpager

I am using ViewPager in my app. In each fragment there is a toolbar. On a single tap on the image the the toolbar is animated to the top out of the screen. But I have to notify all the remaining fragments to do the same thing. So that when the user scrolls to the next fragment he doesn't see the toolbar.
I tried adding setUserVisibleHint(), but it did not work as it was called only when the fragment was completely visible, thus showing the toolbar exiting to the user.
Then I tried it in onResume and setting pager.offscreenpagelimit=1, it worked fine for the fragment next to next but did not work for the next fragment.
Thanks!!

First Notify your activity from fragment using:
In Fragment on Animation End:
((YourActivity)getActivity()).hideToolbar();
In Activity:
public void hideToolbar() {
// Redraw view pager without toolbar (notify your adapter create pager without toolbar)
}
Well, why don't you get your toolbar out of your fragments and just create one in activity and change its state on page change (definitely it will not slide but may

You have 2 problems to face.
How to call existing fragments to hide/show their toolbars.
How to create another fragments with hidden toolbar.
First problem can be easly done by using Otto event library found here. Just paste this code in your viewpager fragments:
Bus bus = new Bus();
#Override
protected void onResume() {
super.onResume();
bus.register(this);
}
#Override
protected void onPause() {
super.onPause();
bus.unregister(this);
}
#Subscribe
public void onToolbarEvent(ToolbarEvent event) {
//do your toolbar logic
}
Then in your onClick event on image just put (of course creating bus object before)
bus.post(new ToolbarEvent());
ToolbarEvent can be just empty class. If you read about Otto events you will understand how it works.
Another problem is how to know that the toolbar should be hidden/shown, when viewpager instantiates new fragments? Simply add a boolean flag in your shared prefferences, so every time fragment is created, it can check if it can show toolbar or not e.g. in onViewCreated() method. The example how to use shared prefferences can be found here
Hope I helped a little bit.

How to save state of fragment in android?

i am using four fragments in one activity
Four buttons at bottom are used to switch between fragments
I have search button of action bar
But when i am clicking on search button keyboard appears and then after that fragment started loading again..
So how to save state of fragment on configuration change..
I have also tried this
android:configChanges="orientation|screenSize|keyboardHidden|keyboard"

Use public void setRetainInstance (true) in fragment.
#Override
public void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setRetainInstance(true);
...
...
}
This will retain only when there is change in orientation, not on back stack.

You can use setRetainInstance(true). No matter where you write - in onActivityCreated or OnCreateView. But in this case you can have problems with memory or link on old Activity in future.
As for me, I think that it's better to save your data in onSaveInstanceState and get them, for example, in onRestoreInstanceState.

