components/AppBar/examples/AppBarCustomButtonThemeExample.swift

// Copyright 2020-present the Material Components for iOS authors. All Rights Reserved.
//
// 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.

import Foundation
import MaterialComponents.MaterialButtons_Theming
import MaterialComponents.MaterialAppBar
import MaterialComponents.MaterialAppBar_Theming
import MaterialComponents.MaterialContainerScheme

class AppBarCustomButtonThemeExample: UITableViewController {

  let appBarViewController = MDCAppBarViewController()
  @objc var containerScheme: MDCContainerScheming = MDCContainerScheme()

  deinit {
    // Required for pre-iOS 11 devices because we've enabled observesTrackingScrollViewScrollEvents.
    appBarViewController.headerView.trackingScrollView = nil
  }

  init() {
    super.init(nibName: nil, bundle: nil)

    self.title = "Custom button theme"

    // Behavioral flags.
    appBarViewController.inferTopSafeAreaInsetFromViewController = true
    appBarViewController.headerView.minMaxHeightIncludesSafeArea = false

    // Step 2: Add the headerViewController as a child.
    self.addChild(appBarViewController)
  }

  required init?(coder aDecoder: NSCoder) {
    super.init(coder: aDecoder)
  }

  override func viewDidLoad() {
    super.viewDidLoad()

    appBarViewController.headerView.observesTrackingScrollViewScrollEvents = true
    appBarViewController.headerView.trackingScrollView = self.tableView

    view.addSubview(appBarViewController.view)
    appBarViewController.didMove(toParent: self)

    appBarViewController.applySurfaceTheme(withScheme: containerScheme)

    // To create a custom-themed button we create a custom button placed inside a container which
    // will be set as a custom view on the navigationItem.
    let containerView = UIView()
    let button = MDCButton()
    button.applyContainedTheme(withScheme: containerScheme)
    button.setTitle("Right", for: .normal)
    button.sizeToFit()
    // Give the button horizontal insets so that it's not flush with the device's edge.
    containerView.frame = CGRect(x: 0,
                                 y: 8,
                                 width: button.bounds.width + 16,
                                 height: button.bounds.height)
    // Vertically center the button:
    button.autoresizingMask = [.flexibleTopMargin, .flexibleBottomMargin]
    containerView.addSubview(button)
    self.navigationItem.rightBarButtonItem = UIBarButtonItem(customView: containerView)
  }

  // Optional step: If you allow the header view to hide the status bar you must implement this
  //                method and return the headerViewController.
  override var childForStatusBarHidden: UIViewController? {
    return appBarViewController
  }

  // Optional step: The Header View Controller does basic inspection of the header view's background
  //                color to identify whether the status bar should be light or dark-themed.
  override var childForStatusBarStyle: UIViewController? {
    return appBarViewController
  }

  override func viewWillAppear(_ animated: Bool) {
    super.viewWillAppear(animated)

    self.navigationController?.setNavigationBarHidden(true, animated: animated)
  }
}

// MARK: Catalog by convention
extension AppBarCustomButtonThemeExample {

  @objc class func catalogMetadata() -> [String: Any] {
    return [
      "breadcrumbs": ["App Bar", "Custom button theme"],
      "primaryDemo": false,
      "presentable": false,
    ]
  }

  @objc func catalogShouldHideNavigation() -> Bool {
    return true
  }
}

// MARK: - Typical application code (not Material-specific)

// MARK: UITableViewDataSource
extension AppBarCustomButtonThemeExample {

  override func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
    return 50
  }

  override func tableView(
    _ tableView: UITableView,
    cellForRowAt indexPath: IndexPath) -> UITableViewCell {
    
    let cell = self.tableView.dequeueReusableCell(withIdentifier: "cell") ??
        UITableViewCell(style: .default, reuseIdentifier: "cell")
      cell.layoutMargins = .zero
      cell.textLabel?.text = "\(indexPath.row)"
      cell.selectionStyle = .none
      return cell
  }
}