Skip to content

Commit

Permalink
[AppBarLayout] Use an accessibility delegate to add and perform actions
Browse files Browse the repository at this point in the history 
This replaces the use of `ViewCompat#add/removeAccessibilityAction`

Both are valid strategies, but each call to `remove` or `add` triggers an accessibility event. Since this check is done in layout (originally to fix a11y scroll state) it's sending a high number of events that create noise for accessibility services.

To avoid this, we move this code to the delegate `onInitialize` and `performAction` methods. Instead of the view dynamically adding and removing actions to itself, the node is initialized with actions only when an a11y service sends a request with a new node (likely due to some UI change).

The flow here would look like:
1. UI is scrolled/page is loaded
2. TalkBack gets a scroll event/content change event
3. TalkBack requests new snapshot of the screen
4. ABL populates the node with the actions

For a simple scroll, this change reduces the events from ~40 to ~10.

We also add the Truth library for clearer assertions.

PiperOrigin-RevId: 605333170
(cherry picked from commit 8a71e77)
  • Loading branch information
@hunterstich
Material Design Team authored and hunterstich committed Mar 21, 2024
1 parent 5efdae3 commit 929c80f
Show file tree
Hide file tree
Showing 2 changed files with 96 additions and 115 deletions.
182 changes: 82 additions & 100 deletions lib/java/com/google/android/material/appbar/AppBarLayout.java
View file
Expand Up @@ -38,6 +38,7 @@
import android.os.Build;
import android.os.Build.VERSION;
import android.os.Build.VERSION_CODES;
import android.os.Bundle;
import android.os.Parcel;
import android.os.Parcelable;
import androidx.appcompat.content.res.AppCompatResources;
Expand Down Expand Up @@ -68,8 +69,6 @@
import androidx.core.view.ViewCompat.NestedScrollType;
import androidx.core.view.WindowInsetsCompat;
import androidx.core.view.accessibility.AccessibilityNodeInfoCompat;
import androidx.core.view.accessibility.AccessibilityNodeInfoCompat.AccessibilityActionCompat;
import androidx.core.view.accessibility.AccessibilityViewCommand;
import androidx.customview.view.AbsSavedState;
import com.google.android.material.animation.AnimationUtils;
import com.google.android.material.appbar.AppBarLayout.BaseBehavior.SavedState;
Expand Down Expand Up @@ -1516,8 +1515,6 @@ public abstract static class BaseDragCallback<T extends AppBarLayout> {
@Nullable private WeakReference<View> lastNestedScrollingChildRef;
private BaseDragCallback onDragCallback;

private boolean coordinatorLayoutA11yScrollable;

public BaseBehavior() {}

public BaseBehavior(Context context, AttributeSet attrs) {
Expand Down Expand Up @@ -1610,7 +1607,7 @@ public void onNestedScroll(
if (dyUnconsumed == 0) {
// The scrolling view may scroll to the top of its content without updating the actions, so
// update here.
updateAccessibilityActions(coordinatorLayout, child);
addAccessibilityDelegateIfNeeded(coordinatorLayout, child);
}
}

Expand Down Expand Up @@ -1870,30 +1867,12 @@ public boolean onLayoutChild(
// Make sure we dispatch the offset update
abl.onOffsetChanged(getTopAndBottomOffset());

updateAccessibilityActions(parent, abl);
addAccessibilityDelegateIfNeeded(parent, abl);
return handled;
}

private void updateAccessibilityActions(
private void addAccessibilityDelegateIfNeeded(
CoordinatorLayout coordinatorLayout, @NonNull T appBarLayout) {
ViewCompat.removeAccessibilityAction(coordinatorLayout, ACTION_SCROLL_FORWARD.getId());
ViewCompat.removeAccessibilityAction(coordinatorLayout, ACTION_SCROLL_BACKWARD.getId());
// Don't add a11y actions if the abl has no scroll range.
if (appBarLayout.getTotalScrollRange() == 0) {
return;
}
// Don't add actions if a child view doesn't have the behavior that will cause the abl to
// scroll.
View scrollingView = getChildWithScrollingBehavior(coordinatorLayout);
if (scrollingView == null) {
return;
}

