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Identifiers must have user defined types from the XML file, databinding with observablefield

I want my view visibility to be dependent on condition behaviour so I am using ObservableField and with databinding trying to change view visibility but getting issue like "Identifiers must have user defined types from the XML file. InputType is missing it"
Code:
Kotlin File
var showView: ObservableField<Boolean>? = ObservableField(false)
//API call response
showView.set(true)
Layout File:
<TextView
android:id="#+id/textview"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:visibility="#{viewModel.showView ? View.VISIBLE : View.GONE}"/>
How to apply databinding with Observablefield of type boolean? I have used it for string text also and it's working but not working with boolean conditional statement.

I am not sure if that's the case here, but this error message is usually displayed when you reference a type in your binding expressions that hasn't been declared in the <data> section of your layout. The same way you declare the View type as an import, you should declare the type InputType.
<data>
<!-- Maybe an import for InputType is missing here? -->
<import type="android.view.View" />
<variable
name="viewModel"
type="com.yourpackage.YourViewModel"/>
</data>

Android DataBinding & MVVM - Using same name for layout files in different layout folders

I've been developing an app with data binding & MVVM.
I'm trying to use an alternative layout for my app on landscape mode. I have:
layout/fragment_content.xml
layout-land/fragment_content.xml
Both layouts have same views with different look, and get feeds from same view models, like this:
<layout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto">
<data class="MyBinding">
<variable
name="viewModel"
type="com.myapp.package.viewModel.VMFirst"/>
<variable
name="controlModel"
type="com.myapp.package.viewModel.VMSecond"/>
</data>
<DIFFERENT CONTENT HERE>
All the views and id's exist in both layouts.
Well, problem is, it doesn't compile, error is simply "cannot find symbol method getViewModel" and getter for the other variable.
What I tried so far:
Using layout and layout-land folders ( Failed, error is explained above )
Using layout aliases Use Layout Aliases which I found here Issue 199344: Data binding does not work with layout aliases. I didn't change anything in xml files while trying this approach. This also failed, error is Could not write to com.myapp.package.databinding.MyBinding
Is it not possible to use data binding data tag in multiple layout files ? What should I use to use different layouts for different states while using data binding ? Thanks !
Edit: deleting class="MyBinding" did not change errors.

If anyone searches for this question, after 2 years I tried to do the same, and I saw it's working all fine now.
I created a layout file activity_main under layout and layout_sw600dp. Here's the layout under layout resources:
<layout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools">
<variable
name="small_variable"
type="Integer"/>
<androidx.constraintlayout.widget.ConstraintLayout
android:id="#+id/myRoot"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".MainActivity">
<View
android:id="#+id/small_square"
android:layout_width="60dp"
android:layout_height="60dp"
android:background="#android:color/holo_blue_bright"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent" />
</androidx.constraintlayout.widget.ConstraintLayout>
</layout>
This one is the layout under layout_sw600dp folder:
<?xml version="1.0" encoding="utf-8"?>
<layout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools">
<variable
name="big_variable"
type="Long"/>
<androidx.constraintlayout.widget.ConstraintLayout
android:id="#+id/myRoot"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".MainActivity">
<View
android:id="#+id/big_square"
android:layout_width="60dp"
android:layout_height="60dp"
android:background="#android:color/holo_blue_bright"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent" />
</androidx.constraintlayout.widget.ConstraintLayout>
</layout>
Both has a view but it has different id in each: small_square and big_square.
I run the project on phone & tablet. Here are my findings:
DataBinding creates an implementation that contains ALL views and variables under all layout files of same name in different layout folders.
Views that exists in all layouts are not nullable, all others are nullable. In above XML's, myRoot is not a nullable view when using binding from Kotlin, while big_square and small_square are nullable views. Variables are nullable whether or not they exists in all layouts ( which is expected behaviour ).
You cannot name binding classes different in each file. It has to be same ( MainBinding in above examples, or if you don't define it LayoutResourceName + Binding by default ).
Names for views and variables on binding implementation are camel case. So my small_variable & small_square was binding.smallVariable and binding.smallSquare on code side.
With Kotlin, you can just use views like binding.bigSquare?.operation, which is great that you don't need to check if it's tablet or phone or view is null or not beforehand.
Just a tip, you can assign binding fields even if layout that they are in won't be used. You can still say binding.smallVariable = 3 on code and it'll do the assignment and save the value. I think it's good to be careful.

