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<ol class="chapter"><li class="chapter-item expanded affix "><a href="../index.html">Introduction</a></li><li class="chapter-item expanded "><a href="../getting_started/index.html"><strong aria-hidden="true">1.</strong> Getting Started</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="../getting_started/desktop.html"><strong aria-hidden="true">1.1.</strong> Desktop</a></li><li class="chapter-item expanded "><a href="../getting_started/web.html"><strong aria-hidden="true">1.2.</strong> Web</a></li><li class="chapter-item expanded "><a href="../getting_started/ssr.html"><strong aria-hidden="true">1.3.</strong> Server-Side Rendering</a></li><li class="chapter-item expanded "><a href="../getting_started/fullstack.html"><strong aria-hidden="true">1.4.</strong> Fullstack</a></li><li class="chapter-item expanded "><a href="../getting_started/liveview.html"><strong aria-hidden="true">1.5.</strong> Liveview</a></li><li class="chapter-item expanded "><a href="../getting_started/tui.html"><strong aria-hidden="true">1.6.</strong> Terminal UI</a></li><li class="chapter-item expanded "><a href="../getting_started/mobile.html"><strong aria-hidden="true">1.7.</strong> Mobile</a></li><li class="chapter-item expanded "><a href="../getting_started/hot_reload.html"><strong aria-hidden="true">1.8.</strong> Hot Reloading</a></li></ol></li><li class="chapter-item expanded "><a href="../describing_ui/index.html"><strong aria-hidden="true">2.</strong> Describing the UI</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="../describing_ui/special_attributes.html"><strong aria-hidden="true">2.1.</strong> Special Attributes</a></li><li class="chapter-item expanded "><a href="../describing_ui/components.html"><strong aria-hidden="true">2.2.</strong> Components</a></li><li class="chapter-item expanded "><a href="../describing_ui/component_props.html"><strong aria-hidden="true">2.3.</strong> Props</a></li><li class="chapter-item expanded "><a href="../describing_ui/component_children.html"><strong aria-hidden="true">2.4.</strong> Component Children</a></li></ol></li><li class="chapter-item expanded "><a href="../interactivity/index.html"><strong aria-hidden="true">3.</strong> Interactivity</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="../interactivity/event_handlers.html" class="active"><strong aria-hidden="true">3.1.</strong> Event Listeners</a></li><li class="chapter-item expanded "><a href="../interactivity/hooks.html"><strong aria-hidden="true">3.2.</strong> Hooks & Component State</a></li><li class="chapter-item expanded "><a href="../interactivity/user_input.html"><strong aria-hidden="true">3.3.</strong> User Input</a></li><li class="chapter-item expanded "><a href="../interactivity/sharing_state.html"><strong aria-hidden="true">3.4.</strong> Sharing State</a></li><li class="chapter-item expanded "><a href="../interactivity/custom_hooks.html"><strong aria-hidden="true">3.5.</strong> Custom Hooks</a></li><li class="chapter-item expanded "><a href="../interactivity/dynamic_rendering.html"><strong aria-hidden="true">3.6.</strong> Dynamic Rendering</a></li><li class="chapter-item expanded "><a href="../interactivity/router.html"><strong aria-hidden="true">3.7.</strong> Routing</a></li></ol></li><li class="chapter-item expanded "><a href="../async/index.html"><strong aria-hidden="true">4.</strong> Async</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="../async/use_future.html"><strong aria-hidden="true">4.1.</strong> UseFuture</a></li><li class="chapter-item expanded "><a href="../async/use_coroutine.html"><strong aria-hidden="true">4.2.</strong> UseCoroutine</a></li><li class="chapter-item expanded "><a href="../async/spawn.html"><strong aria-hidden="true">4.3.</strong> Spawning Futures</a></li></ol></li><li class="chapter-item expanded "><a href="../best_practices/index.html"><strong aria-hidden="true">5.</strong> Best Practices</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="../best_practices/error_handling.html"><strong aria-hidden="true">5.1.</strong> Error Handling</a></li><li class="chapter-item expanded "><a href="../best_practices/antipatterns.html"><strong aria-hidden="true">5.2.</strong> Antipatterns</a></li></ol></li><li class="chapter-item expanded "><a href="../publishing/index.html"><strong aria-hidden="true">6.</strong> Publishing</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="../publishing/desktop.html"><strong aria-hidden="true">6.1.</strong> Desktop</a></li><li class="chapter-item expanded "><a href="../publishing/web.html"><strong aria-hidden="true">6.2.</strong> Web</a></li><li class="spacer"></li></ol></li><li class="chapter-item expanded "><a href="../fullstack/index.html"><strong aria-hidden="true">7.</strong> Fullstack</a></li><li><ol class="section"><li class="chapter-item expanded 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<h1 id="event-handlers"><a class="header" href="#event-handlers">Event Handlers</a></h1>
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<p>Event handlers are used to respond to user actions. For example, an event handler could be triggered when the user clicks, scrolls, moves the mouse, or types a character.</p>
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<p>Event handlers are attached to elements. For example, we usually don't care about all the clicks that happen within an app, only those on a particular button.</p>
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<p>Event handlers are similar to regular attributes, but their name usually starts with <code>on</code>- and they accept closures as values. The closure will be called whenever the event it listens for is triggered and will be passed that event.</p>
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<p>For example, to handle clicks on an element, we can specify an <code>onclick</code> handler:</p>
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<pre><pre class="playground"><code class="language-rust edition2018">
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<span class="boring">#![allow(unused)]
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</span><span class="boring">fn main() {
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</span>cx.render(rsx! {
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button {
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onclick: move |event| println!("Clicked! Event: {event:?}"),
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"click me!"
