Develop Reference

What is the use of Android static inner activity class and where exactly we can use?

I have created a Activity called MainActivity Which extends from ThirdActivity.
Next, I have an inner static activity called AnotherActivity which extends from SecondActivity. Below is my code:
1)MainActivity: which is the first activity that calls at first when app loads.
public class MainActivity extends ThirdActivity {
public static class AnotherActivity extends SecondActivity{
}
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
System.out.println("Main Activity");
}
}
2) ThirdActivty Code follows:
public abstract class ThirdActivity extends Activity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_third);
System.out.println("Third Activity");
}
}
3) Inner static activity extended from SecondActivity which consists of:
public abstract class SecondActivity extends Activity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_second);
System.out.println("Second Activity");
}
}
Now the output of the above android program is:
Third Activity
MainActivity
In order to access the inner activities we need to do declare in manifest as:
<activity android:name="MainActivity$AnotherActivity" ></activity>
So, My question goes like this:
1) How to access Static inner Activity classes.
2) When to use this scenario.?
3) Will the inner activity runs the life cycle process and what happens to already running MainActivity?

I love answering bizarre questions before having coffee.
1) How to access Static inner Activity classes
What do you mean by "access"? The fact that this is a static inner class is pretty much irrelevant. It will run like an normal Activity. When it is running, its onCreate method, e.g., will be called. When that happens, there is a reference to the running instance of AnotherActivity in the canonical variable this.
2) When to use this scenario.
I can't think of a single reason. In fact, I can think of a million reasons not to use it. Ever.
3) Will the inner activity runs the life cycle process and what
happens to already running MainActivity?
Yes. The "inner" activity will run through a normal Activity lifecycle. Nothing happens to the MainActivity because it is not running when the AnotherActivity is running. When AnotherActivity is started, MainActivity is stopped (onPause, maybe onStop, etc).

How to work with AsyncTask when screen rotates

I have an activity in my android app that calls an asynctask on onCreateView()
Here is my code :
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_weeklyprofit);
fromDateTxt=(TextView)findViewById(R.id.fromDate);
toDateTxt = (TextView)findViewById(R.id.toDate);
GetXYPoints getXY = new GetXYPoints();
getXY.execute(fromDateTxt.getText().toString(),toDateTxt.getText().toString());
}
now my application needs to rotate, so i need to store data when rotate :
I have implemented this as below :
#Override
public void onSaveInstanceState(Bundle savedInstanceState) {
super.onSaveInstanceState(savedInstanceState);
savedInstanceState.putString("from", fromDateTxt.getText().toString());
savedInstanceState.putString("to", toDateTxt.getText().toString());
}
#Override
public void onRestoreInstanceState(Bundle savedInstanceState) {
super.onRestoreInstanceState(savedInstanceState);
SystemClock.sleep(500);
fromDateTxt.setText(savedInstanceState.getString("from"));
toDateTxt.setText(savedInstanceState.getString("to"));
GetXYPoints getXY = new GetXYPoints();
getXY.execute(fromDateTxt.getText().toString(),toDateTxt.getText().toString());
}
So i recall the asynctask again with restored data, my problem is that the activity run again when rotate and the it calls onRestoreInstanceState so how can i prevent the activity from calling the first asyncktask?
In other way what is the best solution to store data returned by an asynck task when screen is rotate?

i would suggest you to to make sure you actually need your activity to be reset on a screen rotation (the default behavior). Every time I've had issues with rotation I've added this attribute to my tag in the AndroidManifest.xml, and been just fine.
android:configChanges="keyboardHidden|orientation"
source How to handle an AsyncTask during Screen Rotation?

In your AndroidManifest.xml add following for prevent reloading activity when orientation change
android:configChanges="orientation|screenSize"
So, you'll have something like this:
<activity android:name="Activity"
android:configChanges="orientation|screenSize">
</activity>
Hope it works!

lock android activity in portrait mode without doing it for each activity

So I know that I can do android:screenOrientation="portrait" for each activity in my manifest and that will lock the activity to portrait mode. But I am wondering if there is a place in the manifest where I can enter this once and have it apply to the entire application.

