MaterialButtonToggleGroup.java

/*
 * Copyright (C) 2019 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.google.android.material.button;

import com.google.android.material.R;

import static com.google.android.material.theme.overlay.MaterialThemeOverlay.wrap;

import android.content.Context;
import android.content.res.TypedArray;
import android.graphics.Canvas;
import android.text.TextUtils.TruncateAt;
import android.util.AttributeSet;
import android.util.Log;
import android.view.View;
import android.view.ViewGroup;
import android.view.accessibility.AccessibilityNodeInfo;
import android.widget.LinearLayout;
import androidx.annotation.BoolRes;
import androidx.annotation.IdRes;
import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import androidx.annotation.VisibleForTesting;
import androidx.core.view.AccessibilityDelegateCompat;
import androidx.core.view.MarginLayoutParamsCompat;
import androidx.core.view.ViewCompat;
import androidx.core.view.accessibility.AccessibilityNodeInfoCompat;
import androidx.core.view.accessibility.AccessibilityNodeInfoCompat.CollectionInfoCompat;
import androidx.core.view.accessibility.AccessibilityNodeInfoCompat.CollectionItemInfoCompat;
import com.google.android.material.button.MaterialButton.OnPressedChangeListener;
import com.google.android.material.internal.ThemeEnforcement;
import com.google.android.material.internal.ViewUtils;
import com.google.android.material.shape.AbsoluteCornerSize;
import com.google.android.material.shape.CornerSize;
import com.google.android.material.shape.ShapeAppearanceModel;
import java.util.ArrayList;
import java.util.Comparator;
import java.util.LinkedHashSet;
import java.util.List;
import java.util.SortedMap;
import java.util.TreeMap;

/**
 * A common container for a set of related, toggleable {@link MaterialButton}s. The {@link
 * MaterialButton}s in this group will be shown on a single line.
 *
 * <p>This layout currently only supports child views of type {@link MaterialButton}. Buttons can be
 * added to this view group via XML, as follows:
 *
 * <pre>
 * &lt;com.google.android.material.button.MaterialButtonToggleGroup
 *     xmlns:android="http://schemas.android.com/apk/res/android"
 *     android:id="@+id/toggle_button_group"
 *     android:layout_width="wrap_content"
 *     android:layout_height="wrap_content"&gt;
 *
 *     &lt;com.google.android.material.button.MaterialButton
 *         style="?attr/materialButtonOutlinedStyle"
 *         android:layout_width="wrap_content"
 *         android:layout_height="wrap_content"
 *         android:text="@string/button_label_private"/&gt;
 *     &lt;com.google.android.material.button.MaterialButton
 *         style="?attr/materialButtonOutlinedStyle"
 *         android:layout_width="wrap_content"
 *         android:layout_height="wrap_content"
 *         android:text="@string/button_label_team"/&gt;
 *     &lt;com.google.android.material.button.MaterialButton
 *         style="?attr/materialButtonOutlinedStyle"
 *         android:layout_width="wrap_content"
 *         android:layout_height="wrap_content"
 *         android:text="@string/button_label_everyone"/&gt;
 *     &lt;com.google.android.material.button.MaterialButton
 *         style="?attr/materialButtonOutlinedStyle"
 *         android:layout_width="wrap_content"
 *         android:layout_height="wrap_content"
 *         android:text="@string/button_label_custom"/&gt;
 *
 * &lt;/com.google.android.material.button.MaterialButtonToggleGroup&gt;
 * </pre>
 *
 * <p>Buttons can also be added to this view group programmatically via the {@link #addView(View)}
 * methods.
 *
 * <p>Note: Styling must applied to each child button individually. It is recommended to use the
 * {@code materialButtonOutlinedStyle} attribute for all child buttons. {@code
 * materialButtonOutlinedStyle} will most closely match the Material Design guidelines for this
 * component, and supports the checked state for child buttons.
 *
 * <p>Any {@link MaterialButton}s added to this view group are automatically marked as {@code
 * checkable}, and by default multiple buttons within the same group can be checked. To enforce that
 * only one button can be checked at a time, set the {@code
 * app:singleSelection} attribute to {@code true} on the MaterialButtonToggleGroup or call {@link
 * #setSingleSelection(boolean) setSingleSelection(true)}.
 *
 * <p>MaterialButtonToggleGroup is a {@link LinearLayout}. Using {@code
 * android:layout_width="MATCH_PARENT"} and removing {@code android:insetBottom} {@code
 * android:insetTop} on the children is recommended if using {@code VERTICAL}.
 *
 * <p>In order to cohesively group multiple buttons together, MaterialButtonToggleGroup overrides
 * the start and end margins of any children added to this layout such that child buttons are placed
 * directly adjacent to one another.
 *
 * <p>MaterialButtonToggleGroup also overrides any {@code shapeAppearance}, {@code
 * shapeAppearanceOverlay}, or {@code cornerRadius} attribute set on MaterialButton children such
 * that only the left-most corners of the first child and the right-most corners of the last child
 * retain their shape appearance or corner size.
 */
public class MaterialButtonToggleGroup extends LinearLayout {