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}
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})
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<span class="boring">}
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</span></code></pre></pre>
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<h2 id="the-event-object"><a class="header" href="#the-event-object">The <code>Event</code> object</a></h2>
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<p>Event handlers receive an <a href="https://docs.rs/dioxus-core/latest/dioxus_core/struct.Event.html"><code>Event</code></a> object containing information about the event. Different types of events contain different types of data. For example, mouse-related events contain <a href="https://docs.rs/dioxus/latest/dioxus/events/struct.MouseData.html"><code>MouseData</code></a>, which tells you things like where the mouse was clicked and what mouse buttons were used.</p>
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<p>In the example above, this event data was logged to the terminal:</p>
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<pre><code>Clicked! Event: UiEvent { bubble_state: Cell { value: true }, data: MouseData { coordinates: Coordinates { screen: (242.0, 256.0), client: (26.0, 17.0), element: (16.0, 7.0), page: (26.0, 17.0) }, modifiers: (empty), held_buttons: EnumSet(), trigger_button: Some(Primary) } }
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Clicked! Event: UiEvent { bubble_state: Cell { value: true }, data: MouseData { coordinates: Coordinates { screen: (242.0, 256.0), client: (26.0, 17.0), element: (16.0, 7.0), page: (26.0, 17.0) }, modifiers: (empty), held_buttons: EnumSet(), trigger_button: Some(Primary) } }
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</code></pre>
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<p>To learn what the different event types for HTML provide, read the <a href="https://docs.rs/dioxus-html/latest/dioxus_html/events/index.html">events module docs</a>.</p>
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<h3 id="event-propagation"><a class="header" href="#event-propagation">Event propagation</a></h3>
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<p>Some events will trigger first on the element the event originated at upward. For example, a click event on a <code>button</code> inside a <code>div</code> would first trigger the button's event listener and then the div's event listener.</p>
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<blockquote>
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<p>For more information about event propigation see <a href="https://developer.mozilla.org/en-US/docs/Learn/JavaScript/Building_blocks/Events#event_bubbling">the mdn docs on event bubling</a></p>
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</blockquote>
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<p>If you want to prevent this behavior, you can call <code>stop_propagation()</code> on the event:</p>
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<pre><pre class="playground"><code class="language-rust edition2018">
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<span class="boring">#![allow(unused)]
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</span><span class="boring">fn main() {
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</span>cx.render(rsx! {
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div {
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onclick: move |_event| {},
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"outer",
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button {
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onclick: move |event| {
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// now, outer won't be triggered
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event.stop_propagation();
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},
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"inner"
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}
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}
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})
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<span class="boring">}
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</span></code></pre></pre>
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<h2 id="prevent-default"><a class="header" href="#prevent-default">Prevent Default</a></h2>
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<p>Some events have a default behavior. For keyboard events, this might be entering the typed character. For mouse events, this might be selecting some text.</p>
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<p>In some instances, might want to avoid this default behavior. For this, you can add the <code>prevent_default</code> attribute with the name of the handler whose default behavior you want to stop. This attribute can be used for multiple handlers using their name separated by spaces:</p>
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<pre><pre class="playground"><code class="language-rust edition2018">
|
|
<span class="boring">#![allow(unused)]
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|
</span><span class="boring">fn main() {
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|
</span>cx.render(rsx! {
|
|
input {
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|
prevent_default: "oninput onclick",
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|
}
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|
})
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<span class="boring">}
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|
</span></code></pre></pre>
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<p>Any event handlers will still be called.</p>
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<blockquote>
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<p>Normally, in React or JavaScript, you'd call "preventDefault" on the event in the callback. Dioxus does <em>not</em> currently support this behavior. Note: this means you cannot conditionally prevent default behavior based on the data in the event.</p>
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</blockquote>
|
|
<h2 id="handler-props"><a class="header" href="#handler-props">Handler Props</a></h2>
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<p>Sometimes, you might want to make a component that accepts an event handler. A simple example would be a <code>FancyButton</code> component, which accepts an <code>on_click</code> handler:</p>
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|
<pre><pre class="playground"><code class="language-rust edition2018">
|
|
<span class="boring">#![allow(unused)]
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|
</span><span class="boring">fn main() {
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|
</span>#[derive(Props)]
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pub struct FancyButtonProps<'a> {
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|
on_click: EventHandler<'a, MouseEvent>,
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}
|
|
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|
pub fn FancyButton<'a>(cx: Scope<'a, FancyButtonProps<'a>>) -> Element<'a> {
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|
cx.render(rsx!(button {
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|
class: "fancy-button",
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|
onclick: move |evt| cx.props.on_click.call(evt),
|
|
"click me pls."
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|
}))
|
|
}
|
|
<span class="boring">}
|
|
</span></code></pre></pre>
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|
<p>Then, you can use it like any other handler:</p>
|
|
<pre><pre class="playground"><code class="language-rust edition2018">
|
|
<span class="boring">#![allow(unused)]
|
|
</span><span class="boring">fn main() {
|
|
</span> cx.render(rsx! {
|
|
FancyButton {
|
|
on_click: move |event| println!("Clicked! {event:?}")
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|
}
|
|
})
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|
<span class="boring">}
|
|
</span></code></pre></pre>
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<blockquote>
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<p>Note: just like any other attribute, you can name the handlers anything you want! Though they must start with <code>on</code>, for the prop to be automatically turned into an <code>EventHandler</code> at the call site.</p>
|
|
<p>You can also put custom data in the event, rather than e.g. <code>MouseData</code></p>
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</blockquote>
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