Create a custom activity
public class CustomActivity extends Activity{
#Override
public void onConfigurationChanged(Configuration newConfig){
super.onConfigurationChanged(newConfig);
if(newConfig.orientation == Configuration.ORIENTATION_PORTRAIT){
setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_LANDSCAPE);
}else{
setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_LANDSCAPE);
}
}
}
Then for all activities you create , for example ActicityA,ActivityB extend it from CustomActivity .
public class ActicityA extends CustomActivity {}
public class ActivityB extends CustomActivity {}

Create a custom Activity in which you define the orientation and fix it to your desired position.
Inherit all the Activities in your application from your CustomActivity which has been defined with a fixed orientation.
EDIT : This answer provides yet another way of doing the same thing, but I like to believe that mine is more elegant because you wouldn't need to call the function for each and every Activity.

In you manifest file you can give like this
<activity
android:name="com.androidcalapp.MainActivity"
android:label="#string/app_name"
android:screenOrientation="landscape">
As far as I know we have to repeat it for every activity in manifest.
Or else you can handle it at runtime, by overriding onConfigurationChanged()method in Activity.
#Override
public void onConfigurationChanged(Configuration newConfig){
super.onConfigurationChanged(newConfig);
if(newConfig.orientation == Configuration.ORIENTATION_PORTRAIT){
setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_LANDSCAPE);
}else{
setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_LANDSCAPE);
}

Why do OnCreate should be called only once on the start of Activity?

I would like to know, why OnCreate() is called only once at the start of an activity?
Can we call OnCreate() more than once in the same activity?
If yes, than how can we call it? can anyone give an example?
Thanks a lot!!!

Why would you want to called it again? unless the activity is reconstructed, which is called by system. You cannot call OnCreate manually , it is the same reason why you won't call setContentView() twice. as docs:
onCreate(Bundle) is where you initialize your activity. Most
importantly, here you will usually call setContentView(int) with a
layout resource defining your UI, and using findViewById(int) to
retrieve the widgets in that UI that you need to interact with
programmatically.
Once you finish init your widgets Why would you?
UPDATE
I take some words back, you CAN do this manually but I still don't understand why would this be called. Have you tried Fragments ?
Samplecode:
public class MainActivity extends Activity implements OnClickListener {
private Button btPost;
private Bundle state;
private int counter = 0;
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
state = savedInstanceState;
btPost = (Button) findViewById(R.id.btPost);
btPost.setOnClickListener(this);
Toast.makeText(getBaseContext(), " " + counter, Toast.LENGTH_LONG)
.show();
}
#Override
public void onClick(View v) {
counter++;
this.onCreate(state);
}
}

onCreate() method performs basic application startup logic that should happen only once for the entire life of the activity .
Once the onCreate() finishes execution, the system calls the onStart() and onResume() methods in quick succession.
The initialization process consumes lot of resources and to avoid this the activity once created is never completely destroyed but remains non visible to user in background so that once it is bring back to front , reinitialization doesn't happen .

Where you want to call onCreate manually.
Then just do this.
finish();
Intent intent = new Intent(Main.this, Main.class);
startActivity(intent);
finish() calls the current stuff.
And if you are doing somethong getExtra in this activity then do this,
#Override
protected void onSaveInstanceState(Bundle outState) {
outState.putString("key",your_variable);
super.onSaveInstanceState(outState);
}
And add this to your onCreate()
protected void onCreate(Bundle savedInstanceState) {
// TODO Auto-generated method stub
super.onCreate(savedInstanceState);
if(savedInstanceState != null)
{
your_variable= savedInstanceState.getString("key");
}
}

Why would you want to call onCreate more than once? You will be re-creating the activity. If this is what you need for whatever reason then finish the activity and use an intent to create a new instance of that activity. Otherwise, you have two instances of the activity at the same time. Hope that helps but if that doesn't make sense then add more information as to what you want so we have context

OnCreate is basically use to create your activity (UI). If you have already created your activity then you need not create it again as you have already created.
It is basically used to initialize your activity and to create user interface of your activity. Activity is a visual part which you can use again and again so.. I think your problem is not to recreate activity but to reinitialize all components of your activity. For that purpose you can create a method initialize_act() and call it from anywhere...