I heavily use MVVM in my apps and am also building a library around it.
I follow the convention that there is a single ViewModel in every XML. Also, the name of the viewmodel variable is same in all XMLs.
So, in your case, you can create another ViewModel class that contains VMFirst and VMSecond.
public class ParentVM {
VMFirst first;
VMSecond second;
}
Both the XMLs (portrait and landscape) will have same names, say activity_main.xml.
<layout>
<data>
<variable
type="ParentViewModel"
name="vm"/>
</data>
Then no check is required in MainActivity code.
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
ViewDataBinding binding = DataBindingUtil.setContentView(this, R.layout.activity_main);
binding.setVariable(BR.vm, new ParentViewModel());
}
This works.
Advantages of single ViewModel
In fact, because I follow same variable name throughout all xmls, I am able to include the binding logic in a base class MvvmActivity itself. So, all my activities look like:
public class MainActivity extends MvvmActivity {
#NonNull
#Override
protected ViewModel createViewModel() {
return new MainViewModel();
}
#Override
protected int getLayoutId() {
return R.layout.activity_main;
}
}
MvvmActivity implementation: MvvmActivity.java
Another advantage of keeping a constant data binding variable is that you can setup RecyclerView or ViewPager adapters in XML itself. See Setup RecyclerView from XML for more details.

By default, a Binding class will be generated based on the name of the layout file, converting it to Pascal case and suffixing "Binding" to it. The above layout file was main_activity.xml so the generate class was MainActivityBinding. --Binding Data
and generated at compile time.
so, select different layout by java code.
layout/
R.layout.activity_main
R.layout.activity_main_tablet
values/
<bool name="is_mobile">true</bool>
<bool name="is_tablet">false</bool>
values-w820dp/
<bool name="is_mobile">false</bool>
<bool name="is_tablet">true</bool>
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
if(getResources().getBoolean(R.bool.is_mobile)) {
ActivityMainBinding binding = DataBindingUtil.setContentView(this, R.layout.activity_main);
} else {
ActivityMainTabletBinding binding = DataBindingUtil.setContentView(this, R.layout.activity_main_tablet);
}
}

set android:textAppearance with DataBinding

I am trying to set android:textAppearance with use of DataBinding , but it is not allowing me to use ?android:attr/textAppearanceLarge with ternary operator.
android:textAppearance="#{position==1 ? ?android:attr/textAppearanceLarge : ?android:attr/textAppearanceMedium}"
It is showing me compile time error <expr> expected, got '?'.
Does there any other way to use this with DataBinding?

You cannot use it directly, however here's trick I use in such cases. Create own styles using textAppearanceLarge and textAppearanceMedium as parents and then set these styles instead:
First create Foo style:
<style name="Foo" parent="TextAppearance.AppCompat.Large">
... [whatever you need to set or override ] ...
</style>
and do the same for for FooMedium. Then edit your layout file as shown below. Note you must import project's R class in <data> block first:
<data>
<import type="<your-package-id>.R"
</data>
Finally apply the appearance as you formerly wanted:
android:textAppearance="#{ position==1 ? R.style.Foo : R.style.FooMedium }"

You can use android.R.attr package instead of the ?android:attr
<?xml version="1.0" encoding="utf-8"?>
<layout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools">
<data>
<import type="android.R.attr"/>
</data>
<LinearLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical">
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="hello world"
android:textAppearance='#{age==1 ? android.R.attr.textAppearanceLarge : android.R.attr.textAppearanceMedium}'
tools:textAppearance="?android:textAppearanceLarge"
/>
</LinearLayout>
</layout>

Looks like DataBinding treats android:textAppearance in some special way (at least on Android Studio 3.2.1).
For example the following expression according to this should be fine, but it is not.
The following expression is being accepted by the compiler but it is doing nothing:
android:textAppearance="#{R.style.MyStyleTest}"
I have tried several options and only vanilla way worked for me:
android:textAppearance="#style/MyStyleTest"
As a Solution
I would suggest to use #BindingAdapter and perform all the logic there.
For example if you would like to work with references to attributes (which looks like: ?attr/...) use the following approach:
layout.xml
<TextView
...
bind:textAppearanceAttr="#{position==1 ? android.R.attr.textAppearanceLarge: android.R.attr.textAppearanceMedium}"
/>
sources.kt
#BindingAdapter(value = ["textAppearanceAttr"])
fun textAppearanceAttr(textView: TextView, #AttrRes attrRef: Int?) {
attrRef?.also {
val attrs = textView.context.obtainStyledAttributes(intArrayOf(attrRef))
val styleRes = attrs.getResourceId(0, -1)
attrs.recycle()
if (styleRes != -1) {
TextViewCompat.setTextAppearance(textView, styleRes)
}
}
}
or in case of style resource ids (#style/...):
layout.xml
bind:textAppearanceStyle="#{position==1 ? R.style.MyStyleTest1: R.style.MyStyleTest2}"
sources.kt
#BindingAdapter(value = ["textAppearanceStyle"])
fun textAppearanceStyle(textView: TextView, #StyleRes style: Int?) {
style?.also { TextViewCompat.setTextAppearance(textView, it) }
}

