Android Layouts and Attributes in Android Development

When working on apps, Android developers often use layouts – this way, they can connect graphic designs and the backend of the app. In software development, a layout is defined as a visual structure of the page. It is a part of a ViewGroup – a family of app screen structures.

In this post, you will find out what Android layouts are, how to declare and manage them.

What Is an Android Layout?

Layouts are structural elements that can be created using widgets, via a programming language, or through editing XML files. There are two most common ways for Android developers to declare a layout:

Declaring interfaces as XML

Android integrated development environments support XML file editing – a developer can access all the vocabulary needed to create layouts and widgets, as well as views and view groups.

With this approach, a developer can separate the interface from the back-end code. Also, layouts declared as XML files are easy to edit without having to change the codebase of the app.

Declaring XML layouts offers development teams a clear view of the app’s UI and facilitates debugging.

Declare runtime layouts

Another way to go about initiating a new layout is by declaring views and ViewGroups on a programmatic basis. Although building UI from Java code is not a preferable practice, it is sometimes a faster and more efficient one. 
To declare a layout at runtime, you need to use margins like LayoutParams to change the View during runtime.

Types of Android Layouts

Depending on the interface a design team chooses, Android developers can work with different layouts. Here are the most common layout types in Android apps:

1. Linear layout

A linear layout is a group of views aligned either vertically or horizontally and parallel to each other. All the components of the layout are aligned and separated by margins. To declare a linear layout, developers use a LinearLayout attribute.

Linear layouts can be distributed equally and unequally. In the latter case, one vertical column will occupy more space than the others and will be declared more important.

2. Relative layout

A relative layout determines the position of page elements in relation to each other. A designer can either specify the relationship between sibling elements or between a parent and a child view.
To declare a Relative Layout, a developer should use RelativeLayout attribute.

Using relative layouts as opposed to linear ones improves the performance of the app and creates a flatter design. That’s why it’s a preferred layout type among tech teams. However, it takes more time to set a relative layout up since you have to specify the position of each view manually by choosing available properties from RelativeLayout.LayoutParams.

3. Grid view

This view group has a look of a 2D grid users can scroll through. The components of the grid are added to the view via a ListAdapter. To set up the grid, developers use the ImageAdapter by calling the setAdapter() method.

After the grid is set up, feel free to adjust its properties. For instance, you can change setAdjustViewBounds to setLayoutParams and vice versa.

4. List view

A list view is another layout type that looks like a scrollable list of items. Developers can add new items to the list by using Adapters. To declare a list, a software engineer has to add a ListView instance to the adapter. The content for lists is typically pulled from database queries.

LayoutAttributes

To change the relationship between parent and children view and influence the way view groups interact with each other, developers use Layout Attributes. These attributes are a part of a child group but the instructions they carry address the parent view group.

Here are the most common Android attributes:

Android:id

The attribute is used to mark an element used as a reference for the ViewGroup.

android:layout_width

The attribute sets the width value for a view.

android:layout_height

The attribute is used similarly to android:layout_width

layout

The layout attribute is used to mark layout resources.

<requestFocus>

The attribute determines which element gets more focus on the device screen. The attribute can be assigned to one element per file – a chosen component has to represent a view.

include

The attribute is used to attach a different layout to the layout file.

<merge>

This attribute can be used to merge parent and child views together. <merge> is often used in conjunction with the include attribute but can only be applied to layouts that don’t require a new ViewGroup.

All layout attributes are typically stored in LayoutParams. There’s a separate LayoutParams for each ViewGroup. Android:layout_width and android:layout_height are default attributes stored in every LayoutParams – you can always add new ones.

In case you are too challenged to wrap your head around managing XML files, integrated development environments like Android Studio or IntelliJ both have fully functional UI builders that don’t require an in-depth knowledge of XML.

Conclusion

Android layouts are an important concept in mobile app development. Getting a hang of them is crucial for front-end developers because views and view groups are needed to integrate designs into an application.

The good news is, app layouts are easy to manage. The attributes and methods used in the process are fairly straightforward – also, there’s plenty of documentation of the official platform for Android developers to use as a reference.

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