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<fragment> tag in XML and Databinding gives inflate exception

I am working on an existing project which uses DrawerLayout and a custom fragment for side navigation, but when I use data binding it gives inflate exception in XML file at <fragment> tag. Below is my code.
activity_home.xml
<?xml version="1.0" encoding="utf-8"?>
<layout>
<androidx.drawerlayout.widget.DrawerLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:id="#+id/drawer_layout"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:fitsSystemWindows="true"
tools:openDrawer="start">
<include
android:id="#+id/layoutParent"
layout="#layout/activity_parent_list_new" />
<fragment
android:id="#+id/navigation_view"
android:name="com.myApp.home.fragment.NavigationDrawerFragment"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_gravity="start"
android:fitsSystemWindows="true" />
</androidx.drawerlayout.widget.DrawerLayout>
</layout>
HomeActivity.java
public class HomeActivity extends AppCompatActivity{
private ActivityHomeBinding binding;
#Override
protected void onCreate(#Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
binding = ActivityHomeBinding.inflate(getLayoutInflater());
mExitToast = Toast.makeText(this, getString(R.string.press_to_exit), Toast.LENGTH_SHORT);
mNavigationDrawerFragment = (NavigationDrawerFragment) getSupportFragmentManager().findFragmentById(R.id.navigation_view);
mNavigationDrawerFragment.setupViews();
mNavigationDrawerFragment.setDrawerListener(this);
}
/*Other Code*/
}
Exception stack trace
Process: com.myApp.debug, PID: 18493
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.myApp.debug/com.myApp.home.HomeActivity}: android.view.InflateException: Binary XML file line #27 in com.myApp.debug:layout/activity_home: Binary XML file line #27 in com.myApp.debug:layout/activity_home: Error inflating class fragment
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3780)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3942)
at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:109)
at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:135)
at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:95)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2345)
at android.os.Handler.dispatchMessage(Handler.java:106)
at android.os.Looper.loopOnce(Looper.java:233)
at android.os.Looper.loop(Looper.java:344)
at android.app.ActivityThread.main(ActivityThread.java:8212)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:584)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1034)
Caused by: android.view.InflateException: Binary XML file line #27 in com.myApp.debug:layout/activity_home: Binary XML file line #27 in com.myApp.debug:layout/activity_home: Error inflating class fragment
Caused by: android.view.InflateException: Binary XML file line #27 in com.myApp.debug:layout/activity_home: Error inflating class fragment
Caused by: java.lang.IllegalArgumentException: Binary XML file line #27: Duplicate id 0x7f0a0682, tag null, or parent id 0x7f0a02e9 with another fragment for com.myApp.home.fragment.NavigationDrawerFragment
at androidx.fragment.app.FragmentLayoutInflaterFactory.onCreateView(FragmentLayoutInflaterFactory.java:117)
at androidx.fragment.app.FragmentController.onCreateView(FragmentController.java:135)
at androidx.fragment.app.FragmentActivity.dispatchFragmentsOnCreateView(FragmentActivity.java:295)
at androidx.fragment.app.FragmentActivity.onCreateView(FragmentActivity.java:274)
at android.view.LayoutInflater.tryCreateView(LayoutInflater.java:1078)
at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:1006)
at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:970)
at android.view.LayoutInflater.rInflate(LayoutInflater.java:1132)
at android.view.LayoutInflater.rInflateChildren(LayoutInflater.java:1093)
at android.view.LayoutInflater.inflate(LayoutInflater.java:692)
at android.view.LayoutInflater.inflate(LayoutInflater.java:542)
at androidx.databinding.DataBindingUtil.inflate(DataBindingUtil.java:126)
at androidx.databinding.ViewDataBinding.inflateInternal(ViewDataBinding.java:1409)
at com.myApp.databinding.ActivityHomeBinding.inflate(ActivityHomeBinding.java:72)
at com.myApp.databinding.ActivityHomeBinding.inflate(ActivityHomeBinding.java:58)
at com.myApp.home.HomeActivity.onCreate(HomeActivity.java:118)
at android.app.Activity.performCreate(Activity.java:8129)
at android.app.Activity.performCreate(Activity.java:8109)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1344)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3749)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3942)
at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:109)
at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:135)
at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:95)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2345)
at android.os.Handler.dispatchMessage(Handler.java:106)
at android.os.Looper.loopOnce(Looper.java:233)
PS: Code is working fine without Databinding, but when I try to use data binding it gives this error.

