Data binding: how to bind different data variables in one view

user_5944547 0
Viewed 814

I'm using MVVM design pattern and so the native data binding.

Is it possible to use multiple data variable for one view in data binding?

I mean that I have one xml layout that use data binding and I want to use it for multiple recyclerview items.

It's the first data model class for one recyclerview items:

data class Sample1 (
    val name: String,
    val id: Int
)

And this is the second one for another recyclerview items:

data class Sample2 (
    val name: String,
    val type: String
)

And it's the xml code that use in both recyclerview:

<layout>

<data class="SampleDataBinding">

    <variable
        name="Sample1"
        type="model.Sample1" />

    <variable
        name="Sample2"
        type="model.Sample2" />

</data>

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:gravity="center_vertical"
    android:orientation="horizontal"
    android:padding="8dp">

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:paddingStart="8dp"
        android:paddingEnd="8dp"
        android:text="@{Sample1.component1()}" // this line may be different in another recyclerview item
        android:textColor="@color/black" />

</LinearLayout>

I don't mean the concatation two Strings. I mean that the TextView may be different in first recyclerview items and second one.

If it's possible how I can do it?

Thanks in advance

android-databinding android-recyclerview android-layout android
2 Answers

You can achieve it using an interface and your XML/data-binding will work with that interface. For instance, you need a title in that xml and you can create an interface (SampleRecyclerItem) and its implementers have to provide a title: String.

interface SampleRecyclerItem{
    val title: String
}

data class Sample1 (
    val name: String,
    val id: Int
) : SampleRecyclerItem {
    override val title get() = name // either using a getter
}


data class Sample2 (
    val name: String,
    val type: String
) : SampleRecyclerItem {
    override val title by this::name // or using delegation (easier for vars for not providing setter and getter)
}

and then, your XML can use this interface instead of the data classes directly

<layout>

<data class="SampleDataBinding">

    <variable
        name="sample"
        type="model.SampleRecyclerItem" />

</data>

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:gravity="center_vertical"
    android:orientation="horizontal"
    android:padding="8dp">

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:paddingStart="8dp"
        android:paddingEnd="8dp"
        android:text="@{sample.title}"
        android:textColor="@color/black" />

</LinearLayout>
user_19059650

This can be reach with elvis operator but you need to compare some thing to select desired value. If it's only about text. Provide logic at adapter class and pass text to data binding instead of many useless objects. If you need more complex solution you need to use different view types and ViewHolders. Example link

user_30842050
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