  /**
   * Interface definition for a callback to be invoked when a {@link MaterialButton} is checked or
   * unchecked in this group.
   */
  public interface OnButtonCheckedListener {
    /**
     * Called when a {@link MaterialButton} in this group is checked or unchecked.
     *
     * @param group The group in which the MaterialButton's checked state was changed
     * @param checkedId The unique identifier of the MaterialButton whose check state changed
     * @param isChecked Whether the MaterialButton is currently checked
     */
    void onButtonChecked(MaterialButtonToggleGroup group, @IdRes int checkedId, boolean isChecked);
  }

  private static final String LOG_TAG = MaterialButtonToggleGroup.class.getSimpleName();
  private static final int DEF_STYLE_RES =
      R.style.Widget_MaterialComponents_MaterialButtonToggleGroup;

  private final List<CornerData> originalCornerData = new ArrayList<>();

  private final CheckedStateTracker checkedStateTracker = new CheckedStateTracker();
  private final PressedStateTracker pressedStateTracker = new PressedStateTracker();
  private final LinkedHashSet<OnButtonCheckedListener> onButtonCheckedListeners =
      new LinkedHashSet<>();
  private final Comparator<MaterialButton> childOrderComparator =
      new Comparator<MaterialButton>() {
        @Override
        public int compare(MaterialButton v1, MaterialButton v2) {
          int checked = Boolean.valueOf(v1.isChecked()).compareTo(v2.isChecked());
          if (checked != 0) {
            return checked;
          }

          int stateful = Boolean.valueOf(v1.isPressed()).compareTo(v2.isPressed());
          if (stateful != 0) {
            return stateful;
          }

          // don't return 0s
          return Integer.valueOf(indexOfChild(v1)).compareTo(indexOfChild(v2));
        }
      };

  private Integer[] childOrder;
  private boolean skipCheckedStateTracker = false;
  private boolean singleSelection;
  private boolean selectionRequired;

  @IdRes private int checkedId;

  public MaterialButtonToggleGroup(@NonNull Context context) {
    this(context, null);
  }

  public MaterialButtonToggleGroup(@NonNull Context context, @Nullable AttributeSet attrs) {
    this(context, attrs, R.attr.materialButtonToggleGroupStyle);
  }

  public MaterialButtonToggleGroup(
      @NonNull Context context, @Nullable AttributeSet attrs, int defStyleAttr) {
    super(wrap(context, attrs, defStyleAttr, DEF_STYLE_RES), attrs, defStyleAttr);
    // Ensure we are using the correctly themed context rather than the context that was passed in.
    context = getContext();
    TypedArray attributes =
        ThemeEnforcement.obtainStyledAttributes(
            context, attrs, R.styleable.MaterialButtonToggleGroup, defStyleAttr, DEF_STYLE_RES);

    setSingleSelection(
        attributes.getBoolean(R.styleable.MaterialButtonToggleGroup_singleSelection, false));
    checkedId =
        attributes.getResourceId(R.styleable.MaterialButtonToggleGroup_checkedButton, View.NO_ID);
    selectionRequired =
        attributes.getBoolean(R.styleable.MaterialButtonToggleGroup_selectionRequired, false);
    setChildrenDrawingOrderEnabled(true);
    attributes.recycle();

