v-ons-tabbar

A component to display a tab bar on the bottom of a page. Used with <v-ons-tab> to manage pages using tabs.

Tutorial

Tabs

The VOnsTabbar component is used to add tab navigation to an app. It is a very common navigation pattern in mobile apps.

The tabs prop includes all the necessary information to render VOnsTab components and their linked VOnsPage components. This prop must be an array of object containing at least one of the next keys: icon, label or page. It can include other optional keys such as activeIcon, badge, active, etc. A special props key can also be provided in order to specify props for the corresponding page.

<v-ons-tabbar
  :tabs="[
    { label: 't1', page: p1 },
    { label: 't2', page: p2, props: { aPageProp: 'hello' } }
  ]"
>
</v-ons-tabbar>

The mentioned tabs prop is the preferred way to provide tabs information to VOnsTabbar, although it is not the only one. It is also possible to provide slot="pages" and VOnsTab components directly as children instead:

<v-ons-tabbar>
  <template slot="pages">
    <home-page></home-page>
    <news-page></news-page>
    <settings-page></settings-page>
  </template>

  <v-ons-tab v-for="(tab, i) in tabs"
    :icon="tabs[i].icon"
    :label="tabs[i].label"
    :badge="tabs[i].badge"
    ></v-ons-tab>
</v-ons-tabbar>

This is a longer version that offers higher control. It can be combined with tabs prop by, for example, providing only VOnsTab-related information (everything except page key) in tabs prop and also slot="pages" at the same time (the VOnsTab will match page’s DOM index).

Synchronizing :index prop

The VOnsTabbar component implements an optional index prop which is used to specify the page that is currently visible. This component fires update:index events whenever the user taps on a VOnsTab. This is useful to synchronize the value of index prop and can be directly handled by using Vue’s sync modifier:

<v-ons-tabbar :index.sync="tabbarIndex"></v-ons-tabbar>

index prop is not completely necessary. If you don’t need to set an active tab in any other way than tapping, then it would be enough to provide active attribute (or key in tabs prop) to the desired VOnsTab in order to set the initial active tab.

The VOnsTab component

VOnsTab components have the following attributes/props:

  • icon: specifies the displayed icon.
  • label: specifies the displayed text label.
  • badge: shows a small badge on top of the tab.
  • activeIcon: allows to change the icon when the tab becomes active.
  • active: Whether the tab should be displayed as active or not. This is not necessary when using index prop.

Every tab has, by default, the same width. 50% with two tabs, 25% with four tabs and so on. To allow tabs grow depending on their content (i.e. shorter/ longer labels), use the autogrow modifier in v-ons-tabbar component. Optionally, max-width CSS property can be specified to set the width of the tab (for each v-ons-tab).

Swipes and Animations

By default, the tab bar will slide from one page to another on tab click. Use animation="none" attribute to have an instant change.

swipeable attribute can be used to enable this functionality. It can be toggled to allow or prevent swipes at different moments of the app.

These attributes can be combined to have a tab bar with instant changes that can also be swiped:

<v-ons-tabbar swipeable animation="none">...</v-ons-tabbar>

For iOS, tab-border attribute can be included to show a tab border that updates position during swipe (this is always default on Android).

Advanced usage

VOnsTab behavior can be overridden by running event.preventDefault on click event handler.

For example, this can provide fine control to support some of Vue’s cool features:

<v-ons-tabbar>
  <template slot="pages">
    <transition>
      <keep-alive>
        <component :is="currentPage"></component>
      </keep-alive>
    </transition>
  </template>

  <v-ons-tab
    @click.prevent="currentPage = 'home'"
    :active="currentPage === 'home'"
  ></v-ons-tab>
  <v-ons-tab
    @click.prevent="currentPage = 'settings'"
    :active="currentPage === 'settings'"
  ></v-ons-tab>
</v-ons-tabbar>

Notice that preventing the default behavior means that VOnsTabbar events (prechange, postchange, reactive…) are not fired. Also, it won’t be swipeable if only 1 page is provided at a time (when using :is="component", for example).

See also

Props

Name Type Description
hide-tabs Boolean Whether to hide the tabs. Optional.
ignore-edge-width Number Distance in pixels from both edges. Swiping on these areas will prioritize parent components such as ons-splitter or ons-navigator. Optional.
index Number If exists, specifies the current active index. It is also used as the initial index. Must be modified on update:index event. Optional.
modifier String The appearance of the tabbar. Optional.
on-swipe Function Hook called whenever the user slides the tabbar. It gets a decimal index and an animationOptions object as arguments. Optional.
options.animation String If this attribute is set to "none" the transitions will not be animated. Optional.
options.animationOptions Expression Specify the animation’s duration, timing and delay with an object literal. E.g. {duration: 0.2, delay: 1, timing: 'ease-in'}. Optional.
position String Tabbar’s position. Available values are "bottom" and "top". Use "auto" to choose position depending on platform (bottom for iOS flat design, top for Material Design). Optional.
swipeable Boolean If this attribute is set the tab bar can be scrolled by drag or swipe. Optional.
tab-border Boolean If this attribute is set the tabs show a dynamic bottom border. Only works for iOS flat design since the border is always visible in Material Design. Optional.
tabbar-style Boolean Optional style for the actual tabbar component. Accepts any Vue valid style. Optional.
tabs Array Contains as many objects as desired tabs in the tabbar. Every object describes a VOnsTab component. Every object must include at least one of the next properties: page, icon or label (see VOnsTab reference for more options). It is also possible to pass props to the pages through a props object for each tab. Example: tabs: [ { label: 'p1', page: p1 }, { label: 'p2', page: p2, props: { myPage2Prop: 'something' } } ]. This can be omitted if using slot="pages" and slot="tabs" components. Optional.

Preset Modifiers

Name Description
material A tabbar in Material Design.
autogrow Tabs automatically grow depending on their content instead of having a fixed width.
top-border Shows a static border-bottom in tabs for iOS top tabbars.

Events

Name Description
prechange Fires just before the tab is changed.
postchange Fires just after the tab is changed.
reactive Fires if the already open tab is tapped again.
update:index Fired right after user interaction. Useful to update index prop.
prechange

Fires just before the tab is changed.

Parameters
Name Type Description
event Object Event object.
event.index Number Current index.
event.tabItem Object Tab item object.
event.cancel Function Call this function to cancel the change event.
postchange

Fires just after the tab is changed.

Parameters
Name Type Description
event Object Event object.
event.index Number Current index.
event.tabItem Object Tab item object.
reactive

Fires if the already open tab is tapped again.

Parameters
Name Type Description
event Object Event object.
event.index Number Current index.
event.tabItem Object Tab item object.
update:index

Fired right after user interaction. Useful to update index prop.

Parameters
Name Type Description
event Number New value for index prop.

Discussion

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