You should use textStyle instead of textAppearance,
Try to use code give below:
android:textStyle="#{position==1 ? #style/TextAppearance.Material.Large :#style/TextAppearance.Material.Medium}"
For more reference use below image

Android dataBinding - #BindingAdapter custom app namespace being ignored

I have created a custom bindingAdapter in android and when i pass in the color i want the color to change, this is actually for a test im working on just to make sure it works. Here is the code:
here is my view Model for the data binding:
public class User {
public ObservableInt visible;
public User(int visible) {
this.visible=new ObservableInt(visible);
}
#BindingAdapter({"app:bindColor"}) //notice the bindColor custom attribute
public static void setTextColor(TextView view,String color) {
if("green".equals(color))
view.setTextColor(Color.parseColor("#63f421"));
}
}
Now in my xml file which is binded to this model im expected to pass in a color so that the setTextColor method can use it:
<?xml version="1.0" encoding="utf-8"?>
<layout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto">
<data class="MainActivityBinder">
<variable name="user" type="com.example.android.floatingactionbuttonbasic.User"/>
</data>
<LinearLayout
android:orientation="vertical"
android:layout_width="match_parent"
android:layout_height="match_parent">
<TextView android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:id="#+id/tv_one"
android:text="my first textview"/>
<TextView android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:id="#+id/tv_two"
android:text="my second textview"
android:visibility="#{user.visible}"
app:bindColor="#{'green'}" //see im passing in the green string here
android:textColor="#android:color/holo_green_dark"/>
</LinearLayout>
</layout>
I am getting the error at runtime time of:
Error:(27, 65) error: package com.example.android.floatingactionbuttonbasic.databinding does not exist
Warning:Application namespace for attribute app:bindColor will be ignored.
Error:(24, 33) Identifiers must have user defined types from the XML file. een is missing it
Error:Execution failed for task ':Application:compileDebugJavaWithJavac'.
> java.lang.RuntimeException: Found data binding errors.
if i take out the bindingAdapter stuff it works perfectly with the other databinding stuff. Its just this custom binding thats not working. My project is titled floatingactionbuttonbasic btw.

I was able to get this to work. The issue was how i was passing in the string. It should have the `` around it.
app:bindColor="#{`green`}"
you can also do this :
app:bindColor='#{"green"}'
But what seems to not be allowed is this notation:
app:bindColor="#{'green'}"
i wrote a blog about it to help others if interested.

Possibility to add parameters in button xml?

I currently have an activity with some buttons.
In my xml, buttons are defined like this:
<ImageButton (...) android:onClick="GoToPageX"/>
and I have in my activity:
public void GotoPageX() {
startActivity(new Intent(this, PageX.class));
finish();
}
The problem is that I have hundreds of buttons and do not want to write
<ImageButton (...) android:onClick="GoToPage1"/>
<ImageButton (...) android:onClick="GoToPage2"/>
<ImageButton (...) android:onClick="GoToPage3"/>
...
<ImageButton (...) android:onClick="GoToPage100"/>
and all the scripts.
I am now using
public void GotoPage( int i) {
startActivity(new Intent(getBaseContext(), activities.get(i)));
finish();
}
and would like to give the parameter i from the xml, is that possible?
Thank a lot for any help.

It is not directly possible. However, maybe you could use android:tag to get your parameter.
<ImageButton (...) android:onClick="goToPage" android:tag="25"/>
public void goToPage(View v) {
String pageNumber = v.getTag().toString();
/* ... */
}