    ViewCompat.setImportantForAccessibility(this, ViewCompat.IMPORTANT_FOR_ACCESSIBILITY_YES);
  }

  @Override
  protected void onFinishInflate() {
    super.onFinishInflate();

    // Checks the appropriate button as requested via XML
    if (checkedId != View.NO_ID) {
      checkForced(checkedId, true);
    }
  }

  @Override
  protected void dispatchDraw(@NonNull Canvas canvas) {
    updateChildOrder();
    super.dispatchDraw(canvas);
  }

  /**
   * This override prohibits Views other than {@link MaterialButton} to be added. It also makes
   * updates to the add button shape and margins.
   */
  @Override
  public void addView(View child, int index, ViewGroup.LayoutParams params) {
    if (!(child instanceof MaterialButton)) {
      Log.e(LOG_TAG, "Child views must be of type MaterialButton.");
      return;
    }

    super.addView(child, index, params);
    MaterialButton buttonChild = (MaterialButton) child;
    setGeneratedIdIfNeeded(buttonChild);
    // Sets sensible default values and an internal checked change listener for this child
    setupButtonChild(buttonChild);

    // Reorders children if a checked child was added to this layout
    if (buttonChild.isChecked()) {
      updateCheckedStates(buttonChild.getId(), true);
      setCheckedId(buttonChild.getId());
    }

    // Saves original corner data
    ShapeAppearanceModel shapeAppearanceModel = buttonChild.getShapeAppearanceModel();
    originalCornerData.add(
        new CornerData(
            shapeAppearanceModel.getTopLeftCornerSize(),
            shapeAppearanceModel.getBottomLeftCornerSize(),
            shapeAppearanceModel.getTopRightCornerSize(),
            shapeAppearanceModel.getBottomRightCornerSize()));

    ViewCompat.setAccessibilityDelegate(
        buttonChild,
        new AccessibilityDelegateCompat() {
          @Override
          public void onInitializeAccessibilityNodeInfo(
              View host, @NonNull AccessibilityNodeInfoCompat info) {
            super.onInitializeAccessibilityNodeInfo(host, info);
            info.setCollectionItemInfo(
                CollectionItemInfoCompat.obtain(
                    /* rowIndex= */ 0,
                    /* rowSpan= */ 1,
                    /* columnIndex= */ getIndexWithinVisibleButtons(host),
                    /* columnSpan= */ 1,
                    /* heading= */ false,
                    /* selected= */ ((MaterialButton) host).isChecked()));
          }
        });
  }

  @Override
  public void onViewRemoved(View child) {
    super.onViewRemoved(child);

    if (child instanceof MaterialButton) {
      ((MaterialButton) child).removeOnCheckedChangeListener(checkedStateTracker);
      ((MaterialButton) child).setOnPressedChangeListenerInternal(null);
    }

    int indexOfChild = indexOfChild(child);
    if (indexOfChild >= 0) {
      originalCornerData.remove(indexOfChild);
    }

    updateChildShapes();
    adjustChildMarginsAndUpdateLayout();
  }

  @Override
  protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
    updateChildShapes();
    adjustChildMarginsAndUpdateLayout();

    super.onMeasure(widthMeasureSpec, heightMeasureSpec);
  }

  @NonNull
  @Override
  public CharSequence getAccessibilityClassName() {
    return MaterialButtonToggleGroup.class.getName();
  }

