Mouse event listeners
In your desktop project, you can listen to various mouse events, like clicking, moving, scrolling, or entering and exiting the input region.
Click listeners
Click listeners are available in both Compose Multiplatform for Android and Compose Multiplatform for desktop, so your code will work on both platforms. For example, here is how to set up simple click listeners with the onClick, onDoubleClick, and onLongClick modifiers:
import androidx.compose.foundation.ExperimentalFoundationApi
import androidx.compose.foundation.background
import androidx.compose.foundation.combinedClickable
import androidx.compose.foundation.layout.Box
import androidx.compose.foundation.layout.Column
import androidx.compose.foundation.layout.fillMaxHeight
import androidx.compose.foundation.layout.fillMaxWidth
import androidx.compose.material.Text
import androidx.compose.runtime.getValue
import androidx.compose.runtime.mutableIntStateOf
import androidx.compose.runtime.mutableStateOf
import androidx.compose.runtime.remember
import androidx.compose.runtime.setValue
import androidx.compose.ui.Alignment
import androidx.compose.ui.Modifier
import androidx.compose.ui.graphics.Color
import androidx.compose.ui.unit.sp
import androidx.compose.ui.window.singleWindowApplication
fun main() = singleWindowApplication(title = "Mouse clicks") {
var count by remember { mutableIntStateOf(0) }
Box(contentAlignment = Alignment.Center, modifier = Modifier.fillMaxWidth()) {
var text by remember { mutableStateOf("Click magenta box!") }
Column {
@OptIn(ExperimentalFoundationApi::class)
Box(modifier = Modifier
.background(Color.Magenta)
.fillMaxWidth(0.7f)
.fillMaxHeight(0.7f)
.combinedClickable(
onClick = {
text = "Click! ${count++}"
},
onDoubleClick = {
text = "Double click! ${count++}"
},
onLongClick = {
text = "Long click! ${count++}"
}
)
)
Text(text = text, fontSize = 40.sp)
}
}
}
The combinedClickable modifier supports only the primary button (left mouse button) and touch events. If you need to handle buttons differently, see the Modifier.onClick section.
Move listeners
To create a pointer move listener that changes the background color of the window according to the mouse pointer position, add the following code:
import androidx.compose.foundation.background
import androidx.compose.foundation.layout.Box
import androidx.compose.foundation.layout.fillMaxSize
import androidx.compose.foundation.layout.wrapContentSize
import androidx.compose.runtime.getValue
import androidx.compose.runtime.mutableStateOf
import androidx.compose.runtime.remember
import androidx.compose.runtime.setValue
import androidx.compose.ui.Alignment
import androidx.compose.ui.ExperimentalComposeUiApi
import androidx.compose.ui.Modifier
import androidx.compose.ui.graphics.Color
import androidx.compose.ui.input.pointer.PointerEventType
import androidx.compose.ui.input.pointer.onPointerEvent
import androidx.compose.ui.window.singleWindowApplication
@OptIn(ExperimentalComposeUiApi::class)
fun main() = singleWindowApplication(title = "Mouse move listeners") {
var color by remember { mutableStateOf(Color(0, 0, 0)) }
Box(modifier = Modifier
.wrapContentSize(Alignment.Center)
.fillMaxSize()
.background(color = color)
.onPointerEvent(PointerEventType.Move) {
val position = it.changes.first().position
color = Color(position.x.toInt() % 256, position.y.toInt() % 256, 0)
}
)
}
Enter listeners
Compose Multiplatform for desktop supports handlers of the pointer entering and exiting the input region. For example, the following code will change the font style of a line on hover:
import androidx.compose.foundation.background
import androidx.compose.foundation.layout.Arrangement
import androidx.compose.foundation.layout.Column
import androidx.compose.foundation.layout.fillMaxWidth
import androidx.compose.material.Text
import androidx.compose.runtime.getValue
import androidx.compose.runtime.mutableStateOf
import androidx.compose.runtime.remember
import androidx.compose.runtime.setValue
import androidx.compose.ui.ExperimentalComposeUiApi
import androidx.compose.ui.Modifier
import androidx.compose.ui.graphics.Color
import androidx.compose.ui.input.pointer.PointerEventType
import androidx.compose.ui.input.pointer.onPointerEvent
import androidx.compose.ui.text.font.FontStyle
import androidx.compose.ui.text.style.TextAlign
import androidx.compose.ui.unit.dp
import androidx.compose.ui.unit.sp
import androidx.compose.ui.window.singleWindowApplication