Make sure you have correctly implemented data binding in your project by following the instructions in the Android documentation: https://developer.android.com/topic/libraries/data-binding/start
In your XML layout file, remove the tag for your custom fragment and replace it with a tag. This will allow you to include the layout for your fragment within the DrawerLayout, without using a fragment tag.
In your Java code, use the FragmentManager to add your fragment to the DrawerLayout programmatically. This will allow you to use data binding with your custom fragment without causing conflicts.
Make sure you are using the correct data binding syntax in your XML layout file. For example, if you are using a ViewModel to manage the data for your fragment, you should use tags to define the variables in your layout and use the bind: namespace to access them in your layout.

Android how to create simple custom UI elements

I would like to create simple custom UI elements in Android like the ones from the screenshot:
The light bulb should always have the same size but the rectangle should vary in the width. One option of doing this is to use Canvas elements. But I would like to ask whether there is also an easier approach for doing this. Is it possible to maybe only do this by using XML files? I would like to use these UI elements then in the LayoutEditor like e.g. a TextView where I can adjust the widht and height either in the XML layout file or programmatically.
Any idea how I can do that in an easy way?
Update: I tried the suggested approach from Cheticamp and I have the following code inside my Fragment:
public class Test extends Fragment implements Runnable {
/*
Game variables
*/
public static final int DELAY_MILLIS = 100;
public static final int TIME_OF_A_LEVEL_IN_SECONDS = 90;
private int currentTimeLeftInTheLevel_MILLIS;
private Handler handler = new Handler();
private FragmentGameBinding binding;
private boolean viewHasBeenCreated = false;
public Test() {
// Required empty public constructor
}
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
binding = FragmentGameBinding.inflate(inflater, container, false);
getActivity().setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_LANDSCAPE);
container.getContext();
viewHasBeenCreated = true;
startRound();
return binding.getRoot();
}
public void startRound () {
currentTimeLeftInTheLevel_MILLIS =TIME_OF_A_LEVEL_IN_SECONDS * 1000;
updateScreen();
handler.postDelayed(this, 1000);
}
private void updateScreen() {
binding.textViewTimeLeftValue.setText("" + currentTimeLeftInTheLevel_MILLIS/1000);
/*
IMPORTANT PART: This should create a simple custom UI element but it creates an error
*/
View view = new View(getActivity());
view.setLayoutParams(new ViewGroup.LayoutParams(100, 100));
Drawable dr = ContextCompat.getDrawable(getActivity(),R.drawable.light_bulb_layer_list);
view.setBackground(dr);
ConstraintLayout constraintLayout = binding.constraintLayout;
ConstraintSet constraintSet = new ConstraintSet();
constraintSet.clone(constraintLayout);
constraintSet.connect(view.getId(),ConstraintSet.BOTTOM, ConstraintSet.PARENT_ID,ConstraintSet.BOTTOM,0);
constraintSet.connect(view.getId(),ConstraintSet.TOP,ConstraintSet.PARENT_ID ,ConstraintSet.TOP,0);
constraintSet.connect(view.getId(),ConstraintSet.LEFT,ConstraintSet.PARENT_ID ,ConstraintSet.LEFT,0);
constraintSet.connect(view.getId(),ConstraintSet.RIGHT,ConstraintSet.PARENT_ID ,ConstraintSet.RIGHT,0);
constraintSet.setHorizontalBias(view.getId(), 0.16f);
constraintSet.setVerticalBias(view.getId(), 0.26f);
constraintSet.applyTo(constraintLayout);
}
private void countDownTime(){
currentTimeLeftInTheLevel_MILLIS = currentTimeLeftInTheLevel_MILLIS -DELAY_MILLIS;
updateScreen();
}
#Override
public void run() {
if(viewHasBeenCreated) {
countDownTime();
}
}
}
Unfortunately, this code leads to a "java.lang.NullPointerException: Attempt to invoke virtual method 'boolean android.content.Context.isUiContext()' on a null object reference". It is thrown by the line View view = new View(getActivity());. Here is the complete error message:
E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.game, PID: 12176
java.lang.NullPointerException: Attempt to invoke virtual method 'boolean android.content.Context.isUiContext()' on a null object reference
at android.view.ViewConfiguration.get(ViewConfiguration.java:502)
at android.view.View.<init>(View.java:5317)
at com.example.game.Test.updateScreen(Test.java:72)
at com.example.game.Test.countDownTime(Test.java:91)
at com.example.game.Test.run(Test.java:97)
at android.os.Handler.handleCallback(Handler.java:938)
at android.os.Handler.dispatchMessage(Handler.java:99)
at android.os.Looper.loop(Looper.java:223)
at android.app.ActivityThread.main(ActivityThread.java:7656)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:592)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:947)
Any idea what the problem is? Without the custom UI element the Fragment works fine.

