Gestione memoria WebView

Question

Un'applicazione che sto sviluppando conserva diverse WebViews utilizzate per consentire un'esperienza di navigazione Web incorporata per alcune attività centralizzate intorno all'applicazione. Il problema che sto avendo è che dopo diverse ore di apertura e dopo un sacco di utilizzo le viste iniziano a costruire memoria. La mia comprensione della gestione della memoria in Objective-C è che una volta e l'oggetto viene rilasciato interamente (retain count = 0) e viene deallocato la quantità di memoria utilizzata dall'applicazione nel suo complesso diminuisce. Questo non sembra applicarsi alla mia situazione.

[webviewObject release]; 
webviewObject = nil; 

webviewObject = [[self createNewViewWithName:name] retain]; 

Quanto sopra è il codice che sto utilizzando. Ho provato a rilasciare la memoria e non creare una nuova istanza, ma senza fortuna. L'utilizzo della memoria continua semplicemente a crescere e, secondo gli strumenti, gli oggetti vengono rilasciati interamente. Mi sto perdendo qualcosa? La domanda potrebbe essere memorizzata nella cache come?

Answer 1

Ho avuto un problema simile in una visualizzazione Web in una delle mie app. Sembra che ci sia qualche perdita di memoria con le visualizzazioni web in iphone SDK. La mia app si è arrestata in modo anomalo quando c'era un testo di grandi dimensioni nella visualizzazione Web e altri problemi. This code mi ha aiutato a prevenire perdite di memoria. Spero che funzioni anche per te.

Ecco le istruzioni che puntano:

Prevenire perdite di memoria legati alla UIWebView può essere difficile. La documentazione di Apple sull'argomento è sparsa e non diretta, semplicemente perché UIWebView è una bestia complessa con molte classi sottostanti utilizzate all'interno. Questa Categoria Objective-C rappresenta una raccolta di idee, e le teorie (pensate alla magia piuttosto che alla scienza ..) hanno raccolto da vari blog e discussioni sull'argomento. Per ulteriori idee di gestione della memoria Objective-C , consultare WIJL: IOS Memory Gestione. Utilizzando la categoria è semplice:

scaricare il codice: UIWebView + Clean.zip

1. aggiungere i file .m UIWebView + Clean.h e al progetto. .
2. Import UIWebView+Clean.h in tutti i file che si desidera utilizzare la categoria in
3. utilizzare il metodo cleanForDealloc ovunque si ha intenzione di rilasciare un UIWebView:

[self.webView cleanForDealloc]; 
self.webView = nil; 

Questo è UIWebView+Clean.h:

/* 

    UIWebView+Clean.h 

    A simple category that performs recommended UIWebView clean before dealloc 

    Created by Jason Baker (jason@onejasonforsale.com) for TumbleOn on 3/18/12. 

    Copyright (c) 2012, Pocket Sized Giraffe, LLC 
    All rights reserved. 

    Redistribution and use in source and binary forms, with or without 
    modification, are permitted provided that the following conditions are met: 

    1. Redistributions of source code must retain the above copyright notice, this 
    list of conditions and the following disclaimer. 
    2. Redistributions in binary form must reproduce the above copyright notice, 
    this list of conditions and the following disclaimer in the documentation 
    and/or other materials provided with the distribution. 

    THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND 
    ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED 
    WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE 
    DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR 
    ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES 
    (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; 
    LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND 
    ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 
    (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS 
    SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 

    The views and conclusions contained in the software and documentation are those 
    of the authors and should not be interpreted as representing official policies, 
    either expressed or implied. 

*/ 

#import <Foundation/Foundation.h> 

@interface UIWebView (clean) 

// performs various cleanup activities recommended for UIWebView before dealloc. 
// see comments in implementation for usage examples 
- (void) cleanForDealloc; 

@end 

E questo è UIWebView+Clean.m:

/* 

UIWebView+Clean.h 

A simple category that performs recommended UIWebView clean before dealloc 

Created by Jason Baker (jason@onejasonforsale.com) for TumbleOn on 3/18/12. 

Copyright (c) 2012, Pocket Sized Giraffe, LLC 
All rights reserved. 

Redistribution and use in source and binary forms, with or without 
modification, are permitted provided that the following conditions are met: 

1. Redistributions of source code must retain the above copyright notice, this 
list of conditions and the following disclaimer. 
2. Redistributions in binary form must reproduce the above copyright notice, 
this list of conditions and the following disclaimer in the documentation 
and/or other materials provided with the distribution. 

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND 
ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED 
WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE 
DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR 
ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES 
(INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; 
LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND 
ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 
(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS 
SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 

The views and conclusions contained in the software and documentation are those 
of the authors and should not be interpreted as representing official policies, 
either expressed or implied. 

