[Slider] Keyboard navigation fix

Resolves #1364

GIT_ORIGIN_REV_ID=8a0fb870fafba516db529ffee13ea448964b0a9b
PiperOrigin-RevId: 315302829

lib/java/com/google/android/material/slider/BaseSlider.java

@@ -1825,13 +1825,11 @@ public boolean onKeyDown(int keyCode, @NonNull KeyEvent event) {
         switch (keyCode) {
           case KeyEvent.KEYCODE_TAB:
             if (event.hasNoModifiers()) {
-              moveFocus(1);
-              return true;
+              return moveFocus(1);
             } else if (event.isShiftPressed()) {
-              moveFocus(-1);
-              return true;
+              return moveFocus(-1);
             }
-            return false;
+            // fall through
           case KeyEvent.KEYCODE_DPAD_LEFT:
           case KeyEvent.KEYCODE_MINUS:
             moveFocus(-1);
@@ -1850,7 +1848,7 @@ public boolean onKeyDown(int keyCode, @NonNull KeyEvent event) {
         }
       } else {
         isLongPress |= event.isLongPress();
-        Float increment = calculateIncrementForKey(event, keyCode);
+        Float increment = calculateIncrementForKey(keyCode);
         if (increment != null) {
           if (ViewCompat.getLayoutDirection(this) == ViewCompat.LAYOUT_DIRECTION_RTL) {
             increment = -increment;
@@ -1863,6 +1861,25 @@ public boolean onKeyDown(int keyCode, @NonNull KeyEvent event) {
           }
           return true;
         }
+        switch (keyCode) {
+          case KeyEvent.KEYCODE_TAB:
+            if (event.hasNoModifiers()) {
+              return moveFocus(1);
+            } else if (event.isShiftPressed()) {
+              return moveFocus(-1);
+            }
+            // fall through
+          case KeyEvent.KEYCODE_DPAD_CENTER:
+          case KeyEvent.KEYCODE_ENTER:
+            activeThumbIdx = -1;
+            for (TooltipDrawable label : labels) {
+              ViewUtils.getContentViewOverlay(this).remove(label);
+            }
+            postInvalidate();
+            return true;
+          default:
+            // Nothing to do in this case.
+        }
       }
     }
 
@@ -1875,31 +1892,36 @@ public boolean onKeyUp(int keyCode, @NonNull KeyEvent event) {
     return super.onKeyUp(keyCode, event);
   }
 
-  private void moveFocus(int direction) {
+  /**
+   * Attempts to move focus to next or previous thumb and returns whether the focused thumb changed.
+   * If focused thumb didn't change, we're at the view boundary for specified {@code direction} and
+   * focus should be moved to next or previous view instead.
+   */
+  private boolean moveFocus(int direction) {
+    int oldFocusedThumbIdx = focusedThumbIdx;
     focusedThumbIdx += direction;
     focusedThumbIdx = MathUtils.clamp(focusedThumbIdx, 0, values.size() - 1);
-    if (activeThumbIdx != -1) {
-      activeThumbIdx = focusedThumbIdx;
+    if (focusedThumbIdx == oldFocusedThumbIdx) {
+      // Move focus to next or previous view.
+      return false;
+    } else {
+      if (activeThumbIdx != -1) {
+        activeThumbIdx = focusedThumbIdx;
+      }
+      updateHaloHotspot();
+      postInvalidate();
+      return true;
     }
-    updateHaloHotspot();
-    postInvalidate();
   }
 
-  private Float calculateIncrementForKey(KeyEvent event, int keyCode) {
+  private Float calculateIncrementForKey(int keyCode) {
     // If this is a long press, increase the increment so it will only take around 20 steps.
     // Otherwise choose the smallest valid increment.
     float increment = isLongPress ? calculateStepIncrement(20) : calculateStepIncrement();
     switch (keyCode) {
-      case KeyEvent.KEYCODE_TAB:
-        if (event.isShiftPressed()) {
-          return -increment;
-        } else {
-          return increment;
-        }
       case KeyEvent.KEYCODE_DPAD_LEFT:
       case KeyEvent.KEYCODE_MINUS:
-        increment = -increment;
-        // fallthrough
+        return -increment;
       case KeyEvent.KEYCODE_DPAD_RIGHT:
       case KeyEvent.KEYCODE_PLUS:
       case KeyEvent.KEYCODE_EQUALS:
@@ -1937,12 +1959,35 @@ protected void onFocusChanged(
       for (TooltipDrawable label : labels) {
         ViewUtils.getContentViewOverlay(this).remove(label);
       }
-      accessibilityHelper.requestKeyboardFocusForVirtualView(ExploreByTouchHelper.INVALID_ID);
+      accessibilityHelper.clearKeyboardFocusForVirtualView(focusedThumbIdx);
     } else {
+      focusThumbOnFocusGained(direction);
       accessibilityHelper.requestKeyboardFocusForVirtualView(focusedThumbIdx);
     }
   }
 
+  private void focusThumbOnFocusGained(int direction) {
+    switch (direction) {
+      case FOCUS_BACKWARD:
+      case FOCUS_LEFT:
+        moveFocus(Integer.MAX_VALUE);
+        break;
+      case FOCUS_FORWARD:
+      case FOCUS_RIGHT:
+        moveFocus(Integer.MIN_VALUE);
+        break;
+      case FOCUS_UP:
+      case FOCUS_DOWN:
+      default:
+        // Don't make assumptions about where exactly focus came from. Use previously focused thumb.
+    }
+  }
+
+  @VisibleForTesting
+  final int getAccessibilityFocusedVirtualViewId() {
+    return accessibilityHelper.getAccessibilityFocusedVirtualViewId();
+  }
+
   @NonNull
   @Override
   public CharSequence getAccessibilityClassName() {

lib/javatests/com/google/android/material/slider/SliderHelper.java

@@ -116,7 +116,7 @@ static float calculateXPositionFromValue(Slider s, float value) {
     return s.getTrackSidePadding() + x;
   }
 
-  static void activateFocusedThumb(Slider s) {
+  static void clickDpadCenter(Slider s) {
     new KeyEventBuilder(KeyEvent.KEYCODE_DPAD_CENTER).dispatchEvent(s);
   }