Using databinding to highlight selected recyclerview row

Question

I'm trying to highlight a row of my recyclerview when a user clicks on it.

Recyclerview row layout:

<data>
    <variable name="model" type="ItemRow" />
    <variable name="listener" type="ItemClickListener" />
</data>

<com.google.android.material.card.MaterialCardView       
    android:layout_width="wrap_content"
    android:layout_height="wrap_content">

    <TextView            
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@{model.name}"
        android:onClick="@{() -> listener.onItemClicked(model)}"           
        android:background="@{model.isSelected ? @drawable/white : @drawable/blue}"/>

</com.google.android.material.card.MaterialCardView>

The onClickListener is instantiated in the activity:

ItemClickListener listener = item -> viewModel.selectItem(item);

The viewmodel sets the isSelected property of Item to true:

public void selectItem(Item item)
{
    item.setSelected(true);        
}

However, this doesn't change the row's background. Debugging through the code shows me that the item's isSelected property is set to true. Is there something I'm missing?

Shouldn't you notify the adapter that the item changed? [`notifyItemChanged(`](https://developer.android.com/reference/android/support/v7/widget/RecyclerView.Adapter.html#notifyItemChanged(int)). Also, any reason why you don't use selectors instead of doing it with databinding? — Fred, Apr 23 '19 at 21:04
@Fred selectors as in the recyclerview-selection library? figured it was overkill as I just want 1 row selected. I tried using notifyItemChanged and notififydatasetchanged but it didn't seem to help — user8114848, Apr 24 '19 at 03:19
TBH I never heard of such library. I was referring to the Android selectors that are meant for this exact use case. There's another name for it - [StateList](https://developer.android.com/guide/topics/resources/drawable-resource#StateList) — Fred, Apr 24 '19 at 05:13

score 0 · Answer 1 · answered Nov 29 '20 at 20:28

Use BaseObservable

class Item extends BaseObservable {
    private boolean isSelected = false;

    @Bindable
    public boolean getIsSelected() {
        return isSelected;
    }

    public void setSelected(Boolean isSelected) {
        this.isSelected = isSelected;
        //Probably it'll has other name, i haven't testing it
        notifyPropertyChanged(BR.selected); 
    }

}

It will works without notfiyDataSetChanged

Using databinding to highlight selected recyclerview row

1 Answers1