---
title: "Trigger"
description: Play a change effect from code, such as a click or an event, with no value to watch.
---

`Modifier.changeEffect(trigger, effect)` plays the effect each time you call `trigger.fire()`. It is the way to start an effect from a click, a view model event or a button elsewhere on the screen. See the [triggers guide](/guides/triggers) for interactions, edges and `playOnStart`.

## Usage

```kotlin
import androidx.compose.foundation.clickable
import androidx.compose.foundation.layout.Box
import androidx.compose.foundation.layout.size
import androidx.compose.runtime.Composable
import androidx.compose.ui.Modifier
import androidx.compose.ui.unit.dp
import com.jantursky.kapow.ChangeEffect
import com.jantursky.kapow.ParticleContent
import com.jantursky.kapow.ParticleShape
import com.jantursky.kapow.changeEffect
import com.jantursky.kapow.rememberKapowTrigger

@Composable
fun LikeButton() {
    val trigger = rememberKapowTrigger()
    Box(
        Modifier
            .size(64.dp)
            .changeEffect(trigger, ChangeEffect.spray(ParticleContent.shape(ParticleShape.Heart)))
            .clickable { trigger.fire() },
    )
}
```

## Parameters

| Parameter | Default | Description |
| --- | --- | --- |
| `trigger` | | The `KapowTrigger` from `rememberKapowTrigger()`. Several elements may share one. |
| `effect` | | Any `ChangeEffect`, with its `.delay`, `.cooldown`, `.times`, `.speed` and `.reducedMotion`. |
| `isEnabled` | `true` | While false, fires play nothing and send no feedback. |
| `feedback` | `null` | A `KapowFeedbackEvent` sent each time the effect plays. |
| `playOnStart` | `false` | Plays once when the element first appears. |

## Reduced motion

The effect follows its own reduced-motion behavior, exactly as when a value changes.

## Notes

- `fire()` can be called from any thread and never recomposes.
- Fires within one frame play once, and a fire from before the element was composed plays nothing.

## Live example

<iframe class="live-example" src="https://kapow-demo.vercel.app/#more-trigger" title="Live example: more-trigger" loading="lazy" allow="autoplay"></iframe>