Constraint Layout: How to Speed Up Responsive UI Development in Kotlin?

The problem you face with the UI stability 😞😫

Android app developers are very well familiar with the traditional layout, linear layout, and relative layout, but using these layouts may bring down your app performance.

Moreover handling complex and large layouts can be frustrating as you manually need to create some improvement in the view hierarchy with some nested views.

The solution we have to improve UI stability 😍💃

To solve the above problem, Google introduced an “Android Constraint Layout Editor” at the Google I/O conference 2016. This new Layout Editor has a set of powerful tools that empower developers to create flat-UI hierarchies for complex layout. This new layout is called Constraint Layout.

At the same time, Kotlin has emerged as the go-to language for Android development due to its simplicity, modern features, and developer-friendly syntax. Combining Kotlin with Constraint Layout can significantly streamline the development process, making it easier and faster to build responsive Android apps. In this blog, we’ll explore how you can use Constraint Layout in Kotlin-based Android apps to speed up UI development, reduce layout complexity, improve performance, and write cleaner, more maintainable code.

More about Constraint Layout and how it improves UI performance for Android Apps

What is Constraint Layout in Android?

Constraint Layout is a flexible and powerful layout system introduced in Android to help developers create complex UIs with fewer nested elements. It allows you to position UI components relative to each other and to the parent layout, providing more control over the positioning and behavior of elements on different screen sizes and orientations.

Creating Constraint Layout for Kotlin

Kotlin’s concise syntax and powerful language features make it a perfect companion for Constraint Layout. Together, they allow developers to build responsive, dynamic layouts more efficiently, using less boilerplate code and leveraging Kotlin’s features like extension functions, lazy initialization, and DSL (Domain-Specific Language) for programmatic layouts.

• Reduce Layout Nesting: Constraint Layout was designed to minimize the deeply nested hierarchies that can occur with traditional layouts like LinearLayout and RelativeLayout, improving performance.

• Ideal for Building Responsive UIs: It provides a more efficient way to handle complex layouts, making it perfect for apps that need to adapt to various screen sizes and orientations.

• Seamless Kotlin Integration: Kotlin’s features, such as null safety, lambdas, and extension functions, simplify the process of creating and managing layouts programmatically with Constraint Layout.

Overall, with constraint layout, developers can build complex and responsive user interfaces without using nested view groups, which is otherwise not possible with the relative layout. The view group used by constraint layout allows developers to position and size widgets in a flexible way.

The performance comparison between Constraint Layout and Relative Layout shows the following result.

Traditional layout vs Constraint layout

In the above performance comparison, you can see that the constraint layout has 40% better performance than the traditional layout.

Further, developers can simply drag and drop view widgets from the Palette to the designer editor and create great user interfaces. Following is the list of constraint layouts currently available to use.

• Relative positioning
• Margins
• Centering Position
• Circular Positioning
• Visibility behavior
• Dimension Constraint
• Chains
• Virtual Helper objects
• Optimizer

Thus, constraint layout helps developers to improve the performance of layout files and also provides more versatility to use layouts.

Pros and Cons of using Constraint Layout

Pros 👍

• Empower developers to build highly complex interfaces while reducing the nesting.
• Eliminates the issues in the Relative layout and helps to improve the app's performance.
• Provides seamless experience across a wide range of screens.
• With a constraint layout, one can control a group of widgets through a single line of code.
• With a constraint layout, animations can be easily added to the UI components.

Cons 👎

• Sometimes developers might feel a little overwhelmed to understand the code.
• The results obtained can be different from what we got to see in the design editor.
• Sometimes you need to create another layout for landscape mode to adjust the views and widgets as it may not be up to your expectations.

Why Use Constraint Layout in Kotlin-Based Android Projects?

1. Enhanced Layout Flexibility

Constraint Layout allows for more flexible and complex UI designs than LinearLayout or RelativeLayout, making it ideal for responsive designs. You can position views relative to one another or to the parent layout, and the layout automatically adapts to different screen sizes.

