Infer Schema from Android XML Layouts

Android Layout XML to JSON Schema

Android applications use XML layout files to define user interfaces. These files are attribute-heavy, use namespace prefixes extensively, and have a hierarchical structure of view groups and views.

Example Layout

<LinearLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:orientation="vertical"
    android:padding="16dp">

    <TextView
        android:id="@+id/title"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="Hello World"
        android:textSize="24sp"
        android:textColor="#333333"/>

    <EditText
        android:id="@+id/input"
        android:layout_width="match_parent"
        android:layout_height="48dp"
        android:hint="Enter text"
        android:inputType="text"/>

    <Button
        android:id="@+id/submit"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Submit"/>
</LinearLayout>

Namespace Prefixes in Schema

Android layouts use the android: namespace prefix extensively. In the generated schema, these become properties like @android:layout_width, @android:orientation, etc. The namespace prefix is preserved to maintain the mapping to the original XML.

Schema Observations

• All attributes are strings: Dimension values like 16dp, 24sp, 48dp contain units, so they stay as strings
• Resource references: Values like @+id/title, match_parent, wrap_content are strings
• Color values: #333333 is a string
• Mixed child views: If the LinearLayout contains different view types, each gets its own property in the schema

Practical Limitations

Android layouts are complex XML documents. The tool handles the structural aspects well, but Android-specific semantics (like resource resolution, style inheritance, and data binding expressions) are beyond what type inference can capture.

Extending the Schema

For a comprehensive Android layout schema, you would add:

• Enums for known attribute values (match_parent, wrap_content, visible, gone)
• Pattern matching for resource references (@+id/*, @string/*)
• Pattern matching for dimension values (\d+dp, \d+sp)