  @Override
  public void onInitializeAccessibilityNodeInfo(@NonNull AccessibilityNodeInfo info) {
    super.onInitializeAccessibilityNodeInfo(info);
    AccessibilityNodeInfoCompat infoCompat = AccessibilityNodeInfoCompat.wrap(info);
    infoCompat.setCollectionInfo(
        CollectionInfoCompat.obtain(
            /* rowCount= */ 1,
            /* columnCount= */ getVisibleButtonCount(),
            /* hierarchical= */ false,
            /* selectionMode = */ isSingleSelection()
                ? CollectionInfoCompat.SELECTION_MODE_SINGLE
                : CollectionInfoCompat.SELECTION_MODE_MULTIPLE));
  }

  /**
   * Sets the {@link MaterialButton} whose id is passed in to the checked state. If this
   * MaterialButtonToggleGroup is in {@link #isSingleSelection() single selection mode}, then all
   * other MaterialButtons in this group will be unchecked. Otherwise, other MaterialButtons will
   * retain their checked state.
   *
   * @param id View ID of {@link MaterialButton} to set checked
   * @see #uncheck(int)
   * @see #clearChecked()
   * @see #getCheckedButtonIds()
   * @see #getCheckedButtonId()
   */
  public void check(@IdRes int id) {
    if (id == checkedId) {
      return;
    }

    checkForced(id, true);
  }

  /**
   * Sets the {@link MaterialButton} whose id is passed in to the unchecked state.
   *
   * @param id View ID of {@link MaterialButton} to set unchecked
   * @see #check(int)
   * @see #clearChecked()
   * @see #getCheckedButtonIds()
   * @see #getCheckedButtonId()
   */
  public void uncheck(@IdRes int id) {
    checkForced(id, false);
  }

  /**
   * Clears the selections. When the selections are cleared, no {@link MaterialButton} in this group
   * is checked and {@link #getCheckedButtonIds()} returns an empty list.
   *
   * @see #check(int)
   * @see #uncheck(int)
   * @see #getCheckedButtonIds()
   * @see #getCheckedButtonId()
   */
  public void clearChecked() {
    skipCheckedStateTracker = true;
    for (int i = 0; i < getChildCount(); i++) {
      MaterialButton child = getChildButton(i);
      child.setChecked(false);

      dispatchOnButtonChecked(child.getId(), false);
    }
    skipCheckedStateTracker = false;

    setCheckedId(View.NO_ID);
  }

  /**
   * When in {@link #isSingleSelection() single selection mode}, returns the identifier of the
   * selected button in this group. Upon empty selection, the returned value is {@link View#NO_ID}.
   * If not in single selection mode, the return value is {@link View#NO_ID}.
   *
   * @return The unique id of the selected {@link MaterialButton} in this group in {@link
   *     #isSingleSelection() single selection mode}. When not in {@link #isSingleSelection() single
   *     selection mode}, returns {@link View#NO_ID}.
   * @see #check(int)
   * @see #uncheck(int)
   * @see #clearChecked()
   * @see #getCheckedButtonIds()
   * @attr ref R.styleable#MaterialButtonToggleGroup_checkedButton
   */
  @IdRes
  public int getCheckedButtonId() {
    return singleSelection ? checkedId : View.NO_ID;
  }

  /**
   * Returns the identifiers of the selected {@link MaterialButton}s in this group. Upon empty
   * selection, the returned value is an empty list.
   *
   * @return The unique IDs of the selected {@link MaterialButton}s in this group. When in {@link
   *     #isSingleSelection() single selection mode}, returns a list with a single ID. When no
   *     {@link MaterialButton}s are selected, returns an empty list.
   * @see #check(int)
   * @see #uncheck(int)
   * @see #clearChecked()
   * @see #getCheckedButtonId()
   */
  @NonNull
  public List<Integer> getCheckedButtonIds() {
    List<Integer> checkedIds = new ArrayList<>();
    for (int i = 0; i < getChildCount(); i++) {
      MaterialButton child = getChildButton(i);
      if (child.isChecked()) {
        checkedIds.add(child.getId());
      }
    }

