How to detect orientation change in layout in Android?

Use the onConfigurationChanged method of Activity. See the following code:

@Override
public void onConfigurationChanged(@NotNull 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();
    }
}

You also have to edit the appropriate element in your manifest file to include the android:configChanges Just see the code below:

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

NOTE: with Android 3.2 (API level 13) or higher, 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, you must declare android:configChanges="orientation|screenSize" for API level 13 or higher.

Hope this will help you... :)

use this method

@Override
public void onConfigurationChanged(Configuration newConfig) {
    super.onConfigurationChanged(newConfig);
    if (newConfig.orientation == Configuration.ORIENTATION_PORTRAIT)
    {
        Toast.makeText(getActivity(),"PORTRAIT",Toast.LENGTH_LONG).show();
       //add your code what you want to do when screen on PORTRAIT MODE
    }
    else if (newConfig.orientation == Configuration.ORIENTATION_LANDSCAPE)
    {
        Toast.makeText(getActivity(),"LANDSCAPE",Toast.LENGTH_LONG).show();
        //add your code what you want to do when screen on LANDSCAPE MODE
   }
}

And Do not forget to Add this in your Androidmainfest.xml

android:configChanges="orientation|screenSize"

like this

<activity android:name=".MainActivity"
          android:theme="@style/Theme.AppCompat.NoActionBar"
          android:configChanges="orientation|screenSize">

    </activity>

Just wanted to show you a way to save all your Bundle after onConfigurationChanged:

Create new Bundle just after your class:

public class MainActivity extends Activity {
    Bundle newBundy = new Bundle();

Next, after "protected void onCreate" add this:

@Override
public void onConfigurationChanged(Configuration newConfig) {
     super.onConfigurationChanged(newConfig);
     if (newConfig.orientation == Configuration.ORIENTATION_LANDSCAPE) {
            onSaveInstanceState(newBundy);
        } else if (newConfig.orientation == Configuration.ORIENTATION_PORTRAIT) {
            onSaveInstanceState(newBundy);
        }
}

@Override
public void onSaveInstanceState(Bundle outState) {
    super.onSaveInstanceState(outState);
    outState.putBundle("newBundy", newBundy);
}

@Override
protected void onRestoreInstanceState(Bundle savedInstanceState) {
    super.onRestoreInstanceState(savedInstanceState);
    savedInstanceState.getBundle("newBundy");
}

If you add this all your crated classes into MainActivity will be saved.

But the best way is to add this in your AndroidManifest:

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

For loading the layout in layout-land folder means you have two separate layouts then you have to make setContentView in onConfigurationChanged method.

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

    // Checks the orientation of the screen
    if (newConfig.orientation == Configuration.ORIENTATION_LANDSCAPE) {
        setContentView(R.layout.yourxmlinlayout-land);
    } else if (newConfig.orientation == Configuration.ORIENTATION_PORTRAIT){
        setContentView(R.layout.yourxmlinlayoutfolder);
    }
}

If you have only one layout then no necessary to make setContentView in This method. simply

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