Behavior Attributes

Behavior attributes are the main way to add interactivity to a Hyperview app. Behavior attributes enable rich interactions with a declarative syntax, powered by server-side logic.

Behaviors are based on a simple hypermedia model:

1. A behavior executes when it gets triggered, usually due to user input.
2. At the start of execution, the behavior requests new Hyperview content (XML), either from a remote location (via HTTP request) or locally (from a document fragment)
3. The request completes with Hyperview content (XML).
4. The new Hyperview content (XML) gets shown on the device, either by loading it in a new screen, or by injecting it into the current screen.

The set of behavior attributes described in this document give control over the steps outlined above. At a high level, the attributes define:

• trigger: What interaction causes the behavior to execute?
• href: What content should get requested?
• verb: How should the content get requested?
• action: What should the client do with the content?
• target: Where in the app should the client perform the action?

Note: When an href attribute is found on an element, Hyperview wraps the element with a "tappable" view. It is possible to customize the styles applied to that wrapping view by specifying the href-style property. See Styles.

The rest of the document describes in-depth how these attributes work together.

trigger

Type	Required
press (default), longPress, pressIn, pressOut, visible, refresh, load, select, deselect, focus, blur, change, on-event	No

press

Triggers on a press-in/press-out combination on the element, uninterrupted by a gesture.

These elements support the press trigger:

• <view>
• <text>
• <image>

longPress

Triggers on a press and hold without a press-out, uninterraupted by a gesture.

These elements support the longPress trigger:

• <view>
• <text>
• <image>

pressIn

Triggers immediately when the element is touched.

These elements support the pressIn trigger:

• <view>
• <text>
• <image>

pressOut

Triggers immediately when a touch is released from an element.

These elements support the pressOut trigger:

• <view>
• <text>
• <image>

visible

Triggers when the element is visible on the device's display. If the element is visible when the screen loads, the behavior will execute immediately. Otherwise, the action will trigger when the element is scrolled into view.

These elements support the visible trigger:

• <view>
• <text>
• <image>

refresh

Triggers on a pull-to-refresh gesture.

These elements support the refresh trigger:

• <view>
• <text>
• <image>
• <list>
• <section-list>

load

Triggers when the element is first loaded in the screen or update fragment.

Elements with hide="true" are not loaded in the screen. This means any hidden element (or child element) with the load trigger will not be executed.

These elements support the load trigger:

• <view>
• <text>
• <image>

select

Triggers when the element is selected. Only works on selectable elements.

These elements support the select trigger:

• <option>

deselect

Triggers when the element is deselected. Only works on selectable elements.

These elements support the deselect trigger:

• <option>

focus

Triggers when the element is focused. Only works on focusable elements.

These elements support the focus trigger:

• <text-field>
• <text-area>

blur

Triggers when the element loses focus. Only works on focusable elements.

These elements support the blur trigger:

• <text-field>
• <text-area>

change

Triggers when the element value changes. Only works on editable elements.

NOTE: when using the change trigger on a <text-field> that include the mask attribute, the behavior will be triggered even if the mask prevents the pressed key from being set.

NOTE: on a <text-field>, the change trigger can be paired with the debounce attribute, which can be set with the number of milliseconds to debounce change events, i.e. debounce="200" will debounce the change event to 200ms after the last change on the text field occured.

These elements support the change trigger:

• <text-field>
• <text-area>
• <switch>

on-event

Triggers when the element captures an event with the specified event-name. This trigger requires an event-name attribute to be present and may be triggered from any hyperview screen.

These elements support the on-event trigger:

• <view>
• <text>

The on-event trigger may also be combined with once and delay.

Debugging tip

In __DEV__ mode, the console will log the element which captures an event

back

Triggers when the screen is being closed by behavior action (back or close), or by using a swipe gesture or physical back button (Android). As long as there are any visible behaviors with a back trigger, the screen can not be closed.

NOTE: Only works when using internal Navigators. See navigator.

These elements support the back trigger:

• <view>

Supported triggers

Not all elements support behavior attributes or <behavior> elements. Those that do may not support every trigger. This list below defines which elements can have behaviors, and which triggers they support.

