如何以编程方式滚动到UIWebView中的一行？

Question

I want to save the state where the user left the webView (which is loading a local html file) so that the next time when he enters the same view, he is taken to the same line of text that he was reading the previous time. I think that could be achieved by saving the scroll value in an integer every time the user swipe the document, and when he enters the view the next time we use the value that was saved previously and scroll the view using a javascript command or "CG" things. Any idea?

Answer 1

From Lyndsey Scott's Answer:

To save and retrieve your scrollview offset from NSUserDefaults , set your UIWebView's delegate and try this:

var viewLaidoutSubviews = false // <-- variable to prevent the viewDidLayoutSubviews code from happening more than once

// Save your content offset when the view disappears
override func viewWillDisappear(animated: Bool) {
var userDefaults = NSUserDefaults.standardUserDefaults()
userDefaults.setValue(NSStringFromCGPoint(myBrowser.scrollView.contentOffset), forKey: "scroll_offset")
userDefaults.synchronize()

viewLaidoutSubviews = false
}

// Retrieve and set your content offset when the view re-appears
// and its subviews are first laid out
override func viewDidLayoutSubviews() {

if (!viewLaidoutSubviews) {
    // If a scroll_offset is store in NSUserDefaults, use it
    var userDefaults = NSUserDefaults.standardUserDefaults()
    var scrollOffset:CGPoint? = CGPointFromString(userDefaults.valueForKey("scroll_offset") as? NSString)
    if let position:CGPoint = scrollOffset {
        myBrowser.scrollView.delegate = self
        myBrowser.scrollView.setContentOffset(position, animated: false)
    }
    viewLaidoutSubviews = true
}
}

And utilize your UIWebView's webViewDidFinishLoad delegate method to update the scroll offset in the case that the web view didn't finish rendering before the view laid out its subviews:

// Retrieve and set your content offset once the web view has
// finished rendering (in case it hasn't finished rendering
// by the time the view's subviews were laid out)
func webViewDidFinishLoad(webView: UIWebView) {

// If a scroll_offset is store in NSUserDefaults, use it
var userDefaults = NSUserDefaults.standardUserDefaults()
var scrollOffset:CGPoint? = CGPointFromString(userDefaults.valueForKey("scroll_offset") as? NSString)
if let position:CGPoint = scrollOffset {
    myBrowser.scrollView.delegate = self
    myBrowser.scrollView.setContentOffset(position, animated: true)
}
}

But note, your NSUserDefaults value will also persist between app launches unless you delete it.

Answer 2

and an objective c solution:

@interface ViewController () <UIWebViewDelegate>

@property (weak, nonatomic) IBOutlet UIWebView *webView;

@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];

    [self.webView loadRequest:[NSURLRequest requestWithURL:[NSURL URLWithString:@"http://yourwebsite.com"]]];
}

- (void)webViewDidFinishLoad:(UIWebView *)webView {
    NSUserDefaults *userDefaults = [NSUserDefaults standardUserDefaults];
    if ([userDefaults objectForKey:@"contentOffset"]) {
    webView.scrollView.contentOffset = CGPointFromString([userDefaults objectForKey:@"contentOffset"]);
    }
}

- (void)viewWillDisappear:(BOOL)animated {
    [super viewWillDisappear:animated];

    NSUserDefaults *userDefaults = [NSUserDefaults standardUserDefaults];
    [userDefaults setObject:NSStringFromCGPoint(self.webView.scrollView.contentOffset) forKey:@"contentOffset"];
    [userDefaults synchronize];
}