问题
Hi I'm new to programming and I'm trying to make my first app for iPhones on Xcode.
My app contains of a button which opens a UIWebView when pressed and loads up a homepage.
Now I also want to add a Progress View to the WebView like Safari also uses, which indicates the progress of loading the page. How can I do that?
My code so far for loading the URL in the UIWebView:
.h
IBOutlet UIWebView *webView;
.m
- (void)viewDidLoad
{
[webView loadRequest:[NSURLRequest requestWithURL: [NSURL URLWithString:@"http:/www.google.com/"]]];
Thanks for your help!
回答1:
To have an accurate UIProgressView, you need to have some task that:
- You can get information from while it isn't complete
- Quantify its "completeness" as a percentage based on that information.
Now when you are loading your UIWebView, thats not possible. And Apple doesn't do it either. Apple often uses fake UIProgressViews to give you something to look at while the page is loading. Mail also uses fake progress views. Go try it out for yourself. This is how Apple's fake progress views work:
- The progress view starts moving at a slow, constant rate
- If the task finishes before the bar completes, it suddenly zips across the rest to 100% before disappearing
- If the task takes a long time, the progress view will stop at 95% and will stay there until the task is complete.
To achieve this, you will have to animate the progressView manually. You could subclass it but that would probably be a bit advanced for you. The simplest way would be this:
In myViewController.h
@interface myViewController : UIViewController {
BOOL theBool;
//IBOutlet means you can place the progressView in Interface Builder and connect it to your code
IBOutlet UIProgressView* myProgressView;
NSTimer *myTimer;
}
@end
In myViewController.m
#import "myViewController.h"
@implementation myViewController
- (void)webViewDidStartLoad:(UIWebView *)webView{
myProgressView.progress = 0;
theBool = false;
//0.01667 is roughly 1/60, so it will update at 60 FPS
myTimer = [NSTimer scheduledTimerWithTimeInterval:0.01667 target:self selector:@selector(timerCallback) userInfo:nil repeats:YES];
}
- (void)webViewDidFinishLoad:(UIWebView *)webView{
theBool = true;
}
-(void)timerCallback {
if (theBool) {
if (myProgressView.progress >= 1) {
myProgressView.hidden = true;
[myTimer invalidate];
}
else {
myProgressView.progress += 0.1;
}
}
else {
myProgressView.progress += 0.05;
if (myProgressView.progress >= 0.95) {
myProgressView.progress = 0.95;
}
}
}
@end
Then, where your task gets completed, set theBool = true; and the progress view will take care of itself. Change the values in the if statement thing to control the speed of the animation.
回答2:
Swift 2.2
class ViewController: UIViewController,UIWebViewDelegate {
@IBOutlet weak var webView: UIWebView!
@IBOutlet weak var activityIndicator: UIActivityIndicatorView!
@IBOutlet weak var myProgressView: UIProgressView!
var myTimer = NSTimer()
var theBool = Bool()
override func viewDidLoad() {
super.viewDidLoad()
let url = NSURL(string: "https://www.youtube.com")
let request = NSURLRequest(URL: url!)
activityIndicator.hidesWhenStopped = true
activityIndicator.startAnimating()
webView.loadRequest(request)
}
func timerCallback(){
if theBool {
if myProgressView.progress >= 1 {
myProgressView.hidden = true
myTimer.invalidate()
}else{
myProgressView.progress += 0.1
}
}else{
myProgressView.progress += 0.05
if myProgressView.progress >= 0.95 {
myProgressView.progress = 0.95
}
}
}
func webViewDidStartLoad(webView: UIWebView) {
activityIndicator.startAnimating()
myProgressView.progress = 0
theBool = false
myTimer = NSTimer.scheduledTimerWithTimeInterval(0.01667,target: self,selector: #selector(ViewController.timerCallback),userInfo: nil,repeats: true)
}
func webViewDidFinishLoad(webView: UIWebView) {
activityIndicator.stopAnimating()
theBool = true
}
}
回答3:
If anyone wants to do it in swift 3, I spent a few days trying to figure it out and finally did.
