这篇文章主要为大家展示了swift4.2如何实现新闻首页导航，内容简而易懂，希望大家可以学习一下，学习完之后肯定会有收获的，下面让小编带大家一起来看看吧。

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对于仿照新闻首页的页面，已经有比较好用的OC版本，现在我们来写一个swift版本的。

设备：xcode 10.2     语言：swift 4.2

效果图：

我们先创建一个多控制器的导航栏，直接上代码：

//
// JHSBarItemView.swift
// ScrollBarController
//
// Created by yaojinhai on 2019/4/15.
// Copyright © 2019年 yaojinhai. All rights reserved.
//
 
import UIKit
 
enum BarItemBorderType {
  case defualt
  case barItem
  case maskView
  case customItem
}
 
protocol JHSBarItemViewDelegate: NSObjectProtocol {
  func selectedIndexItem(view: JHSBarItemView,index: Int) -> Void
}
 
class JHSBarItemView: UIView {
 
  var minMargin: CGFloat = BarConfig.minMargin;
  
  weak var delegate: JHSBarItemViewDelegate?
  var lineBarView: UIView!
  
  var barType = BarItemBorderType.defualt {
    didSet{
      configBarType();
      removeBarItem(idx: selectedIndex);
    }
  }
  
  
  
  var selectedIndex = 0;
  var titles: [String]!{
    didSet{
      caculateItemSize();
 
    }
  }
  
  private var titlesView: UICollectionView!
  private var cachesSize = [String:CGSize]();
 
  
  override init(frame: CGRect) {
    super.init(frame: frame);
    createContentView();
  }
  
  convenience init(frame: CGRect,titles: [String]) {
    self.init(frame: frame);
    self.titles = titles;
    createContentView();
    caculateItemSize();
 
  }
  
  func progressWidth() -> Void {
    
  }
  
  
  required init?(coder aDecoder: NSCoder) {
    fatalError("init(coder:) has not been implemented")
  }
  
  
}
 
extension JHSBarItemView: UICollectionViewDataSource,UICollectionViewDelegateFlowLayout {
  
  private func caculateItemSize() -> Void {
 
    guard let itemTitles = titles ,itemTitles.count > 0 else {
      return;
    }
    
    var maxWidth: CGFloat = 0;
    for item in itemTitles {
      let size = item.textSize(size: CGSize(width: width, height: height), font: BarConfig.normalFont);
      cachesSize[item] = CGSize(width: size.width, height: height);
      maxWidth += size.width;
    }
    let gap = (width - maxWidth) / CGFloat(itemTitles.count + 1);
    minMargin = max(gap, BarConfig.minMargin);
    titlesView.reloadData();
    removeBarItem(idx: selectedIndex);
 
  }
  
  private func createContentView() -> Void {
    
    if titlesView != nil {
      return;
    }
    let layout = UICollectionViewFlowLayout();
    layout.minimumLineSpacing = 0;
    layout.minimumInteritemSpacing = 0;
    layout.scrollDirection = .horizontal;
    titlesView = FMBaseCollectionView(frame: .init(x: 0, y: 0, width: width, height: height), collectionViewLayout: layout);
    addSubview(titlesView);
    titlesView.register(BarItemViewCell.self, forCellWithReuseIdentifier: "title");
    titlesView.delegate = self;
    titlesView.dataSource = self;
    
    let lineView = createView(rect: .init(x: 0, y: height - 1, width: width, height: 1));
    lineView.backgroundColor = rgbColor(rgb: 234);
    