<view>

<view> supports behavior attributes (or <behavior> elements as direct children) with the following triggers:

• press
• longPress
• pressIn
• pressOut
• visible
• refresh
• load
• on-event
• back

<text>

• <text> supports behavior attributes (or <behavior> elements as direct children) with the following triggers:
  • press
  • longPress
  • pressIn
  • pressOut
  • visible
  • refresh
  • load
  • on-event

<image>

<image>: supports behavior attributes (or <behavior> elements as direct children) with the following triggers:

• press
• longPress
• pressIn
• pressOut
• visible
• refresh
• load

<list>

<list>: supports behavior attributes (or <behavior> elements as direct children) with the following triggers:

• refresh

<section-list>

• <section-list>: supports behavior attributes (or <behavior> elements as direct children) with the following triggers:
  • refresh

<option>

<option>: supports behavior attributes (or <behavior> elements as direct children) with the following triggers:

• select
• deselect

<text-field>

<text-field>: supports behavior attributes (or <behavior> elements as direct children) with the following triggers:

• focus
• blur

<text-area>

<text-area>: supports behavior attributes (or <behavior> elements as direct children) with the following triggers:

• focus
• blur

href

Type	Required
string	Yes

The href attribute is required for all built-in behaviors. However, custom behaviors may not require an href.

The only required attribute to create a behavior, href specifies how to retrieve new app content in response to a trigger. There are three accepted formats:

Relative URIs

In the "relative URI" format, href is a path starting with a /. This path is combined with the protocol and host of the request used to fetch the current document to create a URL. When the behavior triggers, new content will be fetched via HTTP from the full URL.

For example, assume the following doc is loaded from https://mysite.com:

<doc xmlns="https://hyperview.org/hyperview">
  <screen>
    <body>
      <text href="/hello/world?param=true">Hello</text>
    </body>
  </screen>
</doc>

When the user presses "Hello", content for the next screen will be requested from https://mysite.com/hello/world?param=true.

Absolute URLs

In the "absolute URL" format, href is a full URL, with protocol, host, path, query params, etc. New content will be fetched via HTTP from the URL as-is.

For example, assume the following doc is loaded from https://mysite.com/home:

<doc xmlns="https://hyperview.org/hyperview">
  <screen>
    <body>
      <text href="https://othersite.com/hello/world?param=true">Hello</text>
    </body>
  </screen>
</doc>

When the user presses "Hello", content for the next screen will be requested from https://othersite.com/hello/world?param=true.

Document fragments

In the "document fragment" format, href is an element id prepended by a #. The id must refer to an element in the current document.

For example, assume the following doc is loaded from https://mysite.com/home:

<doc xmlns="https://hyperview.org/hyperview">
  <screen>
    <body>
      <text href="#hello-content" action="replace">Hello</text>
      <view hide="true">
        <text id="hello-content">Hi there!</text>
      </view>
    </body>
  </screen>
</doc>

When the user presses "Hello", the content of the text element will be replaced with the content of the text element identified as hello-content:

When using document fragment hrefs, form data will be ignored, and the verb attribute has no meaning.

Unspecified

An unspecified href looks like "#". This can only be used with back and close actions, to indicate that the navigation should happen with no fetched href.

verb

Type	Required
get (default), post	No

The verb attribute defines the HTTP method used to request the content specified by href. If not specified, defaults to "get".

• When using get, any <form> values will be URL-encoded and added to the href.
• When using post, any <form> values will be form-URL encoded (x-www-form-urlencoded).
• verb only has meaning when making remote requests. If a behavior has a document fragment href and a verb, the verb attribute will be ignored.

action

Type	Required
push (default), new, back, close, navigate, deep-link, open-settings, replace, replace-inner, append, prepend, reload, dispatch-event, show, hide, toggle, set-value, copy-to-clipboard, select-all, unselect-all	No

The action attribute defines what to do with the Hyperview XML resource described by the href attribute. The possible actions are divided into navigation actions, which load or navigate to a screen, and update actions, which update the elements on the current screen.

The navigation actions include:

• push
• new
• back
• close
• navigate
• reload
• deep-link
• open-settings

The update actions include:

• replace
• replace-inner
• append
• prepend
• dispatch-event
• show
• hide
• toggle
• set-value
• copy-to-clipboard
• select-all
• unselect-all

push

The push navigation action will push a new screen onto the stack, and the fetched content will be displayed in the new screen.

When using push, the fetched content must be either a full Hyperview XML document (with <doc> root), or a <screen> element from the current screen's document.

