phonegap-plugin-mobile-accessibility

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This plugin exposes information on the status of various accessibility features of mobile operating systems, including, for example, whether a screen reader is running, invert colors is enabled, and the preferred scaling for text. It also allows an application to send a string to be spoken by the screen reader, or a command to stop the screen reader from speaking.

Installation

$ cordova plugin add https://github.com/phonegap/phonegap-mobile-accessibility.git

Supported Platforms

• Amazon Fire OS
• Android
• iOS

MobileAccessibility

The MobileAccessibility object, exposed by window.MobileAccessibility, provides methods for determining the status of accessibility features active on the user's device, methods changing the text zoom of the Cordova web view and for using the user's preferred text zoom as set in the operating system settings, and methods for sending a string to be spoken by the screen reader or to stop the screen reader from speaking.

Methods

• MobileAccessibility.isScreenReaderRunning
• MobileAccessibility.isVoiceOverRunning
• MobileAccessibility.isTalkBackRunning
• MobileAccessibility.isChromeVoxActive
• MobileAccessibility.isClosedCaptioningEnabled
• MobileAccessibility.isGuidedAccessEnabled
• MobileAccessibility.isInvertColorsEnabled
• MobileAccessibility.isMonoAudioEnabled
• MobileAccessibility.isTouchExplorationEnabled
• MobileAccessibility.getTextZoom
• MobileAccessibility.setTextZoom
• MobileAccessibility.updateTextZoom
• MobileAccessibility.usePreferredTextZoom
• MobileAccessibility.postNotification
• MobileAccessibility.speak
• MobileAccessibility.stop

MobileAccessibility.isScreenReaderRunning(callback)

Makes an asynchronous call to native MobileAccessibility to determine if a screen reader is running.

Parameters

• callback (Function) A callback method to receive the boolean result asynchronously from the native MobileAccessibility plugin.

Usage

    function isScreenReaderRunningCallback(boolean) {
        if (boolean) {
            console.log("Screen reader: ON");
            // Do something to improve the behavior of the application while a screen reader is active.
        } else {
            console.log("Screen reader: OFF");
        }
    }

    MobileAccessibility.isScreenReaderRunning(isScreenReaderRunningCallback);

Supported Platforms

• Amazon Fire OS
• Android
• iOS

MobileAccessibility.isVoiceOverRunning(callback)

An iOS-specific proxy for the MobileAccessibility.isScreenReaderRunning method. This method will return false on Android and Amazon Fire OS.

Parameters

• callback (Function) A callback method to receive the boolean result asynchronously from the native MobileAccessibility plugin.

Usage

    function isVoiceOverRunningCallback(boolean) {
        if (boolean) {
            console.log("Screen reader: ON");
            // Do something to improve the behavior of the application while a screen reader is active.
        } else {
            console.log("Screen reader: OFF");
        }
    }

    MobileAccessibility.isVoiceOverRunning(isVoiceOverRunningCallback);

Supported Platforms

• iOS

MobileAccessibility.isTalkBackRunning(callback)

An Android/Amazon Fire OS-specific proxy for the MobileAccessibility.isScreenReaderRunning method. This method will return false on iOS.

Parameters

• callback (Function) A callback method to receive the boolean result asynchronously from the native MobileAccessibility plugin.

Usage

    function isTalkBackRunningCallback(boolean) {
        if (boolean) {
            console.log("Screen reader: ON");
            // Do something to improve the behavior of the application while a screen reader is active.
        } else {
            console.log("Screen reader: OFF");
        }
    }

    MobileAccessibility.isTalkBackRunning(isTalkBackRunningCallback);

Supported Platforms

• Amazon Fire OS
• Android

MobileAccessibility.isChromeVoxActive()

On Android, this method returns true if ChromeVox is active and properly initialized with access to the text to speech API in the WebView. If TalkBack is running but ChromeVox is not active, this method is useful to alert the user of a potential problem.

Returns

• boolean (Boolean) Returns true if ChromeVox is active and properly initialized with access to the text to speech API in the WebView.

Usage

    MobileAccessibility.isTalkBackRunning(
        function (bool) {
            console.log('Talkback status: ' + bool);
            if (bool) {
                /* Use setTimeout to account for latency in initialization of ChromeVox */
                setTimeout(function() {
                    if (MobileAccessibility.isChromeVoxActive()) {
                        console.log('ChromeVox is active.');
                    } else {
                        console.log('ChromeVox is not active.');

                        /* Notify the user of a potential problem */
                        MobileAccessibility.speak('The ChromeVox screen reader has failed to initialize. You may wish to close and restart this app.');
                    }
                }, 5000);
            }
        });

Supported Platforms

• Amazon Fire OS
• Android

MobileAccessibility.isClosedCaptioningEnabled(callback)

Makes an asynchronous call to native MobileAccessibility to determine if system-level closed captioning is enabled on the device.