    return checkedIds;
  }

  /**
   * Add a listener that will be invoked when the check state of a {@link MaterialButton} in this
   * group changes. See {@link OnButtonCheckedListener}.
   *
   * <p>Components that add a listener should take care to remove it when finished via {@link
   * #removeOnButtonCheckedListener(OnButtonCheckedListener)}.
   *
   * @param listener listener to add
   */
  public void addOnButtonCheckedListener(@NonNull OnButtonCheckedListener listener) {
    onButtonCheckedListeners.add(listener);
  }

  /**
   * Remove a listener that was previously added via {@link
   * #addOnButtonCheckedListener(OnButtonCheckedListener)}.
   *
   * @param listener listener to remove
   */
  public void removeOnButtonCheckedListener(@NonNull OnButtonCheckedListener listener) {
    onButtonCheckedListeners.remove(listener);
  }

  /** Remove all previously added {@link OnButtonCheckedListener}s. */
  public void clearOnButtonCheckedListeners() {
    onButtonCheckedListeners.clear();
  }

  /**
   * Returns whether this group only allows a single button to be checked.
   *
   * @return whether this group only allows a single button to be checked
   * @attr ref R.styleable#MaterialButtonToggleGroup_singleSelection
   */
  public boolean isSingleSelection() {
    return singleSelection;
  }

  /**
   * Sets whether this group only allows a single button to be checked.
   *
   * <p>Calling this method results in all the buttons in this group to become unchecked.
   *
   * @param singleSelection whether this group only allows a single button to be checked
   * @attr ref R.styleable#MaterialButtonToggleGroup_singleSelection
   */
  public void setSingleSelection(boolean singleSelection) {
    if (this.singleSelection != singleSelection) {
      this.singleSelection = singleSelection;
      clearChecked();
    }
  }

  /**
   * Sets whether we prevent all child buttons from being deselected.
   *
   * @attr ref R.styleable#MaterialButtonToggleGroup_selectionRequired
   */
  public void setSelectionRequired(boolean selectionRequired) {
    this.selectionRequired = selectionRequired;
  }

  /**
   * Returns whether we prevent all child buttons from being deselected.
   *
   * @attr ref R.styleable#MaterialButtonToggleGroup_selectionRequired
   */
  public boolean isSelectionRequired() {
    return selectionRequired;
  }

  /**
   * Sets whether this group only allows a single button to be checked.
   *
   * <p>Calling this method results in all the buttons in this group to become unchecked.
   *
   * @param id boolean resource ID of whether this group only allows a single button to be checked
   * @attr ref R.styleable#MaterialButtonToggleGroup_singleSelection
   */
  public void setSingleSelection(@BoolRes int id) {
    setSingleSelection(getResources().getBoolean(id));
  }

  private void setCheckedStateForView(@IdRes int viewId, boolean checked) {
    View checkedView = findViewById(viewId);
    if (checkedView instanceof MaterialButton) {
      skipCheckedStateTracker = true;
      ((MaterialButton) checkedView).setChecked(checked);
      skipCheckedStateTracker = false;
    }
  }

  private void setCheckedId(int checkedId) {
    this.checkedId = checkedId;

    dispatchOnButtonChecked(checkedId, true);
  }

  /**
   * Sets a negative marginStart on all but the first child, if two adjacent children both have a
   * stroke width greater than 0. This prevents a double-width stroke from being drawn for two
   * adjacent stroked children, and instead draws the adjacent strokes directly on top of each
   * other.
   *
   * <p>The negative margin adjustment amount will be equal to the smaller of the two adjacent
   * stroke widths.
   *
   * <p>Also rearranges children such that they are shown in the correct visual order.
   */
  private void adjustChildMarginsAndUpdateLayout() {
    int firstVisibleChildIndex = getFirstVisibleChildIndex();
    if (firstVisibleChildIndex == -1) {
      return;
    }

    for (int i = firstVisibleChildIndex + 1; i < getChildCount(); i++) {
      // Only adjusts margins if both adjacent children are MaterialButtons
      MaterialButton currentButton = getChildButton(i);
      MaterialButton previousButton = getChildButton(i - 1);

