--- title: "Indicador de carga" description: "Muestra que hay en curso una espera breve de duración desconocida, en línea o sobre el contenido." url: "https://tanrei.chnotchy.com/es/components/loading-indicator/" last_updated: 2026-10-23T21:17:12.000Z --- # Indicador de carga > Muestra que hay en curso una espera breve de duración desconocida, en línea o sobre el contenido. ## Descripción general > [!NOTE] > **Una especificación revisada, que aún no está en todas las plataformas** > > Esta página describe el indicador de carga tal como lo define ahora la especificación: espera antes de mostrarse y luego entra. El componente web ya lo hace, y también las demostraciones, que aparecen después del retardo. SwiftUI, Compose, Flutter y React Native están marcados arriba como rezagados: hasta que se pongan al día, dibujan y exponen el indicador en cuanto se inserta, y no admiten las tres propiedades nuevas, así que sus ejemplos de más abajo muestran solo lo que ofrecen. ### Uso **Web** ```html
``` **React** ```tsx import { LoadingIndicator } from '@tanrei/react';
{loading ? : }
``` **SwiftUI** ```swift import Tanrei TanreiLoadingIndicator("Cargando mensajes") // Encima del contenido, sobre su propio contenedor elevado. TanreiLoadingIndicator("Actualizando", size: .large, contained: true) ``` **Compose** ```kotlin import io.github.chnotchy.tanrei.components.TanreiContainedLoadingIndicator import io.github.chnotchy.tanrei.components.TanreiLoadingIndicator import io.github.chnotchy.tanrei.tokens.TanreiLoadingIndicatorSize TanreiLoadingIndicator(contentDescription = "Cargando mensajes") // La forma con contenedor es un segundo composable con los mismos parámetros. TanreiContainedLoadingIndicator(contentDescription = "Actualizando", size = TanreiLoadingIndicatorSize.Large) ``` **Flutter** ```dart import 'package:tanrei/tanrei.dart'; const TanreiLoadingIndicator(semanticsLabel: 'Cargando mensajes'); const TanreiLoadingIndicator( semanticsLabel: 'Actualizando', size: TanreiLoadingIndicatorSize.large, contained: true, ); ``` **React Native** ```tsx import { LoadingIndicator } from '@tanrei/react-native'; ``` ## Especificaciones - Category: Communication - Level: base - Listing: default - Page: https://tanrei.chnotchy.com/components/loading-indicator/ - Spec: https://github.com/chnotchy/tanrei/blob/main/specs/loading-indicator.spec.json ### Availability | Design system | Has it | Notes | | --- | --- | --- | | Tanrei (`tanrei`) | Yes | — | | Cupertino (Apple HIG-inspired) (`cupertino`) | Yes | — | | M3 Expressive-like (Material 3 Expressive-inspired) (`m3-expressive-like`) | Yes | — | | M3-like (Material 3-inspired) (`m3-like`) | Yes | — | ### Platforms - Web: the element ``, registered by importing `@tanrei/web` (or only its own module, `@tanrei/web/components/loading-indicator`). - React: `LoadingIndicator` from `@tanrei/react`. | Platform | Name | Status | | --- | --- | --- | | Web | `tanrei-loading-indicator` | lagging | | SwiftUI | `TanreiLoadingIndicator` | lagging | | Jetpack Compose | `TanreiLoadingIndicator` | lagging | | Flutter | `TanreiLoadingIndicator` | lagging | | React Native | `LoadingIndicator` | lagging | Names a platform gives in its own idiom: | Spec | Web | SwiftUI | Jetpack Compose | Flutter | React Native | | --- | --- | --- | --- | --- | --- | | `contained` (prop) | `contained` | `contained` | `TanreiContainedLoadingIndicator` | `contained` | `contained` | | `label` (prop) | `label` | `label` | `contentDescription` | `semanticsLabel` | `accessibilityLabel` | | `showDelay` (prop) | `showDelay` | `showDelay` | `showDelayMillis` | `showDelay` | `showDelay` | | `enterDuration` (prop) | `enterDuration` | `enterDuration` | `enterDurationMillis` | `enterDuration` | `enterDuration` | Statuses: `planned` — In the inventory. Nothing shippable exists yet. `lagging` — An implementation of an earlier spec exists; it has not caught up with the current one. `alpha` — Implemented with tests. The API may still change. `beta` — Feature complete and at parity. Only fixes are expected. `stable` — Covered by semantic versioning. `deprecated` — Still shipped; scheduled for removal. ### Anatomy - `indicator`: The moving mark: an arc a quarter of a circle long that turns. It has no track, because there is no value to read. - `container` (optional): A filled, raised circle behind the indicator, drawn only when contained, so the indicator can be seen over content. ### Props | Prop | Type | Default | Web attribute | Description | | --- | --- | --- | --- | --- | | `size` | `enum`: `small`, `medium`, `large` | `"medium"` | `size` | The