android data binding with a custom view

Question

The Android data binding guide discusses binding values within an activity or fragment, but is there a way to perform data binding with a custom view?

I would like to do something like:

<LinearLayout
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <com.mypath.MyCustomView
        android:id="@+id/my_view"
        android:layout_width="match_parent"
        android:layout_height="40dp"/>

</LinearLayout>

with my_custom_view.xml:

<layout>

<data>
    <variable
        name="myViewModel"
        type="com.mypath.MyViewModelObject" />
</data>

<LinearLayout
    android:layout_width="match_parent"
    android:layout_height="match_parent">

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

</LinearLayout>

</layout>

While it appears possible to do this by setting custom attributes on the custom view, this would quickly become cumbersome if there's a lot of values to bind.

Is there a good way to accomplish what I'm trying to do?

Did you try binding the data in your MyCustomView class after inflating the custome view? — Meiyappan Kannappa
– Meiyappan Kannappa, Commented Jan 14, 2016 at 21:37
I tried a few things to accomplish this, but the binding functions seem to require information contained within an activity or fragment. Their examples didn't give a sample on how to accomplish this within a custom view. A brief code snippet on how to accomplish this would be very much appreciated. — Dave
– Dave, Commented Jan 14, 2016 at 22:12
FYI: I think xml layout files are named with underscore notation by convention. — IgorGanapolsky
– IgorGanapolsky, Commented Jan 25, 2016 at 20:45
This article explains the 2-way data-binding process with a custom view and custom attributes: medium.com/@douglas.iacovelli/… — Ricardo
– Ricardo, Commented Nov 21, 2017 at 17:07

George Mount · Accepted Answer · 2016-01-15 18:35:05Z

111

In your Custom View, inflate layout however you normally would and provide a setter for the attribute you want to set:

private MyCustomViewBinding mBinding;
public MyCustomView(...) {
    ...
    LayoutInflater inflater = (LayoutInflater)
        context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
    mBinding = MyCustomViewBinding.inflate(inflater);
}

public void setMyViewModel(MyViewModelObject obj) {
    mBinding.setMyViewModel(obj);
}

Then in the layout you use it in:

<layout xmlns...>
    <data>
        <variable
            name="myViewModel"
            type="com.mypath.MyViewModelObject" />
    </data>

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent">

        <com.mypath.MyCustomView
            android:id="@+id/my_view"
            app:myViewModel="@{myViewModel}"
            android:layout_width="match_parent"
            android:layout_height="40dp"/>

    </LinearLayout>
</layout>

In the above, an automatic binding attribute is created for app:myViewModel because there is a setter with the name setMyViewModel.

answered Jan 15, 2016 at 18:35

George Mount

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14 Comments

IgorGanapolsky Over a year ago

Where does the type MyCustomViewBinding get created?

George Mount Over a year ago

MyCustomViewBinding is generated via an annotation processor as part of the data binding framework. The xml file (Dave used MyCustomView.xml, but he really meant my_custom_view.xml, since case should to be all lower case for resource files) causes a default Binding class name of MyCustomViewBinding (camel cased, suffixed with Binding). You can also customize the Binding class name: developer.android.com/tools/data-binding/…

Bitcoin Cash - ADA enthusiast Over a year ago

The solution described in stackoverflow.com/a/36068337/1369016 (also posted by George Mount) is the one that worked for me.

Jan Kalfus Over a year ago

Use LayoutInflater.from(context), it's much nicer - shorter and you don't have to do a type conversion.

bearlysophisticated Over a year ago

Also, remember to define and attach to root: inflate(inflater, this, true). I needed it in my case to have the custom view visible.

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Marek Brezina · Accepted Answer · 2019-09-30 15:16:04Z

16

Data binding works even with merge only parent had to be "this" and attach to parent true.

binding = DataBindingUtil.inflate(inflater, R.layout.view_toolbar, this, true)

answered Sep 30, 2019 at 15:16

Marek Brezina

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Comments

androidguy · Accepted Answer · 2017-08-17 00:44:12Z

15

First, don't do this if this custom view is already being <include> in another layout, such as activity etc. You'll just get an exception about the tag being unexpected value. The data binding already ran the binding on it, so you're set.