2. Improved Performance

By reducing the view hierarchy, Constraint Layout helps improve performance. Fewer nested views mean less work for the Android rendering engine, resulting in faster layout rendering and smoother app performance. Combined with Kotlin’s streamlined syntax, you can write clean, efficient UI code that boosts both app speed and maintainability.

3. Fewer XML Layout Files

Constraint Layout’s flexibility reduces the need for multiple XML files for different screen sizes and orientations. Using guidelines, barriers, and bias, you can create adaptive layouts that work well across various devices, reducing the overhead of managing multiple layout resources.

4. Better Integration with Kotlin Features

Kotlin enhances the usability of Constraint Layout by providing:

• Extension Functions: Add functionality to existing classes, making it easier to manipulate views and constraints.
• Domain-Specific Language (DSL): Use Kotlin’s DSL support to create layouts programmatically in a concise, readable way.
• Lazy Initialization: Initialize views only when needed, optimizing performance.

Key Features of Constraint Layout in Kotlin Development

Constraints in Kotlin

Constraints define the relationships between UI elements, allowing you to position them relative to each other or to the parent layout. In Kotlin, you can set these constraints programmatically, giving you more flexibility and control over your UI.

Example: Setting constraints dynamically in Kotlin:

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val button = Button(this).apply {
    text = "Click Me"
}

val layoutParams = ConstraintLayout.LayoutParams(
    ConstraintLayout.LayoutParams.WRAP_CONTENT,
    ConstraintLayout.LayoutParams.WRAP_CONTENT
)

layoutParams.startToStart = ConstraintLayout.LayoutParams.PARENT_ID
layoutParams.endToEnd = ConstraintLayout.LayoutParams.PARENT_ID
layoutParams.topToTop = ConstraintLayout.LayoutParams.PARENT_ID

constraintLayout.addView(button, layoutParams)

Chains in Kotlin

Chains allow you to create horizontal and vertical linear arrangements of views, giving you more control over distribution, weight, and positioning than LinearLayout.

Example: Creating a horizontal chain in Kotlin:

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val button1 = Button(this).apply { text = "Button 1" }
val button2 = Button(this).apply { text = "Button 2" }

val layoutParams1 = ConstraintLayout.LayoutParams(
    ConstraintLayout.LayoutParams.WRAP_CONTENT,
    ConstraintLayout.LayoutParams.WRAP_CONTENT
).apply {
    startToStart = ConstraintLayout.LayoutParams.PARENT_ID
    endToStart = button2.id
}

val layoutParams2 = ConstraintLayout.LayoutParams(
    ConstraintLayout.LayoutParams.WRAP_CONTENT,
    ConstraintLayout.LayoutParams.WRAP_CONTENT
).apply {
    startToEnd = button1.id
    endToEnd = ConstraintLayout.LayoutParams.PARENT_ID
}

constraintLayout.addView(button1, layoutParams1)
constraintLayout.addView(button2, layoutParams2)

Guidelines & Barriers in Kotlin

Guidelines help position views as a percentage of the parent layout’s size, while barriers ensure that views don’t overlap.

Example: Adding guidelines and barriers:

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val guideline = Guideline(this).apply {
    id = View.generateViewId()
    setGuidelinePercent(0.5f) // 50% from the top
}
constraintLayout.addView(guideline)

val button = Button(this).apply { text = "Aligned to Guideline" }
val layoutParams = ConstraintLayout.LayoutParams(
    ConstraintLayout.LayoutParams.WRAP_CONTENT,
    ConstraintLayout.LayoutParams.WRAP_CONTENT
).apply {
    topToTop = guideline.id
}
constraintLayout.addView(button, layoutParams)

Bias and Ratios

Bias allows you to adjust the position of a view along a constraint, while aspect ratios help maintain the size ratio of views like images.