Parameters

• callback (Function) A callback method to receive the boolean result asynchronously from the native MobileAccessibility plugin.

Usage

    function isClosedCaptioningEnabledCallback(boolean) {
        if (boolean) {
            console.log("Closed Captioning: ON");
            // Do something to improve the behavior of the application while closed captioning is enabled.
        } else {
            console.log("Closed Captioning: OFF");
        }
    }

    MobileAccessibility.isClosedCaptioningEnabled(isClosedCaptioningEnabledCallback);

Supported Platforms

• Amazon Fire OS
• Android
• iOS

MobileAccessibility.isGuidedAccessEnabled(callback)

Makes an asynchronous call to native MobileAccessibility to determine if Guided Access is enabled.

Parameters

• callback (Function) A callback method to receive the boolean result asynchronously from the native MobileAccessibility plugin.

Usage

    function isGuidedAccessEnabledCallback(boolean) {
        if (boolean) {
            console.log("Guided Access: ON");
            // Do something to improve the behavior of the application while Guided Access is enabled.
        } else {
            console.log("Guided Access: OFF");
        }
    }

    MobileAccessibility.isGuidedAccessEnabledEnabled(isGuidedAccessEnabledCallback);

Supported Platforms

• iOS

MobileAccessibility.isInvertColorsEnabled(callback)

Makes an asynchronous call to native MobileAccessibility to determine if the display colors have been inverted.

Parameters

• callback (Function) A callback method to receive the boolean result asynchronously from the native MobileAccessibility plugin.

Usage

    function isInvertColorsEnabledCallback(boolean) {
        if (boolean) {
            console.log("Invert Colors: ON");
            // Do something to improve the behavior of the application while Invert Colors is enabled.
        } else {
            console.log("Invert Colors: OFF");
        }
    }

    MobileAccessibility.isInvertColorsEnabled(isInvertColorsEnabledCallback);

Supported Platforms

• iOS

MobileAccessibility.isMonoAudioEnabled(callback)

Makes an asynchronous call to native MobileAccessibility to determine if mono audio is enabled.

Parameters

• callback (Function) A callback method to receive the boolean result asynchronously from the native MobileAccessibility plugin.

Usage

    function isMonoAudioEnabledCallback(boolean) {
        if (boolean) {
            console.log("Mono Audio: ON");
            // Do something to improve the behavior of the application while Mono Audio is enabled.
        } else {
            console.log("Mono Audio: OFF");
        }
    }

    MobileAccessibility.isMonoAudioEnabled(isMonoAudioEnabledCallback);

Supported Platforms

• iOS

MobileAccessibility.isTouchExplorationEnabled(callback)

Makes an asynchronous call to native MobileAccessibility to determine if Touch Exploration is enabled on Android.

Parameters

• callback (Function) A callback method to receive the boolean result asynchronously from the native MobileAccessibility plugin.

Usage

    function isTouchExplorationEnabledCallback(boolean) {
        if (boolean) {
            console.log("Touch Exploration: ON");
            // Do something to improve the behavior of the application with Touch Exploration enabled.
        } else {
            console.log("Touch Exploration: OFF");
            // Do something to improve the behavior of the application with Touch Exploration disabled.

        }
    }

    MobileAccessibility.isTouchExplorationEnabled(isTouchExplorationEnabledCallback);

Supported Platforms

• Amazon Fire OS
• Android

MobileAccessibility.getTextZoom(callback)

Makes an asynchronous call to native MobileAccessibility to return the current text zoom percent value for the WebView.

Parameters

• callback (Function) A callback method to receive the text zoom percent value asynchronously from the native MobileAccessibility plugin.

Usage

    function getTextZoomCallback(textZoom) {
        console.log('Current text zoom = ' + textZoom + '%')
    }

    MobileAccessibility.getTextZoom(getTextZoomCallback);

Supported Platforms

• Amazon Fire OS
• Android
• iOS

MobileAccessibility.setTextZoom(textZoom, callback)

Makes an asynchronous call to native MobileAccessibility to set the current text zoom percent value for the WebView.

Parameters

• textZoom (Number) A percentage value by which text in the WebView should be scaled.
• callback (Function) A callback method to receive the new text zoom percent value asynchronously from the native MobileAccessibility plugin.

Usage

    function setTextZoomCallback(textZoom) {
        console.log('WebView text should be scaled ' + textZoom + '%')
    }

    MobileAccessibility.setTextZoom(200, setTextZoomCallback);

Supported Platforms

• Amazon Fire OS
• Android
• iOS

MobileAccessibility.updateTextZoom(callback)

Makes an asynchronous call to native MobileAccessibility to retrieve the user's preferred text zoom from system settings and apply it to the application WebView.