#OnCreate is only for initial creation, and thus should only be called once.
If you have any processing you wish to complete multiple times you should put it elsewhere, perhaps in the #OnResume method.

Recently i realized that onCreate is called on every screen orientation change (landscape/portrait). You should be aware of this while planning your initialization process.
Recreation can be suppressed in AndroidManifest.xml:
<activity
android:configChanges="keyboardHidden|orientation"
android:name=".testActivity"
android:label="#string/app_name"></activity>

When I rotate the screen, my activity restart? how can I stop this? [duplicate]

In my Android application, when I rotate the device (slide out the keyboard) then my Activity is restarted (onCreate is called). Now, this is probably how it's supposed to be, but I do a lot of initial setting up in the onCreate method, so I need either:
Put all the initial setting up in another function so it's not all lost on device rotation or
Make it so onCreate is not called again and the layout just adjusts or
Limit the app to just portrait so that onCreate is not called.

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).
From http://web.archive.org/web/20120805085007/http://developer.android.com/guide/topics/resources/runtime-changes.html

Instead of trying to stop the onCreate() from being fired altogether, maybe try checking the Bundle savedInstanceState being passed into the event to see if it is null or not.
For instance, if I have some logic that should be run when the Activity is truly created, not on every orientation change, I only run that logic in the onCreate() only if the savedInstanceState is null.
Otherwise, I still want the layout to redraw properly for the orientation.
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_game_list);
if(savedInstanceState == null){
setupCloudMessaging();
}
}
not sure if this is the ultimate answer, but it works for me.

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.

You might also consider using the Android platform's way of persisting data across orientation changes: onRetainNonConfigurationInstance() and getLastNonConfigurationInstance().
This allows you to persist data across configuration changes, such as information you may have gotten from a server fetch or something else that's been computed in onCreate or since, while also allowing Android to re-layout your Activity using the xml file for the orientation now in use.
See here or here.
It should be noted that these methods are now deprecated (although still more flexible than handling orientation change yourself as most of the above solutions suggest) with the recommendation that everyone switch to Fragments and instead use setRetainInstance(true) on each Fragment you want to retain.

The approach is useful but is incomplete when using Fragments.
Fragments usually get recreated on configuration change. If you don't wish this to happen, use
setRetainInstance(true); in the Fragment's constructor(s)
This will cause fragments to be retained during configuration change.
http://developer.android.com/reference/android/app/Fragment.html#setRetainInstance(boolean)

I just simply added:
android:configChanges="keyboard|keyboardHidden|orientation"
in the AndroidManifest.xml file and did not add any onConfigurationChanged method in my activity.
So every time the keyboard slides out or in nothing happens! Also checkout this article about this problem.

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

Put the code below inside your <activity> tag in Manifest.xml:
android:configChanges="screenLayout|screenSize|orientation"

It is very simple just do the following steps:
<activity
android:name=".Test"
android:configChanges="orientation|screenSize"
android:screenOrientation="landscape" >
</activity>
This works for me :
Note: orientation depends on your requitement

onConfigurationChanged is called when the screen rotates.
(onCreate is no longer called when the screen rotates due to manifest, see:
android:configChanges)
What part of the manifest tells it "don't call onCreate()"?
Also,
Google's docs say to avoid using android:configChanges (except as a last resort). But then the alternative methods they suggest all DO use android:configChanges.
It has been my experience that the emulator ALWAYS calls onCreate() upon rotation.
But the 1-2 devices that I run the same code on... do not.
(Not sure why there would be any difference.)

Changes to be made in the Android manifest are:
android:configChanges="keyboardHidden|orientation"
Additions to be made inside activity are:
public void onConfigurationChanged(Configuration newConfig) {
super.onConfigurationChanged(newConfig);
// Checks the orientation of the screen
if (newConfig.orientation == Configuration.ORIENTATION_LANDSCAPE) {
Toast.makeText(this, "landscape", Toast.LENGTH_SHORT).show();
} else if (newConfig.orientation == Configuration.ORIENTATION_PORTRAIT) {
Toast.makeText(this, "portrait", Toast.LENGTH_SHORT).show();
}
}