Example: Adjusting bias in Kotlin:

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val imageView = ImageView(this).apply {
    setImageResource(R.drawable.sample_image)
}

val layoutParams = ConstraintLayout.LayoutParams(
    0, // width constrained by aspect ratio
    ConstraintLayout.LayoutParams.WRAP_CONTENT
).apply {
    dimensionRatio = "H, 16:9" // 16:9 aspect ratio
    horizontalBias = 0.7f // Position 70% across the parent
}

constraintLayout.addView(imageView, layoutParams)

Practical Examples: Speeding Up UI Development with Kotlin and Constraint Layout

Building a Responsive Login Screen

• Problem: Creating a login screen with username and password fields and a login button, ensuring it is responsive across devices.

• Solution: Use Constraint Layout in combination with Kotlin code to dynamically adjust constraints for different screen sizes.

Example: Kotlin code to build the layout:

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val username = EditText(this).apply { hint = "Username" }
val password = EditText(this).apply { hint = "Password" }
val loginButton = Button(this).apply { text = "Login" }

val layoutParamsUsername = ConstraintLayout.LayoutParams(
    ConstraintLayout.LayoutParams.MATCH_PARENT,
    ConstraintLayout.LayoutParams.WRAP_CONTENT
).apply {
    topToTop = ConstraintLayout.LayoutParams.PARENT_ID
    marginStart = 16
    marginEnd = 16
}

val layoutParamsPassword = ConstraintLayout.LayoutParams(
    ConstraintLayout.LayoutParams.MATCH_PARENT,
    ConstraintLayout.LayoutParams.WRAP_CONTENT
).apply {
    topToBottom = username.id
    marginStart = 16
    marginEnd = 16
}

val layoutParamsLogin = ConstraintLayout.LayoutParams(
    ConstraintLayout.LayoutParams.WRAP_CONTENT,
    ConstraintLayout.LayoutParams.WRAP_CONTENT
).apply {
    topToBottom = password.id
    startToStart = ConstraintLayout.LayoutParams.PARENT_ID
    endToEnd = ConstraintLayout.LayoutParams.PARENT_ID
}

constraintLayout.addView(username, layoutParamsUsername)
constraintLayout.addView(password, layoutParamsPassword)
constraintLayout.addView(loginButton, layoutParamsLogin)

Integrating Kotlin-Specific Features with Constraint Layout

1. Kotlin DSL for Constraint Layout

Introduce Kotlin’s DSL support for creating layouts programmatically without XML, making layouts more readable and maintainable.

2. Extension Functions

Kotlin’s extension functions reduce boilerplate by allowing you to add new functionalities to existing classes without modifying them.

3. ViewBinding and Kotlin Coroutines

ViewBinding makes accessing views safer, while Kotlin coroutines simplify managing asynchronous UI updates and animations, especially within Constraint Layout.

Common Mistakes and How to Avoid Them When Using Constraint Layout in Kotlin

• Overcomplicating Simple Layouts: Avoid using Constraint Layout for simple UIs.
• Incorrectly Applied Constraints: Ensure constraints aren’t conflicting.
• Misusing Chains: Properly configure chains to avoid uneven distribution of UI elements.
• Avoid Hardcoded Dimensions: Leverage percentage-based positioning instead of fixed values.

Best Practices for Combining Constraint Layout with Kotlin

• Write Clean, Readable Kotlin Code: Use extension functions and data binding to keep your code clean.
• Keep Your Layout Hierarchy Flat: Minimize nesting for better performance.
• Utilize the Visual Editor: Leverage Android Studio’s visual editor to fine-tune layout constraints.
• Use Kotlin Coroutines for Asynchronous UI Updates: Ensure smooth UI transitions using Coroutines.

Bottom Line

By combining Kotlin with Constraint Layout, developers can accelerate UI development by reducing layout complexity, improving performance, and creating more responsive designs. The synergy between Kotlin’s concise syntax and Constraint Layout’s powerful layout features enables faster, cleaner, and more efficient Android development.🎁