我想要一个 UIProgressView 在导航栏底部显示进度（就像在 iOS 7 中发送 iMessage 或短信时一样）。但是我在导航控制器的每个表视图视图上都需要这个。所以对我来说很清楚：我必须将它添加到 UINavigationController。但问题是，无法将 UIProgressView 添加到 UINavigationController。所以我尝试了两件事：
第一次我尝试以编程方式将它添加到 UINavigationController 的视图中。但问题是定位 UIProgressView 并使其在更改设备旋转时看起来不错。
我尝试的第二件事是将 UIProgressView 添加到每个 UITableView，但是我真的必须为每个视图都这样做。它看起来也不好看，因为它不在导航栏的顶部，而是在它的下方。但是我不喜欢第二种解决方案的主要原因是因为 ProgressViews 随他们的 TableView 一起出现，所以你没有静态的，而是变化的。
在此之后，我没有任何想法这样做，所以我问你......有没有人知道如何做到这一点？
它应该是这样的：
我终于找到了解决方案：
我制作了一个自定义 UINavigationController 并将其添加到viewDidLoad
- (void)viewDidLoad
{
[super viewDidLoad];
// Do any additional setup after loading the view.
progress = [[UIProgressView alloc] init];
[[self view] addSubview:progress];
UIView *navBar = [self navigationBar];
[[self view] addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"V:[navBar]-[progress(2@20)]"
options:NSLayoutFormatDirectionLeadingToTrailing
metrics:nil
views:NSDictionaryOfVariableBindings(progress, navBar)]];
[[self view] addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"H:|[progress]|"
options:NSLayoutFormatDirectionLeadingToTrailing
metrics:nil
views:NSDictionaryOfVariableBindings(progress)]];
[progress setTranslatesAutoresizingMaskIntoConstraints:NO];
[progress setProgress:0 animated:NO];
}
我创建了一个新的 UIProgressView（我在 中声明@interface）添加了约束以将其定位在导航栏下方，并且（这一步很重要：）设置translatesAutoresizingMaskIntoConstraints为NO
我修改了原始海报的答案，以便该栏实际上就在导航栏内。这样做的好处是，当它显示时，它与一个像素的底线重叠（实际上是替换它），因此当您将进度条设置为隐藏时，进度条会淡出，而分隔线会淡入。此解决方案是将进度条添加到导航控制器的视图，而不是导航栏。
- (void)viewDidLoad
{
[super viewDidLoad];
// Do any additional setup after loading the view.
UIProgressView *progress = [[UIProgressView alloc] initWithProgressViewStyle:UIProgressViewStyleBar];;
[self.view addSubview:progress];
UINavigationBar *navBar = [self navigationBar];
#if 1
[self.view addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"V:[navBar]-0-[progress]"
options:NSLayoutFormatDirectionLeadingToTrailing
metrics:nil
views:NSDictionaryOfVariableBindings(progress, navBar)]];
[self.view addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"H:|[progress]|"
options:NSLayoutFormatDirectionLeadingToTrailing
metrics:nil
views:NSDictionaryOfVariableBindings(progress)]];
#else
NSLayoutConstraint *constraint;
constraint = [NSLayoutConstraint constraintWithItem:progress attribute:NSLayoutAttributeBottom relatedBy:NSLayoutRelationEqual toItem:navBar attribute:NSLayoutAttributeBottom multiplier:1 constant:-0.5];
[self.view addConstraint:constraint];
constraint = [NSLayoutConstraint constraintWithItem:progress attribute:NSLayoutAttributeLeft relatedBy:NSLayoutRelationEqual toItem:navBar attribute:NSLayoutAttributeLeft multiplier:1 constant:0];
[self.view addConstraint:constraint];
constraint = [NSLayoutConstraint constraintWithItem:progress attribute:NSLayoutAttributeRight relatedBy:NSLayoutRelationEqual toItem:navBar attribute:NSLayoutAttributeRight multiplier:1 constant:0];
[self.view addConstraint:constraint];
#endif
[progress setTranslatesAutoresizingMaskIntoConstraints:NO];
[progress setProgress:0.5 animated:NO];
}
我不确定为什么有必要将 0.5 偏移量添加到 NSLayoutContstraints 代码以获得相同的匹配，但确实如此。我使用这些不是视觉格式，但选择权在你。请注意，对底部的约束也使旋转无缝。