indicator's box (16 / 24 / 40): small replaces an icon in a control, medium sits next to text, large fills an empty section. Contained, the container is 24 / 32 / 48. A design system may add values. | | `contained` | `boolean` | `false` | `contained` | Draws the indicator on a raised container of its own, for places where it floats over content (pull to refresh, over an image or a list). | | `label` | `string` | `""` | `label` | The accessible name: what is loading ("Loading messages"). Required: a moving mark alone is not a name. | | `showDelay` | `number` | — | `show-delay` | How long, in milliseconds, this indicator waits from the moment it is inserted before it is drawn and exposed to assistive technology; 0 shows it as it is inserted. Null takes comp.loading-indicator.motion.show-delay, the system's answer for every indicator. Set it only where one indicator needs another pace than the rest (a wait the product knows is never instant, a busy button that should answer the press at once). | | `entrance` | `enum`: `auto`, `fade`, `grow` | `"auto"` | `entrance` | How this indicator enters once its show delay has passed: fade eases it in, grow eases it in while it grows from its center. Auto takes comp.loading-indicator.motion.entrance, the system's answer for every indicator. Under reduced motion grow enters as fade (LDG-13). | | `enterDuration` | `number` | — | `enter-duration` | How long, in milliseconds, this indicator's entrance lasts; 0 shows it whole at once. Null takes comp.loading-indicator.motion.enter-duration. | ### States `enabled` ### Accessibility - Role: `progressbar` - Labeling: label is the accessible name. The indicator has no value: once shown, it is exposed as a progressbar in the platform's busy (indeterminate) state, never as a status message; during its show delay it is not exposed at all (LDG-11). - Minimum target size: yes - Not interactive: the indicator takes no input and is never focusable (LDG-6), so the minimum target holds without extending anything. - comp.loading-indicator.indicator.color must stay at least 3:1 against the surface behind it, and comp.loading-indicator.contained.indicator.color against comp.loading-indicator.contained.container.color (non-text contrast): the moving mark is the only sign that something is happening. - Text size does not change the indicator: it is not text. Where it replaces an icon in a control, the control keeps its size. - A product marks the region it loads as busy (aria-busy on the web) and says when the content has arrived; a wait that may exceed a few seconds, or whose length can be measured, belongs to the progress indicator. - A wait shorter than the show delay shows and exposes nothing (LDG-11): no mark that flashes for a sighted person, and no progressbar that appears and vanishes for a screen-reader user. The product's own busy marking of the region does not wait for the delay; aria-busy and its equivalents announce nothing by themselves. - Reduced motion replaces the turning arc with an opacity pulse of at most one per second (LDG-4), below the three-per-second flash threshold, and turns a grow entrance into a fade (LDG-13). The show delay is kept: it is a wait, not motion (LDG-15). ### Behaviour Requirements in EARS form, each with its stable id. - **LDG-1** THE loading indicator SHALL draw, inside a comp.loading-indicator.indicator.size.medium square for medium (and so on for each size), an arc a quarter of the circle long with round caps and a stroke of comp.loading-indicator.indicator.thickness.medium for medium (and so on), whose outer edge touches the square, and SHALL turn it clockwise once per comp.loading-indicator.motion.cycle-duration at constant speed (sys.motion.easing.linear); it SHALL draw no track. - **LDG-2** WHILE contained is false THE loading indicator SHALL take exactly its indicator square, draw no container, and draw the arc in comp.loading-indicator.indicator.color. - **LDG-3** WHILE contained is true THE loading indicator SHALL draw a container of comp.loading-indicator.container.size.medium for medium (and so on for each size) with corners of comp.loading-indicator.container.shape, filled with comp.loading-indicator.contained.container.color and raised by comp.loading-indicator.contained.container.elevation, center the indicator in it, and draw the arc in comp.loading-indicator.contained.indicator.color. - **LDG-4** WHERE reduced motion is requested THE loading indicator SHALL NOT turn: it SHALL draw the whole circle at the indicator's size and stroke and ease its opacity from 1 to 0 and back to 1 once per