    
  }
  
  // MARK: - collection view delegate and dataSource
  
  func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
    return titles?.count ?? 0;
  }
  func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, insetForSectionAt section: Int) -> UIEdgeInsets {
    return UIEdgeInsets(top: 0, left: minMargin, bottom: 0, right: minMargin);
  }
 
  
  func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize {
    if titles == nil {
      return CGSize.zero;
    }
    let item = titles[indexPath.row];
    if let size = cachesSize[item] {
      return CGSize(width: size.width + minMargin, height: height);
    }
    let size = titles[indexPath.row].textSize(size: CGSize.init(width: width, height: height), font: BarConfig.normalFont);
    let newSize = CGSize(width: size.width + minMargin, height: height);
    cachesSize[item] = size;
    return newSize;
  }
  
  
  func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
    let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "title", for: indexPath) as! BarItemViewCell;
    cell.titleLabel.text = titles[indexPath.row];
    cell.titleLabel.isHighlighted = selectedIndex == indexPath.row;
    return cell;
  }
  
  func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {
    didSelected(idx: indexPath.row);
    delegate?.selectedIndexItem(view: self, index: indexPath.row);
  }
  
  func didSelected(idx: Int) -> Void {
    let indexPath = IndexPath(item: idx, section: 0);
    titlesView.scrollToItem(at: indexPath, at: .centeredHorizontally, animated: true);
 
    
    let cell = titlesView.cellForItem(at: indexPath) as? BarItemViewCell;
    cell?.titleLabel.isHighlighted = true;
    cell?.RunAnimation();
    
    removeBarItem(idx: indexPath.row);
    
    
    if selectedIndex != indexPath.row {
      let preCell = titlesView.cellForItem(at: .init(row: selectedIndex, section: 0)) as? BarItemViewCell;
      preCell?.titleLabel.isHighlighted = false;
      preCell?.RunAnimation();
      selectedIndex = indexPath.row;
      
    }
  }
}
 
extension JHSBarItemView {
  
  private func removeBarItem(idx: Int) {
    if barType == .barItem {
      let size = getMaxWidthAt(index: idx);
      lineBarView.frame = .init(x: size.width, y: height - 2, width: size.height, height: 2);
    }else if barType == .maskView {
      let size = getMaxWidthAt(index: idx);
      lineBarView.frame = .init(x: size.width - minMargin/2, y: 0, width: size.height + minMargin, height: height);
    }
  }
  func getMaxWidthAt(index: Int) -> CGSize {
    if titles == nil || titles.count == 0 {
      return CGSize.zero;
    }
    
    var maxWidth: CGFloat = minMargin;
    var sizeWidth: CGFloat = cachesSize[titles[0]]!.width;
    if index > 0 {
      for item in 1...index {
        let title = titles[item];
        let size = cachesSize[title]!;
        maxWidth += size.width + minMargin;
        sizeWidth = size.width;
      }
    }
    return CGSize(width: maxWidth + minMargin/2, height: sizeWidth);
  }
  
  private func configBarType() -> Void {
    if barType == .barItem {
      if lineBarView == nil {
        lineBarView = createView(rect: .init(x: 0, y: height - 2, width: 30, height: 2));
        lineBarView.backgroundColor = UIColor.red;
        lineBarView.layer.cornerRadius = 2;
        lineBarView.layer.masksToBounds = true;
      }
      titlesView.addSubview(lineBarView);
    }else if barType == .maskView {
      if lineBarView == nil {
        lineBarView = createView(rect: .init(x: 0, y: 0, width: 30, height: height));
        lineBarView.backgroundColor = UIColor.green.withAlphaComponent(0.2);
        lineBarView.isUserInteractionEnabled = false;
      }
      titlesView.addSubview(lineBarView);
    }else{
      titlesView?.removeFromSuperview();
 
    }
  }
}
 
class BarItemViewCell: UICollectionViewCell {
  var titleLabel: UILabel!
  override init(frame: CGRect) {
    super.init(frame: frame);
    titleLabel = createLabel(rect: bounds, text: "");
    titleLabel.textAlignment = .center;
    titleLabel.textColor = BarConfig.normalColor;
    titleLabel.highlightedTextColor = BarConfig.hlightedColor;
    titleLabel.font = BarConfig.normalFont;
  }
  
  required init?(coder aDecoder: NSCoder) {
    fatalError("init(coder:) has not been implemented")
  }
  func RunAnimation(animation: Bool = true) -> Void {
    self.titleLabel.font = self.titleLabel.isHighlighted ? BarConfig.hlightedFont : BarConfig.normalFont;
    
    
  }
}

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