基于这里已经建议的内容，如果你想让它显示在应用程序的每个导航栏上，你可以将它变成 UINavigationController 上的扩展（Swift）：
extension UINavigationController {
public override func viewDidLoad() {
super.viewDidLoad()
let progressView = UIProgressView(progressViewStyle: .Bar)
self.view.addSubview(progressView)
let navBar = self.navigationBar
self.view.addConstraints(NSLayoutConstraint.constraintsWithVisualFormat("V:[navBar]-0-[progressView]", options: .DirectionLeadingToTrailing, metrics: nil, views: ["progressView" : progressView, "navBar" : navBar]))
self.view.addConstraints(NSLayoutConstraint.constraintsWithVisualFormat("H:|[progressView]|", options: .DirectionLeadingToTrailing, metrics: nil, views: ["progressView" : progressView]))
progressView.translatesAutoresizingMaskIntoConstraints = false
progressView.setProgress(0.5, animated: false)
}
}
更新（使用 Swift 3 语法）
这是一个更完整的解决方案。我将此扩展名放入一个名为UINavigationController+Progress.swift的文件中。（请注意，我使用UIViewtag 属性来查找UIProgressView具有可选progressView属性的 。可能有更优雅的方法可以做到这一点，但这似乎是最直接的）
import UIKit
let kProgressViewTag = 10000
let kProgressUpdateNotification = "kProgressUpdateNotification"
extension UINavigationController {
open override func viewDidLoad() {
super.viewDidLoad()
let progressView = UIProgressView(progressViewStyle: .bar)
progressView.tag = kProgressViewTag
self.view.addSubview(progressView)
let navBar = self.navigationBar
self.view.addConstraints(NSLayoutConstraint.constraints(withVisualFormat: "V:[navBar]-0-[progressView]", options: .directionLeadingToTrailing, metrics: nil, views: ["progressView" : progressView, "navBar" : navBar]))
self.view.addConstraints(NSLayoutConstraint.constraints(withVisualFormat: "H:|[progressView]|", options: .directionLeadingToTrailing, metrics: nil, views: ["progressView" : progressView]))
progressView.translatesAutoresizingMaskIntoConstraints = false
progressView.setProgress(0.0, animated: false)
NotificationCenter.default.addObserver(self, selector: #selector(UINavigationController.didReceiveNotification(notification:)), name: NSNotification.Name(rawValue: kProgressUpdateNotification), object: nil)
}
var progressView : UIProgressView? {
return self.view.viewWithTag(kProgressViewTag) as? UIProgressView
}
func didReceiveNotification(notification:NSNotification) {
if let progress = notification.object as? ProgressNotification {
if progress.current == progress.total {
self.progressView?.setProgress(0.0, animated: false)
} else {
let perc = Float(progress.current) / Float(progress.total)
self.progressView?.setProgress(perc, animated: true)
}
}
}
}
class ProgressNotification {
var current: Int = 0
var total: Int = 0
}
所以我在这里给出了一个具体的实现，假设你想要一个当前计数和一个总计数值来更新进度条。现在，您需要从正在执行任何用于确定进度的任务的代码中发布通知——例如下载文件列表。这是发布通知的代码：
let notification = ProgressNotification()
notification.current = processedTaskCount
notification.total = totalTaskCount
DispatchQueue.main.async {
NotificationCenter.default.post(name: NSNotification.Name(rawValue: kProgressUpdateNotification), object: notification)
}
您可以在 navigationController 的根 viewController 中执行此操作：
override func viewDidLoad() {
super.viewDidLoad()
// if VC is pushed in a navigation controller I add a progress bar
if let navigationVC = self.navigationController {
// create progress bar with .bar style and add it as subview
