Activity restart on rotation Android

Using the Application Class

Depending on what you're doing in your initialization you could consider creating a new class that extends Application and moving your initialization code into an overridden onCreate method within that class.

public class MyApplicationClass extends Application {
  @Override
  public void onCreate() {
    super.onCreate();
    // TODO Put your application initialization code here.
  }
}

The onCreate in the application class is only called when the entire application is created, so the Activity restarts on orientation or keyboard visibility changes won't trigger it.

It's good practice to expose the instance of this class as a singleton and exposing the application variables you're initializing using getters and setters.

NOTE: You'll need to specify the name of your new Application class in the manifest for it to be registered and used:

<application
    android:name="com.you.yourapp.MyApplicationClass"

Reacting to Configuration Changes [UPDATE: this is deprecated since API 13; see the recommended alternative]

As a further alternative, you can have your application listen for events that would cause a restart – like orientation and keyboard visibility changes – and handle them within your Activity.

Start by adding the android:configChanges node to your Activity's manifest node

 <activity android:name=".MyActivity"
      android:configChanges="orientation|keyboardHidden"
      android:label="@string/app_name">

or for Android 3.2 (API level 13) and newer:

<activity android:name=".MyActivity"
      android:configChanges="keyboardHidden|orientation|screenSize"
      android:label="@string/app_name">

Then within the Activity override the onConfigurationChanged method and call setContentView to force the GUI layout to be re-done in the new orientation.

@Override
public void onConfigurationChanged(Configuration newConfig) {
  super.onConfigurationChanged(newConfig);
  setContentView(R.layout.myLayout);
}

Update for Android 3.2 and higher:

Caution: Beginning with Android 3.2 (API level 13), the "screen size" also changes when the device switches between portrait and landscape orientation. Thus, if you want to prevent runtime restarts due to orientation change when developing for API level 13 or higher (as declared by the minSdkVersion and targetSdkVersion attributes), you must include the "screenSize" value in addition to the "orientation" value. That is, you must declare android:configChanges="orientation|screenSize". However, if your application targets API level 12 or lower, then your activity always handles this configuration change itself (this configuration change does not restart your activity, even when running on an Android 3.2 or higher device).

what I did...

in the manifest, to the activity section, added:

android:configChanges="keyboardHidden|orientation"

in the code for the activity, implemented:

//used in onCreate() and onConfigurationChanged() to set up the UI elements
public void InitializeUI()
{
    //get views from ID's
    this.textViewHeaderMainMessage = (TextView) this.findViewById(R.id.TextViewHeaderMainMessage);

    //etc... hook up click listeners, whatever you need from the Views
}

//Called when the activity is first created.
@Override
public void onCreate(Bundle savedInstanceState)
{
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);

    InitializeUI();
}

//this is called when the screen rotates.
// (onCreate is no longer called when screen rotates due to manifest, see: android:configChanges)
@Override
public void onConfigurationChanged(Configuration newConfig)
{
    super.onConfigurationChanged(newConfig);
    setContentView(R.layout.main);

    InitializeUI();
}

What you describe is the default behavior. You have to detect and handle these events yourself by adding:

android:configChanges

to your manifest and then the changes that you want to handle. So for orientation, you would use:

android:configChanges="orientation"

and for the keyboard being opened or closed you would use:

android:configChanges="keyboardHidden"

If you want to handle both you can just separate them with the pipe command like:

android:configChanges="keyboardHidden|orientation"

This will trigger the onConfigurationChanged method in whatever Activity you call. If you override the method you can pass in the new values.

Hope this helps.

I just discovered this lore:

For keeping the Activity alive through an orientation change, and handling it through onConfigurationChanged, the documentation and the code sample above suggest this in the Manifest file:

<activity android:name=".MyActivity"
      android:configChanges="orientation|keyboardHidden"
      android:label="@string/app_name">

which has the extra benefit that it always works.