Add this line to your manifest :-
android:configChanges="orientation|keyboard|keyboardHidden|screenSize|screenLayout|uiMode"
and this snippet to the activity :-
#Override
public void onConfigurationChanged(Configuration newConfig) {
super.onConfigurationChanged(newConfig);
getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN,
WindowManager.LayoutParams.FLAG_FULLSCREEN);
}

There are several ways to do this:
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
}
}
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 portrait mode here
} else if (newConfig.orientation == Configuration.ORIENTATION_LANDSCAPE){
//Handle rotation from portrait to landscape mode here
}
}
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);
}

The way I have found to do this is use the onRestoreInstanceState and the onSaveInstanceState events to save something in the Bundle (even if you dont need any variables saved, just put something in there so the Bundle isn't empty). Then, on the onCreate method, check to see if the Bundle is empty, and if it is, then do the initialization, if not, then do it.

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.

Every time when the screen is rotated, opened activity is finished and onCreate() is called again.
1 . You can do one thing save the state of activity when the screen is rotated so that, You can recover all old stuff when the activity's onCreate() is called again.
Refer this link
2 . If you want to prevent restarting of the activity just place the following lines in your manifest.xml file.
<activity android:name=".Youractivity"
android:configChanges="orientation|screenSize"/>

you need to use the onSavedInstanceState method to store all the values to its parameter is has which is a bundle
#Override
public void onSaveInstanceState(Bundle outState, PersistableBundle outPersistentState) {
super.onSaveInstanceState(outState, outPersistentState);
outPersistentState.putBoolean("key",value);
}
and use
#Override
protected void onRestoreInstanceState(Bundle savedInstanceState) {
super.onRestoreInstanceState(savedInstanceState);
savedInstanceState.getBoolean("key");
}
to retrieve and set the value to view objects
it will handle the screen rotations

Note: I post this answer if someone in the future face the same problem as me. For me the following line wasn't enough:
android:configChanges="orientation"
When I rotated the screen, the method `onConfigurationChanged(Configuration new config) didn't get called.
Solution: I also had to add "screenSize" even if the problem had to do with the orientation. So in the AndroidManifest.xml - file, add this:
android:configChanges="keyboardHidden|orientation|screenSize"
Then implement the method onConfigurationChanged(Configuration newConfig)

In the activity section of the manifest, add:
android:configChanges="keyboardHidden|orientation"

Add this line in manifest : android:configChanges="orientation|screenSize"

