Using DataBinding library for binding events

Question

I'm trying to bind events with views in xml using DataBinding Library shipped with Android M. I'm following examples from Android Developers and implementing step-by-step. for the view's attributes like visibility,text its working fine but if I try to bind with onclick, it doesn't work as expected. Here's the sample code that I've tried so far:

 <data>     <import type="android.view.View"/>     <variable name="user" type="com.example.databinding.User"/>     <variable name="handlers" type="com.example.databinding.MyHandlers"/> </data>   <TextView     android:layout_width="wrap_content"     android:layout_height="wrap_content"     android:text="@{user.firstName}"     android:visibility="@{user.isFriend ? View.VISIBLE : View.GONE}" />  <Button     android:layout_width="wrap_content"     android:layout_height="wrap_content"     android:text="Click Me"     android:id="@+id/button"     android:layout_gravity="left"     android:onClick="@{handlers.onClickFriend}"/> 

MainActivity :

  public class MainActivity extends AppCompatActivity {    User user;   @Override  protected void onCreate(Bundle savedInstanceState) {     super.onCreate(savedInstanceState);     ActivityMainBinding binding =      DataBindingUtil.setContentView(this,R.layout.activity_main);     user = new User("Pankaj","Kumar",true,true);     binding.setUser(user);    }  } 

MyHandlers:

public class MyHandlers { public void onClickFriend(View view){     Log.i(MyHandlers.class.getSimpleName(),"Now Friend"); }  public void onClickEnemy(View view){     Log.i(MyHandlers.class.getSimpleName(),"Now Enemy");   } } 

I've written only required code to improve readability. Could someone help me on this.

Answer 1

I think you will need to bind the handlers as well, maybe something like this in onCreate:

MyHandlers handlers = new MyHandlers(); binding.setHandlers(handlers); 

Answer 2

Many Ways for setting Click

1. Pass handler to binding.

   ActivityMainBinding binding = DataBindingUtil.setContentView(this,R.layout.activity_main); Hander handler = new Handler(); binding.setHandler(handler);

2. Set clicks (use any of below)

   android:onClick="@{handler::onClickMethodReference}"

OR

android:onClick="@{handler.onClickMethodReference}" 

OR

android:onClick="@{() -> handler.onClickLamda()}" 

OR

android:onClick="@{(v) -> handler.onClickLamdaWithView(v)}" 

OR

android:onClick="@{() -> handler.onClickLamdaWithView(model)}" 

See Handler class for understanding.

public class Handler {     public void onClickMethodReference(View view) {         //     }     public void onClickLamda() {         //     }     public void onClickLamdaWithView(View view) {         //     }     public void onClickLamdaWithObject(Model model) {         //     } } 

Note that

• You can use Method Reference (::) when you have same argument as the attribute onClick.
• You can pass any object like onClickLamdaWithObject example.
• If you need to pass View object then just use (v)-> expression.

Further reading

https://developer.android.com/topic/libraries/data-binding/expressions