Parameters

• callback (Function) A callback method to receive the new text zoom percent value asynchronously from the native MobileAccessibility plugin.

Usage

    function updateTextZoomCallback(textZoom) {
        console.log('WebView text should be scaled ' + textZoom + '%')
    }

    MobileAccessibility.updateTextZoom(callback);

Supported Platforms

• Amazon Fire OS
• Android
• iOS7+

MobileAccessibility.usePreferredTextZoom(boolean)

Specifies whether or not the application should use the user's preferred text zoom from system settings to scale text within the WebView. When set to true, this method calls MobileAccessibility.updateTextZoom() to apply new text zoom settings to the application WebView. When set to false, the application WebView text zoom will be reset to the default value of 100 percent. The plugin uses local storage to retain the preference and will call MobileAccessibility.updateTextZoom() after a Cordova resume event.

Parameters

• boolean (Boolean) A Boolean value which specifies whether to use the preferred text zoom of a default percent value of 100.

Usage

    MobileAccessibility.usePreferredTextZoom(true);

    function getTextZoomCallback(textZoom) {
        console.log('WebView text should be scaled to the preferred value ' + textZoom + '%')
    }

    MobileAccessibility.getTextZoom(getTextZoomCallback);

Supported Platforms

• Amazon Fire OS
• Android
• iOS7+

MobileAccessibility.postNotification(mobileAccessibilityNotification, string, callback)

Posts a notification with a string for the screen reader to announce if it is running.

Parameters

• mobileAccessibilityNotification (uint) A numeric constant for the type of notification to send. Constants are defined in MobileAccessibilityNotifications.
• string (string) A string to be announced by a screen reader.
• callback (function) A callback method to receive the asynchronous result from the native MobileAccessibility, when the announcement is finished, the function should expect an object containing the stringValue that was voiced and a boolean indicating that the announcement wasSuccessful.

Constants

The following constants are for sending notifications to the accessibility API using the MobileAccessibility.postNotification method. They correspond to notification constants defined in UIAccessibilityNotifications on iOS.

• MobileAccessibilityNotifications.SCREEN_CHANGED
• MobileAccessibilityNotifications.LAYOUT_CHANGED
• MobileAccessibilityNotifications.ANNOUNCEMENT
• MobileAccessibilityNotifications.PAGE_SCROLLED

    MobileAccessibility.postNotification(
        MobileAccessibilityNotifications.ANNOUNCEMENT,
        'String to be announced by screen reader.',
        function(info) {
            if (info) {
                console.log("Screen Reader announced \"" + info.stringValue + "\" success : " + info.wasSuccessful);
            }
        });

Supported Platforms

• iOS

MobileAccessibility.speak(string, queueMode, properties)

Speaks a given string through the screenreader. On Android, if ChromeVox is active, it will use the specified queueMode and properties.

Parameters

• string (string) A string to be announced by a screen reader.
• queueMode (Optional number) Valid modes are 0 for flush; 1 for queue.
• properties (Optional Object) Speech properties to use for this utterance.

    MobileAccessibility.speak('This string will be announced when a screen reader is active on the device.');

Supported Platforms

• Amazon Fire OS
• Android
• iOS

MobileAccessibility.stop()

Stops speech.

    MobileAccessibility.stop();

Supported Platforms

• Amazon Fire OS
• Android
• iOS

Events

Constants

The following event constants are for window events, to which an application can listen for notification of changes in the status of the accessibility features on the device.

• MobileAccessibilityNotifications.SCREEN_READER_STATUS_CHANGED
• MobileAccessibilityNotifications.CLOSED_CAPTIONING_STATUS_CHANGED
• MobileAccessibilityNotifications.GUIDED_ACCESS_STATUS_CHANGED
• MobileAccessibilityNotifications.INVERT_COLORS_STATUS_CHANGED
• MobileAccessibilityNotifications.MONO_AUDIO_STATUS_CHANGED
• MobileAccessibilityNotifications.TOUCH_EXPLORATION_STATUS_CHANGED

MobileAccessibilityNotifications.SCREEN_READER_STATUS_CHANGED (screenreaderstatuschanged)

The event fires when a screen reader on the device turns on or off. The event returns an object, info, with the current status of accessibility features on the device. If a screen reader is active, info.isScreenReaderRunning will equal true.

