material-components_material-components-android/lib/java/com/google/android/material/bottomnavigation/BottomNavigationView.java

/*
 * Copyright (C) 2016 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.bottomnavigation;

import com.google.android.material.R;

import static androidx.annotation.RestrictTo.Scope.LIBRARY_GROUP;

import android.content.Context;
import android.os.Build.VERSION;
import androidx.appcompat.widget.TintTypedArray;
import android.util.AttributeSet;
import android.view.View;
import android.view.ViewGroup;
import android.widget.FrameLayout;
import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import androidx.annotation.RestrictTo;
import androidx.coordinatorlayout.widget.CoordinatorLayout;
import androidx.core.content.ContextCompat;
import com.google.android.material.behavior.HideBottomViewOnScrollBehavior;
import com.google.android.material.internal.ThemeEnforcement;
import com.google.android.material.navigation.NavigationBarMenuView;
import com.google.android.material.navigation.NavigationBarView;
import com.google.android.material.shape.MaterialShapeDrawable;

/**
 * Represents a standard bottom navigation bar for application. It is an implementation of <a
 * href="https://material.google.com/components/bottom-navigation.html">material design bottom
 * navigation</a>.
 *
 * <p>Bottom navigation bars make it easy for users to explore and switch between top-level views in
 * a single tap. They should be used when an application has three to five top-level destinations.
 *
 * <p>The bar can disappear on scroll, based on {@link
 * com.google.android.material.behavior.HideBottomViewOnScrollBehavior}, when it is placed within a
 * {@link CoordinatorLayout} and one of the children within the {@link CoordinatorLayout} is
 * scrolled. This behavior is only set if the {@code layout_behavior} property is set to {@link
 * HideBottomViewOnScrollBehavior}.
 *
 * <p>The bar contents can be populated by specifying a menu resource file. Each menu item title,
 * icon and enabled state will be used for displaying bottom navigation bar items. Menu items can
 * also be used for programmatically selecting which destination is currently active. It can be done
 * using {@code MenuItem#setChecked(true)}
 *
 * <pre>
 * layout resource file:
 * &lt;com.google.android.material.bottomnavigation.BottomNavigationView
 *     xmlns:android="http://schemas.android.com/apk/res/android"
 *     xmlns:app="http://schema.android.com/apk/res/res-auto"
 *     android:id="@+id/navigation"
 *     android:layout_width="match_parent"
 *     android:layout_height="56dp"
 *     android:layout_gravity="start"
 *     app:menu="@menu/my_navigation_items" /&gt;
 *
 * res/menu/my_navigation_items.xml:
 * &lt;menu xmlns:android="http://schemas.android.com/apk/res/android"&gt;
 *     &lt;item android:id="@+id/action_search"
 *          android:title="@string/menu_search"
 *          android:icon="@drawable/ic_search" /&gt;
 *     &lt;item android:id="@+id/action_settings"
 *          android:title="@string/menu_settings"
 *          android:icon="@drawable/ic_add" /&gt;
 *     &lt;item android:id="@+id/action_navigation"
 *          android:title="@string/menu_navigation"
 *          android:icon="@drawable/ic_action_navigation_menu" /&gt;
 * &lt;/menu&gt;
 * </pre>
 */
public class BottomNavigationView extends NavigationBarView {
  static final int MAX_ITEM_COUNT = 5;

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

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

  public BottomNavigationView(
      @NonNull Context context, @Nullable AttributeSet attrs, int defStyleAttr) {
    this(context, attrs, defStyleAttr, R.style.Widget_Design_BottomNavigationView);
  }

  public BottomNavigationView(
      @NonNull Context context, @Nullable AttributeSet attrs, int defStyleAttr, int defStyleRes) {
    super(context, attrs, defStyleAttr, defStyleRes);

    // Ensure we are using the correctly themed context rather than the context that was passed in.
    context = getContext();

