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Jetpack Compose Animations: A Quick Guide

Jetpack Compose, the modern Android UI toolkit, has revolutionized how we build user interfaces. With its declarative approach, Compose simplifies UI development and makes it more intuitive. One of the exciting aspects of Compose is its built-in animation capabilities. In this blog post, we’ll explore how to create engaging animations using Jetpack Compose.

Animate Common Composable Properties

Compose provides convenient APIs for animating common properties of a composable. Let’s dive into some examples:

1. Animating Visibility

You can use AnimatedVisibility to hide or show a composable. Here’s a basic example:var visible by remember { mutableStateOf(true) } AnimatedVisibility(visible) { // Your composable here // ... }

The enter and exit parameters of AnimatedVisibility allow you to configure how a composable behaves when it appears and disappears. Alternatively, you can animate the alpha over time using animateFloatAsState:val animatedAlpha by animateFloatAsState( targetValue = if (visible) 1.0f else 0f, label = "alpha" ) Box( modifier = Modifier .size(200.dp) .graphicsLayer { alpha = animatedAlpha } .clip(RoundedCornerShape(8.dp)) .background(colorGreen) .align(Alignment.TopCenter) ) { // Your content here }

Keep in mind that changing the alpha keeps the composable in the composition, whereas AnimatedVisibility eventually removes it.

2. Animating Background Color

To animate the background color of a composable, use animateColorAsState:val animatedColor by animateColorAsState( if (animateBackgroundColor) colorGreen else colorBlue, label = "color" ) Column( modifier = Modifier.drawBehind { drawRect(animatedColor) } ) { // Your composable here }

This approach is more performant than using Modifier.background(), especially when animating colors over time.

Practical Magic with Animations

Compose offers many other animation mechanisms, such as animating size, position, and more. For a comprehensive understanding, explore the full set of API options in the Compose Animation documentation.

In summary, Jetpack Compose empowers developers to create delightful and interactive UIs with ease. Whether you’re building a simple app or a complex interface, animations play a crucial role in enhancing the user experience. Happy animating! 🚀

Source: Conversation with Bing, 3/24/2024
(1) Quick guide to Animations in Compose | Jetpack Compose | Android Developers. https://developer.android.com/jetpack/compose/animation/quick-guide.
(2) Quick Start Guide on Animations in Jetpack Compose – Finotes Blog. https://www.blog.finotes.com/post/quick-start-guide-on-animations-in-jetpack-compose.
(3) Animate Your Jetpack Compose UI: A Comprehensive Overview. https://blog.realogs.in/animating-jetpack-compose-ui/.
(4) Jetpack compose: Custom animations | by Hardik P | Canopas. https://blog.canopas.com/jetpack-compose-custom-animations-550dcdcded83.
(5) Animations in Jetpack Compose: animateContentSize – Medium. https://medium.com/@timacosta06/animations-in-compose-animatecontentsize-1eca1194ca1e.

Demystifying LazyColumns in Jetpack Compose

Let’s dive into the world of Jetpack Compose and explore how to use LazyColumn effectively. 🚀

Introduction

Jetpack Compose is a modern Android UI toolkit that simplifies building native user interfaces. One of its powerful features is the LazyColumn, which provides an efficient way to display large lists. Think of it as the successor to the good old RecyclerView and its adapter.

In this blog post, we’ll explore what LazyColumn is, how it works, and how you can leverage it to create dynamic and performant lists in your Android apps.

What is `LazyColumn`?

LazyColumn is a vertically scrolling list that only composes and lays out the currently visible items. Unlike a regular Column, which renders all items regardless of visibility, LazyColumn is “lazy.” It means that it efficiently handles large lists by rendering only the items currently visible on the screen. This lazy behavior significantly improves performance when dealing with extensive datasets.

Basic Usage

Let’s get started with some code examples. Suppose you want to create a simple list of messages using LazyColumn. Here’s how you can do it:@Composable fun MessageList(messages: List<Message>) { LazyColumn { items(messages) { message -> MessageRow(message) } } }

In the above snippet:

We define a MessageList composable that takes a list of Message objects.
Inside the LazyColumn block, we use the items function to iterate over the messages and compose each MessageRow.

DSL for Describing Items

The magic of LazyColumn lies in its DSL (domain-specific language). Instead of directly emitting composables like in a regular Column, we work with a LazyListScope block. This scope allows us to describe the item contents efficiently.

Adding Single Items

The most basic function in the DSL is item(), which adds a single item:LazyColumn { item { Text(text = "First item") } items(5) { index -> Text(text = "Item: $index") } item { Text(text = "Last item") } }

Handling Collections

We can also add collections of items using extensions like items() or itemsIndexed():LazyColumn { items(messages) { message -> MessageRow(message) } }

The itemsIndexed() extension even provides the index for more advanced scenarios.

Conclusion

And there you have it! LazyColumn is your go-to solution for efficiently displaying lists in Jetpack Compose. Whether you’re building a chat app, a news feed, or any other data-driven UI, give LazyColumn a try.

