Data Binding Not Working Android

Question

I am using the data binding library and i got it so for but there are issues that i cant't seem to get.For starters

This is a part of my xml layout activity_login.xml

 <data>

    <variable
        name="viewModel"
        type="com.ViewModel.LoginViewModel" />

</data>
<EditText
                android:id="@+id/edit_text_username_register"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:hint="@string/username"
                android:imeOptions="actionNext"
                android:inputType="text"
                android:textSize="15sp"
                android:theme="@style/EditTextTheme"
                app:addTextChangedListener="@{viewModel.getUsername}" />

And my ViewModel contains

    public TextWatcher getUsername() {
    return new TextWatcher() {
        @Override
        public void beforeTextChanged(CharSequence s, int start, int count, int after) {

        }

        @Override
        public void onTextChanged(CharSequence s, int start, int before, int count) {
            Log.i("username", s.toString());
        }

        @Override
        public void afterTextChanged(Editable s) {

        }
    };
}

The above code is to fetch the username as the user types.Is that the correct way of using data binding or am i doing it wrong?The above code works perfectly. The problem is when i try to do it the way i found it online that is by adding

android:addTextChangedListener="@{viewModel.getUsername}"

it does not work and i get a warning saying unknown attribute and if i try compiling it i get a databinding does not exist error.I am also using a radiogroup containing 2 radio buttons and i would like to fetch which one was selected using databinding.I found online sources which use android:onCheckedChanged which i tried using but i get an error again saying binding does not exist and unknown attribute

Answer 1

InverseBindingMethod is a good stuff here, follow an example.

class

public class Handlers {
    public void onKeywordChanged(CharSequence s, int start, int before, int count) {
           // Your code here
    }
}

layout

<layout>
     <data>
        <variable name="handlers"
             type="my.package.Handlers" />
     </data>

     ...
     <EditText
       ...
        android:onTextChanged="@{handlers::onKeywordChanged}"
     />
</layout>

For more information https://developer.android.com/reference/android/databinding/InverseBindingMethod.html