Android data binding is not working with <merge> attributes

Question

I'm trying to use databinding with custom views (a possible usage George Mount showed here).

One can't imagine building compound views without <merge> tag. However, in this situation databinding fails:

MyCompoundView class:

public class MyCompoundView extends RelativeLayout {  MyCompoundViewBinding binding;  public MyCompoundView (Context context, AttributeSet attrs) {     super(context, attrs);     init(context); }  private void init(Context context){     LayoutInflater inflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);     binding = MyCompoundViewBinding.inflate(inflater, this, true); } 

my_compound_view.xml: by app:isGone="@{!data.isViewVisible}" i hoped to control the visibility of the whole compound view

<?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>         <variable name="data" type="com.example.MyViewModel"/>     </data>      <merge         android:layout_width="wrap_content"         android:layout_height="wrap_content"         app:isGone="@{!data.isViewVisible}">          <ImageView             android:id="@+id/image_image"             android:layout_width="60dp"             android:layout_height="60dp"             app:imageUrl="@{data.imagePhotoUrl}"/>           <!-- tons of other views-->      </merge>  </layout> 

The compiler errors:

Error:(13) No resource identifier found for attribute 'isGone' in package 'com.example' Error:(17, 21) No resource type specified (at 'isGone' with value '@{!data.isViewVisible}'). 

I have all needed @BindingAdapter methods. Now I inherit the view from FrameLayout and use <RelativeLayout> instead of <merge> - and it works. But I have extra nested layout.

Question: merge attrs are ignored. Is there any way to workaround that?

Android Studio 1.5.1 stable

Gradle plugin com.android.tools.build:gradle:1.5.0

Answer 1

There is no merge object after inflation, so there is nothing to assign values to with a merge tag. I can't think of any binding tag that will work on merge.

You can assign the tag to the root element and use the BindingAdapter to do what you want.

<layout     xmlns:android="http://schemas.android.com/apk/res/android"     xmlns:app="http://schemas.android.com/apk/res-auto"     >      <data>         <variable name="data" type="com.example.MyViewModel"/>     </data>      <merge         android:layout_width="wrap_content"         android:layout_height="wrap_content">         <ImageView             app:isGone="@{!data.isViewVisible}"             android:id="@+id/image_image"             android:layout_width="60dp"             android:layout_height="60dp"             app:imageUrl="@{data.imagePhotoUrl}"/>          <!-- tons of other views-->     </merge> </layout> 

If you want to do something with the Binding class itself, you can use the DataBindingUtil to find the object from the View.

@BindingAdapter("isGone") public static void setGone(View view, boolean isGone) {     ViewDataBinding binding = DataBindingUtil.findBinding(view);     //... do what you want with the binding. } 

Answer 2

Actually you can use <merge> tag inside <include> and do data binding.

Ex:

incl_button.xml

<layout>     <merge xmlns:android="http://schemas.android.com/apk/res/android">          <Button android:id="btn"              android:layout_width="wrap_content"              android:layout_height="wrap_content"              android:text="Click"          />      </merge> </layout> 

fragment_example.xml

<layout xmlns:android="http://schemas.android.com/apk/res/android">      <LinearLayout         android:layout_width="match_parent"         android:layout_height="match_parent">          <include             layout="@layout/incl_button"             android:id="@+id/layout_btn" />      </LinearLayout> </layout> 

ExampleFragment.kt

binding.layoutBtn.btn.setOnClickListener{    //... }