Binding to the H(eight)

As would probably be obvious by now, I have been investing a lot of time in learning and using data binding.

Yesterday, we were trying to bind a view’s height and width to a value from a model. Directly using data binding did not work, and Googling for the issue says we have to do two things:

Provide a default value
Create a BindingAdapter

Remember that data binding strips out any data binding-related things in the XML. Without a default, the widget is left without a height and width. Hence the importance of including a default value.

<ImageView
    android:id="@+id/agent_photo"
    android:layout_width="@{entry.agentPhotoSize, default=@dimen/default_photo_size}"
    android:layout_height="@{entry.agentPhotoSize, default=@dimen/default_photo_size}" />

We set about creating the BindingAdapter as illustrated in the issue tracker. But running the code shows us that the height being set to the view is a massive value. The view seems to go on and on forever. Not good.

I was ready to give up and chalk it up to “Welp maybe RecyclerView does not like what we’re doing.” But I can’t just give up like that! But then suddenly…

I don’t know how I missed it the first time, but I realised that we are passing in a dimension. Our BindingAdapter does work. But it is using the raw value of the dimension resource as the view’s height. Duh. Resolving the resource to the actual value makes us all happy again.

@BindingAdapter({"android:layout_height"})
public static void setAgencyBrandingHeight(View view, @DimenRes int height) {
    ViewGroup.LayoutParams layoutParams = view.getLayoutParams();
    layoutParams.height = view.getContext().getResources().getDimensionPixelSize(height);
    view.setLayoutParams(layoutParams);
}

And then of course after figuring this out, I remembered that I already wrote about using resources.

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