29. Manual XML Layout Design in Android Studio

While the design of layouts using the Android Studio Layout Editor tool greatly improves productivity, it is still possible to create XML layouts by manually editing the underlying XML. This chapter will introduce the basics of the Android XML layout file format.

29.1 Manually Creating an XML Layout

The structure of an XML layout file is actually quite straightforward and follows the hierarchical approach of the view tree. The first line of an XML resource file should ideally include the following standard declaration:

<?xml version="1.0" encoding="utf-8"?>

This declaration should be followed by the root element of the layout, typically a container view such as a layout manager. This is represented by both opening and closing tags and any properties that need to be set on the view. The following XML, for example, declares a ConstraintLayout view as the root element, assigns the ID activity_main and sets match_parent attributes such that it fills all the available space of the device display:

<?xml version="1.0" encoding="utf-8"?>

<androidx.constraintlayout.widget.ConstraintLayout

    xmlns:android="http://schemas.android.com/apk/res/android"...

29.2 Manual XML vs. Visual Layout Design

When to write XML manually as opposed to using the Layout Editor tool in design mode is a matter of personal preference. There are, however, advantages to using design mode.

First, design mode will generally be quicker given that it avoids the necessity to type lines of XML. Additionally, design mode avoids the need to learn the intricacies of the various property values of the Android SDK view classes. Rather than continually refer to the Android documentation to find the correct keywords and values, most properties can be located by referring to the Attributes panel.

All the advantages of design mode aside, it is important to keep in mind that the two approaches to user interface design are in no way mutually exclusive. As an application developer, it is quite likely that you will end up creating user interfaces within design mode while performing fine-tuning and layout tweaks of the design by directly editing the generated XML resources...

29.3 Summary

The Android Studio Layout Editor tool provides a visually intuitive method for designing user interfaces. Using a drag and drop paradigm combined with a set of property editors, the tool provides considerable productivity benefits to the application developer.

User interface designs may also be implemented by manually writing the XML layout resource files, the format of which is well structured and easily understood.

The fact that the Layout Editor tool generates XML resource files means that these two approaches to interface design can be combined to provide a “best of both worlds” approach to user interface development.