Use a TextView. The light bulb can be a left compound drawable. Set the background to a rounded rectangle shape drawable. This can all be specified in XML. See TextView.
This can also be accomplished with a LayerList drawable if text is not wanted. (The TextView solution also works without text - just set the text to "" or null.)
<layer-list>
<item>
<shape android:shape="rectangle">
<corners android:radius="5dp" />
<solid android:color="#FF9800" />
</shape>
</item>
<item
android:drawable="#drawable/ic_baseline_lightbulb_24"
android:width="48dp"
android:height="48dp"
android:gravity="left|center_vertical" />
</layer-list>
The layer list is set as a background to a simple View.
<View
android:layout_width="250dp"
android:layout_height="56dp"
android:layout_marginStart="16dp"
android:layout_marginTop="16dp"
android:layout_marginEnd="16dp"
android:layout_marginBottom="16dp"
android:background="#drawable/light_bulb_layer_list" />
To create the View in code:
View view = new View(context);
view.setLayoutParams(new ViewGroup.LayoutParams(width, height));
Drawable dr = ContextCompat.getDrawable(context,R.drawable.light_bulb_layer_list)
view.setBackground(dr);

Sure thing.
In this case a simple xml file like so would suffice. Let's name it something.xml inside the layout folder.
<LinearLayout ...>
<ImageView ...>
</LinearLayout>
In another layout xml file you may just:
<ConstraintLayout ...>
<include android:id="#+id/something"" layout="#layout/something" android:layout_width="70dp">
</ConstraintLayout>
See Reusing layouts
If you'd like to get a children you can always get them by using findViewById on your Activity or Fragment. If you're using Databinding or Viewbinding it just gets better: They'll appear as fields in the XBinding class that was generated out of the XML file
Hi VanessaF, going a little bit further with the clarifications you asked in the comments:
<include />
The <include /> tag is a special XML tag that we can use in our Android XML layout files to indicate that where we placed the <include/> we'd like it to be replaced by some other XML determined via the layout attribute inside the <include /> tag.
Here's an example:
Considering layout/example.xml
<TextView
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="Hello!"/>
And considering layout/parent.xml
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="vertical">
<Button .../>
<include layout="#layout/example"/>
<ImageView android:drawable="#drawable/ic_send"/>
</LinearLayout>
Whenever I use R.layout.parent somewhere (for example in setContent from the Activity the view that would get generated would be as follows:
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="vertical">
<Button .../>
<!-- PLEASE NOTICE THAT <include/> IS GONE -->
<!-- AND HAS BEEN REPLACED WITH THE CONTENTS the specified layout -->
<TextView
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="Hello!"/>
<ImageView android:drawable="#drawable/ic_send"/>
</LinearLayout>
Effectively re-using the layout without writing a full-blown custom view.
Notice: All attributes you specify inside the <include/> tag will effectively override the others specified inside the layout file. Let me illustrate this using an example:
Consider again layout/example.xml. Notice that this time the TextView will shrink to the size of the text both in height and width.
<TextView
android:text="Hello!"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
/>
And consider the parent: layout/parent.xml. Notice that I am setting the attributes android:layout_width and android:layout_height.
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="vertical">
<include
layout="#layout/example"
android:layout_width="match_parent"
android:layout_height="match_parent"
/>
</LinearLayout>
In this case, when Android replaces <include/> for the contents of #layout/example it will also set android:layout_width="match_parent" and android:layout_height="match_parent" because they were specified on the <include/> tag effectively ignoring the original attributes set inside layout/example.xml (which were set to "wrap_content")

