Showkase

Showkase is an annotation-processor based Android library that helps you organize, discover, search and visualize Jetpack Compose UI elements. With minimal configuration it generates a UI browser that helps you easily find your components, colors & typography. It also renders your components in common situations like dark mode, right-to-left layouts, and scaled fonts which help in finding issues early.

Jetpack Compose is in alpha so Showkase may need breaking changes in order to keep up with changes in Compose.

Why should you use Showkase?

• When using component based UI toolkits (like React, Compose, Flutter, etc), our codebase often ends up with hundreds of components that are hard to discover, visualize, search and organize.
• Showkase eliminates the manual work of maintaining a UI preview/browser app that each company is forced to build in order to maintain their design system.
• Since all the available UI elements are now easily searchable and discoverable, there is better reuse of UI elements in your repo. This makes it useful for maintaining consistency across your app. The biggest problem for enforcing a design system is discoverability and Showkase hopefully solves that problem for your team.
• It allows you to quickly visualize @Composable components, Color properties and TextStyle (Typography) as you are building them. The goal is to improve the turnaround time in creating production-ready UI elements.
• Showkase aids in catching common UI issues early with the help of auto-generated permutations of your components.

Features

• Super simple setup
• Support for visualizing composables(@ShowkaseComposable), colors(@ShowkaseColor) & typography(@ShowkaseTypography).
• First class support for @Preview annotation. If you are already using @Preview for previews in Android Studio, using Showkase is even easier as all those components are included in the Showkase browser.
• Support for top level, class, object & companion object functions and properties to be annotated with the Showkase annotations.
• 5 Permutations are auto created for each composable (Basic Example, Dark Mode, RTL, Font Scaled, Display Scaled. Look in the gif above for examples)'. More to be added in the future!
• Support for searching a Showkase UI element by name or group.
• KDoc support that shows the documentation that you added for a component in the Showkase browser.
• Multi-module support for showcasing UI elements across multiple modules.
• Support for constraining a component with a custom height/width using additional parameters in the annotation.
• Descriptive error messages so that the users of the library can fix any incorrect setup.
• Incremental annotation processor that makes the code-gen more performant.

Installation

Using Showkase is straightforward and takes just a couple of minutes to get started.

Step 1: Add the dependency to your module's build.gradle file. If you have a multi-module setup, add this dependency to all the modules with UI elements that should be displayed inside the Showkase browser.

implementation "com.airbnb.android:showkase:1.0.0-alpha08"
kapt "com.airbnb.android:showkase-processor:1.0.0-alpha08"

Step 2: Add the relevant annotations for every UI element that should be a part of the Showkase browser.

For @Composable components, you can either use the @Preview annotation that Compose comes with or use the @ShowkaseComposable annotation:

@Preview(name = "Custom name for component", group = "Custom group name")
@Composable
fun MyComponent() { ... }

// or

@ShowkaseComposable(name = "Name of component", group = "Group Name")
@Composable
fun MyComponent() { ... }

For Color properties, you can add the @ShowkaseColor annotation to the field:

@ShowkaseColor(name = "Primary Color", group = "Material Design")
val primaryColor = Color(0xFF6200EE)

For TextStyle properties that are useful for typography, you can add the @ShowkaseTypography annotation to the field:

@ShowkaseTypography(name = "Custom name for style", group = "Custom group name")
val h1 = TextStyle(
    fontWeight = FontWeight.Light,
    fontSize = 96.sp,
    letterSpacing = (-1.5).sp
)

Step 3: Define an implementation of the ShowkaseRootModule interface in your root module. If your setup involves only a single module, add this implementation in that module. Ensure that this implementation is also annotated with the @ShowkaseRoot annotation.

@ShowkaseRoot
class MyRootModule: ShowkaseRootModule

Step 4: Showkase is now ready for use! Showkase comes with an Activity that you need to start for accessing the UI browser. Typically you would start this activity from the debug menu of your app but you are free to start this from any place you like! A nice helper function createShowkaseBrowserIntent is generated for you so you might have to build the app once before it's available for use. Just start the intent and that's all you need to do for accessing Showkase!

startActivity(createShowkaseBrowserIntent(this))

Documentation

1. @ShowkaseComposable

Used to annotate @Composable functions that should be displayed inside the Showkase browser. If you are using the @Preview annotation with your @Composable function already then you don't need to use this annotation. Showkase has first class support for @Preview.