If the element triggering the push is a <form> or contained in a <form> element, the form's data will be serialized as query parameters and included in the request. The form data has no effect when the href refers to a local <screen> element.

new

The new navigation action will open a new screen on top of the current screen, and the fetched content will be displayed in the new screen.

When using new, the fetched content must be either a full Hyperview XML document (with <doc> root), or a <screen> element from the current screen's document.

If the element triggering the modal is a <form> or contained in a <form> element, the form's data will be serialized as query parameters and included in the request. The form data has no effect when the href refers to a local <screen> element.

back

The back navigation action will undo a push, by popping the current screen off the stack and revealing the previous screen on the stack.

If the provided href attribute would load data from the same source as the previous screen, no request happens. However, if the provided href is different, a request will be made to reload the previous screen.

For example, take this document for the first screen in an app, loaded from https://mystie.com/first:

<doc xmlns="https://hyperview.org/hyperview">
  <screen>
    <body>
      <text href="/second" action="push">Go to second screen</text>
    </body>
  </screen>
</doc>

And the second screen:

<doc xmlns="https://hyperview.org/hyperview">
  <screen>
    <body>
      <text href="/first" action="back">Go back</text>
      <text href="/third" action="back">Go back to a different place</text>
    </body>
  </screen>
</doc>

When the user presses "Go to second screen", the second screen will be pushed onto the stack. Then, if the user pushes "Go back", the stack will unwind, and the user will see screen 1 again. However, if the user pushes "Go back to a different place", the stack will unwind, and Hyperview will make a request to https://mysite.com/third. The content of the first screen will be replaced with the content from the third request.

Any change in the URL will cause a reload, including changes in the search string.

Use href="#" to navigate back to the previous screen without reloading or knowing the URL.

If the element triggering the back navigation is a <form> or contained in a <form> element, the form's data will be serialized as query parameters and included in the request. The form data has no effect when the href refers to a local <screen> element.

close

The close navigation action will undo a new, by closing the current modal screen and revealing the previous screen on the stack.

If the provided href attribute would load data from the same source as the previous screen, no request happens. However, if the provided href is different, a request will be made to reload the previous screen.

For example, take this document for the first screen in an app, loaded from https://mystie.com/first:

<doc xmlns="https://hyperview.org/hyperview">
  <screen>
    <body>
      <text href="/second" action="new">Go to second screen</text>
    </body>
  </screen>
</doc>

And the second screen:

<doc xmlns="https://hyperview.org/hyperview">
  <screen>
    <body>
      <text href="/first" action="close">Go back</text>
      <text href="/third" action="close">Go back to a different place</text>
    </body>
  </screen>
</doc>

When the user presses "Go to second screen", the second screen will be opened on top of the first screen. Then, if the user pushes "Go back", the modal screen will close, and the user will see the first screen again. However, if the user pushes "Go back to a different place", the modal will close, and Hyperview will make a request to https://mysite.com/third. The content of the first screen will be replaced with the content from the third request.

Any change in the URL will cause a reload, including changes in the search string.

Use href="#" to close the modal without reloading or knowing the URL of the previous screen.

If the element triggering the close navigation is a <form> or contained in a <form> element, the form's data will be serialized as query parameters and included in the request. The form data has no effect when the href refers to a local <screen> element.

navigate

The navigate navigation action will either push a screen onto the stack, or unwind the stack to a screen loaded from the given URL.

reload

The reload navigation action will re-request the current screen. This is similar to a reload button in a web browser.

If the reload behavior contains an href, the given href will be used to request the new content for the current screen.

deep-link

The deep-link navigation action delegates the navigation to the operating system, in order to decide which app should open the given URL.

open-settings

The open-settings navigation action opens the app settings in the OS Settings app.

replace

The replace update action will replace the target element on the current screen with the fetched content. By default, the target element is the element that triggered the behavior execution, although that can be controlled with the target attribute.

When using replace, the fetched content must be a document fragment, ie not a <doc> or <screen> but a <view>, <text>, etc.

replace-inner

The replace-inner update action will replace the children of the target element on the current screen with the fetched content. By default, the target element is the element that triggered the behavior execution, although that can be controlled with the target attribute.

When using replace-inner, the fetched content must be a document fragment, ie not a <doc> or <screen> but a <view>, <text>, etc.

append

The append update action will add the fetched content as the last child of the target element on the current screen. By default, the target element is the element that triggered the behavior execution, although that can be controlled with the target attribute.

