android - 在自定义 View 上实现可访问性不会提供口头反馈

Question

我已打开辅助功能，我的设备会在我四处导航时说话。

我有一个自定义的 seekbar 并实现了以下内容:

onTouchEvent 摘录:

...
case MotionEvent.ACTION_MOVE:

    getParent().requestDisallowInterceptTouchEvent(true);

    setTouchAngle(pointToAngle(touchX, touchY));
    score = getScoreFromAngle(angleStart,touchAngle);
    if (onScoreSetListener != null) {
        onScoreSetListener.onScorePoll(this, score);
        sendAccessibilityEvent(AccessibilityEvent.TYPE_VIEW_TEXT_CHANGED);
    }
    break;
...

onPopulateAccessibilityEvent 方法:

    @Override
    public void onPopulateAccessibilityEvent(AccessibilityEvent event) {
        super.onPopulateAccessibilityEvent(event);

        LogUtils.i(TAG,"onPopulateAccessibilityEvent()",null);

        switch (event.getEventType()) {
            case AccessibilityEvent.TYPE_VIEW_TEXT_CHANGED:

                LogUtils.d(TAG,"dispatchPopulateAccessibilityEvent() TYPE_VIEW_TEXT_CHANGED",null);

                event.getText().add(String.valueOf(getScore()));
                break;
            }
    }

我可以看到在 LogCat 中成功调用了 onPopulateAccessibilityEvent，但设备没有给出任何反馈。我希望读回当前乐谱，但什么也没有。

有没有人有什么见解？

Answer 1

如果您正在扩展 ProgressBar，您可以为传出的 TYPE_VIEW_SELECTED 事件设置文本。这些在用户调整搜索栏时自动发送。

@Override
public void onInitializeAccessibilityEvent(AccessibilityEvent event) {
    super.onInitializeAccessibilityEvent(event);
    event.getText().add(...);
}

但是，看起来您可能已经扩展了View。在这种情况下，您需要使用一种轻微的解决方法并通过在 ICS 上发送 VIEW_FOCUSED 事件来触发公告，或者在 JellyBean 及更高版本上使用 announceForAccessibility API。这需要 support-v4 库并且看起来像这样:

/** The parent context. Used to obtain string resources. */
private final Context mContext;

/**
 * The accessibility manager for this context. This is used to check the
 * accessibility enabled state, as well as to send raw accessibility events.
 */
private final AccessibilityManager mA11yManager;

/**
 * Generates and dispatches an SDK-specific spoken announcement.
 * <p>
 * For backwards compatibility, we're constructing an event from scratch
 * using the appropriate event type. If your application only targets SDK
 * 16+, you can just call View.announceForAccessibility(CharSequence).
 * </p>
 *
 * @param text The text to announce.
 */
private void announceForAccessibilityCompat(CharSequence text) {
    if (!mA11yManager.isEnabled()) {
        return;
    }

    // Prior to SDK 16, announcements could only be made through FOCUSED
    // events. Jelly Bean (SDK 16) added support for speaking text verbatim
    // using the ANNOUNCEMENT event type.
    final int eventType;
    if (Build.VERSION.SDK_INT < 16) {
        eventType = AccessibilityEvent.TYPE_VIEW_FOCUSED;
    } else {
        eventType = AccessibilityEventCompat.TYPE_ANNOUNCEMENT;
    }

    // Construct an accessibility event with the minimum recommended
    // attributes. An event without a class name or package may be dropped.
    final AccessibilityEvent event = AccessibilityEvent.obtain(eventType);
    event.getText().add(text);
    event.setEnabled(isEnabled());
    event.setClassName(getClass().getName());
    event.setPackageName(mContext.getPackageName());

    // JellyBean MR1 requires a source view to set the window ID.
    final AccessibilityRecordCompat record = new AccessibilityRecordCompat(event);
    record.setSource(this);

    // Sends the event directly through the accessibility manager. If your
    // application only targets SDK 14+, you should just call
    // getParent().requestSendAccessibilityEvent(this, event);
    mA11yManager.sendAccessibilityEvent(event);
}