Here's how you would use it with your @Composable function:

@ShowkaseComposable(name = "Name", group = "Group")
@Composable
fun MyComposable() {
    .......
    .......
}

Name and group are optional. Look at the properties section to understand the behavior when you don't pass any properties.

Note: Make sure that you add this annotation to only those functions that meet the following criteria:

• Functions that don't have any parameters
• If it does have a parameter, it has to be annotated with @PreviewParameter that is provided a PreviewParameterProvider implementation.

This is identical to how @Preview works in Compose as well so Showkase just adheres to the same rules.

// Consider a simple data class
data class Person(
    val name: String,
    val age: Int
)

// In order to pass a person object as a parameter to our composable function, we will annotate 
// our parameter with `@PreviewParameter` and pass a `PreviewParameterProvider` implementation.
@ShowkaseComposable(name = "Name", group = "Group") or @Preview(name = "Name", group = "Group")
@Composable
fun MyComposable(
    @PreviewParameter(provider = ParameterProvider::class) person: Person
) {
    ...
}

class ParameterProvider : PreviewParameterProvider<Person> {
    override val values: Sequence<Person>
        get() = sequenceOf(
            Person("John", 12),
            Person("Doe", 20)
        )

    override val count: Int
        get() = super.count
}

// Since we return 2 objects through our ParameterProvider, Showkase will create 2 previews 
// for this single composable function. Each preview will have it's own parameter that's passed 
// to it - Person("John", 12) for the first preview and Person("Doe", 20) for the second one. 
// This is an effective way to preview your composables against different sets of data.

Alternatively, you could simply wrap your function inside another function that doesn't accept any parameters -

@Composable
fun MyComposable(name: String) {
    .......
    .......
}

In order to make this function compatible with Showkase, you could further wrap this function inside a method that doesn't accept parameters in the following way:

@ShowkaseComposable(name = "Name", group = "Group")
@Composable
fun MyComposablePreview() {
    MyComposable("Name")
}

@ShowkaseComposable currently supports the following properties:

2. @ShowkaseColor

Used to annotate Color properties that should be presented inside the Showkase browser. Here's how you would use it with your Color fields:

@ShowkaseColor(name = "Name", group = "Group")
val redColor = Color.Red

@ShowkaseColor("Primary", "Light Colors")
val primaryColor = Color(0xFF6200EE)

Name and group are optional. Look at the properties section below to understand the behavior when you don't pass any properties.

@ShowkaseColor currently supports the following properties:

3. @ShowkaseTypography

Used to annotate TextStyle properties that should be presented inside the Showkase browser. Here's how you would use it with your TextStyle fields:

@ShowkaseTypography(name = "Name", group = "Group")
val h1 = TextStyle(
    fontWeight = FontWeight.Light,
    fontSize = 96.sp,
    letterSpacing = (-1.5).sp
)

Name and group are optional. Look at the properties section below to understand the behavior when you don't pass any properties.

@ShowkaseTypography currently supports the following properties:

4. @ShowkaseRoot

Used to annotate the ShowkaseRootModule implementation class. This is needed to let Showkase know more about the module that is going to be the root module for aggregating all the Showkase supported UI elements across all the different modules(if you are using a multi-module project). If you are only using a single module in your project, add it to that module. You are allowed to have only one @ShowkaseRoot per module.

Here's an example of how you would use it:

@ShowkaseRoot
fun MyRootModule: ShowkaseRootModule

Note: The root module is the main module of your app that has a dependency on all other modules in the app. This is relevant because we generate the Showkase related classes in the package of the root module and we need to be able to access the UI elements across all the sub modules. This is only possible from the root module as it typically has a dependency on all the sub-modules.

Frequently Asked Questions

Coming Soon!

Here are some ideas that we are thinking about. We are also not limited to these and would love to learn more about your use cases.

• Support for passing a @PreviewParameter parameter to @Preview/@ShowkaseComposable components.
• Hooks for screenshot testing. Since all your components are a part of the Showkase browser, this would be a good opportunity to make this a part of your CI and detect diffs in components.
• Support for other UI elements that are a part of your design system (like icons, spacing, etc)
• Generating a web version of the Showkase browser with documentation, search and screenshots.

Contributing

Pull requests are welcome! We'd love help improving this library. Feel free to browse through open issues to look for things that need work. If you have a feature request or bug, please open a new issue so we can track it.

License

Copyright 2020 Airbnb, Inc.

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

   http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.