comp.loading-indicator.motion.cycle-duration with sys.motion.easing.standard; a container, when contained, SHALL stay still and opaque. - **LDG-5** WHILE the loading indicator is shown (LDG-12) THE loading indicator SHALL expose the progressbar role to assistive technology with label as its name, no current value, and the platform's busy or indeterminate state. - **LDG-6** THE loading indicator SHALL NOT be focusable and SHALL NOT announce itself when it appears or disappears; the region being loaded is marked busy, and its completion announced, by the product. - **LDG-7** WHILE the loading indicator is not visible (scrolled out of view, in a hidden view, or in an app in the background) THE loading indicator SHALL NOT run its animation, and SHALL resume it when it becomes visible. - **LDG-8** WHERE the layout direction is right-to-left THE loading indicator SHALL NOT be mirrored: it turns clockwise in every direction. - **LDG-9** WHEN size names a value that the active design system does not have THE loading indicator SHALL render with the default value's tokens, and in debug builds report the unknown value. - **LDG-10** WHILE label is empty THE loading indicator SHALL still render, and in debug builds report that it has no accessible name. - **LDG-11** WHEN the loading indicator is inserted into a view THE loading indicator SHALL wait for its show delay (LDG-14) before it is shown, and WHILE it waits SHALL draw nothing (no indicator, no container, no shadow), SHALL run no animation, SHALL be absent from the accessibility tree (no role, no name, no busy state), and SHALL still take the box it takes when shown (LDG-2, LDG-3), so that nothing around it moves when it appears; a show delay of 0 SHALL show it as it is inserted. - **LDG-12** WHEN its show delay ends THE loading indicator SHALL be shown: it SHALL expose itself as LDG-5 says, without announcing itself (LDG-6), start its entrance (LDG-13), and start the turn of LDG-1, or the pulse of LDG-4, at the beginning of a cycle. - **LDG-13** WHEN the loading indicator is shown THE loading indicator SHALL enter over its enter duration (LDG-14) with comp.loading-indicator.motion.enter-easing, as its entrance names: fade SHALL ease the opacity of the whole component (the indicator and, when contained, the container and its shadow) from 0 to 1, and grow SHALL ease the opacity the same way while scaling the whole component from nothing to its full size about its center, on the same curve over the same time. The entrance SHALL be drawn only: the box SHALL keep its full size throughout, and the entrance SHALL run to its end whether or not the indicator is visible (LDG-7 pauses the cycle, not the entrance). An enter duration of 0 SHALL show the indicator whole at once. WHERE reduced motion is requested THE loading indicator SHALL NOT scale: grow SHALL enter as fade, and on a platform whose reduced-motion setting removes every animation (Android's) the indicator SHALL appear at once. - **LDG-14** THE loading indicator SHALL take its show delay from showDelay and its enter duration from enterDuration, each a number of milliseconds used as given (the motion dial does not scale it), and its kind of entrance from entrance. WHILE showDelay or enterDuration is null THE loading indicator SHALL use comp.loading-indicator.motion.show-delay or comp.loading-indicator.motion.enter-duration in its place, and WHILE entrance is auto it SHALL use comp.loading-indicator.motion.entrance; IF showDelay or enterDuration is negative or not a finite number, or entrance names a kind the indicator does not know, THE loading indicator SHALL use the token likewise and in debug builds report the value it ignored. - **LDG-15** THE loading indicator SHALL treat its show delay as a waiting time, not motion: WHERE motion is reduced it SHALL keep it, on every platform, including one whose reduced-motion setting removes every animation; and it SHALL keep counting it while the indicator cannot be seen (scrolled out of view, in a hidden view), because the delay measures the wait, not what is seen. - **LDG-16** WHEN the loading indicator is removed before its show delay ends THE loading indicator SHALL have drawn, exposed and announced nothing, and WHEN it is removed while shown, during its entrance included, it SHALL disappear at once. WHEN it is inserted again THE loading indicator SHALL wait its whole show delay again; hiding it without removing it (a hidden ancestor, scrolling) SHALL neither restart nor pause the delay (LDG-15). WHEN showDelay, entrance or enterDuration changes while the delay or the entrance is running THE loading