// Don't add actions if the children do not have scrolling flags.
if (!childrenHaveScrollFlags(appBarLayout)) {
return;
}

if (!ViewCompat.hasAccessibilityDelegate(coordinatorLayout)) {
ViewCompat.setAccessibilityDelegate(
coordinatorLayout,
Expand All @@ -1902,14 +1881,87 @@ private void updateAccessibilityActions(
public void onInitializeAccessibilityNodeInfo(
View host, @NonNull AccessibilityNodeInfoCompat info) {
super.onInitializeAccessibilityNodeInfo(host, info);
info.setScrollable(coordinatorLayoutA11yScrollable);
info.setClassName(ScrollView.class.getName());
if (appBarLayout.getTotalScrollRange() == 0) {
return;
}
View scrollingView = getChildWithScrollingBehavior(coordinatorLayout);
// Don't add actions if a child view doesn't have the behavior that will cause the
// ABL to scroll.
if (scrollingView == null) {
return;
}

// Don't add actions if the children do not have scrolling flags.
if (!childrenHaveScrollFlags(appBarLayout)) {
return;
}

if (getTopBottomOffsetForScrollingSibling()
!= -appBarLayout.getTotalScrollRange()) {
// Add a collapsing action/forward if the view offset isn't the ABL scroll range.
// (The same offset means the view is completely collapsed).
info.addAction(ACTION_SCROLL_FORWARD);
info.setScrollable(true);
}

// Don't add an expanding action if the sibling offset is 0, which would mean the
// ABL is completely expanded.
if (getTopBottomOffsetForScrollingSibling() != 0) {
if (scrollingView.canScrollVertically(-1)) {
final int dy = -appBarLayout.getDownNestedPreScrollRange();
// Offset by non-zero.
if (dy != 0) {
info.addAction(ACTION_SCROLL_BACKWARD);
info.setScrollable(true);
}
} else {
info.addAction(ACTION_SCROLL_BACKWARD);
info.setScrollable(true);
}
}
}

@Override
public boolean performAccessibilityAction(View host, int action, Bundle args) {

if (action == AccessibilityNodeInfoCompat.ACTION_SCROLL_FORWARD) {
appBarLayout.setExpanded(false);
return true;
} else if (action == AccessibilityNodeInfoCompat.ACTION_SCROLL_BACKWARD) {
if (getTopBottomOffsetForScrollingSibling() != 0) {
View scrollingView = getChildWithScrollingBehavior(coordinatorLayout);
if (scrollingView.canScrollVertically(-1)) {
// Expanding action. If the view can scroll down, expand the app bar
// reflecting the logic
// in onNestedPreScroll.
final int dy = -appBarLayout.getDownNestedPreScrollRange();
// Offset by non-zero.
if (dy != 0) {
onNestedPreScroll(
coordinatorLayout,
appBarLayout,
scrollingView,
0,
dy,
new int[] {0, 0},
ViewCompat.TYPE_NON_TOUCH);
return true;
}
} else {
// If the view can't scroll down, we are probably at the top of the
// scrolling content so expand completely.
appBarLayout.setExpanded(true);
return true;
}
}
} else {
return super.performAccessibilityAction(host, action, args);
}
return false;
}
});
}

coordinatorLayoutA11yScrollable =
addAccessibilityScrollActions(coordinatorLayout, appBarLayout, scrollingView);
}

@Nullable
Expand Down Expand Up @@ -1941,74 +1993,6 @@ private boolean childrenHaveScrollFlags(AppBarLayout appBarLayout) {
return false;
}

private boolean addAccessibilityScrollActions(
final CoordinatorLayout coordinatorLayout,
@NonNull final T appBarLayout,
@NonNull final View scrollingView) {
boolean a11yScrollable = false;
if (getTopBottomOffsetForScrollingSibling() != -appBarLayout.getTotalScrollRange()) {
// Add a collapsing action if the view offset isn't the abl scroll range.
// (The same offset means the view is completely collapsed). Collapse to minimum height.
addActionToExpand(coordinatorLayout, appBarLayout, ACTION_SCROLL_FORWARD, false);
a11yScrollable = true;
}
// Don't add an expanding action if the sibling offset is 0, which would mean the abl is
// completely expanded.
if (getTopBottomOffsetForScrollingSibling() != 0) {
if (scrollingView.canScrollVertically(-1)) {
// Expanding action. If the view can scroll down, expand the app bar reflecting the logic
// in onNestedPreScroll.
final int dy = -appBarLayout.getDownNestedPreScrollRange();
// Offset by non-zero.
if (dy != 0) {
ViewCompat.replaceAccessibilityAction(
coordinatorLayout,
ACTION_SCROLL_BACKWARD,
null,
new AccessibilityViewCommand() {
@Override
public boolean perform(@NonNull View view, @Nullable CommandArguments arguments) {
onNestedPreScroll(
coordinatorLayout,
appBarLayout,
scrollingView,
0,
dy,
new int[] {0, 0},
ViewCompat.TYPE_NON_TOUCH);
return true;
}
});
a11yScrollable = true;
}
} else {
// If the view can't scroll down, we are probably at the top of the scrolling content so
// expand completely.
addActionToExpand(coordinatorLayout, appBarLayout, ACTION_SCROLL_BACKWARD, true);
a11yScrollable = true;
}
}
return a11yScrollable;
}