      // Calculates the margin adjustment to be the smaller of the two adjacent stroke widths
      int smallestStrokeWidth =
          Math.min(currentButton.getStrokeWidth(), previousButton.getStrokeWidth());

      LayoutParams params = buildLayoutParams(currentButton);
      if (getOrientation() == HORIZONTAL) {
        MarginLayoutParamsCompat.setMarginEnd(params, 0);
        MarginLayoutParamsCompat.setMarginStart(params, -smallestStrokeWidth);
        params.topMargin = 0;
      } else {
        params.bottomMargin = 0;
        params.topMargin = -smallestStrokeWidth;
        MarginLayoutParamsCompat.setMarginStart(params, 0);
      }

      currentButton.setLayoutParams(params);
    }

    resetChildMargins(firstVisibleChildIndex);
  }

  private MaterialButton getChildButton(int index) {
    return (MaterialButton) getChildAt(index);
  }

  private void resetChildMargins(int childIndex) {
    if (getChildCount() == 0 || childIndex == -1) {
      return;
    }

    MaterialButton currentButton = getChildButton(childIndex);
    LayoutParams params = (LayoutParams) currentButton.getLayoutParams();
    if (getOrientation() == VERTICAL) {
      params.topMargin = 0;
      params.bottomMargin = 0;
      return;
    }

    MarginLayoutParamsCompat.setMarginEnd(params, 0);
    MarginLayoutParamsCompat.setMarginStart(params, 0);
    params.leftMargin = 0;
    params.rightMargin = 0;
  }

  /** Sets all corner radii to 0 except for leftmost and rightmost corners. */
  @VisibleForTesting
  void updateChildShapes() {
    int childCount = getChildCount();
    int firstVisibleChildIndex = getFirstVisibleChildIndex();
    int lastVisibleChildIndex = getLastVisibleChildIndex();
    for (int i = 0; i < childCount; i++) {
      MaterialButton button = getChildButton(i);
      if (button.getVisibility() == GONE) {
        continue;
      }

      ShapeAppearanceModel.Builder builder = button.getShapeAppearanceModel().toBuilder();
      CornerData newCornerData = getNewCornerData(i, firstVisibleChildIndex, lastVisibleChildIndex);
      updateBuilderWithCornerData(builder, newCornerData);

      button.setShapeAppearanceModel(builder.build());
    }
  }

  private int getFirstVisibleChildIndex() {
    int childCount = getChildCount();
    for (int i = 0; i < childCount; i++) {
      if (isChildVisible(i)) {
        return i;
      }
    }

    return -1;
  }

  private int getLastVisibleChildIndex() {
    int childCount = getChildCount();
    for (int i = childCount - 1; i >= 0; i--) {
      if (isChildVisible(i)) {
        return i;
      }
    }

    return -1;
  }

  private boolean isChildVisible(int i) {
    View child = getChildAt(i);
    return child.getVisibility() != View.GONE;
  }

  private int getVisibleButtonCount() {
    int count = 0;
    for (int i = 0; i < getChildCount(); i++) {
      if (this.getChildAt(i) instanceof MaterialButton && isChildVisible(i)) {
        count++;
      }
    }
    return count;
  }

  private int getIndexWithinVisibleButtons(@Nullable View child) {
    if (!(child instanceof MaterialButton)) {
      return -1;
    }
    int index = 0;
    for (int i = 0; i < getChildCount(); i++) {
      if (this.getChildAt(i) == child) {
        return index;
      }
      if (this.getChildAt(i) instanceof MaterialButton && isChildVisible(i)) {
        index++;
      }
    }
    return -1;
  }