@OptIn(ExperimentalComposeUiApi::class)
fun main() = singleWindowApplication(title = "Mouse enter listeners") {
Column(
Modifier.background(Color.White),
verticalArrangement = Arrangement.spacedBy(10.dp),
) {
repeat(10) { index ->
var active by remember { mutableStateOf(false) }
Text(modifier = Modifier
.fillMaxWidth()
.background(color = if (active) Color.Green else Color.White)
.onPointerEvent(PointerEventType.Enter) { active = true }
.onPointerEvent(PointerEventType.Exit) { active = false },
fontSize = 30.sp,
fontStyle = if (active) FontStyle.Italic else FontStyle.Normal,
text = "Item $index",
textAlign = TextAlign.Center
)
}
}
}
Scroll listeners
The following code sample demonstrates how you can increase or decrease the displayed number depending on the mouse scroll direction:
import androidx.compose.foundation.layout.Box
import androidx.compose.foundation.layout.fillMaxSize
import androidx.compose.material.Text
import androidx.compose.runtime.getValue
import androidx.compose.runtime.mutableFloatStateOf
import androidx.compose.runtime.remember
import androidx.compose.runtime.setValue
import androidx.compose.ui.Alignment
import androidx.compose.ui.ExperimentalComposeUiApi
import androidx.compose.ui.Modifier
import androidx.compose.ui.input.pointer.PointerEventType
import androidx.compose.ui.input.pointer.onPointerEvent
import androidx.compose.ui.unit.sp
import androidx.compose.ui.window.singleWindowApplication
@OptIn(ExperimentalComposeUiApi::class)
fun main() = singleWindowApplication(title = "Mouse scroll listeners") {
var number by remember { mutableFloatStateOf(0f) }
Box(
Modifier
.fillMaxSize()
.onPointerEvent(PointerEventType.Scroll) {
number += it.changes.first().scrollDelta.y
},
contentAlignment = Alignment.Center
) {
Text("Scroll to change the number: $number", fontSize = 30.sp)
}
}
Experimental onClick handlers
Modifier.onClick provides independent callbacks for clicks, double clicks, and long clicks. It handles clicks originating from pointer events only and doesn't handle accessibility click events out of the box.
You can configure each onClick to target specific pointer events using matcher: PointerMatcher and keyboardModifiers: PointerKeyboardModifiers.() -> Boolean:
matcherallows you to choose which mouse button should trigger a click event.keyboardModifiersallows you to filter pointer events that have specified key pressed.
You can also create a chain of multiple onClick modifiers to handle different clicks with different conditions of the matcher and keyboard modifiers. Unlike clickable, onClick doesn't have default Modifier.indication and Modifier.semantics, and it doesn't trigger a click event when you press Enter. If necessary, add these modifiers separately. You should declare the most generic (with the least number of conditions) onClick handlers before others to ensure correct propagation of events.
import androidx.compose.animation.AnimatedContent
import androidx.compose.foundation.ExperimentalFoundationApi
import androidx.compose.foundation.LocalIndication
import androidx.compose.foundation.PointerMatcher
import androidx.compose.foundation.background
import androidx.compose.foundation.indication
import androidx.compose.foundation.interaction.MutableInteractionSource
import androidx.compose.foundation.layout.Box
import androidx.compose.foundation.layout.Column
import androidx.compose.foundation.layout.size
import androidx.compose.foundation.onClick
import androidx.compose.material.Text
import androidx.compose.runtime.*
import androidx.compose.ui.Alignment
import androidx.compose.ui.Modifier
import androidx.compose.ui.graphics.Color
import androidx.compose.ui.input.pointer.PointerButton
import androidx.compose.ui.input.pointer.isAltPressed
import androidx.compose.ui.input.pointer.isShiftPressed
import androidx.compose.ui.text.style.TextAlign
import androidx.compose.ui.unit.dp
import androidx.compose.ui.window.singleWindowApplication
@OptIn(ExperimentalFoundationApi::class)
fun main() = singleWindowApplication(title = "Mouse clicks") {
Column {
var topBoxText by remember { mutableStateOf("Click me\nusing LMB or LMB + Shift") }
var topBoxCount by remember { mutableIntStateOf(0) }
// No indication on interaction
Box(modifier = Modifier
.size(300.dp, 200.dp)
.background(Color.LightGray)
// The most generic click handler (without extra conditions) should be the first one
.onClick {
// Receives all left mouse button clicks except for when Shift is pressed