Remember, it’s all about being lazy in the right way—rendering only what’s necessary and keeping your UI smooth and responsive. Happy composing! 🎨

References:

Source: Conversation with Bing, 3/23/2024
(1) Jetpack Compose | Implementing a LazyColumn / RecyclerView | Part I. https://www.youtube.com/watch?v=_G0ndJLbaJI.
(2) How to Create a Lazy Column With Categories in Jetpack Compose. https://www.youtube.com/watch?v=XfYlRn_Jy1g.
(3) How to Implement a Multi-Select LazyColumn in Jetpack Compose – Android Studio Tutorial. https://www.youtube.com/watch?v=pvNcJXprrKM.
(4) Lists and grids | Jetpack Compose | Android Developers. https://developer.android.com/jetpack/compose/lists.
(5) LazyColumn in Jetpack Compose – Jetpack Compose World. https://jetpackcomposeworld.com/lazycolumn-in-jetpack-compose/.
(6) Column vs LazyColumn in Android Jetpack Compose. https://codingwithrashid.com/column-vs-lazycolumn-in-android-jetpack-compose/.
(7) LazyColumn – Jetpack Compose Playground – GitHub Pages. https://foso.github.io/Jetpack-Compose-Playground/foundation/lazycolumn/.
(8) undefined. https://pl-coding.com/premium-courses/.

How to use composable functions in Android Jetpack Compose

Android Jetpack Compose is a modern toolkit for building native UI. It simplifies and accelerates UI development on Android with less code, powerful tools, and intuitive Kotlin APIs ¹. In this blog post, we will explore how to use composable functions, which are the building blocks of Jetpack Compose.

What are composable functions?

Composable functions are functions that can be used to describe your UI programmatically by providing data dependencies, rather than focusing on the process of the UI’s construction ¹. To create a composable function, you just need to add the @Composable annotation to the function name. For example:

@Composable fun Greeting(name: String) { Text(text = "Hello, $name!") }

This function defines a simple UI element that displays a text label with a greeting message. You can call this function from another composable function, such as the setContent block that defines the activity’s layout:

override fun onCreate(savedInstanceState: Bundle?) { super.onCreate(savedInstanceState) setContent { Greeting(name = "World") } }

This will render the text “Hello, World!” on the screen. You can also pass different parameters to the composable function to customize its behavior. For example:

setContent { Greeting(name = "Android") }

This will render the text “Hello, Android!” on the screen.

How to preview composable functions in Android Studio?

One of the advantages of using composable functions is that you can preview them in Android Studio without having to build and install the app to an Android device or emulator ¹. To do this, you need to use the @Preview annotation on a composable function that does not take in parameters. For example:

@Preview @Composable fun PreviewGreeting() { Greeting(name = "Compose") }

This function calls the Greeting function with a parameter of “Compose”. You can then see a preview of this function in Android Studio by clicking on the split (design/code) view. You can also refresh the preview at any time by clicking on the refresh button at the top of the preview window.

How to use different types of composable functions?

There are many types of composable functions that you can use to create different UI elements and layouts in Jetpack Compose. Some of the most common ones are:

Text: This function displays a text label on the screen. You can customize its appearance by passing parameters such as color, fontSize, fontWeight, etc.
Image: This function displays an image on the screen. You can load an image from a resource or a URL by using the painterResource or rememberImagePainter functions respectively. You can also adjust its size and shape by using parameters such as modifier, contentScale, contentDescription, etc.
Button: This function displays a button on the screen. You can handle its click event by passing a lambda expression to the onClick parameter. You can also style it by using parameters such as colors, shape, elevation, etc.
Row: This function arranges its children horizontally in a row. You can control how they are aligned and spaced by using parameters such as horizontalArrangement, verticalAlignment, modifier, etc.
Column: This function arranges its children vertically in a column. You can control how they are aligned and spaced by using parameters such as verticalArrangement, horizontalAlignment, modifier, etc.
Box: This function stacks its children on top of each other in a box. You can control how they are positioned and sized by using parameters such as alignment, contentAlignment, modifier, etc.

Here is an example of how to use some of these composable functions to create a simple UI:

@Composable fun ProfileCard(name: String, image: Int) { Row( modifier = Modifier .padding(16.dp) .fillMaxWidth() .border(1.dp, Color.Gray) ) { Image( painter = painterResource(id = image), contentDescription = null, modifier = Modifier .size(64.dp) .clip(CircleShape) ) Spacer(modifier = Modifier.width(8.dp)) Column( verticalArrangement = Arrangement.Center ) { Text(text = name, fontWeight = FontWeight.Bold) Text(text = "Android Developer", fontStyle = FontStyle.Italic) } } }

This function creates a profile card with an image and some text. You can preview it in Android Studio by adding another function with the @Preview annotation:

@Preview @Composable fun PreviewProfileCard() { ProfileCard(name = "John Doe", image = R.drawable.profile_pic) }

This will show you how the profile card looks like in the preview window.