I suggest reading Custom View Components from the official Android documentation. In fact, you should become very familiar with this documentation for everything you do with Android apps.

java.lang.ClassCastException on CardView only when SearchView is present in layout

I have a problem regarding android layout that I am not able to resolve. I have a fragment with a layout that contains lots of elements and in particular this CardView element
<androidx.cardview.widget.CardView
android:id="#+id/search_button"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginStart="20dp"
android:layout_marginTop="10dp"
android:layout_marginEnd="20dp"
app:cardBackgroundColor="#color/chartMax"
app:cardCornerRadius="20dp"
app:cardElevation="2dp">
<TextView
android:layout_width="match_parent"
android:layout_height="match_parent"
android:padding="5dp"
android:text="Cerca"
android:textAlignment="center"
android:textColor="#fff"
android:textSize="23sp" />
</androidx.cardview.widget.CardView>
I access this element in fragment
private lateinit var searchButton: CardView
searchButton = view.search_button
and everything works fine, I can use it normally.
The problems start when I add a normal SearchView to the fragment.
<androidx.appcompat.widget.SearchView
android:layout_width="wrap_content"
android:layout_height="wrap_content">
When I run the application it crash on this instruction
searchButton = view.search_button
This is the stacktrace
E/AndroidRuntime: FATAL EXCEPTION: main
Process: io.atoka.mobile, PID: 31291
java.lang.ClassCastException: androidx.appcompat.widget.AppCompatImageView cannot be cast to androidx.cardview.widget.CardView
at io.atoka.mobile.fragments.SearchFragment.getViewElements(SearchFragment.kt:57)
at io.atoka.mobile.fragments.SearchFragment.onCreateView(SearchFragment.kt:73)
at androidx.fragment.app.Fragment.performCreateView(Fragment.java:2439)
at androidx.fragment.app.FragmentManagerImpl.moveToState(FragmentManager.java:1460)
at androidx.fragment.app.FragmentManagerImpl.moveFragmentToExpectedState(FragmentManager.java:1784)
at androidx.fragment.app.FragmentManagerImpl.moveToState(FragmentManager.java:1852)
at androidx.fragment.app.BackStackRecord.executeOps(BackStackRecord.java:802)
at androidx.fragment.app.FragmentManagerImpl.executeOps(FragmentManager.java:2625)
at androidx.fragment.app.FragmentManagerImpl.executeOpsTogether(FragmentManager.java:2411)
at androidx.fragment.app.FragmentManagerImpl.removeRedundantOperationsAndExecute(FragmentManager.java:2366)
at androidx.fragment.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:2273)
at androidx.fragment.app.FragmentManagerImpl.dispatchStateChange(FragmentManager.java:3273)
at androidx.fragment.app.FragmentManagerImpl.dispatchActivityCreated(FragmentManager.java:3229)
at androidx.fragment.app.FragmentController.dispatchActivityCreated(FragmentController.java:201)
at androidx.fragment.app.FragmentActivity.onStart(FragmentActivity.java:620)
at androidx.appcompat.app.AppCompatActivity.onStart(AppCompatActivity.java:178)
at android.app.Instrumentation.callActivityOnStart(Instrumentation.java:1391)
at android.app.Activity.performStart(Activity.java:7157)
at android.app.ActivityThread.handleStartActivity(ActivityThread.java:2937)
at android.app.servertransaction.TransactionExecutor.performLifecycleSequence(TransactionExecutor.java:180)
at android.app.servertransaction.TransactionExecutor.cycleToPath(TransactionExecutor.java:165)
at android.app.servertransaction.TransactionExecutor.executeLifecycleState(TransactionExecutor.java:142)
at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:70)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1808)
at android.os.Handler.dispatchMessage(Handler.java:106)
at android.os.Looper.loop(Looper.java:193)
at android.app.ActivityThread.main(ActivityThread.java:6669)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:493)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:858)
like if my CardView was an AppCompatImageView that is not. When I remove the SearchView the application works normally.
Anyone knows the solution? Is there any bug regarding this particular case?
Thank you

