如何从UIWebview或dealloc UIWebview中删除缓存

Question

Every time I load a new page with UIWebView the before loaded page is shown for a short time.

How can I clear that cache? Another possibility would be to dealloc UIWebview . I tried that but than my UIWebView is always "empty". How should the alloc and dealloc be done in this case?

I noticed that the UIWebView is consuming about 10 MB RAM. Now the UIWebView is loaded together with the ViewController . And the view is autoreleased as well as the UIWebView is autoreleased. Wouldn't it be better to dealloc the WebView each time?

Solution:

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

    CGRect frame = CGRectMake(0, 0, 320, 480);
    self.webView = [[[UIWebView alloc]initWithFrame:frame] autorelease];
    self.webView.scalesPageToFit = YES;
    [self.view addSubview:self.webView];
}

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

    [self.webView removeFromSuperview];
    self.webView = nil;
}

Answer 1

I had nearly the same problem. I wanted the webview cache to be cleared, because everytime i reload a local webpage in an UIWebView , the old one is shown. So I found a solution by simply setting the cachePolicy property of the request. Use a NSMutableURLRequest to set this property. With all that everything works fine with reloading the UIWebView .

NSURL *url = [NSURL fileURLWithPath:MyHTMLFilePath]; 
 NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:url]; 
 [request setCachePolicy:NSURLRequestReloadIgnoringLocalCacheData];
 [self.webView loadRequest:request];

Hope that helps!

Answer 2

My solution to this problem was to create the UIWebView programmatically on viewWillAppear: and to release it on viewDidDisappear: , like this:

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

    self.webView = [[[UIWebView alloc]initWithFrame:exampleFrame] autorelease];
    self.webView.scalesPageToFit = YES;
    self.webView.delegate = self;
    self.webView.autoresizingMask = webViewBed.autoresizingMask;
    [exampleView addSubview:self.webView];
}
- (void) viewDidDisappear:(BOOL)animated {
    [super viewDidDisappear:animated];

    [self.webView removeFromSuperview];
    self.webView.delegate = nil;
    self.webView = nil;
}

If you do this and your UIWebView doesn't get released you should check it's retain count and understand who is retaining it.

Answer 3

如果要删除所有缓存的响应，您可能还想尝试这样的事情：

[[NSURLCache sharedURLCache] removeAllCachedResponses];

Answer 4

If I had to make a guess your property for webView is

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

Correct? The important part is the retain.

self.webView = [[UIWebView alloc]initWithFrame:frame];

The above code allocates a UIWebView (meaning retainCount = 1) and then adds it to self.webView, where it is retained again (retainCount = 2).

Change the code to the following, and your webView should be deallocated.

self.webView = [[[UIWebView alloc]initWithFrame:frame] autorelease];

---

addSubview: can only be called on UIViews.

//[self.navigationController addSubview:self.webView];

should be

[self.navigationController.view addSubview:self.webView];

Answer 5

I did something simpler, I just set the webView's alpha to 0 on loadRequest and 1 on webViewDidFinishLoad.

thewebview.alpha=0.0;
thewebview.backgroundColor=[UIColor whiteColor];
[thewebview loadRequest:[NSURLRequest requestWithURL:url(str)]];

and

- (void)webViewDidFinishLoad:(UIWebView *)webView {
    thewebview.alpha=1.0;
}

(Actually I have a fade-in, as rendering f.ex. a PDF can take 1/5 seconds or so.)

Answer 6

您也可以在webview消失后加载@“about：blank”，然后在您下次访问时它将为空。