let progressBar = UIProgressView(progressViewStyle: .Bar)
navigationVC.navigationBar.addSubview(self.progressView)
// create constraints
// NOTE: bottom constraint has 1 as constant value instead of 0; this way the progress bar will look like the one in Safari
let bottomConstraint = NSLayoutConstraint(item: navigationVC.navigationBar, attribute: .Bottom, relatedBy: .Equal, toItem: progressBar, attribute: .Bottom, multiplier: 1, constant: 1)
let leftConstraint = NSLayoutConstraint(item: navigationVC.navigationBar, attribute: .Leading, relatedBy: .Equal, toItem: progressBar, attribute: .Leading, multiplier: 1, constant: 0)
let rightConstraint = NSLayoutConstraint(item: navigationVC.navigationBar, attribute: .Trailing, relatedBy: .Equal, toItem: progressBar, attribute: .Trailing, multiplier: 1, constant: 0)
// add constraints
progressBar.translatesAutoresizingMaskIntoConstraints = false
navigationVC.view.addConstraints([bottomConstraint, leftConstraint, rightConstraint])
}
}
但是，如果您希望在导航栏中始终为所有推送的 VC 提供相同的进度条，那么最好将 UINavigationController 子类化，并且：
override func viewDidLoad() {
super.viewDidLoad()
// create progress bar with .bar style and keep reference with a property
let progressBar = UIProgressView(progressViewStyle: .Bar)
self.progressBar = progressBar
// add progressBar as subview
self.navigationBar.addSubview(progressBar)
// create constraints
// NOTE: bottom constraint has 1 as constant value instead of 0; this way the progress bar will look like the one in Safari
let bottomConstraint = NSLayoutConstraint(item: self.navigationBar, attribute: .Bottom, relatedBy: .Equal, toItem: progressBar, attribute: .Bottom, multiplier: 1, constant: 1)
let leftConstraint = NSLayoutConstraint(item: self.navigationBar, attribute: .Leading, relatedBy: .Equal, toItem: progressBar, attribute: .Leading, multiplier: 1, constant: 0)
let rightConstraint = NSLayoutConstraint(item: self.navigationBar, attribute: .Trailing, relatedBy: .Equal, toItem: progressBar, attribute: .Trailing, multiplier: 1, constant: 0)
// add constraints
progressBar.translatesAutoresizingMaskIntoConstraints = false
self.view.addConstraints([bottomConstraint, leftConstraint, rightConstraint])
}
您可以在 UInavigationController 的 titleView 中添加 ProgressBar，如下图所示：
UIView *customView = [[UIView alloc] initWithFrame:CGRectMake(0,0,200,30)];
[customView setBackgroundColor:[UIColor whiteColor]];
UIProgressView *p = [[UIProgressView alloc] initWithFrame:CGRectMake(10, 20, 180,20)]; // Here pass frame as per your requirement
p.progress = 0.5f;
[customView addSubview:p];
self.navigationItem.titleView = customView;
输出 ：
希望它可以帮助你。
SnapKit用户的解决方案。也将progressView上面的navigationBar.
extension UINavigationController {
public override func viewDidLoad() {
super.viewDidLoad()
let progressView = UIProgressView(progressViewStyle: .bar)
self.view.addSubview(progressView)
let navBar = self.navigationBar
progressView.snp.makeConstraints { make in
make.leading.trailing.equalToSuperview()
make.top.equalTo(navBar.snp.top)
}
progressView.setProgress(0.5, animated: false)
view.bringSubviewToFront(progressView)
}
}
我已经在我的博客文章中概述了如何做到这一点
TL;博士
创建将 UIProgressView 呈现为 UINavigationController 子视图的协议
创建更新 UIProgressView 的协议