println("Click with primary button")
topBoxText = "LMB ${topBoxCount++}"
}.onClick(
keyboardModifiers = { isShiftPressed } // Accepts clicks only when Shift is pressed
) {
// Receives all left mouse button clicks when Shift is pressed
println("Click with primary button and shift pressed")
topBoxCount++
topBoxText = "LMB + Shift ${topBoxCount++}"
}
) {
AnimatedContent(
targetState = topBoxText,
modifier = Modifier.align(Alignment.Center)
) {
Text(text = it, textAlign = TextAlign.Center)
}
}
var bottomBoxText by remember { mutableStateOf("Click me\nusing LMB or\nRMB + Alt") }
var bottomBoxCount by remember { mutableStateOf(0) }
val interactionSource = remember { MutableInteractionSource() }
// With indication on interaction
Box(modifier = Modifier
.size(300.dp, 200.dp)
.background(Color.Yellow)
.onClick(
enabled = true,
interactionSource = interactionSource,
matcher = PointerMatcher.mouse(PointerButton.Secondary), // Right mouse button
keyboardModifiers = { isAltPressed }, // Accepts clicks only when Alt is pressed
onLongClick = { // Optional
bottomBoxText = "RMB Long Click + Alt ${bottomBoxCount++}"
println("Long Click with secondary button and Alt pressed")
},
onDoubleClick = { // Optional
bottomBoxText = "RMB Double Click + Alt ${bottomBoxCount++}"
println("Double Click with secondary button and Alt pressed")
},
onClick = {
bottomBoxText = "RMB Click + Alt ${bottomBoxCount++}"
println("Click with secondary button and Alt pressed")
}
)
.onClick(interactionSource = interactionSource) { // Uses default parameters
bottomBoxText = "LMB Click ${bottomBoxCount++}"
println("Click with primary button (mouse left button)")
}
.indication(interactionSource, LocalIndication.current)
) {
AnimatedContent(
targetState = bottomBoxText,
modifier = Modifier.align(Alignment.Center)
) {
Text(text = it, textAlign = TextAlign.Center)
}
}
}
}
Experimental onDrag modifier
With Modifier.onDrag, you can specify the pointer that should trigger the drag via matcher: PointerMatcher. Similar to onClick, you can chain together many onDrag modifiers.
You can also check the state of keyboard modifiers via LocalWindowInfo.current.keyboardModifier for cases when keys can alter the behavior of the drag. For example, when you move an item with a simple drag, and copy/paste an item with a drag and Ctrl pressed.
The following code sample demonstrates how to handle drag events triggered by left and right mouse buttons, and with the keyboard involved:
import androidx.compose.foundation.ExperimentalFoundationApi
import androidx.compose.foundation.PointerMatcher
import androidx.compose.foundation.background
import androidx.compose.foundation.gestures.onDrag
import androidx.compose.foundation.layout.Box
import androidx.compose.foundation.layout.Column
import androidx.compose.foundation.layout.offset
import androidx.compose.foundation.layout.size
import androidx.compose.material.Text
import androidx.compose.runtime.getValue
import androidx.compose.runtime.mutableStateOf
import androidx.compose.runtime.remember
import androidx.compose.runtime.setValue
import androidx.compose.ui.Alignment
import androidx.compose.ui.Modifier
import androidx.compose.ui.geometry.Offset
import androidx.compose.ui.graphics.Color
import androidx.compose.ui.input.pointer.PointerButton
import androidx.compose.ui.input.pointer.isCtrlPressed
import androidx.compose.ui.platform.LocalWindowInfo
import androidx.compose.ui.unit.IntOffset
import androidx.compose.ui.unit.dp
import androidx.compose.ui.window.singleWindowApplication
@OptIn(ExperimentalFoundationApi::class)
fun main() = singleWindowApplication(title = "Drag") {
val windowInfo = LocalWindowInfo.current
Column {
var topBoxOffset by remember { mutableStateOf(Offset(0f, 0f)) }
Box(modifier = Modifier
.offset {
IntOffset(topBoxOffset.x.toInt(), topBoxOffset.y.toInt())
}
.size(200.dp)
.background(Color.Green)
.onDrag { // By default: enabled = true, matcher = PointerMatcher.Primary (left mouse button)
topBoxOffset += it
}
) {
Text(text = "Drag with LMB", modifier = Modifier.align(Alignment.Center))
}
var bottomBoxOffset by remember { mutableStateOf(Offset(0f, 0f)) }
Box(modifier = Modifier
.offset {
IntOffset(bottomBoxOffset.x.toInt(), bottomBoxOffset.y.toInt())
}
.size(200.dp)
.background(Color.LightGray)
.onDrag(
matcher = PointerMatcher.mouse(PointerButton.Secondary), // Right mouse button
onDragStart = {
println("Gray Box: drag start")
},
onDragEnd = {
println("Gray Box: drag end")