private void addActionToExpand(
CoordinatorLayout parent,
@NonNull final T appBarLayout,
@NonNull AccessibilityActionCompat action,
final boolean expand) {
ViewCompat.replaceAccessibilityAction(
parent,
action,
null,
new AccessibilityViewCommand() {
@Override
public boolean perform(@NonNull View view, @Nullable CommandArguments arguments) {
appBarLayout.setExpanded(expand);
return true;
}
});
}

@Override
boolean canDragView(T view) {
if (onDragCallback != null) {
Expand Down Expand Up @@ -2112,7 +2096,7 @@ int setHeaderTopBottomOffset(
offsetDelta = 0;
}

updateAccessibilityActions(coordinatorLayout, appBarLayout);
addAccessibilityDelegateIfNeeded(coordinatorLayout, appBarLayout);
return consumed;
}

Expand Down Expand Up @@ -2410,8 +2394,6 @@ public boolean onDependentViewChanged(
public void onDependentViewRemoved(
@NonNull CoordinatorLayout parent, @NonNull View child, @NonNull View dependency) {
if (dependency instanceof AppBarLayout) {
ViewCompat.removeAccessibilityAction(parent, ACTION_SCROLL_FORWARD.getId());
ViewCompat.removeAccessibilityAction(parent, ACTION_SCROLL_BACKWARD.getId());
ViewCompat.setAccessibilityDelegate(parent, null);
}
}
Expand Down
29 changes: 14 additions & 15 deletions tests/javatests/com/google/android/material/appbar/AppBarLayoutBaseTest.java
View file
Expand Up @@ -25,11 +25,8 @@
import static com.google.android.material.testutils.SwipeUtils.swipeUp;
import static com.google.android.material.testutils.TestUtilsActions.setText;
import static com.google.android.material.testutils.TestUtilsActions.setTitle;
import static org.hamcrest.CoreMatchers.equalTo;
import static com.google.common.truth.Truth.assertThat;
import static org.junit.Assert.assertEquals;
import static org.junit.Assert.assertFalse;
import static org.junit.Assert.assertThat;
import static org.junit.Assert.assertTrue;

import android.graphics.Color;
import android.os.Build;
Expand Down Expand Up @@ -135,29 +132,31 @@ protected boolean matchesSafely(View view) {

protected void assertAccessibilityHasScrollForwardAction(boolean hasScrollForward) {
if (VERSION.SDK_INT >= 21) {
AccessibilityNodeInfoCompat info = AccessibilityNodeInfoCompat.obtain();
ViewCompat.onInitializeAccessibilityNodeInfo(mCoordinatorLayout, info);
assertThat(
AccessibilityUtils.hasAction(
mCoordinatorLayout, AccessibilityNodeInfoCompat.ACTION_SCROLL_FORWARD),
equalTo(hasScrollForward));
AccessibilityUtils.hasAction(
info,
AccessibilityNodeInfoCompat.AccessibilityActionCompat.ACTION_SCROLL_FORWARD))
.isEqualTo(hasScrollForward);
}
}

protected void assertAccessibilityHasScrollBackwardAction(boolean hasScrollBackward) {
if (VERSION.SDK_INT >= 21) {
AccessibilityNodeInfoCompat info = AccessibilityNodeInfoCompat.obtain();
ViewCompat.onInitializeAccessibilityNodeInfo(mCoordinatorLayout, info);
assertThat(
AccessibilityUtils.hasAction(
mCoordinatorLayout, AccessibilityNodeInfoCompat.ACTION_SCROLL_BACKWARD),
equalTo(hasScrollBackward));
AccessibilityUtils.hasAction(
info,
AccessibilityNodeInfoCompat.AccessibilityActionCompat.ACTION_SCROLL_BACKWARD))
.isEqualTo(hasScrollBackward);
}
}

protected void assertAccessibilityScrollable(boolean isScrollable) {
AccessibilityNodeInfoCompat info = AccessibilityNodeInfoCompat.obtain();
ViewCompat.onInitializeAccessibilityNodeInfo(mCoordinatorLayout, info);
if (isScrollable) {
assertTrue(info.isScrollable());
} else {
assertFalse(info.isScrollable());
}
assertThat(info.isScrollable()).isEqualTo(isScrollable);
}
}

0 comments on commit 929c80f

Please sign in to comment.