indicator SHALL finish the running one as it started and use the new value from its next insertion. - **LDG-17** THE loading indicator SHALL take its layout direction from where it is used — the direction of the nearest ancestor that sets one, and the platform's own where none does — and SHALL have no direction setting of its own; WHEN that direction changes while the loading indicator is shown THE loading indicator SHALL draw itself for the new direction at once, without a motion of its own, keeping its place in its cycle. - **LDG-18** WHERE the platform has ARIA attributes (the web), the host carries its progressbar role (LDG-5) itself, so what the product writes on it is not moved, but for a name: WHILE label is not empty THE loading indicator SHALL hold the product's aria-label and aria-labelledby on that host as their data-aria- twins, so that label is its whole name although the platform gives aria-labelledby the precedence, and WHEN label is emptied SHALL give them back as they were written; WHILE label is empty a name the product gives so — aria-label, or aria-labelledby naming an element — SHALL be its name and SHALL NOT be reported as having none in debug builds (LDG-10). WHILE it waits to be shown (LDG-11) it has no role, and SHALL hold them as well, so that nothing names an element with no role, and give them back when it is shown. WHEN the product removes one, or its data-aria- twin, or sets the ARIA property that reflects it (ariaLabel, ariaLabelledByElements) to null, THE loading indicator SHALL take it away. ### Tokens As written in the token documents (DTCG): an alias in braces names the token it takes its value from, which each design system resolves. On the web each token is a CSS custom property: `--tanrei` and the name after `tanrei`, joined by hyphens (`tanrei.comp.loading-indicator.…` → `--tanrei-comp-loading-indicator-…`). #### `tanrei.comp.loading-indicator` | Token | Type | Value | | --- | --- | --- | | `comp.loading-indicator.indicator.size.small` | `dimension` | `16px` | | `comp.loading-indicator.indicator.size.medium` | `dimension` | `24px` | | `comp.loading-indicator.indicator.size.large` | `dimension` | `40px` | | `comp.loading-indicator.indicator.thickness.small` | `dimension` | `{tanrei.sys.border.thick}` | | `comp.loading-indicator.indicator.thickness.medium` | `dimension` | `{tanrei.sys.border.thick}` | | `comp.loading-indicator.indicator.thickness.large` | `dimension` | `{tanrei.sys.border.thick}` | | `comp.loading-indicator.indicator.color` | `color` | `{tanrei.sys.color.on-surface-variant}` | | `comp.loading-indicator.container.size.small` | `dimension` | `24px` | | `comp.loading-indicator.container.size.medium` | `dimension` | `32px` | | `comp.loading-indicator.container.size.large` | `dimension` | `48px` | | `comp.loading-indicator.container.shape` | `dimension` | `{tanrei.sys.shape.corner.full}` | | `comp.loading-indicator.contained.container.color` | `color` | `{tanrei.sys.color.surface-container-lowest}` | | `comp.loading-indicator.contained.container.elevation` | `shadow` | `{tanrei.sys.elevation.level2}` | | `comp.loading-indicator.contained.indicator.color` | `color` | `{tanrei.sys.color.on-surface-variant}` | | `comp.loading-indicator.motion.cycle-duration` | `duration` | `{tanrei.sys.motion.duration.extra-long4}` | | `comp.loading-indicator.motion.show-delay` | `duration` | `{tanrei.sys.motion.role.show-delay}` | | `comp.loading-indicator.motion.entrance` | `number` | `0` | | `comp.loading-indicator.motion.enter-duration` | `duration` | `{tanrei.sys.motion.role.state.large}` | | `comp.loading-indicator.motion.enter-easing` | `cubicBezier` | `{tanrei.sys.motion.easing.enter}` | ## Pautas ### Cuándo usarlo Usa un indicador de carga para una espera breve cuya duración no puedes conocer: una lista que obtiene su página siguiente, un control que guarda, una vista previa que se está generando. Dice que algo está ocurriendo y nada sobre cuánto va a tardar. Cuando la espera pueda durar más de unos segundos, o cuando puedas medir cuánto ha avanzado, usa en su lugar un [indicador de progreso](https://tanrei.chnotchy.com/es/components/progress-indicator/). Un valor, aunque sea aproximado, hace más llevadera una espera larga. ### Cómo elegir un tamaño | Tamaño | Indicador / contenedor en el sistema predeterminado | Úsalo para | | --- | --- | --- | | Small | 16 / 24 | En lugar de un icono dentro de un control, como un botón que está guardando. | | Medium | 24 / 32 | Junto a una línea de texto. Es el valor predeterminado. | | Large | 40 / 48 | Una sección vacía o una vista entera que