When using append, the fetched content must be a document fragment, ie not a <doc> or <screen> but a <view>, <text>, etc.

prepend

The prepend update action will add the fetched content as the first child of the target element on the current screen. By default, the target element is the element that triggered the behavior execution, although that can be controlled with the target attribute.

When using append, the fetched content must be a document fragment, ie not a <doc> or <screen> but a <view>, <text>, etc.

dispatch-event

The dispatch-event action fires an event specified with the event-name attribute on the element. The element must have an event-name attribute. A matching event (having same event-name) will then trigger on-event behavior on any hyperview screen(s).

The dispatch-event action may also be combined with once and delay.

Debugging tip

In __DEV__ mode, the console will log the element which dispatches an event

show

The show action will show the target element if the target is currently hidden (with hide="true"). If the target is not hidden, this action will have no effect. This action can be used in conjunction with delay to show the element after the given number of milliseconds. When using delay, you can also specify show-during-load and hide-during-load attributes to show and hide indicators during the delay.

<view action="show" style="Button" target="show-content">
  <text style="Button__Label">Show</text>
</view>
<text id="show-content" hide="true">Content to be shown</text>

In this example, pressing "Show" will show the text below. See the repo for more examples.

hide

The hide action will hide the target element by applying hide="true" to the target. If the target is already hidden, this action will have no effect. This action can be used in conjunction with delay to hide the element after the given number of milliseconds. When using delay, you can also specify show-during-load and hide-during-load attributes to show and hide indicators during the delay.

<view action="hide" style="Button" target="hide-content">
  <text style="Button__Label">Hide</text>
</view>
<text id="hide-content">Content to be hidden</text>

In this example, pressing "Hide" will hide the text below. See the repo for more examples.

toggle

The toggle action will toggle the visibility of the target element by applying or removing hide="true". If the target is already hidden, this action will show it. If the target is not hidden, this action will hide it. This action can be used in conjunction with delay to toggle the element after the given number of milliseconds. When using delay, you can also specify show-during-load and hide-during-load attributes to show and hide indicators during the delay.

<view action="toggle" style="Button" target="toggle-content">
  <text style="Button__Label">Hide</text>
</view>
<text id="toggle-content">Content to be toggled</text>

In this example, pressing "Toggle" will toggle the text below. See the repo for more examples.

set-value

The set-value action allows setting the input value of the target element. The behavior attributes must include a new-value attribute specifying the new value.

Note that the target element must only be one of the following elements:

• <text-field>
• <text-area>
• <picker-field>
• <date-field>
• <select-single>
• <switch>

Notable, <select-multiple> is not currently supported. Also note that using set-value will ignore any validation or restrictions set by the input element, like masks or other requirements.

<text-field id="id_tf" />
<text style="link" action="set-value" new-value="Test" target="id_tf">Set</text>
<text style="link" action="set-value" new-value="" target="id_tf">Clear value</text>

In this example, pressing "Set" will fill in the text field with "Test". Pressing "Clear value" will fill in the text field with "". See the repo for more examples.

copy-to-clipboard

The copy-to-clipboard action allows copying a value to the clipboard. The behavior attributes must include a [copy-to-clipboard-value] attribute specifying the value to be copied.

<view>
  <behavior
    trigger="press"
    action="copy-to-clipboard"
    copy-to-clipboard-value="Hello World!"
  />
  <text style="link">Copy to clipboard</text>
</view>

In this example, pressing "Copy to clipboard" will copy the value "Hello World!" to the clipboard. See the repo for examples.

select-all

The select-all action allows selecting all the options of the target element.

Note that the target element must be a <select-multiple> element.

<select-multiple id="id_sm">
    <option value="1">
      <text>1st option</text>
    </option>
    <option value="2">
      <text>2nd option</text>
    </option>
    <option value="3" selected="true">
      <text>3rd option</text>
    </option>
</select-multiple>
<text style="link" action="select-all" target="id_sm">Select all</text>

In this example, pressing "Select all" will select "1st option" and "2nd option", in addition to the already selected "3rd option". See the repo for more examples.

unselect-all

The unselect-all action allows unselecting all the options of the target element.

