How to bind method on RadioGroup on checkChanged event with data-binding

Question

I was searching over the internet for how to perform the new cool android data-binding over the RadioGroup and I didn't find a single blog post about it.

Its a simple scenario, based on the radio button selected, I want to attach a callback event using android data binding. I don't find any method on the xml part which allows me to define a callback.

Like here is my RadioGroup:

      <RadioGroup             android:id="@+id/split_type_radio"             android:layout_width="match_parent"             android:layout_height="wrap_content"             android:layout_marginBottom="10dp"             android:checkedButton="@+id/split_type_equal"             android:gravity="center"             <!-- which tag ? -->             android:orientation="horizontal">             ...         </RadioGroup> 

How do I attach a handler method which will be called on RadioGroup's checkChnged event will fire using data-binding?

I have tried using onClick (don't know if it is the same) in layout file and defining method in the Activity and located it using this in the layout file:

   <variable         name="handler"         type="com.example.MainActivity"/>    ...    <RadioGroup         android:onClick="handler.onCustomCheckChanged"         .. > 

And defined method onCustomCheckChanged like this:

public void onCustomCheckChanged(RadioGroup radio, int id) {      // ... } 

But, it gives me the compilation error:

Error:(58, 36) Listener class android.view.View.OnClickListener with method onClick did not match signature of any method handler.onCustomCheckChanged

I have seen many blogs mentioning it is possible with RadioGroup but non of them really say how. How can I handle this with data-binding ?

Answer 1

After digging to the bunch of methods, I found this question on SO which helped me understand how to bind single methods of listeners.

Here is what to do with RadioGroup:

In RadioGroup listener you have a method onCheckedChanged(RadioGroup g, int id). So you can directly bound that method to your handler or your activity by passing an instance of it as a variable in layout file and calling a method with the same signature.

So call on layout file like this:

  <RadioGroup         android:id="@+id/split_type_radio"         android:layout_width="match_parent"         android:layout_height="wrap_content"         android:layout_marginBottom="10dp"         android:checkedButton="@+id/split_type_equal"         android:gravity="center"         android:onCheckedChanged="@{handler.onSplitTypeChanged}"         android:orientation="horizontal">         ...     </RadioGroup> 

And in my activity or handler, I need to simply provide the method with same name and signature like this:

public void onSplitTypeChanged(RadioGroup radioGroup,int id) {   // ... } 

Just make sure method is public.

NOTE: This works for any (most of, I have not tried all) listener methods. Like for EditText you can provide android:onTextChanged and so on.

Answer 2

I am using a string, and in this case I have bindable based on viewModel.getCommuteType() viewModel.setCommuteType(String)

<RadioGroup android:orientation="horizontal" android:layout_width="wrap_content" android:layout_height="wrap_content">  <RadioButton     android:checked="@{viewModel.commuteType.equals(Commute.DRIVING)}"     android:onClick="@{()->viewModel.setCommuteType(Commute.DRIVING)}"     android:layout_width="wrap_content"     android:layout_height="wrap_content"     android:text="D"/>  <RadioButton     android:checked="@{viewModel.commuteType.equals(Commute.BICYCLE)}"     android:onClick="@{()->viewModel.setCommuteType(Commute.BICYCLE)}"     android:layout_width="wrap_content"     android:layout_height="wrap_content"     android:text="B"/>  <RadioButton     android:checked="@{viewModel.commuteType.equals(Commute.WALKING)}"     android:onClick="@{()->viewModel.setCommuteType(Commute.WALKING)}"     android:layout_width="wrap_content"     android:layout_height="wrap_content"     android:text="W"/>  <RadioButton     android:checked="@{viewModel.commuteType.equals(Commute.BUS)}"     android:onClick="@{()->viewModel.setCommuteType(Commute.BUS)}"     android:layout_width="wrap_content"     android:layout_height="wrap_content"     android:text="T"/>