How to use Lazy lists on Android Jetpack Compose

By / Jetpack Compose /

Introduction

Lazy lists are a powerful feature of Jetpack Compose that allows you to efficiently display large amounts of data. By using a lazy list, you only need to render the items that are currently visible on the screen. This can significantly improve the performance and memory usage of your app, especially when dealing with a large dataset

In this article, I will explain to you how to use three types of lazy lists.

  • Lazy Column: List items vertically.
  • Lazy Row: List items horizontally.
  • Lazy Vertical and Horizontal Grids: List items in a grid.

Let’s get started.

LazyColumn

The LazyColumn composable in Android is a powerful tool for building efficient and performant lists in your Android app. It is part of the Jetpack Compose UI toolkit, which introduced a declarative way of building user interfaces.

Here’s an example of how you can use LazyColumn:

@Composable
fun MyLazyColumn(items: List<String>) {
    LazyColumn(
        contentPadding = PaddingValues(16.dp),
        verticalArrangement = Arrangement.spacedBy(16.dp)
    ) {
        items(items) { text ->
            // item layout goes here
            Card(
                colors = CardDefaults.cardColors(containerColor = Color(0xFFF8BBD0)),
                modifier = Modifier.fillMaxWidth()
            ) {
                Text(text = "Item $text", modifier = Modifier.padding(16.dp))
            }
        }
    }
}
Kotlin

In this example, we define a Composable function called MyLazyColumn that takes a list of strings as input. Inside the LazyColumn block, we use the items function to iterate over the list and display a Text composable for each item inside a Card with containerColor set to 0xFFF8BBD0.

Here is what it will look like:

The contentPadding allow you to add padding to the edges of the List without clipping the items when scrolling past the padded area.

The verticalArrangement let you control the arrangement of items vertically, in this case, I choose to add space between items.

Additionally, LazyColumn provides various customization options, such as reverseLayout, contentPadding, and userScrollEnabled which are all parameters of the LazyColumn Composable.

LazyRow

The LazyRow composable in Android is another powerful tool provided by Jetpack Compose for building efficient and performant horizontal lists in your Android app. It follows the same concept of lazy loading as the LazyColumn, rendering only the visible items on the screen.

Here’s an example of how you can use LazyRow:

@Composable
fun MyLazyRow(items: List<String>) {
    LazyRow(
        contentPadding = PaddingValues(16.dp),
        horizontalArrangement = Arrangement.spacedBy(16.dp)
    ) {
        items(items) { text ->
            // item layout goes here
            Card(
                colors = CardDefaults.cardColors(containerColor = Color(0xFFF8BBD0)),
                modifier = Modifier.fillMaxWidth()
            ) {
                Text(text = "Item $text", modifier = Modifier.padding(16.dp))
            }
        }
    }
}
Kotlin

In this example, we define a Composable function called MyLazyRow that takes a list of strings as input. Inside the LazyRow block, we use the items function to iterate over the list and display a Text composable for each item inside a Card with containerColor set to 0xFFF8BBD0.

Here is what it will look like:

The horizontalArrangement let you control the arrangement of items horizontally, in this case, I choose to add space between items.

Similar to LazyColumn, LazyRow also provides various customization options like reverseLayout, contentPadding, and userScrollEnabled which can be used to further tailor the behavior of your horizontal list.

By using LazyRow, you can efficiently display horizontally scrollable lists in your app, handling large amounts of data smoothly and optimizing memory usage.

LazyVerticalGrid

LazyVerticalGrid is another powerful component provided by Jetpack Compose for building efficient and performant grid layouts in your Android app. It follows the same concept of lazy loading as the LazyColumn and LazyRow, rendering only the visible items on the screen.

Here’s an example of how you can use LazyVerticalGrid:

@Composable
fun MyLazyVerticalGrid(items: List<String>) {
    LazyVerticalGrid(
        contentPadding = PaddingValues(16.dp),
        horizontalArrangement = Arrangement.spacedBy(16.dp),
        verticalArrangement = Arrangement.spacedBy(16.dp),
        columns = GridCells.Fixed(3)
    ) {
        items(items) { text ->
            // item layout goes here
            Card(
                colors = CardDefaults.cardColors(containerColor = Color(0xFFF8BBD0)),
            ) {
                Text(text = "Item $text", modifier = Modifier.padding(16.dp))
            }
        }
    }
}
Kotlin

In this example, we define a Composable function called MyLazyVerticalGrid that takes a list of strings as input. Inside the LazyVerticalGrid block, we use the items function to iterate over the list and display a Text composable for each item inside a Card with containerColor set to 0xFFF8BBD0.

