支援電視應用程式中的 TalkBack

TV 應用程式有時具有某些用途，會導致仰賴 TalkBack 的使用者難以使用應用程式。如要為這些使用者提供更優質的 TalkBack 體驗，請詳閱本指南中的各節，並視需要在應用程式中實作變更。如果您的應用程式使用自訂檢視畫面，您也應參閱對應指南，瞭解如何以自訂檢視畫面支援無障礙功能。

處理巢狀檢視區塊

TalkBack 使用者可能難以瀏覽巢狀檢視畫面。請盡可能讓 TalkBack 的父項或子項檢視畫面可聚焦，但請勿兩者並用。

如要讓 TalkBack 可聚焦檢視畫面，請將 focusable 和 focusableInTouchMode 屬性設為 true。這是必要步驟，因為部分電視裝置可能會在 TalkBack 啟用時進入及退出觸控模式。

如要將檢視畫面設為不可聚焦，只要將 focusable 屬性設為 false 即可。不過，如果檢視畫面可以操作 (也就是其對應的 AccessibilityNodeInfo 具有 ACTION_CLICK)，則可能仍可聚焦。

變更動作的說明

根據預設，TalkBack 會針對可操作的檢視畫面朗讀「按下選取即可啟動」。在某些動作中，「啟用」一詞可能較不適合。如要提供更準確的說明，您可以進行變更：

findViewById<View>(R.id.custom_actionable_view).accessibilityDelegate = object : View.AccessibilityDelegate() {
  override fun onInitializeAccessibilityNodeInfo(host: View, info: AccessibilityNodeInfo) {
    super.onInitializeAccessibilityNodeInfo(host, info)
    info.addAction(
      AccessibilityAction(
        AccessibilityAction.ACTION_CLICK.id,
        getString(R.string.custom_label)
      )
    )
  }
}

findViewById(R.id.custom_actionable_view).setAccessibilityDelegate(new AccessibilityDelegate() {
  @Override
  public void onInitializeAccessibilityNodeInfo(View host, AccessibilityNodeInfo info) {
    super.onInitializeAccessibilityNodeInfo(host, info);
    AccessibilityAction action = new AccessibilityAction(
        AccessibilityAction.ACTION_CLICK.getId(), getString(R.string.custom_label));
    info.addAction(action);
  }
});

新增滑桿支援功能

電視的 TalkBack 特別支援滑桿。如要啟用滑桿模式，請將 ACTION_SET_PROGRESS 和 RangeInfo 物件一起加入檢視畫面。

使用者按下電視遙控器中間的按鈕，即可進入滑桿模式。在此模式下，箭頭按鈕會產生 ACTION_SCROLL_FORWARD 和 ACTION_SCROLL_BACKWARD 無障礙動作。

以下範例會實作等級介於 1 到 10 的音量滑桿：

/**
 *   This example only provides slider functionality for TalkBack users. Additional logic should
 *   be added for other users. Such logic may reuse the increase and decrease methods.
 */
class VolumeSlider(context: Context?, attrs: AttributeSet?) : LinearLayout(context, attrs) {
  private val min = 1
  private val max = 10
  private var current = 5
  private var textView: TextView? = null

  init {
    isFocusable = true
    isFocusableInTouchMode = true
    val rangeInfo =
      AccessibilityNodeInfo.RangeInfo(
        AccessibilityNodeInfo.RangeInfo.RANGE_TYPE_INT,
        min.toFloat(),
        max.toFloat(),
        current.toFloat()
      )
    accessibilityDelegate =
      object : AccessibilityDelegate() {
        override fun onInitializeAccessibilityNodeInfo(host: View, info: AccessibilityNodeInfo) {
          super.onInitializeAccessibilityNodeInfo(host, info)
          info.addAction(AccessibilityNodeInfo.AccessibilityAction.ACTION_SET_PROGRESS)
          info.rangeInfo = rangeInfo
        }

        override fun performAccessibilityAction(host: View, action: Int, args: Bundle?): Boolean {
          if (action == AccessibilityNodeInfo.AccessibilityAction.ACTION_SCROLL_FORWARD.id) {
            increase()
            return true
          }
          if (action == AccessibilityNodeInfo.AccessibilityAction.ACTION_SCROLL_BACKWARD.id) {
            decrease()
            return true
          }
          return super.performAccessibilityAction(host, action, args)
        }
      }
  }

  override fun onFinishInflate() {
    super.onFinishInflate()
    textView = findViewById(R.id.text)
    textView!!.text = context.getString(R.string.level, current)
  }

  private fun increase() {
    update((current + 1).coerceAtMost(max))
  }

  private fun decrease() {
    update((current - 1).coerceAtLeast(min))
  }

  private fun update(newLevel: Int) {
    if (textView == null) {
      return
    }
    val newText = context.getString(R.string.level, newLevel)
    // Update the user interface with the new volume.
    textView!!.text = newText
    // Announce the new volume.
    announceForAccessibility(newText)
    current = newLevel
  }
}

/**
 *   This example only provides slider functionality for TalkBack users. Additional logic should
 *   be added for other users. Such logic can reuse the increase and decrease methods.
 */
public class VolumeSlider extends LinearLayout {
  private final int min = 1;
  private final int max = 10;
  private int current = 5;
  private TextView textView;

  public VolumeSlider(Context context, AttributeSet attrs) {
    super(context, attrs);
    setFocusable(true);
    setFocusableInTouchMode(true);
    RangeInfo rangeInfo = new RangeInfo(RangeInfo.RANGE_TYPE_INT, min, max, current);
    setAccessibilityDelegate(
        new AccessibilityDelegate() {
          @Override
          public void onInitializeAccessibilityNodeInfo(View host, AccessibilityNodeInfo info) {
            super.onInitializeAccessibilityNodeInfo(host, info);
            info.addAction(AccessibilityAction.ACTION_SET_PROGRESS);
            info.setRangeInfo(rangeInfo);
          }

          @Override
          public boolean performAccessibilityAction(View host, int action, Bundle args) {
            if (action == AccessibilityAction.ACTION_SCROLL_FORWARD.getId()) {
              increase();
              return true;
            }
            if (action == AccessibilityAction.ACTION_SCROLL_BACKWARD.getId()) {
              decrease();
              return true;
            }
            return super.performAccessibilityAction(host, action, args);
          }
        });
  }

  @Override
  protected void onFinishInflate() {
    super.onFinishInflate();
    textView = findViewById(R.id.text);
    textView.setText(getContext().getString(R.string.level, current));
  }

  private void increase() {
    update(Math.min(current + 1, max));
  }

  private void decrease() {
    update(Math.max(current - 1, min));
  }

  private void update(int newLevel) {
    if (textView == null) {
      return;
    }
    String newText = getContext().getString(R.string.level, newLevel);
    // Update the user interface with the new volume.
    textView.setText(newText);
    // Announce the new volume.
    announceForAccessibility(newText);
    current = newLevel;
  }
}