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How to handle Screen rotation of activity which have more data?

I have one activity which has more than 20 fields, most of these fields will prompt user to set data.
Now the problem with the Configuration changes. If user set all the fields & he/she changed screen orientation, then all the fields will be reset because the activity will restart.
If I have only few fields means, then I would have gone with onSaveInstanceState() & onRestoreInstanceState().
But how to handle these many fields? Whether I have to go by storing all the fields? or Is there any better approach?

Try this way
<activity
android:name=".ActivityName"
android:configChanges="orientation|screenSize|keyboardHidden"/>

While you can prevent the activity from rotating to avoid the problem, this should only be done in special circumstances. Also, there are other situations where configuration changes can take place and cause problems. For a full discussion, see this: Why not use always android:configChanges="keyboardHidden|orientation"?
So my suggestion is that instead you create a holder class that implements Parcelable. Then on onSaveInstanceState(Bundle outState) simply call outState.putParcelable(key, yourParcelableObject). You would still need to update the corresponding fields on and this class but at least you would avoid having several keys and calling individual put to the bundle.

add android:configChanges="keyboardHidden|orientation|screenSize" to activity tag in manifest file but that is not best way please read Why not use always android:configChanges="keyboardHidden|orientation"? and http://developer.android.com/guide/topics/manifest/activity-element.html#config and http://developer.android.com/guide/topics/resources/runtime-changes.html for selecting best way for yourself here is a good example for using from parcle .

Restart activity as e.g. orientation change does

I want my app to support different layouts for right-handed and left-handed users. So after changing the respective preference I want to restart the activity in the same way as it restarts when e.g. orientation changes.
What I tried so far:
1.
Intent intent = getIntent();
finish();
startActivity(intent);
This does not store and load the saved instance state
2.
View cv = findViewById(android.R.id.content);
SparseArray<Parcelable> state = new SparseArray<Parcelable>();
cv.saveHierarchyState(state);
setContentView(desiredCv);
cv = findViewById(android.R.id.content);
cv.restoreHierarchyState(state);
Even then many things aren't as they should be.
I think that in the end I could figure out how to change layout properly without restarting but it would be much easier to do it in the same way as for system-defined configuration changes.

You could use Fragments and do it programmatically. Following the same way you could also rearrange dinamically your elements in the UI but I think it would be complicated to maintain.
OnSaveInstanceState() is not called on an Activity being finish-ed. And I'm not aware of a way to let Android handle this for you.
The solution may be to create 2 different layout files. Then you programmatically select the right one in the onCreate() method based on the preference value that has been updated.
If your two layouts use the same ids for those views that you need to restore, then you can implement two methods that save these states in a Bundle and retrieve these states from the Bundle. When you want to change layout, start a new activity with the proper intent (telling the activity which layout to load); in the bundle associated with this intent save what you need and retrieve it in onCreate() to update the views. You don't need to duplicate the code in the case you use layout dx or sx; you can use the same code since the two layouts use the same ids.
In this way you still have your one activity and can reuse your code. And the same code you use to restore the state between layout changes can still be used with onSaveInstanceState() and onRestoreInstanceState(), since, again, the ids are the same.
To make it short, use bundles.

If you are using API level 11 or higher (Android 3.0 or later), you can call recreate() in your activity. This will destroy the current instance and create a new one and should do the same thing as what happens during a configuration change (ie onSaveInstanceState() will be called, etc.).

setRetainInstance not working for configuration changes in android

I have different design for potrait and landscape for activity.so i used layout-land layout .I put webview inside fragment and giving setRetainInstance(true) and loding url like google. when configuration changes it again loading can anybody tell how to avoid that .i didn't mention android:configchanges="orientation" in android manifestfile because
different design can anybody help in this question?
Thanks

Fragments can actually make this a lot easier. Just use the method Fragment.setRetainInstance(boolean) to have your fragment instance retained across configuration changes. Note that this is the recommended replacement for Activity.onRetainnonConfigurationInstance() in the docs.
If for some reason you really don't want to use a retained fragment, there are other approaches you can take. Note that each fragment has a unique identifier returned by Fragment.getId(). You can also find out if a fragment is being torn down for a config change through
Fragment.getActivity().isChangingConfigurations(). So, at the point where you would decide to stop your AsyncTask (in onStop() or onDestroy() most likely), you could for example check if the configuration is changing and if so stick it in a static SparseArray under the fragment's identifier, and then in your onCreate() or onStart() look to see if you have an AsyncTask in the sparse array available.

includeed layouts - update in multiple activities

I have an app with multiple activities and multiple layouts. However, one piece of layout is included on several activities. I also have a thread which updates this layout. However, when i switch activity it doesn't work. Since the layout is included the elements have the same ID's, shouldn't it just work? Or do I really need to fetch an object for each element in the layout and feed it into my thread in order to make it update the elements in a new activity?

You should run the update code for each Activity/View, although the XML included is the same, each is a different instance.
My suggestion is on Restart verify is there is any modification to do in each activity, a simple way is to each Activity extend a BaseActivity that has this code.

I include a layout for adverts in my app, but on each activity that uses it, the adverts need to be reloaded.
If I call an activity from one that is using the same included layout when I go back to the previous activity it's still there.
I guess this is what you are seeing....

So you can also save that data inside sharedPreferences (if it is little data and primitive objets or parceable objects).
Also you can extend the Application class and store the data there and update every activity inside the onResume() method. that i believe is the best way to handle this. and this is quite simple to do.
Ask google about extending the application class and he will provide tons of results on how to do it. its an easy way to pass data between activities and/or keep a reference to a single object which you will use throughout the app. Just be carefull to clear it when you wont need it anymore because it will stay in existance untill the application is finished() (which comes with the application extension living thru the whole application lifetime).

Android ListView in Activity getting Refreshed on Changing Orientation

I have Activity with ListView inside it and in the onCreate method of the Activity I have code for populating the Data of the ListView this Data is a server based and so populating includes calling Network URLs. I have the ArrayAdapter of the ListView in the Same Activity Class.
Now the Issue I'am facing is that, in Rest all scenarios my Activity is behaving in a proper way but when the Orientation [ Portrait to Landscaped or other way round] is taking place the Data is Getting lost and Newer Data calls are Required to Populate the Same Old Data now this is something that is not intended out the code how should I deal with it.

Android will stop and restart your activity unless you've told it you will handle orientation changes yourself. It does this so that you can specify different resources (such as layouts) that are orientation-specific (among other reasons).
You need to add android:configChanges="orientation" to your activity delcaration in your AndroidManifest.xml, and you need to override onConfigurationChanged(). I don't believe you need to do anything special inside onConfigurationChanged(), simply implementing it should do the trick.

For those targeting API 13 or higher, "screenSize" should also be used. If that is your case, add
android:configChanges="orientation|screenSize"
to your Android manifest.
More information here.

AFAIK the whole Activity gets recreated on an orientation change!
The same is true if you switch to anoter app and return back later.
I would suggest to store the data is the SharedPreferences or serialize them into XML and store them.
Another possibility could be to register your own service that stores the data in memory and the activity poluplates the data from the service.

Why not saving any data into a parceable and if the bundle you get in onCreate contains a saved state of data re-set the list adapter? Here is a nice code sample on this: http://blog.cluepusher.dk/2009/10/28/writing-parcelable-classes-for-android/

android:configChanges="orientation|screenSize"
this code will work only if we don't have another layout for landscape mode!