Drag Select Compose

This is a Compose Multiplatform library that allows you to easily implement a "Google Photos"-style multi-selection in your Compose apps.

You can run the demo at demo.dragselectcompose.com and view the KDocs at docs.dragselectcompose.com

Table of Contents

• Platforms
• Inspiration
• Setup
  • Single Platform
  • Multiplatform
  • Version Catalog
• Usage
• Extensions
• Grid Wrapper
• Demo
  • Android
  • Multiplatform
• License

Platforms

This library is written for Compose Multiplatform, and can be used on the following platforms:

• Android
• iOS
• JVM (Desktop)
• JavaScript/wasm (Browser)

Inspiration

This library was inspired by this article and the gist.

As well as the drag-select-recyclerview library.

Setup

You can add this library to your project using Gradle.

Single Platform

To add to a single platform like Android, add the dependency to your app level build.gradle.kts file:

dependencies {
    // Includes the core functionality along with all of the optional modules
    implementation("com.dragselectcompose:dragselect:2.4.1")

    // Or use the modules you want

    // Core functionality
    implementation("com.dragselectcompose:core:2.4.1")

    // Optional extensions for adding semantics and toggle Modifiers to Grid items
    implementation("com.dragselectcompose:extensions:2.4.1")

    // Optional wrappers around LazyGrid that implement the selection UI for you
    implementation("com.dragselectcompose:grid:2.4.1")
}

Multiplatform

To add to a multiplatform project, add the dependency to the common source-set:

kotlin {
    sourceSets {
        commonMain {
            dependencies {
                // Includes the core functionality along with all of the optional modules
                implementation("com.dragselectcompose:dragselect:2.4.1")

                // Or use the modules you want

                // Core functionality
                implementation("com.dragselectcompose:core:2.4.1")

                // Optional extensions for adding semantics and toggle Modifiers to Grid items
                implementation("com.dragselectcompose:extensions:2.4.1")

                // Optional wrappers around LazyGrid that implement the selection UI for you
                implementation("com.dragselectcompose:grid:2.4.1")
            }
        }
    }
}

For the supported platforms, see the badges at the top of the README.

Version catalog

[versions]
dragselectcompose = "2.4.1"

[libraries]
dragselect = { module = "com.dragselectcompose:dragselect", version.ref = "dragselectcompose" }
dragselect-core = { module = "com.dragselectcompose:core", version.ref = "dragselectcompose" }
dragselect-extensions = { module = "com.dragselectcompose:extensions", version.ref = "dragselectcompose" }
dragselect-grid = { module = "com.dragselectcompose:grid", version.ref = "dragselectcompose" }

Usage

The :core artifact provides a Modifier extension for adding a drag-to-select functionality to your LazyGrid:

fun <Item> Modifier.gridDragSelect(
    items: List<Item>,
    state: DragSelectState<Item>,
    enableAutoScroll: Boolean = true,
    autoScrollThreshold: Float? = null,
    enableHaptics: Boolean = true,
    hapticFeedback: HapticFeedback? = null,
): Modifier

It provides the following functionality:

• Adds a long-press drag gesture to select items.
• Maintains a list of selected items.
• Expose a inSelectionMode: Boolean which you can use to display a unselected state.
• If enableAutoScroll is true then the list will start to scroll when reaching the top or bottom of the list.
• Will trigger a "long-press" haptics if enableHaptics is true.

Note: By default selected items will be compared using an equality check. If your item is not a data class you must implement equals and hashCode for your item. Or you can pass a lambda to rememberDragSelectState to compare your items:

val dragSelectState = rememberDragSelectState<Foo>(compareSelector = { it.someProperty })

You can then use DragSelectState to render your list of items:

Basic Example

data class Model(
    val id: Int,
    val title: String,
    val imageUrl: String,
)

@Composeable
fun MyGrid(models: List<Model>) {
    val dragSelectState = rememberDragSelectState<Model>()
    LazyVerticalGrid(
        columns = GridCells.Adaptive(minSize = 128.dp),
        state = dragSelectState.lazyGridState,
        verticalArrangement = Arrangement.spacedBy(3.dp),
        horizontalArrangement = Arrangement.spacedBy(3.dp),
        modifier = Modifier.gridDragSelect(
            items = models,
            state = dragSelectState,
        ),
    ) {
        items(models, key = { it.id }) { model ->
            val isSelected by remember { derivedStateOf { dragSelectState.isSelected(model) } }
            val inSelectionMode = dragSelectState.inSelectionMode

            // Define your Model Composeable and use `isSelected` or `inSelectionMode`
        }
    }
}

You can see a full basic example in BasicDragSelectPhotoGrid.

Extensions

Included in the :dragselectcompose and :extensions artifact are a couple extensions on Modifer to easily add support for accessibility semantics and toggling selection while the Grid is in selection mode.

• Modifier.dragSelectSemantics()
  • Adds a long click semantics to the modifier for accessibility.
• Modifier.dragSelectToggleable()
  • Allows you to toggle the item when the Grid is in Selection Mode.
• Modifier.dragSelectToggleableItem()
  • Combines the above two extensions.

@Composeable
fun MyGrid(models: List<Model>) {
    val dragSelectState = rememberDragSelectState<Model>()
    LazyVerticalGrid(
        // ...
    ) {
        items(models, key = { it.id }) { model ->
            // Add semantics and toggleable modifiers
            MyItemContent(
                item = model,
                modifier = Modifier.dragSelectToggleable(
                    state = dragSelectState,
                    item = model,
                ),
            )
        }
    }
}

You can see a full extensions example in ExtensionsDragSelectPhotoGrid.

Wrapper

Included in the :grid artifact is a "all-inclusive" drag-select experience. It includes wrappers around LazyHorizontalGrid and LazyVerticalGrid that takes care of adding the Modifier.gridDragSelect.

When using LazyDragSelectVerticalGrid or LazyDragSelectHorizontalGrid the content() is scoped to a custom scope that provides a helper composable for handling the selection indicator, and animating the padding.

Here is a quick example:

@Composeable
fun MyGrid(models: List<Model>) {
    val dragSelectState = rememberDragSelectState<Model>()

    LazyDragSelectVerticalGrid(
        columns = GridCells.Adaptive(minSize = 128.dp),
        items = models,
        state = dragSelectState,
    ) {
        items(key = { it.id }) { model ->
            SelectableItem(item = model) {
                // Your Composeable for your item
            }
        }
    }
}

Now your item will have an animated padding and clipped shape when selected. As well as displaying indicator icons when the grid is in selection mode, and the item is selected or not.

See the documentation for LazyDragSelectVerticalGrid and SelectableItem for all the options you can customize.

You can see a full example in LazyDragSelectPhotoGrid

Demo

To run a demo for the library you can look inside of /demo to see a standard Android application, and a Compose Multiplatform application.

Android Demo

A demo app is included in the :demo:android module, run it by following these steps:

git clone git@github.com:jordond/drag-select-compose.git drag-select-compose
cd drag-select-compose
./gradlew assembleRelease

Then install the demo/android/build/outputs/apk/release/demo-release.apk file on your device.

Multiplatform Demo

The demo is inside of :demo:kmm module. In order to run it you should have the latest version of Android studio installed.

Check out the README for more information.

License

See LICENSE