espera su contenido. | ### Con contenedor La forma con contenedor dibuja el indicador sobre un círculo elevado propio. Úsala donde el indicador flota sobre el contenido, como al tirar para actualizar o encima de una imagen o de una lista, para que siga viéndose sea lo que sea lo que haya detrás. Donde se apoya sobre una superficie lisa, déjalo en línea. ### Retardo de aparición y entrada Una espera que termina en un instante no debería mostrar nada. Por eso el indicador espera antes de mostrarse: 300 ms en el sistema predeterminado, contados desde el momento en que se inserta. Después aparece con un fundido. Una espera más corta que el retardo nunca muestra una marca que se enciende y se apaga. Durante el retardo el indicador ya ocupa su tamaño completo, así que nada de lo que tiene al lado se mueve cuando aparece. Inserta el indicador cuando empiece la espera y quítalo cuando termine. El retardo cuenta desde la inserción: un indicador que se oculta y se vuelve a mostrar sin quitarlo no espera otra vez, y uno que se inserta de nuevo vuelve a esperar el retardo entero. El sistema decide el retardo y la entrada de todos los indicadores. Defínelos en un indicador solo cuando necesite un ritmo distinto: - `showDelay` es la espera en milisegundos. `0` muestra el indicador en cuanto se inserta, para un botón ocupado que debe responder a la pulsación de inmediato. - `entrance` es `fade` o `grow`. Con grow, el indicador aparece con un fundido mientras crece desde su centro. `auto`, el valor predeterminado, toma la elección del sistema. - `enterDuration` es la duración de la entrada en milisegundos. `0` muestra el indicador entero de una vez. Un valor que definas se usa tal como lo das: el dial de movimiento no lo escala. Deja una propiedad sin definir para tomar el valor del sistema. ### Recomendado - Dale una etiqueta que diga qué se está cargando: «Cargando mensajes», no «Cargando». Si se muestra una leyenda a su lado, usa las mismas palabras. - Ponlo donde aparecerá el contenido, para que la persona mire al lugar correcto cuando llegue. - Cuando sustituya a un icono dentro de un control, conserva el tamaño del control, para que nada se mueva a su alrededor. - Deja el retardo en manos del sistema salvo que un indicador necesite otro ritmo. ### Evita - No lo uses para una espera que puedes medir, ni para una que pueda alargarse. Usa un indicador de progreso. - No muestres varios indicadores para una misma espera. Basta con uno por cada región que se está cargando. - No lo pongas sobre una pantalla entera cuando solo se está cargando una parte. Mantén utilizable el resto. - No le des color para decir que algo ha ido mal. Detenlo y muestra un mensaje. - No dejes un indicador en su sitio ocultándolo entre una espera y otra. Quítalo, para que la siguiente espera inicie un retardo nuevo. ## Accesibilidad ### De qué se encarga el componente - Una vez mostrado, expone el rol de barra de progreso en el estado ocupado de la plataforma, con la etiqueta como nombre y sin valor. Flutter todavía no tiene rol de barra de progreso ni estado ocupado, así que ahí expone la etiqueta. - Durante su retardo de aparición no está en el árbol de accesibilidad: sin rol, sin nombre, sin estado ocupado. Una espera demasiado corta para verse tampoco se oye. - Nunca puede recibir el foco, y no se anuncia a sí mismo cuando aparece ni cuando desaparece. - Cuando se pide reducir movimiento, el arco deja de girar y, en su lugar, un círculo completo hace pulsar suavemente su opacidad, como mucho una vez por segundo; un contenedor se queda quieto. Una entrada grow se convierte en un fundido. El retardo de aparición se conserva: es una espera, no movimiento. - Su animación se detiene mientras no se puede ver (en todas partes cuando la aplicación está en segundo plano, y cuando queda desplazado fuera de la vista o en una pantalla oculta donde la plataforma puede saberlo) y se reanuda cuando se puede. - Una etiqueta vacía se notifica en las compilaciones de depuración. ### Qué debes hacer tú - Marca como ocupada la región que se está cargando mientras se carga (`aria-busy` en la web), desde el inicio de la espera, sin aguardar al retardo del indicador, y di cuándo ha llegado el contenido: con un mensaje en una región activa (live region), o llevando el foco al contenido nuevo cuando la persona lo haya pedido. - Si cambias los colores, mantén el color del indicador con un contraste de al menos 3:1 frente a la superficie que tiene detrás, y el color del indicador con contenedor frente a su contenedor. La marca en movimiento es la única señal de que algo está ocurriendo.