    /* Custom attributes */
    TintTypedArray attributes =
        ThemeEnforcement.obtainTintedStyledAttributes(
            context, attrs, R.styleable.BottomNavigationView, defStyleAttr, defStyleRes);

    setItemHorizontalTranslationEnabled(
        attributes.getBoolean(
            R.styleable.BottomNavigationView_itemHorizontalTranslationEnabled, true));

    attributes.recycle();

    if (shouldDrawCompatibilityTopDivider()) {
      addCompatibilityTopDivider(context);
    }
  }

  /**
   * Sets whether the menu items horizontally translate on selection when the combined item widths
   * fill up the screen.
   *
   * @param itemHorizontalTranslationEnabled whether the items horizontally translate on selection
   * @see #isItemHorizontalTranslationEnabled()
   */
  public void setItemHorizontalTranslationEnabled(boolean itemHorizontalTranslationEnabled) {
    BottomNavigationMenuView menuView = (BottomNavigationMenuView) getMenuView();
    if (menuView.isItemHorizontalTranslationEnabled() != itemHorizontalTranslationEnabled) {
      menuView.setItemHorizontalTranslationEnabled(itemHorizontalTranslationEnabled);
      getPresenter().updateMenuView(false);
    }
  }

  /**
   * Returns whether the items horizontally translate on selection when the item widths fill up the
   * screen.
   *
   * @return whether the menu items horizontally translate on selection
   * @see #setItemHorizontalTranslationEnabled(boolean)
   */
  public boolean isItemHorizontalTranslationEnabled() {
    return ((BottomNavigationMenuView) getMenuView()).isItemHorizontalTranslationEnabled();
  }

  @Override
  public int getMaxItemCount() {
    return MAX_ITEM_COUNT;
  }

  /** @hide */
  @RestrictTo(LIBRARY_GROUP)
  @Override
  @NonNull
  protected NavigationBarMenuView createNavigationBarMenuView(@NonNull Context context) {
    return new BottomNavigationMenuView(context);
  }

  /**
   * Returns true a divider must be added in place of shadows to maintain compatibility in pre-21
   * legacy backgrounds.
   */
  private boolean shouldDrawCompatibilityTopDivider() {
    return VERSION.SDK_INT < 21 && !(getBackground() instanceof MaterialShapeDrawable);
  }

  /**
   * Adds a divider in place of shadows to maintain compatibility in pre-21 legacy backgrounds. If a
   * pre-21 background has been updated to a MaterialShapeDrawable, MaterialShapeDrawable will draw
   * shadows instead.
   */
  private void addCompatibilityTopDivider(@NonNull Context context) {
    View divider = new View(context);
    divider.setBackgroundColor(
        ContextCompat.getColor(context, R.color.design_bottom_navigation_shadow_color));
    FrameLayout.LayoutParams dividerParams =
        new FrameLayout.LayoutParams(
            ViewGroup.LayoutParams.MATCH_PARENT,
            getResources().getDimensionPixelSize(R.dimen.design_bottom_navigation_shadow_height));
    divider.setLayoutParams(dividerParams);
    addView(divider);
  }

  /**
   * Set a listener that will be notified when a bottom navigation item is selected. This listener
   * will also be notified when the currently selected item is reselected, unless an {@link
   * OnNavigationItemReselectedListener} has also been set.
   *
   * @param listener The listener to notify
   * @see #setOnNavigationItemReselectedListener(OnNavigationItemReselectedListener)
   */
  public void setOnNavigationItemSelectedListener(
      @Nullable OnNavigationItemSelectedListener listener) {
    setOnItemSelectedListener(listener);
  }

  /**
   * Set a listener that will be notified when the currently selected bottom navigation item is
   * reselected. This does not require an {@link OnNavigationItemSelectedListener} to be set.
   *
   * @param listener The listener to notify
   * @see #setOnNavigationItemSelectedListener(OnNavigationItemSelectedListener)
   */
  public void setOnNavigationItemReselectedListener(
      @Nullable OnNavigationItemReselectedListener listener) {
    setOnItemReselectedListener(listener);
  }

  /** Listener for handling selection events on bottom navigation items. */
  public interface OnNavigationItemSelectedListener extends OnItemSelectedListener {}

  /** Listener for handling reselection events on bottom navigation items. */
  public interface OnNavigationItemReselectedListener extends OnItemReselectedListener {}
}