  @Nullable
  private CornerData getNewCornerData(
      int index, int firstVisibleChildIndex, int lastVisibleChildIndex) {
    CornerData cornerData = originalCornerData.get(index);

    // If only one (visible) child exists, use its original corners
    if (firstVisibleChildIndex == lastVisibleChildIndex) {
      return cornerData;
    }

    boolean isHorizontal = getOrientation() == HORIZONTAL;
    if (index == firstVisibleChildIndex) {
      return isHorizontal ? CornerData.start(cornerData, this) : CornerData.top(cornerData);
    }

    if (index == lastVisibleChildIndex) {
      return isHorizontal ? CornerData.end(cornerData, this) : CornerData.bottom(cornerData);
    }

    return null;
  }

  private static void updateBuilderWithCornerData(
      ShapeAppearanceModel.Builder shapeAppearanceModelBuilder, @Nullable CornerData cornerData) {
    if (cornerData == null) {
      shapeAppearanceModelBuilder.setAllCornerSizes(0);
      return;
    }

    shapeAppearanceModelBuilder
        .setTopLeftCornerSize(cornerData.topLeft)
        .setBottomLeftCornerSize(cornerData.bottomLeft)
        .setTopRightCornerSize(cornerData.topRight)
        .setBottomRightCornerSize(cornerData.bottomRight);
  }

  /**
   * When a checked child is added, or a child is clicked, updates checked state and draw order of
   * children to draw all checked children on top of all unchecked children.
   *
   * <p>If {@code singleSelection} is true, this will unselect any other children as well.
   *
   * <p>If {@code selectionRequired} is true, and the last child is unchecked it will undo the
   * deselection.
   *
   * @param childId ID of child whose checked state may have changed
   * @param childIsChecked Whether the child is checked
   * @return Whether the checked state for childId has changed.
   */
  private boolean updateCheckedStates(int childId, boolean childIsChecked) {
    List<Integer> checkedButtonIds = getCheckedButtonIds();
    if (selectionRequired && checkedButtonIds.isEmpty()) {
      // undo deselection
      setCheckedStateForView(childId, true);
      checkedId = childId;
      return false;
    }

    // un select previous selection
    if (childIsChecked && singleSelection) {
      checkedButtonIds.remove((Integer) childId);
      for (int buttonId : checkedButtonIds) {
        setCheckedStateForView(buttonId, false);
        dispatchOnButtonChecked(buttonId, false);
      }
    }
    return true;
  }

  private void dispatchOnButtonChecked(@IdRes int buttonId, boolean checked) {
    for (OnButtonCheckedListener listener : onButtonCheckedListeners) {
      listener.onButtonChecked(this, buttonId, checked);
    }
  }

  private void checkForced(int checkedId, boolean checked) {
    MaterialButton button = findViewById(checkedId);
    if (button != null) {
      button.setChecked(checked);
    }
  }

  private void setGeneratedIdIfNeeded(@NonNull MaterialButton materialButton) {
    // Generates an ID if none is set, for relative positioning purposes
    if (materialButton.getId() == View.NO_ID) {
      materialButton.setId(ViewCompat.generateViewId());
    }
  }

  /**
   * Sets sensible default values for {@link MaterialButton} child of this group, set child to
   * {@code checkable}, and set internal checked change listener for this child.
   *
   * @param buttonChild {@link MaterialButton} child to set up to be added to this {@link
   *     MaterialButtonToggleGroup}
   */
  private void setupButtonChild(@NonNull MaterialButton buttonChild) {
    buttonChild.setMaxLines(1);
    buttonChild.setEllipsize(TruncateAt.END);
    buttonChild.setCheckable(true);

    buttonChild.addOnCheckedChangeListener(checkedStateTracker);
    buttonChild.setOnPressedChangeListenerInternal(pressedStateTracker);