Did you try using onFinishInflate to run the bind? (Kotlin example)

override fun onFinishInflate() {
    super.onFinishInflate()
    this.dataBinding = MyCustomBinding.bind(this)
}

Keep in mind that if you use the binding in your view, it won't be able to be created programmatically, at least it would be very convoluted to support both even if you can.

edited Aug 17, 2017 at 0:44

answered Sep 14, 2016 at 6:56

androidguy

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1 Comment

Hossein Over a year ago

god bless you dude :))

Community · Accepted Answer · 2017-05-23 12:34:29Z

Following the solution presented by george the graphical editor in android studio was no longer able to render the custom view. The reason is, that no view is actually inflated in the following code:

public MyCustomView(...) {
    ...
    LayoutInflater inflater = (LayoutInflater)
        context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
    mBinding = MyCustomViewBinding.inflate(inflater);
}

I suppose that the binding handles the inflation, however the graphical editor did not like it.

In my specific use case I wanted to bind a single field and not an entire view model. I came up with (kotlin incoming):

class LikeButton @JvmOverloads constructor(
        context: Context,
        attrs: AttributeSet? = null,
        defStyleAttr: Int = 0
) : ConstraintLayout(context, attrs, defStyleAttr) {

    val layout: ConstraintLayout = LayoutInflater.from(context).inflate(R.layout.like_button, this, true) as ConstraintLayout

    var numberOfLikes: Int = 0
      set(value) {
          field = value
          layout.number_of_likes_tv.text = numberOfLikes.toString()
      }
}

The like button consists of an image and a text view. The text view holds the number of likes, which I want to set via data binding.

By using the setter for numberOfLikes as an attribute in the following xml, data binding automatically makes the association:

<views.LikeButton
  android:id="@+id/like_btn"
  android:layout_width="wrap_content"
  android:layout_height="wrap_content"
  app:numberOfLikes="@{story.numberOfLikes}" />

Further reading: https://medium.com/google-developers/android-data-binding-custom-setters-55a25a7aea47

I found reported issue for it: issuetracker.google.com/issues/150887082

Jere Chen · Accepted Answer · 2020-03-13 03:40:55Z

Today, I want to use the dataBinding on my Custom View class. But I don't know how to create data binding to my class. so I search the answer on StackOverflow. Firstly I try the answer:

LayoutInflater inflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
BottomBarItemCustomViewBinding binding = BottomBarItemCustomViewBinding.inflate(inflater);

but, I found this is not working for my code

so I change another method:

LayoutInflater inflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
BottomBarItemCustomViewBinding binding = DataBindingUtil.inflate(inflater, R.layout.bottom_bar_item_custom_view, this, true);

It's working for me.

the complete code is: bottom_bar_item_custom_view.xml

<data>

    <variable
        name="contentText"
        type="String" />

    <variable
        name="iconResource"
        type="int" />

</data>

<androidx.constraintlayout.widget.ConstraintLayout xmlns:app="http://schemas.android.com/apk/res-auto"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_gravity="center">

    <ImageView
        android:id="@+id/bottomBarItemIconIv"
        android:layout_width="40dp"
        android:layout_height="40dp"
        android:layout_marginTop="2dp"
        android:src="@{iconResource}"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <TextView
        android:id="@+id/bottomBarItemContentTv"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:gravity="center_horizontal"
        android:text="@{contentText}"
        android:textColor="@color/black"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@id/bottomBarItemIconIv" />


</androidx.constraintlayout.widget.ConstraintLayout>

BottomBarItemCustomView.java

public class BottomBarItemCustomView extends ConstraintLayout {

public BottomBarItemCustomView(Context context, AttributeSet attrs) {
    super(context, attrs);
    init(context, attrs);
}

private void init(Context context, AttributeSet attrs) {
    //use dataBinding on custom view.
    LayoutInflater inflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
    BottomBarItemCustomViewBinding binding = DataBindingUtil.inflate(inflater, R.layout.bottom_bar_item_custom_view, this, true);

    TypedArray typedArray = context.obtainStyledAttributes(attrs, R.styleable.BottomBarItemCustomView);
    int iconResourceId = typedArray.getResourceId(R.styleable.BottomBarItemCustomView_bottomBarIconResource, R.drawable.my_account_icon);
    binding.setIconResource(iconResourceId);

    String contentString = typedArray.getString(R.styleable.BottomBarItemCustomView_bottomBarContentText);
    if (contentString != null) {
        binding.setContentText(contentString);
    }

    typedArray.recycle();
}

hope is useful for you!