The bonus lore is that omitting the keyboardHidden may seem logical, but it causes failures in the emulator (for Android 2.1 at least): specifying only orientation will make the emulator call both OnCreate and onConfigurationChanged sometimes, and only OnCreate other times.

I haven't seen the failure on a device, but I have heard about the emulator failing for others. So it's worth documenting.

The onCreate method is still called even when you change the orientation of android. So moving all the heavy functionality to this method is not going to help you

Even though it is not "the Android way" I have gotten very good results by handling orientation changes myself and simply repositioning the widgets within a view to take the altered orientation into account. This is faster than any other approach, because your views do not have to be saved and restored. It also provides a more seamless experience to the user, because the respositioned widgets are exactly the same widgets, just moved and/or resized. Not only model state, but also view state, can be preserved in this manner.

RelativeLayout can sometimes be a good choice for a view that has to reorient itself from time to time. You just provide a set of portrait layout params and a set of landscaped layout params, with different relative positioning rules on each, for each child widget. Then, in your onConfigurationChanged() method, you pass the appropriate one to a setLayoutParams() call on each child. If any child control itself needs to be internally reoriented, you just call a method on that child to perform the reorientation. That child similarly calls methods on any of its child controls that need internal reorientation, and so on.

People are saying that you should use

android:configChanges="keyboardHidden|orientation"

But the best and most professional way to handle rotation in Android is to use the Loader class. It's not a famous class(I don't know why), but it is way better than the AsyncTask. For more information, you can read the Android tutorials found in Udacity's Android courses.

Of course, as another way, you could store the values or the views with onSaveInstanceState and read them with onRestoreInstanceState. It's up to you really.

One of the best components of android architecture introduced by google will fulfill all the requirements that are ViewModel.

That is designed to store and manage UI-related data in a lifecycle way plus that will allow data to survive as the screen rotates

class MyViewModel : ViewModel() {

Please refer to this: https://developer.android.com/topic/libraries/architecture/viewmodel

You may use the ViewModel object in your activity.

ViewModel objects are automatically retained during configuration changes so that the data they hold is immediately available to the next activity or fragment instance. Read more: https://developer.android.com/topic/libraries/architecture/viewmodel

There are multiple ways to do this:

Handle orientation changes by yourself

Another alternative is to handle the orientation changes by yourself. But this is not considered a good practice.

Add this to your manifest file.

android:configChanges="keyboardHidden|orientation"

for Android 3.2 and later:

android:configChanges="keyboardHidden|orientation|screenSize"

@Override
public void onConfigurationChanged(Configuration config) {
    super.onConfigurationChanged(config);

if (newConfig.orientation == Configuration.ORIENTATION_PORTRAIT) {
        //Handle rotation from landscape to portarit mode here
    } else if (newConfig.orientation == Configuration.ORIENTATION_LANDSCAPE){
        //Handle rotation from portrait to landscape mode here
    }
}

OR Restrict rotation

You can also confine your activity to portrait or landscape mode to avoid rotation.

Add this to the activity tag in your manifest file:

android:screenOrientation="portrait"

Or implement this programmatically in your activity:

@Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_PORTRAIT);
}

OR Save Activity State

You can save the activity state in onSaveInstanceState.

@Override
public void onSaveInstanceState(Bundle outState) {
    /*Save your data to be restored here
    Example : outState.putLong("time_state", time); , time is a long variable*/
    super.onSaveInstanceState(outState);
}

and then use the bundle to restore the state.

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    if(savedInstanceState!= null){
       /*When rotation occurs
        Example : time = savedInstanceState.getLong("time_state", 0); */
    } else {
      //When onCreate is called for the first time
    }
}

add this code to your manifest.xml.

this is your activity.

<activity
....
..
android:configChanges="orientation|screenSize"/>

in that activity set config changes like below

 android:configChanges="orientation|screenSize|keyboardHidden"