Single Activity with Multiple Fragments and Screen Orientation

I'm currently dealing with an issue with Android & It's Re-Creation Cycle on screen rotation:
I have one single Activity and lots of Fragments (Support-V4) within.
For example, the Login it's on a Single Activity with a Fragment, when the logs-in then the App changes it's navigation behavior and uses multiple fragments, I did this, because passing data between Fragment A to Fragment B it's way much easier than passing data Between an Activity A to an Activity B.
So My issue it's presented when I rotate the device, on my first approach, the initial fragment was loaded, but what would happen, if the user it's on Page 15 and it rotates it's device, it would return to Fragment 1 and give a very bad user-experience. I set all my fragments to retain their instance and added this on the MainActivity on Create:
#Override
protected void onCreate(Bundle savedInstanceState) {
// TODO Auto-generated method stub
super.onCreate(savedInstanceState);
setContentView(R.layout.main_layout);
initBackStackManager();
initControllers();
mayDownloadData();
setTitle();
if(savedInstanceState == null){
addAreaFragment();
}
}
Now, the first fragment is not loaded after screen orientation change, but If I try to make a fragment transaction, it says Can not perform FragmentTransaction.commit() after onSaveInstanceState(), is there a way to handle this? Or Do I really really need to use multiple Activities with a Fragment embedded within?
Thank you very much!
EDITED
I forgot to add that this happens only on a specific Fragment... For example I have the following fragment flow:
AreaFragment -> WaiterSelectionFragment -> WaiterOptionsFragment.
If I'm in the AreaFragment and I rotate the device I can still add/replace fragments and nothing happens, no error it's being thrown. If I'm on the WaiterSelectionFragment no error happens too. BUT, If I'm on the WaiterOptionsFragment the error it's being thrown. The WaiterSelectionFragment has the following structure:
LinearLayout
FragmentTabHost
Inside the FragmentTabHost there are some fragments, and that's where the error it's happening. You might wonder Why FragmentTabHost? easy, the Customer wants that App to show the TabBar, If I use Native Android Tabs the Tabs get rearranged to the ActionBar when on
Landscape position.
EDIT 2
I've used the method provided by #AJ Macdonald, but no luck so far.
I have my Current Fragment being saved at onSaveInstanceState(Bundle) method and restore my fragment on onRestoreInstanceState(Bundle) method on the Android Activity, I recover my back button and the current Fragment but when I get to the third Fragment the error still occurs. I'm using a ViewPager that holds 4 Fragments, Will this be causing the Issue? Only on this section of the App Happens. I've 4 (main workflow) fragments, on the First, Second and Third Fragment no error it's being presented, only on the ViewPager part.

Give each of your fragments a unique tag.
In your activity's onSaveInstanceState, store the current fragment. (This will probably be easiest to do if you keep a variable that automatically updates every time the fragment changes.)
In your activity's onCreate or onRestoreInstanceState, pull the tag out of the saved bundle and start a new fragment of that type.
public static final int FRAGMENT_A = 0;
public static final int FRAGMENT_B = 1;
private int currentFragment;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
//other stuff
if(savedInstanceState == null){
addAreaFragment();
currentFragment = FRAGMENT_A;
}else{
currentFragment = savedInstanceState.getInt("currentFragment");
switch(currentFragment){
case FRAGMENT_A:
addAreaFragment();
break;
case FRAGMENT_B:
addFragmentB();
}
}
}
// when you switch fragment A for fragment B:
currentFragment = FRAGMENT_B;
#Override
public void onSaveInstanceState(Bundle savedInstanceState) {
savedInstanceState.putInt("currentFragment", currentFragment);
super.onSaveInstanceState(savedInstanceState);
}

A suggestion to try is to use FragmentTransaction.commitAllowingStateLoss() in place of FragmentTransaction.commit(). That should stop the Exception from being thrown, but the downside is if you rotate the device again the most recent state of the UI may not return. That is a suggestion given that I am not sure of the effect of using FragmentTabHost, if it has any effect at all.

What can I do to save the instance state of a fragment but still provide a landscape layout?

if the question sounds weird at first, here comes the explanation:
I have got an activity that hosts my three fragments. Since I would like one of my fragments to save its instance state when the device is rotated, I defined this in my manifest for my activity that hosts the fragments:
android:configChanges="orientation|screenSize"
This works just fine. However, now I have got an other problem: One of my other fragments uses a special landscape layout. The problem is, that this layout is not used immediately on device rotation. I think it is because the new layout only gets set on onCreate.
What can I do to solve this problem? I want my landscape layout to be set immediately.

You can put
setRetainInstance(true);
in onCreateView(); method of your Fragment. I think it should do the trick.

As far as I know you down need to add the configChanges parameter to your manifest.
You can override onSaveInstanceState() in your Fragment
#Override
public void onSaveInstanceState(Bundle savedInstanceState) {
super.onSaveInstanceState(savedInstanceState);
savedInstanceState.putInt(KEY_INDEX, someIntValue);
}
This methode should be called before your fragment gets destroyed.
Now in your onCreate(Bundle savedInstanceState) (or onCreateView()) methode:
if (savedInstanceState != null) {
someIntValue = savedInstanceState.getInt(KEY_INDEX);
}
This way it shouldn't intervene with any other special fragments.