Note that the target element must only be one of the following elements:

• <select-single>
• <select-multiple>

<select-multiple id="id_sm">
    <option value="1" selected="true">
      <text>1st option</text>
    </option>
    <option value="2" selected="true">
      <text>2nd option</text>
    </option>
    <option value="3">
      <text>3rd option</text>
    </option>
</select-multiple>
<text style="link" action="unselect-all" target="id_sm">Unselect all</text>

In this example, pressing "Unselect all" will unselect "1st option" and "2nd option", that were initially selected. See the repo for more examples.

target

Type	Required
string	No

This attribute specifies the target of the action. The meaning depends on the action type.

Navigation actions

For navigation actions, target refers to the section of the app's navigation stack that should be used to show the new screen or modal. For example, if an app implements a tab navigation, target="tab2" would indicate that the new screen should be pushed in tab2. If the current screen was in a different tab, the app would first switch to tab2, and then push the new screen.

• If target cannot be interpreted by the app, or the app has no navigation targets, setting this attribute will have no effect.

Update actions

For update actions, target should be the id of an element on the current screen.

• If the target element exists on screen, the update action (replace, append, etc) will be applied to the specified element rather than the source of the behavior.
• If the id doesn't point to an element on the screen, the action will be a no-op.
• If "target" is unset, the target of the update action will be the source of the behavior.

show-during-load

Type	Required
string	No

A space-separated list of element ids. The elements with the given ids will be shown while requesting the content identified by href. Most commonly used to implement a loading state. The behavior differs a bit depending on the action type.

Navigation actions

Navigation actions immediately show a new screen or modal before requesting the new content. Since the request can take a while, using show-during-load will copy the referenced element into the new screen. Once the request completes, the requested content will replace the loading state on the new screen. There are a few nuances when using this attribute with navigation actions:

• show-during-load should only contain a single element id for a <screen> element. This screen must be part of the current doc.
• If show-during-load contains multiple space-separated element ids, only the first element will be used.
• If the element id from show-during-load references an element other than a <screen>, that element will not be used as the new screen's loading state.

Only the first <screen> element in <doc> will be displayed on a screen. Therefore, be sure to include indicator <screen> elements at the end of the <doc>.

When using action="back" or action="navigate", the existing screen will be reloaded if the href attribute differs from the href used to request the content originally. During the request, we can show a loading screen using show-during-load.

Update actions

During update actions, the elements referenced in show-during-load will be shown on the current screen. The indicator elements is hidden after the href is fetched. This is a no-op for elements which don't exist on the screen.

• If show-during-load refers to an element ids not present in the screen, the attribute will have no effect.
• If the indicator element itself has behavior attributes with trigger="load", that behavior will trigger when the element appears when the request starts.

To avoid having the indicator elements visible when the screen first loads, make sure to add hide="true" to the indicator elements.

hide-during-load

Type	Required
string	No

A space-separated list of element ids. The elements with the given ids will be hidden while requesting the content identified by href. The behavior differs a bit depending on the action type.

Navigation actions

Navigation actions immediately show a new screen or modal before requesting the new content. Since the old screen is not visible during the request, hide-during-load will have no effect during navigation actions.

Update actions

During update actions, the elements referenced by hide-during-load will be hidden on the current screen during the request. When the request completes, the items will be shown again. A couple of nuances:

• If hide-during-load refers to element ids not present in the screen, the attribute will have no effect.
• It is possible that the update action will remove the hidden element. For example, action="replace" may replace the parent element of the hidden element. In this case, the element will not be shown once the request completes.
• If the indicator element itself has behavior attributes with trigger="load", that behavior will execute when the element re-appears once the request completes.

delay

Type	Required
number	No

delay specifies the number of milliseconds to wait before requesting the content identified by href. Any indicators specified by show-during-load or hide-during-load will be toggled during the delay. If unset, the content will be requested immediately.

This attribute is used commonly in examples to demonstrate loading states. It can be useful to introduce some artificial delay so that users register that content is being loaded.

once

Type	Required
true, false (default)	No

once="true" specifies that the behavior should only execute the first time it triggers. If not provided, the default is to execute the behavior on each trigger . This attribute is often used in conjunction with the "visible" trigger, so that we only execute the behavior the first time an element scrolls into view.

new-value

Type	Required
string	Required when action="set-value", otherwise ignored

When the behavior action is set-value, this attribute defines the value that will be set on the target input element.