How to use data-binding with Fragment

I'm trying to follow data-binding example from official google doc https://developer.android.com/tools/data-binding/guide.html

except that I'm trying to apply data-biding to a fragment, not an activity.

the error I'm currently getting when compiling is

Error:(37, 27) No resource type specified (at 'text' with value '@{marsdata.martianSols}.

onCreate for fragment looks like this:

@Override
public void onCreate(@Nullable Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    MartianDataBinding binding = MartianDataBinding.inflate(getActivity().getLayoutInflater());
    binding.setMarsdata(this);
}

onCreateView for fragment looks like this:

@Nullable
@Override
public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
    return inflater.inflate(R.layout.martian_data, container, false);
}

and parts of my layout file for fragment looks like this:

<?xml version="1.0" encoding="utf-8"?>

<layout xmlns:android="http://schemas.android.com/apk/res/android">
    <data>
        <variable
            name="marsdata"
            type="uk.co.darkruby.app.myapp.MarsDataProvider" />
    </data>
...

        <TextView
            android:layout_height="wrap_content"
            android:layout_width="wrap_content"
            android:text="@{marsdata.martianSols}"
        />

    </RelativeLayout>
</layout>

my suspicion is that MartianDataBinding doesn't know which layout file it's supposed to be bound with - hence the error. Any suggestions?


The data binding implementation must be in the onCreateView method of the fragment, delete any data Binding that exist in your OnCreate method, your onCreateView should look like this:

public View onCreateView(LayoutInflater inflater, 
                         @Nullable ViewGroup container, 
                         @Nullable Bundle savedInstanceState) {
    MartianDataBinding binding = DataBindingUtil.inflate(
            inflater, R.layout.martian_data, container, false);
    View view = binding.getRoot();
    //here data must be an instance of the class MarsDataProvider
    binding.setMarsdata(data);
    return view;
}

You are actually encouraged to use the inflate method of your generated Binding and not the DataBindingUtil:

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
    MainFragmentBinding binding = MainFragmentBinding.inflate(inflater, container, false);
    //set variables in Binding
    return binding.getRoot();
}

Docs for DataBindingUtil.inflate():

Use this version only if layoutId is unknown in advance. Otherwise, use the generated Binding's inflate method to ensure type-safe inflation.


Even the other answers may work well, but I want tell best approach.

Use Binding class's inflate as recommended in Android Documentation.

One option is to inflate by DataBindingUtil but when only you don't know have generated binding class.

--You have auto generated binding class, use that class instead of using DataBindingUtil.

In Java

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
    HomeFragmentBinding binding = HomeFragmentBinding.inflate(inflater, container, false);
    //set binding variables here
    return binding.getRoot();
}

In Kotlin

lateinit var binding: HomeFragmentBinding 
override fun onCreateView(inflater: LayoutInflater?, container: ViewGroup?, savedInstanceState: Bundle?): View? {
    binding = HomeFragmentBinding.inflate(inflater, container, false)
    return binding.root
}

In DataBindingUtil class documentation you can see.

inflate

T inflate (LayoutInflater inflater, 
                int layoutId, 
                ViewGroup parent, 
                boolean attachToParent)

Use this version only if layoutId is unknown in advance. Otherwise, use the generated Binding's inflate method to ensure type-safe inflation.

If your layout biniding class is not generated @See this answer.


If you are using ViewModel and LiveData This is the sufficient syntax

Kotlin Syntax:

override fun onCreateView(
    inflater: LayoutInflater,
    container: ViewGroup?,
    savedInstanceState: Bundle?
): View? {
    return MartianDataBinding.inflate(
        inflater,
        container,
        false
    ).apply {
        lifecycleOwner = viewLifecycleOwner
        vm = viewModel    // Attach your view model here
    }.root
}

Just as most have said, but dont forget to set LifeCycleOwner
Sample in Java i.e

public View onCreateView(LayoutInflater inflater, ViewGroup container,Bundle savedInstanceState) {
    super.onCreateView(inflater, container, savedInstanceState);
    BindingClass binding = DataBindingUtil.inflate(inflater, R.layout.fragment_layout, container, false);
    ModelClass model = ViewModelProviders.of(getActivity()).get(ViewModelClass.class);
    binding.setLifecycleOwner(getActivity());
    binding.setViewmodelclass(model);

    //Your codes here

    return binding.getRoot();
}