Soft Code · Accepted Answer · 2022-03-02 09:53:41Z

2

In Kotlin we can directly use ViewBinding:

class BenefitView(context: Context, attrs: AttributeSet) : ConstraintLayout(context, attrs) {

    init {
        val binding = BenefitViewBinding.inflate(LayoutInflater.from(context), this, true)
        val attributes = context.obtainStyledAttributes(attrs, R.styleable.BenefitView)
        binding.image.setImageDrawable(attributes.getDrawable(R.styleable.BenefitView_image))
        binding.caption.text = attributes.getString(R.styleable.BenefitView_text)
        attributes.recycle()

    }
}

answered Mar 2, 2022 at 9:53

Soft Code

575 bronze badges

Comments

Sam · Accepted Answer · 2018-08-03 15:12:21Z

There are some good answers on here already, but I wanted to offer what I believe to be the simplest.

Create your custom control with the layout tags surrounding it, just like any other layout. See the following toolbar for example. this gets used in each of the activity classes

<layout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    xmlns:app="http://schemas.android.com/apk/res-auto">

<data>
    <variable name="YACustomPrefs" type="com.appstudio35.yourappstudio.models.YACustomPreference" />
</data>

<android.support.design.widget.CoordinatorLayout
    android:layout_width="match_parent"
    android:layout_height="?attr/actionBarSize">

    <android.support.design.widget.AppBarLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:theme="@style/YATheme.AppBarOverlay">

        <android.support.v7.widget.Toolbar
            android:id="@+id/toolbar"
            android:layout_width="match_parent"
            android:layout_height="?attr/actionBarSize"
            android:background="@color/colorPrimary"
            app:popupTheme="@style/YATheme.PopupOverlay"/>

    </android.support.design.widget.AppBarLayout>

</android.support.design.widget.CoordinatorLayout>

Now this custom layout is a child of every Activity. You simply treat it as such in the onCreate binding setup.

  override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)
    binding = DataBindingUtil.setContentView(this, R.layout.activity_main)
    binding.yaCustomPrefs = YACustomPreference.getInstance(this)
    binding.toolbarMain?.yaCustomPrefs = YACustomPreference.getInstance(this)
    binding.navHeader?.yaCustomPrefs = YACustomPreference.getInstance(this)

    binding.activity = this
    binding.iBindingRecyclerView = this
    binding.navHeader?.activity = this

    //local pointer for notify txt badge
    txtNotificationCountBadge = txtNotificationCount

    //setup notify if returned from background so we can refresh the drawer items
    AppLifeCycleTracker.getInstance().addAppToForegroundListener(this)

    setupFilterableCategories()
    setupNavigationDrawer()
}

Notice I set the children's content at the same time I do the parent and it is all done through dot notation access. As long as the files are surrounded with layout tags and you named them, it is simple to do.

Now if the custom class has it's own associated code inflation, then it can easily just do it's own binding in it's onCreate or constructor, but you get the picture. If you have your own class just throw the following in the constructor to match it's named binding class. It follows the name convention of the layout file pascal cased, so it's easy to find and auto fill.

    LayoutInflater inflater = (LayoutInflater)
    context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
mBinding = NameOfCustomControlBinding.inflate(inflater);

Hope that helps.

Muhamed Riyas M · Accepted Answer · 2020-08-12 11:27:56Z

0

I faced the same issue when I am trying to add a child views to a LinearLayout inside my host fragment(Nested fragment UI/UX)

here is my solution

var binding: LayoutAddGatewayBinding? = null
binding = DataBindingUtil.inflate(layoutInflater, R.layout.layout_add_gateway,
            mBinding?.root as ViewGroup?, false)
binding?.lifecycleOwner=this
val nameLiveData = MutableLiveData<String>()
nameLiveData.value="INTIAL VALUE"
binding?.text=nameLiveData

Here mBinding is child fragment ViewDataBinding object and I have used nameLiveData for two-way databinding

answered Aug 12, 2020 at 11:27

Muhamed Riyas M

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