Here is what it will look like:

The columns parameter allows you to specify the number of columns in the grid. In this case, we set it to GridCells.Fixed(3), which means there will be 3 columns in the grid. You can also set it to GridCells.Adaptive(minSizeInDp) and give it the minimum size so that the column number will depend on the screen size. Another possible value is GridCells.FixedSize(sizeInDp) which defines a grid with as many rows or columns as possible on the condition that every cell takes exactly the given size.

Similar to LazyColumn and LazyRow, LazyVerticalGrid provides various customization options like reverseLayout, contentPadding, and userScrollEnabled which can be used to further tailor the behavior of your grid.

By using LazyVerticalGrid, you can efficiently display grid layouts in your app, handling large amounts of data smoothly and optimizing memory usage.

LazyHorizontalGrid

LazyHorizontalGrid is a powerful component provided by Jetpack Compose for building efficient and performant horizontal grid layouts in your Android app. It follows the same concept of lazy loading as LazyColumn, LazyRow, and LazyVerticalGrid, rendering only the visible items on the screen.

Here’s an example of how you can use LazyHorizontalGrid:

@Composable
fun MyLazyHorizontalGrid(items: List<String>) {
    LazyHorizontalGrid(
        contentPadding = PaddingValues(16.dp),
        horizontalArrangement = Arrangement.spacedBy(16.dp),
        verticalArrangement = Arrangement.spacedBy(16.dp),
        rows = GridCells.Fixed(6)
    ) {
        items(items) { text ->
            // item layout goes here
            Card(
                colors = CardDefaults.cardColors(containerColor = Color(0xFFF8BBD0)),
            ) {
                Text(text = "Item $text", modifier = Modifier.padding(16.dp))
            }
        }
    }
}
Kotlin

In this example, we define a Composable function MyLazyHorizontalGrid that takes a list of strings as input. Inside the LazyHorizontalGrid block, we use the items function to iterate over the list and display a Text composable for each item inside a Card with containerColor set to 0xFFF8BBD0.

The cells parameter allows you to specify the number of cells in each row. In this case, we set it to GridCells.Fixed(6), which means there will be 6 rows. Like the LazyVerticalGrid you can also use GridCells.Adaptive(minSizeInDp) or GridCells.FixedSize(sizeInDp).

Here is what it will look like:

LazyHorizontalGrid provides various customization options similar to LazyColumn, LazyRow, and LazyVerticalGrid. You can customize parameters such as reverseLayout, contentPadding, and userScrollEnabled to tailor the behavior of your horizontal grid.

By using LazyHorizontalGrid, you can efficiently display horizontal grid layouts in your app, handling large amounts of data smoothly and optimizing memory usage.

Conclusion

In conclusion, lazy lists in Jetpack Compose are a powerful feature that enables efficient rendering of large amounts of data in Android apps. By using lazy loading, only the items visible on the screen are rendered, resulting in improved performance and reduced memory usage.

In this article, we explored four types of lazy lists: LazyColumn, LazyRow, LazyVerticalGrid, and LazyHorizontalGrid 

  • LazyColumn allows you to create vertically scrolling lists, while LazyRow provides horizontally scrolling lists. Both components support various customization options like padding, arrangement, and scrolling behavior.
  • LazyVerticalGrid and LazyHorizontalGrid are used for displaying items in a grid layout. They offer the flexibility to define the number of columns or rows and provide the same customization options as the other lazy lists.

By leveraging these lazy lists, developers can efficiently handle large datasets, optimize memory consumption, and enhance the performance of their Android apps. This makes it easier to build responsive and performant user interfaces that deliver a seamless experience to the users.

Overall, lazy lists are a valuable tool in the Jetpack Compose toolbox for building efficient and responsive UIs that can handle large amounts of data.

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