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

After a while of trial and error, I found a solution which fits my needs in the most situations. Here is the Code:
Manifest configuration:
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.pepperonas.myapplication">
<application
android:name=".App"
android:allowBackup="true"
android:icon="#mipmap/ic_launcher"
android:label="#string/app_name"
android:supportsRtl="true"
android:theme="#style/AppTheme">
<activity
android:name=".MainActivity"
android:configChanges="orientation|keyboardHidden|screenSize">
<intent-filter>
<action android:name="android.intent.action.MAIN"/>
<category android:name="android.intent.category.LAUNCHER"/>
</intent-filter>
</activity>
</application>
</manifest>
MainActivity:
import android.content.res.Configuration;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentTransaction;
import android.support.v7.app.AppCompatActivity;
import android.util.Log;
import android.view.View;
import android.widget.Button;
public class MainActivity extends AppCompatActivity implements View.OnClickListener {
private static final String TAG = "MainActivity";
private Fragment mFragment;
private int mSelected = -1;
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
Log.d(TAG, "onCreate " + "");
// null check not realy needed - but just in case...
if (savedInstanceState == null) {
initUi();
// get an instance of FragmentTransaction from your Activity
FragmentManager fragmentManager = getSupportFragmentManager();
FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
/*IMPORTANT: Do the INITIAL(!) transaction only once!
* If we call this everytime the layout changes orientation,
* we will end with a messy, half-working UI.
* */
mFragment = FragmentOne.newInstance(mSelected = 0);
fragmentTransaction.add(R.id.frame, mFragment);
fragmentTransaction.commit();
}
}
#Override
public void onConfigurationChanged(Configuration newConfig) {
super.onConfigurationChanged(newConfig);
Log.d(TAG, "onConfigurationChanged " +
(newConfig.orientation
== Configuration.ORIENTATION_LANDSCAPE
? "landscape" : "portrait"));
initUi();
Log.i(TAG, "onConfigurationChanged - last selected: " + mSelected);
makeFragmentTransaction(mSelected);
}
/**
* Called from {#link #onCreate} and {#link #onConfigurationChanged}
*/
private void initUi() {
setContentView(R.layout.activity_main);
Log.d(TAG, "onCreate instanceState == null / reinitializing..." + "");
Button btnFragmentOne = (Button) findViewById(R.id.btn_fragment_one);
Button btnFragmentTwo = (Button) findViewById(R.id.btn_fragment_two);
btnFragmentOne.setOnClickListener(this);
btnFragmentTwo.setOnClickListener(this);
}
/**
* Not invoked (just for testing)...
*/
#Override
protected void onSaveInstanceState(Bundle outState) {
super.onSaveInstanceState(outState);
Log.d(TAG, "onSaveInstanceState " + "YOU WON'T SEE ME!!!");
}
/**
* Not invoked (just for testing)...
*/
#Override
protected void onRestoreInstanceState(Bundle savedInstanceState) {
super.onRestoreInstanceState(savedInstanceState);
Log.d(TAG, "onSaveInstanceState " + "YOU WON'T SEE ME, AS WELL!!!");
}
#Override
protected void onResume() {
super.onResume();
Log.d(TAG, "onResume " + "");
}
#Override
protected void onPause() {
super.onPause();
Log.d(TAG, "onPause " + "");
}
#Override
protected void onDestroy() {
super.onDestroy();
Log.d(TAG, "onDestroy " + "");
}
#Override
public void onClick(View v) {
switch (v.getId()) {
case R.id.btn_fragment_one:
Log.d(TAG, "onClick btn_fragment_one " + "");
makeFragmentTransaction(0);
break;
case R.id.btn_fragment_two:
Log.d(TAG, "onClick btn_fragment_two " + "");
makeFragmentTransaction(1);
break;
default:
Log.d(TAG, "onClick null - wtf?!" + "");
}
}
/**
* We replace the current Fragment with the selected one.
* Note: It's called from {#link #onConfigurationChanged} as well.
*/
private void makeFragmentTransaction(int selection) {
switch (selection) {
case 0:
mFragment = FragmentOne.newInstance(mSelected = 0);
break;
case 1:
mFragment = FragmentTwo.newInstance(mSelected = 1);
break;
}
// Create new transaction
FragmentTransaction transaction = getSupportFragmentManager().beginTransaction();
// Replace whatever is in the fragment_container view with this fragment,
// and add the transaction to the back stack
transaction.replace(R.id.frame, mFragment);
/*This would add the Fragment to the backstack...
* But right now we comment it out.*/
// transaction.addToBackStack(null);
// Commit the transaction
transaction.commit();
}
}
And sample Fragment:
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
/**
* #author Martin Pfeffer (pepperonas)
*/
public class FragmentOne extends Fragment {
private static final String TAG = "FragmentOne";
public static Fragment newInstance(int i) {
Fragment fragment = new FragmentOne();
Bundle args = new Bundle();
args.putInt("the_id", i);
fragment.setArguments(args);
return fragment;
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
Log.d(TAG, "onCreateView " + "");
return inflater.inflate(R.layout.fragment_one, container, false);
}
}
Can be found on github.

Use orientation listener to perform different tasks on different orientation.
#Override
public void onConfigurationChanged(Configuration myConfig)
{
super.onConfigurationChanged(myConfig);
int orient = getResources().getConfiguration().orientation;
switch(orient)
{
case Configuration.ORIENTATION_LANDSCAPE:
setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_LANDSCAPE);
break;
case Configuration.ORIENTATION_PORTRAIT:
setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_PORTRAIT);
break;
default:
setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_UNSPECIFIED);
}
}

Put this below code in your Activity in Android Manifest.
android:configChanges="orientation"
This will not restart your activity when you would change orientation.

Fix the screen orientation (landscape or portrait) in AndroidManifest.xml
android:screenOrientation="portrait" or android:screenOrientation="landscape"
for this your onResume() method is not called.

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