You could also do this by enabling data binding and using a lambda expression for the onClick value. This way is especially useful if you plan to use multiple inputs of different types. Here's an example of a simple MainActivity.xml in which this strategy is used.
<?xml version="1.0" encoding="utf-8"?>
<layout xmlns:android="http://schemas.android.com/apk/res/android">
<data>
<variable name="main" type="com.example.android.myapp.MainActivity" />
</data>
<LinearLayout android:orientation="vertical"
android:layout_width="match_parent"
android:layout_height="match_parent">
<ImageButton (...) android:onClick='#{() -> main.GotoPage(1,"one")}'/>
<ImageButton (...) android:onClick='#{() -> main.GotoPage(2,"two")}'/>
<ImageButton (...) android:onClick='#{() -> main.GotoPage(3,"three")}'/>
...
<ImageButton (...) android:onClick='#{() -> main.GotoPage(100,"one hundred")}'/>
</LinearLayout>
</layout>
and in MainActivity.java
public void GotoPage(int i, String otherVariable) {
/** code using i and otherVariable **/
}
UPDATE: For those who don't know how to set up data binding, I will explain it here so you don't have to google around for it. First, enable dataBinding in the build.gradle file:
android {
...
dataBinding {
enabled = true
}
...
}
Also, make sure jcenter() is in your repositories.
Then, go to the XML of the layout where onClick will be used and wrap its layout in a layout tag with a data section like this:
<?xml version="1.0" encoding="utf-8"?>
<layout xmlns:android="http://schemas.android.com/apk/res/android">
<data>
<variable name="main" type="com.example.android.yourapp.MainActivity" />
</data>
<YourLayout>
...
</YourLayout>
</layout>
For the variable tag's type parameter, you need to put the class that will contain the function which onClick points to. In this example, I will use the main activity class, which is named MainActivity in my test project.
After you have your layout wrapped in a layout tag like in the example above, clean the project in Android Studio. You may also need to invalidate cache/restart or close and reopen Android Studio.
Next, if the the layout with onClick you are trying to set up data binding for is the same layout set by setContentView in your main activity class, open the file that contains your main activity class. If the layout with onClick you are trying to set up data binding for is inflated programmatically in a different file, open the file in which the layout is inflated instead.
Add these imports to that file:
import com.example.android.yourapp.databinding.YourLayoutBinding;
import android.databinding.DataBindingUtil;
That first class you are importing is generated when you clean the project (and possibly have to invalidate cache/restart) and is automatically named after the XML file you added the layout wrapper to. If the layout file is named your_layout.xml, the import class will be named YourLayoutBinding. The exact import path will depend on your app name and structure, but it will always be within a databinding parent class.
The next step depends on whether the layout you are adding data binding to is set with setContentView or is inflated with inflate. Both versions of the following step make use of the method setMain. The setMain method is automatically generated and named using the value of the name parameter in the layout wrapper we added. Since we put name="main", the method is called setMain.
If the layout you are adding data binding to is the same layout set by setContentView find the line in your main activity class that looks like setContentView(R.layout.your_layout); and change it to use DataBindingUtil.setContentView instead of setContentView, adding this as its first argument. Use binding.setMain to point the layout's main variable to the current activity.
YourLayoutBinding binding = DataBindingUtil.setContentView(this, R.layout.your_layout);
binding.setMain(this);
If the layout you are adding data binding to is not set by setContentView but rather inflated go to where it is inflated in your code. It should look something like this:
return inflater.inflate(R.layout.your_layout, container, false);
Modify it to use DataBindingUtil.inflate, adding the previous inflater as its first argument. Use binding.setMain to point the layout's main variable to the main activity, and use binding.getRoot() to get the view. It should end up like this:
YourLayoutBinding binding = DataBindingUtil.inflate(inflater, R.layout.your_layout, container, false);
binding.setMain((MainActivity) getActivity());
return binding.getRoot();
Now the data binding is ready to use. Add a function for onClick to point to within your main activity class.
public void exampleFunction(int number, String text) {
System.out.println("Number: " + number + ", Text: " + text);
}
You can call it from the layout you added data binding to using a lambda expression. This example function doesn't require a View, so it can be used like this:
<Button android:id="#+id/buttonID"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:textSize="26sp"
android:text="Test"
android:onClick='#{() -> main.exampleFunction(123, "test")}'/>
Make sure to use single quotes around the value for onClick if you plan on using a String input.
If you do need to pass the button's view to your function, simply add a View parameter to your function's required arguments and use a lambda expression like this instead:
<Button android:id="#+id/buttonID"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:textSize="26sp"
android:text="Test"
android:onClick='#{(view) -> main.exampleFunction(view, 123, "test")}'/>

If you will create some layout element in xml you can use there
<ImageButton
android:id="#+id/some_id_value" />
where some_id_value is kind of unique string which will be translate into id which is kept in R.java (better for you- don't change anything there) than in code you can get that id by using
R.id.some_id_value
read a little bit there that's really basics.

You can set Tags for a view. Tags are basically a way for views to have memories.
xml:
<ImageButton
...Other Parameters...
android:id="#+id/Button2"
android:tag="2"
android:onClick="GoToPageX"/>
<ImageButton
...Other Parameters...
android:id="#+id/Button3"
android:tag="3"
android:onClick="GoToPageX"/>
The line android:tag="2" set a tag value of 2(string data type) to Button2
Java file:
General Case:
Inside GoToPageX(View v) function,
use v.getTag() to get the tag value of corresponding view(From which ever view the method was called).
Your case:
Add the method as follows
public void GoToPageX(View v){
int i = Integer.parseInt(v.getTag()); //parseInt converts string to integer
startActivity(new Intent(getBaseContext(), activities.get(i)));
finish();
}