שתף באמצעות

Accessibility on Android

  • מאמר

This page describes how to use the Android Accessibility APIs to build apps according to the accessibility checklist. Refer to the iOS accessibility and OS X accessibility pages for other platform APIs.

Describing UI Elements

Android provides a ContentDescription property that is used by screen reading APIs to provide an accessible description of the control's purpose.

The content description can be set in either C# or in the AXML layout file.

C#

The description can be set in code to any string (or a string resource):

saveButton.ContentDescription = "Save data";

AXML layout

In XML layouts use the android:contentDescription attribute:

<ImageButton
    android:id=@+id/saveButton"
    android:src="@drawable/save_image"
    android:contentDescription="Save data" />

Use Hint for TextView

For EditText and TextView controls for data input, use the Hint property to provide a description of what input is expected (instead of ContentDescription). When some text has been entered, the text itself will be "read" instead of the hint.

C#

Set the Hint property in code:

someText.Hint = "Enter some text"; // displays (and is "read") when control is empty

AXML layout

In XML layout files use the android:hint attribute:

<EditText
    android:id="@+id/someText"
    android:hint="Enter some text" />

To associate a label with a data input control, use the LabelFor property to

C#

In C#, set the LabelFor property to the resource ID of the control that this content describes (typically this property is set on a label and references some other input control):

EditText edit = FindViewById<EditText> (Resource.Id.editFirstName);
TextView tv = FindViewById<TextView> (Resource.Id.labelFirstName);
tv.LabelFor = Resource.Id.editFirstName;

AXML layout

In layout XML use the android:labelFor property to reference another control's identifier:

<TextView
    android:id="@+id/labelFirstName"
    android:hint="Enter some text"
    android:labelFor="@+id/editFirstName" />
<EditText
    android:id="@+id/editFirstName"
    android:hint="Enter some text" />

Announce for Accessibility

Use the AnnounceForAccessibility method on any view control to communicate an event or status change to users when accessibility is enabled. This method isn't required for most operations where the built-in narration provides sufficient feedback, but should be used where additional information would be helpful for the user.

The code below shows a simple example calling AnnounceForAccessibility:

button.Click += delegate {
  button.Text = string.Format ("{0} clicks!", count++);
  button.AnnounceForAccessibility (button.Text);
};

Changing Focus Settings

Accessible navigation relies on controls having focus to aid the user in understanding what operations are available. Android provides a Focusable property which can tag controls as specifically able to receive focus during navigation.

C#

To prevent a control from gaining focus with C#, set the Focusable property to false:

label.Focusable = false;

AXML layout

In layout XML files set the android:focusable attribute:

<android:focusable="false" />

You can also control focus order with the nextFocusDown, nextFocusLeft, nextFocusRight, nextFocusUp attributes, typically set in the layout AXML. Use these attributes to ensure the user can navigate easily through the controls on the screen.

Accessibility and Localization

In the examples above the hint and content description are set directly to the display value. It is preferable to use values in a Strings.xml file, such as this:

<?xml version="1.0" encoding="utf-8"?>
<resources>
    <string name="enter_info">Enter some text</string>
    <string name="save_info">Save data</string>
</resources>

Using text from a strings file is shown below in C# and AXML layout files:

C#

Instead of using string literals in code, look up translated values from strings files with Resources.GetText:

someText.Hint = Resources.GetText (Resource.String.enter_info);
saveButton.ContentDescription = Resources.GetText (Resource.String.save_info);

AXML

In layout XML accessibility attributes like hint and contentDescription can be set to a string identifier:

<TextView
    android:id="@+id/someText"
    android:hint="@string/enter_info" />
<ImageButton
    android:id=@+id/saveButton"
    android:src="@drawable/save_image"
    android:contentDescription="@string/save_info" />

The benefit of storing text in a separate file is multiple language translations of the file can be provided in your app. See the Android localization guide to learn how add localized string files to an application project.

Testing Accessibility

Follow these steps to enable TalkBack and Explore by Touch to test accessibility on Android devices.

You may need to install TalkBack from Google Play if it does not appear in Settings > Accessibility.