The Data Binding Library is a support library that allows you to bind UI components in your layouts to data sources in your app using a declarative format rather than programmatically. In databinding set and get value from field directly to xml.

For example, the code below calls findViewById()to find a TextView widget and bind it to the userName property of the viewModel variable:

TextView textView = findViewById(R.id.sample_text);
textView.setText(viewModel.getUserName());

<TextView
android:text="@{viewmodel.userName}" />

One-way data binding :

Using one-way data binding, you can set a value on an attribute and set a listener that reacts to a change in that attribute:

<CheckBox
android:id="@+id/rememberMeCheckBox"
android:checked="@{viewmodel.rememberMe}"
android:onCheckedChanged="@{viewmodel.rememberMeChanged}"
/>

in one data binding use this @{ } notation

Two-way data binding :

The Data Binding Library supports two-way data binding. The notation used for this type of binding supports the ability to receive data changes to a property and listen to user updates to that property at the same time.

Two-way data binding provides a shortcut to this process:

<CheckBox
android:id="@+id/rememberMeCheckBox"
android:checked="@={viewmodel.rememberMe}"
/>

The @={} notation, which importantly includes the “=” sign,
receives data changes to the property and listen to user updates at the same time.