Android Studio Design Time Data Binding Fallback/Default value

Question

I am using Android data binding which works great:

<TextView
android:text="@{ee.Name}"
...

But if I do that the Android Studio designer doesn't show any text. Without text I can't see the TextView at all. Which is understandable because I haven't bound the data yet. Is there something like a fallback value or a default value which can be displayed until there is real data?

Answer 1

You should read the Data Binding Guide posted on the Android developers website. The last section of the document, Android Studio Support for Data Binding explain how you can use a placeholder that can help you during the design phase. It's very simple:

<TextView android:layout_width="wrap_content"
   android:layout_height="wrap_content"
   android:text="@{user.firstName, default=Placeholder}"/>

If you want to have text with spaces as placeholder you can use single quotes ('), back quotes (`) or "

android:text='@{user.firstName, default="Placeholder text"}'
android:text="@{user.firstName, default=`Placeholder text`}"
android:text="@{user.firstName, default="Placeholder text"}"
android:text="@{user.firstName, default=@string/placeholder_text}"

Answer 2

The Preview pane displays default values for data binding expressions.

android:text="@{user.firstName, default=PLACEHOLDER}"

This can set default value .

<TextView
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_gravity="center_horizontal"
    android:text="@{defaultString ?? @string/hello_world}"/>