Your problem occurs because of the name you gave to your cardview
search_button is already define in default androidx.appcompat.widget.SearchView class as below:
final ImageView mSearchButton;
mSearchButton = findViewById(R.id.search_button);
so when you trying to get it from binding it's getting conflicted with the SearchView class search_button parameter
try to change the name of your cardview to something else then try,

NullPointerException error while adding fragment

I am having problem with implementing barcodefragmentlibv2 into my project. As a name says and from previous experience I know that I can add it into fragment. However, I am still getting NullPointerException error when I am trying to get this fragment to work with my app.
This is a part of a code responsible for barcode fragment:
import android.support.v4.app.Fragment;
//...
public class CameraFragment extends Fragment implements IScanResultHandler {
BarcodeFragment fragment;
public static CameraFragment newInstance() {
CameraFragment fragment = new CameraFragment();
return fragment;
}
public CameraFragment() {
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.include_qrfragment, container, false);
fragment = (BarcodeFragment)getActivity().getSupportFragmentManager().findFragmentById(R.id.sample);
fragment.setScanResultHandler(this);
return view;
}
//...
}
Error appears in line:
fragment.setScanResultHandler(this);
I've also tried replacing
getActivity().getSupportFragmentManager().findFragmentById(R.id.sample);
to
getFragmentManager().findFragmentById(R.id.sample);
but the result is this same.
Below are layout files:
fragment_camera
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent"
android:layout_height="match_parent" tools:context=".CameraFragment">
<include
android:layout_width="match_parent"
android:layout_height="match_parent"
layout="#layout/include_qrfragment" />
<TextView
android:id="#+id/status_view"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="bottom|center_horizontal"
android:layout_margin="15dp"
android:background="#99FFFFFF"
android:gravity="center"
android:padding="10dp"
android:text="#string/msg_default_status"
android:textAppearance="?android:attr/textAppearanceMedium" />
<View
android:layout_width="match_parent"
android:layout_height="match_parent" />
</FrameLayout>
include_qrfragment
<?xml version="1.0" encoding="utf-8"?>
<fragment xmlns:android="http://schemas.android.com/apk/res/android"
android:id="#+id/sample"
android:name="com.abhi.barcode.frag.libv2.BarcodeFragment"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_alignParentTop="true"
android:layout_centerHorizontal="true" />
At the beginning I've mentioned that from my own experience that this is possible. The truth is that I've built app utilizing this feature some time ago using eclipse and now I am using Android Studio - maybe there is a problem?
EDIT 1:
This is the whole error's stack trace:
06-22 23:05:56.804 30578-30578/myapp.com.test E/AndroidRuntime﹕ FATAL EXCEPTION: main
java.lang.NullPointerException
at myapp.com.test.CameraFragment.onCreateView(CameraFragment.java:34)
at android.support.v4.app.Fragment.performCreateView(Fragment.java:1789)
at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:955)
at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1138)
at android.support.v4.app.BackStackRecord.run(BackStackRecord.java:740)
at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1501)
at android.support.v4.app.FragmentManagerImpl$1.run(FragmentManager.java:458)
at android.os.Handler.handleCallback(Handler.java:587)
at android.os.Handler.dispatchMessage(Handler.java:92)
at android.os.Looper.loop(Looper.java:130)
at android.app.ActivityThread.main(ActivityThread.java:3683)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:507)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
at dalvik.system.NativeStart.main(Native Method)