    // Define a persistent callback method to handle the event
    function onScreenReaderStatusChanged(info) {
        if (info && typeof info.isScreenReaderRunning !== "undefined") {
            if (info.isScreenReaderRunning) {
                console.log("Screen reader: ON");
                // Do something to improve the behavior of the application while a screen reader is active.
            } else {
                console.log("Screen reader: OFF");
            }
        }
    }

    // Register the callback method to handle the event
    window.addEventListener(MobileAccessibilityNotifications.SCREEN_READER_STATUS_CHANGED, onScreenReaderStatusChanged, false);

MobileAccessibilityNotifications.CLOSED_CAPTIONING_STATUS_CHANGED (closedcaptioningstatuschanged)

The event fires when system-level closed captioning on the device turns on or off. The event returns an object, info, with the current status of accessibility features on the device. If a screen reader is active, info.isClosedCaptioningEnabled will equal true.

    // Define a persistent callback method to handle the event
    function onClosedCaptioningStatusChanged(info) {
        if (info && typeof info.isClosedCaptioningEnabled !== "undefined") {
            if (info.isClosedCaptioningEnabled) {
                console.log("Closed Captioning: ON");
                // Do something to improve the behavior of the application while closed captioning is enabled.
            } else {
                console.log("Closed Captioning: OFF");
            }
        }
    }

    // Register the callback method to handle the event
    window.addEventListener(MobileAccessibilityNotifications.CLOSED_CAPTIONING_STATUS_CHANGED, onClosedCaptioningStatusChanged, false);

MobileAccessibilityNotifications.GUIDED_ACCESS_STATUS_CHANGED (guidedaccessstatuschanged)

The event fires when Guided Access has been enabled on an iOS device. The event returns an object, info, with the current status of accessibility features on the device. If a screen reader is active, info.isGuidedAccessEnabled will equal true.

    // Define a persistent callback method to handle the event
    function onGuidedAccessStatusChanged(info) {
        if (info && typeof info.isGuidedAccessEnabled !== "undefined") {
            if (info.isGuidedAccessEnabled) {
                console.log("Guided Access: ON");
                // Do something to improve the behavior of the application while Guided Access is enabled.
            } else {
                console.log("Guided Access: OFF");
            }
        }
    }

    // Register the callback method to handle the event
    window.addEventListener(MobileAccessibilityNotifications.GUIDED_ACCESS_STATUS_CHANGED, onGuidedAccessStatusChanged, false);

MobileAccessibilityNotifications.INVERT_COLORS_STATUS_CHANGED (invertcolorsstatuschanged)

The event fires when Invert Colors has been enabled on an iOS device. The event returns an object, info, with the current status of accessibility features on the device. If a screen reader is active, info.isInvertColorsEnabled will equal true.

    // Define a persistent callback method to handle the event
    function onInvertColorsStatusChanged(info) {
        if (info && typeof info.isInvertColorsEnabled !== "undefined") {
            if (info.isInvertColorsEnabled) {
                console.log("Invert Colors: ON");
                // Do something to improve the behavior of the application while Invert Colors is enabled.
            } else {
                console.log("Invert Colors: OFF");
            }
        }
    }

    // Register the callback method to handle the event
    window.addEventListener(MobileAccessibilityNotifications.INVERT_COLORS_STATUS_CHANGED, onInvertColorsStatusChanged, false);

MobileAccessibilityNotifications.MONO_AUDIO_STATUS_CHANGED (monoaudiostatuschanged)

The event fires when Mono Audio has been enabled on an iOS device. The event returns an object, info, with the current status of accessibility features on the device. If a screen reader is active, info.isMonoAudioEnabled will equal true.

    // Define a persistent callback method to handle the event
    function onMonoAudioStatusChanged(info) {
        if (info && typeof info.isMonoAudioEnabled !== "undefined") {
            if (info.isMonoAudioEnabled) {
                console.log("Mono Audio: ON");
                // Do something to improve the behavior of the application while Mono Audio is enabled.
            } else {
                console.log("Mono Audio: OFF");
            }
        }
    }

    // Register the callback method to handle the event
    window.addEventListener(MobileAccessibilityNotifications.MONO_AUDIO_STATUS_CHANGED, onMonoAudioStatusChanged, false);

MobileAccessibilityNotifications.TOUCH_EXPLORATION_STATUS_CHANGED (touchexplorationstatuschanged)

The event fires when Touch Exploration has been enabled on an Android device. The event returns an object, info, with the current status of accessibility features on the device. If a screen reader is active, info.isTouchExplorationEnabled will equal true.

    // Define a persistent callback method to handle the event
    function onTouchExplorationChanged(info) {
        if (info && typeof info.isTouchExplorationEnabled !== "undefined") {
            if (info.isTouchExplorationEnabled) {
                console.log("Touch Exploration: ON");
                // Do something to improve the behavior of the application while Touch Exploration is enabled.
            } else {
                console.log("Touch Exploration: OFF");
            }
        }
    }

    // Register the callback method to handle the event
    window.addEventListener(MobileAccessibilityNotifications.TOUCH_EXPLORATION_STATUS_CHANGED, onTouchExplorationChanged, false);