Conclusion

In this blog post, we learned how to use composable functions in Android Jetpack Compose. We saw how to create, preview, and use different types of composable functions to build native UI. Composable functions are a powerful and expressive way to describe your UI with less code and more flexibility. If you want to learn more about Jetpack Compose, you can check out the official documentation ¹ or some of the tutorials ² ³ available online.

I hope this blog post was helpful for you. If you have any questions or feedback, please let me know in the comments. Thank you for reading! 😊

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Image Loading in Jetpack Compose

Jetpack Compose is a modern toolkit for building native UI on Android. It simplifies and accelerates UI development with declarative and reactive programming. One of the common tasks in UI development is to display images from various sources, such as network, local storage, assets or resources. In this blog post, we will explore how to load images in Jetpack Compose using different libraries and techniques.

Loading images from disk

To load an image from disk, such as a PNG, JPEG, WEBP or vector resource, we can use the Image composable with the painterResource API. The painterResource function takes an image reference (such as a resource ID) and returns a Painter object that can be used to draw the image on the screen. We don’t need to know the type of the asset, just use painterResource in Image or paint modifiers ¹.

For example, to load an image from a resource:

Image( painter = painterResource(id = R.drawable.dog), contentDescription = stringResource(id = R.string.dog_content_description) )

To ensure that our app is accessible, we should supply a contentDescription for visual elements on screen. TalkBack reads out the content description, so we must ensure that the text is meaningful if read out loud and translated. In the above example, we use a stringResource function to load up the translated content description from the strings.xml file. If our visual element on screen is purely for visual decoration, we can set our contentDescription to null for the screen reader to ignore it ¹.

If we need lower-level ImageBitmap specific functionality, we can use ImageBitmap.imageResource function to load up a bitmap. For more information on ImageBitmaps, read the ImageBitmap versus ImageVector section ¹.

Loading images from the internet

To load an image from the internet, there are several third-party libraries available that can help us handle the process. Image loading libraries do a lot of the heavy lifting for us; they handle both caching (so we don’t download the image multiple times) and networking logic to download the image and display it on screen ¹.

Some of the popular image loading libraries for Jetpack Compose are:

Coil: An image loading library backed by Kotlin Coroutines (Instacart)² ¹.
Glide: A fast and efficient image loading library for Android focused on smooth scrolling (Google)¹.
Fresco: An image loading library that supports a variety of image formats and sources (Facebook)³.
Landscapist: A pluggable, highly optimized Jetpack Compose image loading solution that fetches and displays network images with Glide, Coil, and Fresco. This library supports tracing image loading states, composing custom implementations, and some valuable animations, such as crossfades, blur transformation, and circular reveals (skydoves)² ³.

To use any of these libraries in our Android app, we need to add the corresponding dependency to our build.gradle file. Then, we can use their provided composables or extensions to load an image from a URL.

For example, to load an image with Coil:

AsyncImage( model = "https://example.com/image.jpg", contentDescription = "Translated description of what the image contains" )

To load an image with Glide:

GlideImage( model = "https://example.com/image.jpg", contentDescription = "Translated description of what the image contains" )

To load an image with Fresco:

FrescoImage( model = "https://example.com/image.jpg", contentDescription = "Translated description of what the image contains" )

To load an image with Landscapist:

NetworkImage( imageUrl = "https://example.com/image.jpg", contentDescription = "Translated description of what the image contains" )

We can also configure the requests with optional parameters or lambdas to customize the loading behavior and appearance of the images.

Code examples

Here are some code examples of using different libraries to load images from the internet in Jetpack Compose:

Loading an image with Coil

AsyncImage( model = "https://coil-kt.github.io/coil/logo.svg", contentDescription = "Coil logo", modifier = Modifier.size(200.dp), loading = { Box(Modifier.matchParentSize()) { CircularProgressIndicator(Modifier.align(Alignment.Center)) } }, error = { Image( painter = painterResource(id = R.drawable.error), contentDescription = "Error image" ) } )

Loading an image with Glide

GlideImage( model = "https://coil-kt.github.io/coil/logo.svg", contentDescription = "Coil logo", modifier = Modifier.size(200.dp), requestBuilder = { crossfade(true) placeholder(R.drawable.placeholder) error(R.drawable.error) } )

Loading an image with Fresco

FrescoImage( model = "https://coil-kt.github.io/coil/logo.svg", contentDescription = "Coil logo", modifier = Modifier.size(200.dp), controllerBuilder = { autoPlayAnimations(true) placeholderImage(R.drawable.placeholder) failureImage(R.drawable.error) } )

Loading an image with Landscapist

NetworkImage( imageUrl = "https://coil-kt.github.io/coil/logo.svg", contentDescription = "Coil logo", modifier = Modifier.size(200.dp), loading = { ShimmerParams( baseColor = Color.LightGray, highlightColor = Color.White, dropOff = 0.65f ) }, failure = { Image( painter = painterResource(id = R.drawable.error), contentDescription = "Error image" ) }, success = { RevealCircularTransition( durationMillis = 600, delayMillis = 100 ) } )