The problem seems to lie in this line:
fragment = (BarcodeFragment)getActivity().getSupportFragmentManager().findFragmentById(R.id.sample);
Your fragment is not yet appended to the activity as getActivity() is null at this point.
Perhaps you should move that particular code to onActivityCreated

You should only inflate the layout at the CreateView, like this:
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
return inflater.inflate(R.layout.your_layout, null);
}
The rest of your code, you should put it in the onActivityCreated as #waqaslam said.
You are getting a null pointer because there is no layout inflated yet.

I have read your responses, and now I am assuming you have tried or moved code of getActivity().getSupportFragmentManager().findFragmentById into onActivityCreated.
The only suspect I see without loading up your project is the GUI ID itself. You named it sample or R.id.sample, which is a suspect in some projects. It is possible that you have another UI element having the same name/ID. If so, that UI cannot be converted to a fragment. My suggestion is to change the name of the ID (with unique name), and use it with findFragmentById().

Using <include> tag with ?attr/myAttr

I'm trying to include different layouts in my View depending on the parent Theme.
Following the idea:
attrs.xml
<attr name="themeLayout" format="reference" />
styles.xml
<style name="AppTheme" parent="Theme.AppCompat.Light.DarkActionBar">
<item name="themeLayout">#layout/layout_a</item>
</style>
<style name="AppThemeSecond" parent="Theme.AppCompat.Light.DarkActionBar">
<item name="themeLayout">#layout/layout_b</item>
</style>
activity.xml
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".MainActivity">
<include layout="?attr/themeLayout" />
</RelativeLayout>
When I run the Code above I'll get the following Exception:
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.my.package/com.my.package.MainActivity}: android.view.InflateException: You must specifiy a valid layout reference. The layout ID ?attr/themeLayout is not valid.
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2325)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2387)
at android.app.ActivityThread.access$800(ActivityThread.java:151)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1303)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5254)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)
Caused by: android.view.InflateException: You must specifiy a valid layout reference. The layout ID ?attr/themeLayout is not valid.
at android.view.LayoutInflater.parseInclude(LayoutInflater.java:866)
What am I doing wrong? Is it possible to do this at all?
Note #1: I set the Theme of my MainActivity to android:theme="#style/AppTheme"
Note #2: In the Design-View of the Layout Editor everything works as expected. If I switch the Theme, the include gets updated properly.
See the following Screenshots as well:

Unfortunately this is not possible but I really like the idea. I have tracked the flow of LayoutInflater and it requieres the layout attribute to be TypedValue.TYPE_REFERENCE which means ?attr is not allowed. They even left a comment in the method to explain.
public int getAttributeResourceValue(int idx, int defaultValue) {
int t = nativeGetAttributeDataType(mParseState, idx);
// Note: don't attempt to convert any other types, because
// we want to count on aapt doing the conversion for us.
if (t == TypedValue.TYPE_REFERENCE) {
return nativeGetAttributeData(mParseState, idx);
}
return defaultValue;
}
android.content.res.XmlBlock.java:385
Basically you have done nothing wrong -- the inflation in Preview works differently which caused the confusion.

Since Lamorak explained everything in detail in his "in-depth" answer I guess it's save to say that there isn't any solution with the <include /> tag for your problem.
So following a different approach that worked in my test project:
#1 - Replace <include /> with <ViewStub />
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".MainActivity">
<ViewStub
android:id="#+id/myStub"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:inflatedId="#+id/myInflatedStub"
android:layout="?attr/themeLayout" />
</RelativeLayout>
#2 - Inflate the ViewStub
ViewStub myStub = (ViewStub) findViewById(R.id.myStub);
myStub.inflate();
Any drawbacks with this method? Well you won't see the ViewStub-Layout in your Design-Tab and using the <merge /> tag won't work.

After some research, I found this problem-"has been fixed in Android23. But bellows, exception will be thrown.