}
) {
val keyboardModifiers = windowInfo.keyboardModifiers
bottomBoxOffset += if (keyboardModifiers.isCtrlPressed) it * 2f else it
}
) {
Text(
text = "Drag with RMB,\ntry with CTRL",
modifier = Modifier.align(Alignment.Center)
)
}
}
}
There is also a non-modifier way to handle drags using suspend fun PointerInputScope.detectDragGestures:
import androidx.compose.foundation.ExperimentalFoundationApi
import androidx.compose.foundation.PointerMatcher
import androidx.compose.foundation.background
import androidx.compose.foundation.gestures.detectDragGestures
import androidx.compose.foundation.layout.Box
import androidx.compose.foundation.layout.offset
import androidx.compose.foundation.layout.size
import androidx.compose.material.Text
import androidx.compose.runtime.getValue
import androidx.compose.runtime.mutableStateOf
import androidx.compose.runtime.remember
import androidx.compose.runtime.setValue
import androidx.compose.ui.Alignment
import androidx.compose.ui.Modifier
import androidx.compose.ui.geometry.Offset
import androidx.compose.ui.graphics.Color
import androidx.compose.ui.input.pointer.pointerInput
import androidx.compose.ui.unit.IntOffset
import androidx.compose.ui.unit.dp
import androidx.compose.ui.window.singleWindowApplication
@OptIn(ExperimentalFoundationApi::class)
fun main() = singleWindowApplication(title = "Drag") {
var topBoxOffset by remember { mutableStateOf(Offset(0f, 0f)) }
Box(modifier = Modifier
.offset {
IntOffset(topBoxOffset.x.toInt(), topBoxOffset.y.toInt())
}
.size(200.dp)
.background(Color.Green)
.pointerInput(Unit) {
detectDragGestures(
matcher = PointerMatcher.Primary
) {
topBoxOffset += it
}
}
) {
Text(text = "Drag with LMB", modifier = Modifier.align(Alignment.Center))
}
}
Accessing raw AWT events with Swing interoperability
Compose Multiplatform for desktop uses Swing under the hood and allows to access raw AWT events:
import androidx.compose.foundation.layout.Box
import androidx.compose.foundation.layout.fillMaxSize
import androidx.compose.material.Text
import androidx.compose.runtime.getValue
import androidx.compose.runtime.mutableStateOf
import androidx.compose.runtime.remember
import androidx.compose.runtime.setValue
import androidx.compose.ui.Alignment
import androidx.compose.ui.ExperimentalComposeUiApi
import androidx.compose.ui.Modifier
import androidx.compose.ui.awt.awtEventOrNull
import androidx.compose.ui.input.pointer.PointerEventType
import androidx.compose.ui.input.pointer.onPointerEvent
import androidx.compose.ui.window.singleWindowApplication
@OptIn(ExperimentalComposeUiApi::class)
fun main() = singleWindowApplication(title = "Raw AWT events") {
var text by remember { mutableStateOf("") }
Box(
Modifier
.fillMaxSize()
.onPointerEvent(PointerEventType.Press) {
text = it.awtEventOrNull?.locationOnScreen?.toString().orEmpty()
},
contentAlignment = Alignment.Center
) {
Text(text)
}
}
Listening for raw events in common code via pointerInput
In the snippets above we use the Modifier.onPointerEvent function, which is a helper function that subscribes to a type of pointer events. It is a new and short variant of the Modifier.pointerInput function. It is currently experimental and desktop-only, so you can't use it in common code.
If you need to subscribe to events in common code, or if you need a stable API, you can use the Modifier.pointerInput function:
import androidx.compose.foundation.layout.Column
import androidx.compose.foundation.layout.fillMaxSize
import androidx.compose.material.Text
import androidx.compose.runtime.mutableStateListOf
import androidx.compose.runtime.remember
import androidx.compose.ui.Modifier
import androidx.compose.ui.input.pointer.PointerEventType
import androidx.compose.ui.input.pointer.pointerInput
import androidx.compose.ui.window.singleWindowApplication
fun main() = singleWindowApplication(title = "Raw events via Modifier.pointerInput") {
val list = remember { mutableStateListOf<String>() }
Column(
Modifier
.fillMaxSize()
.pointerInput(Unit) {
awaitPointerEventScope {
while (true) {
val event = awaitPointerEvent()
val position = event.changes.first().position
// On each relayout, Compose will send a synthetic Move event,
// so we skip it to avoid event spam
if (event.type != PointerEventType.Move) {
list.add(0, "${event.type} $position")
}
}
}
},
) {
for (item in list.take(20)) {
Text(item)
}
}
}
What's next
Explore the tutorials about other desktop components.
Last modified: 01 October 2024