Android Layout Basics

Layout Basics

In Android, layouts are used to organize the UI of an app. Layouts are made up of views, which are the basic building blocks of an Android UI. Views can be text, images, buttons, or any other type of UI element.

There are a number of different layout types available in Android, each with its own strengths and weaknesses. Some of the most common layout types include:

• Linear Layout: A linear layout arranges views in a single row or column.
• TableLayout: A table layout arranges views in a table-like structure.
• FrameLayout: A frame layout places each view in its own rectangular area.
• RelativeLayout: A relative layout positions views relative to each other.
• ConstraintLayout: A constraint layout allows you to position views anywhere on the screen and constrain them to each other or to the edges of the screen.

Linear Layout

A linear layout is the simplest type of layout. It arranges views in a single row or column. To create a linear layout, you use the LinearLayout class.

The LinearLayout class has a number of properties that you can use to control the layout of its child views. These properties include:

• orientation: The orientation of the layout. Can be VERTICAL or HORIZONTAL.
• gravity: The gravity of the layout. This determines how views are aligned within the layout.
• weightSum: The sum of the weights of all the views in the layout. This determines how the space in the layout is distributed between the views.

Constraint Layout

ConstraintLayout is a newer layout type that was introduced in Android 8.0 (Oreo). ConstraintLayout allows you to position views anywhere on the screen and constrain them to each other or to the edges of the screen.

To create a constraint layout, you use the ConstraintLayout class.

The ConstraintLayout class has a number of features that make it more powerful than other layout types. These features include:

• Chains: Chains allow you to group views together and constrain them as a unit.
• Guidelines: Guidelines are invisible lines that you can use to position views.
• Percent dimensions: Percent dimensions allow you to specify the size of a view as a percentage of the size of its parent layout.

Chain

A chain is a group of views that are constrained together. Chains can be used to position views in a variety of ways. For example, you can use chains to create a horizontal row of buttons, a vertical column of text views, or a grid of images.

To create a chain, you use the app:layout_constraintHorizontal_chainStyle and app:layout_constraintVertical_chainStyle attributes. These attributes can be set to spread, spread_inside, or packed.

• spread: The views in the chain are spread out evenly.
• spread_inside: The views in the chain are spread out evenly, but the first and last views are aligned to the edges of the chain.
• packed: The views in the chain are packed together.

Guidelines

Guidelines are invisible lines that you can use to position views. Guidelines can be used to create layouts that are consistent and easy to use.

To create a guideline, you use the android:layout_width and android:layout_height attributes. These attributes can be set to wrap_content or match_parent.

• wrap_content: The guideline will be as wide or tall as it needs to be to contain its child views.
• match_parent: The guideline will be as wide or tall as its parent layout.

Conclusion

Layouts are an essential part of Android development. By understanding the different layout types and their features, you can create UIs that are both visually appealing and functional.