android data binding with a custom view

Question

The Android data binding guide discusses binding values within an activity or fragment, but is there a way to perform data binding with a custom view?

I would like to do something like:

<LinearLayout     android:layout_width="match_parent"     android:layout_height="match_parent">      <com.mypath.MyCustomView         android:id="@+id/my_view"         android:layout_width="match_parent"         android:layout_height="40dp"/>  </LinearLayout> 

with my_custom_view.xml:

<layout>  <data>     <variable         name="myViewModel"         type="com.mypath.MyViewModelObject" /> </data>  <LinearLayout     android:layout_width="match_parent"     android:layout_height="match_parent">      <TextView         android:layout_width="wrap_content"         android:layout_height="wrap_content"         android:text="@{myViewModel.myText}" />  </LinearLayout>  </layout> 

While it appears possible to do this by setting custom attributes on the custom view, this would quickly become cumbersome if there's a lot of values to bind.

Is there a good way to accomplish what I'm trying to do?

Answer 1

In your Custom View, inflate layout however you normally would and provide a setter for the attribute you want to set:

private MyCustomViewBinding mBinding; public MyCustomView(...) {     ...     LayoutInflater inflater = (LayoutInflater)         context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);     mBinding = MyCustomViewBinding.inflate(inflater); }  public void setMyViewModel(MyViewModelObject obj) {     mBinding.setMyViewModel(obj); } 

Then in the layout you use it in:

<layout xmlns...>     <data>         <variable             name="myViewModel"             type="com.mypath.MyViewModelObject" />     </data>      <LinearLayout         android:layout_width="match_parent"         android:layout_height="match_parent">          <com.mypath.MyCustomView             android:id="@+id/my_view"             app:myViewModel="@{myViewModel}"             android:layout_width="match_parent"             android:layout_height="40dp"/>      </LinearLayout> </layout> 

In the above, an automatic binding attribute is created for app:myViewModel because there is a setter with the name setMyViewModel.

Answer 2

First, don't do this if this custom view is already being <include> in another layout, such as activity etc. You'll just get an exception about the tag being unexpected value. The data binding already ran the binding on it, so you're set.

Did you try using onFinishInflate to run the bind? (Kotlin example)

override fun onFinishInflate() {     super.onFinishInflate()     this.dataBinding = MyCustomBinding.bind(this) } 

Keep in mind that if you use the binding in your view, it won't be able to be created programmatically, at least it would be very convoluted to support both even if you can.