*/ 

#import "UIWebView+Clean.h" 

@implementation UIWebView (clean) 

/* 

Using this Category is easy, simply add this to the top of your file where 
you have a UIWebView: 

#import "UIWebView+Clean.h" 

Then, any time you want to throw away or deallocate a UIWebView instance, do 
the following before you throw it away: 

[self.webView cleanForDealloc]; 
self.webView = nil; 

If you still have leak issues, read the notes at the bottom of this class, 
they may help you. 

*/ 


- (void) cleanForDealloc 
{ 
    /* 

    There are several theories and rumors about UIWebView memory leaks, and how 
    to properly handle cleaning a UIWebView instance up before deallocation. This 
    method implements several of those recommendations. 

    #1: Various developers believe UIWebView may not properly throw away child 
    objects & views without forcing the UIWebView to load empty content before 
    dealloc. 

    Source: http://stackoverflow.com/questions/648396/does-uiwebview-leak-memory 

    */   
    [self loadHTMLString:@"" baseURL:nil]; 

    /* 

    #2: Others claim that UIWebView's will leak if they are loading content 
    during dealloc. 

    Source: http://stackoverflow.com/questions/6124020/uiwebview-leaking 

    */ 
    [self stopLoading]; 

    /* 

    #3: Apple recommends setting the delegate to nil before deallocation: 
    "Important: Before releasing an instance of UIWebView for which you have set 
    a delegate, you must first set the UIWebView delegate property to nil before 
    disposing of the UIWebView instance. This can be done, for example, in the 
    dealloc method where you dispose of the UIWebView." 

    Source: UIWebViewDelegate class reference  

    */ 
    self.delegate = nil; 


    /* 

    #4: If you're creating multiple child views for any given view, and you're 
    trying to deallocate an old child, that child is pointed to by the parent 
    view, and won't actually deallocate until that parent view dissapears. This 
    call below ensures that you are not creating many child views that will hang 
    around until the parent view is deallocated. 
    */ 

    [self removeFromSuperview]; 

    /* 

    Further Help with UIWebView leak problems: 

    #1: Consider implementing the following in your UIWebViewDelegate: 

    - (void) webViewDidFinishLoad:(UIWebView *)webView 
    { 
     //source: http://blog.techno-barje.fr/post/2010/10/04/UIWebView-secrets-part1-memory-leaks-on-xmlhttprequest/ 
     [[NSUserDefaults standardUserDefaults] setInteger:0 forKey:@"WebKitCacheModelPreferenceKey"]; 
    } 

    #2: If you can, avoid returning NO in your UIWebViewDelegate here: 

    - (BOOL)webView:(UIWebView *)webView shouldStartLoadWithRequest:(NSURLRequest *)request navigationType:(UIWebViewNavigationType)navigationType 
    { 
     //this source says don't do this: http://stackoverflow.com/questions/6421813/lots-of-uiwebview-memory-leaks 
     //return NO; 
     return YES; 
    } 

    #3: Some leaks appear to be fixed in IOS 4.1 
    Source: http://stackoverflow.com/questions/3857519/memory-leak-while-using-uiwebview-load-request-in-ios4-0 

    #4: When you create your UIWebImageView, disable link detection if possible:   

    webView.dataDetectorTypes = UIDataDetectorTypeNone; 

    (This is also the "Detect Links" checkbox on a UIWebView in Interfacte Builder.) 

    Sources: 
    http://www.iphonedevsdk.com/forum/iphone-sdk-development/46260-how-free-memory-after-uiwebview.html 
    http://www.iphonedevsdk.com/forum/iphone-sdk-development/29795-uiwebview-how-do-i-stop-detecting-links.html 
    http://blog.techno-barje.fr/post/2010/10/04/UIWebView-secrets-part2-leaks-on-release/ 

    #5: Consider cleaning the NSURLCache every so often: 

    [[NSURLCache sharedURLCache] removeAllCachedResponses]; 
    [[NSURLCache sharedURLCache] setDiskCapacity:0]; 
    [[NSURLCache sharedURLCache] setMemoryCapacity:0]; 

    Source: http://blog.techno-barje.fr/post/2010/10/04/UIWebView-secrets-part2-leaks-on-release/ 

    Be careful with this, as it may kill cache objects for currently executing URL 
    requests for your application, if you can't cleanly clear the whole cache in 
    your app in some place where you expect zero URLRequest to be executing, use 
    the following instead after you are done with each request (note that you won't 
    be able to do this w/ UIWebView's internal request objects..): 

    [[NSURLCache sharedURLCache] removeCachedResponseForRequest:request]; 

    Source: http://stackoverflow.com/questions/6542114/clearing-a-webviews-cache-for-local-files 

    */ 
} 

@end