    // Enables surface layer drawing for semi-opaque strokes
    buttonChild.setShouldDrawSurfaceColorStroke(true);
  }

  @NonNull
  private LinearLayout.LayoutParams buildLayoutParams(@NonNull View child) {
    ViewGroup.LayoutParams layoutParams = child.getLayoutParams();
    if (layoutParams instanceof LinearLayout.LayoutParams) {
      return (LayoutParams) layoutParams;
    }

    return new LayoutParams(layoutParams.width, layoutParams.height);
  }

  /**
   * We keep track of which views are pressed and checked to draw them last. This prevents visual
   * issues with overlapping strokes.
   */
  @Override
  protected int getChildDrawingOrder(int childCount, int i) {
    if (childOrder == null || i >= childOrder.length) {
      Log.w(LOG_TAG, "Child order wasn't updated");
      return i;
    }

    return childOrder[i];
  }

  private void updateChildOrder() {
    final SortedMap<MaterialButton, Integer> viewToIndexMap = new TreeMap<>(childOrderComparator);
    int childCount = getChildCount();
    for (int i = 0; i < childCount; i++) {
      viewToIndexMap.put(getChildButton(i), i);
    }

    childOrder = viewToIndexMap.values().toArray(new Integer[0]);
  }

  private class CheckedStateTracker implements MaterialButton.OnCheckedChangeListener {
    @Override
    public void onCheckedChanged(@NonNull MaterialButton button, boolean isChecked) {
      // Prevents infinite recursion
      if (skipCheckedStateTracker) {
        return;
      }

      if (singleSelection) {
        checkedId = isChecked ? button.getId() : View.NO_ID;
      }

      boolean buttonCheckedStateChanged = updateCheckedStates(button.getId(), isChecked);
      if (buttonCheckedStateChanged) {
        // Dispatch button.isChecked instead of isChecked in case its checked state was updated
        // internally.
        dispatchOnButtonChecked(button.getId(), button.isChecked());
      }
      invalidate();
    }
  }

  private class PressedStateTracker implements OnPressedChangeListener {

    @Override
    public void onPressedChanged(@NonNull MaterialButton button, boolean isPressed) {
      invalidate();
    }
  }

  private static class CornerData {

    private static final CornerSize noCorner = new AbsoluteCornerSize(0);

    CornerSize topLeft;
    CornerSize topRight;
    CornerSize bottomRight;
    CornerSize bottomLeft;

    CornerData(
        CornerSize topLeft, CornerSize bottomLeft, CornerSize topRight, CornerSize bottomRight) {
      this.topLeft = topLeft;
      this.topRight = topRight;
      this.bottomRight = bottomRight;
      this.bottomLeft = bottomLeft;
    }

    /** Keep the start side of the corner original data */
    public static CornerData start(CornerData orig, View view) {
      return ViewUtils.isLayoutRtl(view) ? right(orig) : left(orig);
    }

    /** Keep the end side of the corner original data */
    public static CornerData end(CornerData orig, View view) {
      return ViewUtils.isLayoutRtl(view) ? left(orig) : right(orig);
    }

    /** Keep the left side of the corner original data */
    public static CornerData left(CornerData orig) {
      return new CornerData(orig.topLeft, orig.bottomLeft, noCorner, noCorner);
    }

    /** Keep the right side of the corner original data */
    public static CornerData right(CornerData orig) {
      return new CornerData(noCorner, noCorner, orig.topRight, orig.bottomRight);
    }

    /** Keep the top side of the corner original data */
    public static CornerData top(CornerData orig) {
      return new CornerData(orig.topLeft, noCorner, orig.topRight, noCorner);
    }

    /** Keep the bottom side of the corner original data */
    public static CornerData bottom(CornerData orig) {
      return new CornerData(noCorner, orig.bottomLeft, noCorner, orig.bottomRight);
    }
  }
}