Here is the code :)
override func viewDidLoad() {
super.viewDidLoad()
let url = NSURL(string: "http://google.com")
let request = NSURLRequest(url: url as! URL)
webView.loadRequest(request as URLRequest)
webView.delegate=self
}
func webViewDidStartLoad(_ webView: UIWebView) {
self.progressView.setProgress(0.1, animated: false)
}
func webViewDidFinishLoad(_ webView: UIWebView) {
self.progressView.setProgress(1.0, animated: true)
}
func webView(_ webView: UIWebView, didFailLoadWithError error: Error) {
self.progressView.setProgress(1.0, animated: true)
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
// Dispose of any resources that can be recreated.
}
回答4:
I followed Wolflink's answer and found the same problem not having the progressView animated.
After reading NSTimer Class Reference:
https://developer.apple.com/library/Mac/documentation/Cocoa/Reference/Foundation/Classes/NSTimer_Class/Reference/NSTimer.html#//apple_ref/occ/clm/NSTimer/timerWithTimeInterval:target:selector:userInfo:repeats:
In Discussion you can read: "You must add the new timer to a run loop, using addTimer:forMode:. "
so I added
[[NSRunLoop currentRunLoop] addTimer:myTimer forMode:NSDefaultRunLoopMode];
after
myTimer = [NSTimer timerWithTimeInterval:0.01667 target:self selector:@selector(timerCallback) userInfo:nil repeats:YES];
It worked for me (As WolfLink recommended I did subclass UIProgressView )
回答5:
It's difficult (if even possible), since you would have to track all resources loaded by the site, but …
I have one idea. It's more of a trick than a real solution, but I think even Apple uses this in Messages app :)
- When you start loading the page, begin an animation to 90% of the progress (let's say with duration of 1.5 seconds, maybe be different for Wi-Fi, LTE, 3G, …).
- When page loads in meantime, quickly animate the progress to 100%. Done!
- If the page takes more time to load, the progress bar will stop at 90% and will wait there. Frustrating moment when the user watches slow spinning indicator in status bar! And then finally, the page finish loading and (as in bullet 2.) you play quick animation to 100%. Done!
I think we all know, that this is how Messages app works, since I don't believe sending SMS can be tracked with such accurate progress :)
回答6:
Apple now supplies the WebKit framework, which includes the WKWebView class which allows you to query the estimated progress using the property 'estimatedProgress', so you no longer must 'fake' the progress like you do to show a progress bar on a UIWebView.
回答7:
I would have added a comment, instead of adding an answer, but I don't yet have enough reputation to comment!
Only a couple of days ago I asked almost exactly the same question. In that question I included the solution I came up with. My solution is more complicated than WolfLink's but it does track the real progress of loading the page, although it isn't 100% accurate. As WolfLink has said that's not possible. My question can be found here: Progress bar for UIWebView
Note whichever way you do it you'll need to check the loading property of UIWebView to determine when the loading of the page is complete.
回答8:
I have tried the following pattern. It gave me a little bit better result. I am using WKWebview.
@IBOutlet weak var progressView: UIProgressView! // added in storyboard
@IBOutlet weak var webView: WKWebView!
override func viewDidLoad() {
super.viewDidLoad()
// Do any additional setup after loading the view.
setupEstimatedProgressObserver()
}
// Observe the WebViewClient for estimatedProgress value
private func setupEstimatedProgressObserver() {
estimatedProgressObserver = webView.observe(\.estimatedProgress, options: [.new]) { [weak self] webView, _ in
self?.progressView.progress = Float(webView.estimatedProgress)
}
}
//When WebView load finished in WKNavigationDelegate in didFinish method we will use the following approach
func webView(_ webView: WKWebView, didFinish navigation: WKNavigation!) {
self.progressView.progress = 1.0
DispatchQueue.main.asyncAfter(deadline: .now() + 0.5) {
// your code here
self.progressView.isHidden = true
}
}
来源：https://stackoverflow.com/questions/21263358/uiwebview-with-progress-bar