使用WKScriptMessageHandler时内存泄漏

Question

使用WKScriptMessageHandler时内存泄漏

Red*_*den 9 macos memory-leaks webkit ios javascriptcore

不确定我是否遇到了一个错误WebKit或我正在做一些可怕的错误,但我无法弄清楚如何使用WKScriptMessageHandler而不会导致WKScriptMessage.body泄漏中包含的任何值.

我能够组建一个最小的Mac项目来隔离问题,但无济于事.

在主视图控制器中:

class ViewController: NSViewController {
  var webView: WKWebView?

  override func viewDidLoad() {
    super.viewDidLoad()
    let userContentController = WKUserContentController()
    userContentController.addScriptMessageHandler(self, name: "handler")
    let configuration = WKWebViewConfiguration()
    configuration.userContentController = userContentController
    webView = WKWebView(frame: CGRectZero, configuration: configuration)
    view.addSubview(webView!)

    let path = NSBundle.mainBundle().pathForResource("index", ofType: "html")
    let url = NSURL(fileURLWithPath: path!)!
    webView?.loadRequest(NSURLRequest(URL: url))
  }
}

extension ViewController: WKScriptMessageHandler {
  func userContentController(userContentController: WKUserContentController, didReceiveScriptMessage message: WKScriptMessage) {
     print(message.body)
   }
}

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然后在index.html文件中:

<html>
  <head></head>
  <body>
    <script type="text/javascript">
      webkit.messageHandlers.handler.postMessage("Here's a random number for you: " + Math.random() * 10)
    </script>
  </body>
</html>

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当我运行项目然后在Instruments中打开内存调试器时,我看到以下泄漏:

如果我添加一个重新加载请求的按钮,并且这样做了几十次,那么应用程序的内存占用量会不断增长,并在达到某个阈值后崩溃.在这个最小的例子中崩溃可能需要一段时间,但在我的应用程序中,我每秒收到几条消息,崩溃所需的时间不到10秒.

整个项目可以在这里下载.

知道发生了什么事吗？

Answer 1

小智 17

我在iOS 9 SDK上遇到过同样的问题.

我注意到userContentController.addScriptMessageHandler(self, name: "handler")会保留处理程序的引用.要防止泄漏,只需在不再需要时删除消息处理程序.例如,当您解雇所述控制器时,请调用将要呼叫的清理方法removeScriptMessageHandlerForName().

您可以考虑移动addScriptMessageHandler()到viewWillAppear并添加相应的removeScriptMessageHandlerForName()调用viewWillDisappear.

最初的问题是关于作为被泄露的消息正文传递的值.这个答案突出了这样一个事实:`WKUserContentController`保留了注册的处理程序,直到它们被删除,这一点很重要,但与消息体的泄漏无关.这是一个很好的答案,但它是一个不同问题的答案. (3认同)

Answer 2

bda*_*ash 6

您所看到的是一个WebKit错误:https://bugs.webkit.org/show_bug.cgi？ id = 136140.它刚刚在WebKit trunk中修复,但似乎没有合并到任何WebKit更新中.

您可以通过添加一个-dealloc来WKScriptMessage补偿过度保留来解决这个问题.它可能看起来像这样:

//
//  WKScriptMessage+WKScriptMessageLeakFix.m
//  TestWebkitMessages
//
//  Created by Mark Rowe on 6/27/15.
//  Copyright © Mark Rowe.
//
//  Permission is hereby granted, free of charge, to any person obtaining a copy of this software and
//  associated documentation files (the "Software"), to deal in the Software without restriction,
//  including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense,
//  and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so,
//  subject to the following conditions:
//
//  The above copyright notice and this permission notice shall be included in all copies or substantial
//  portions of the Software.
//
//  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT
//  LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
//  IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
//  WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
//  SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

#import <mach-o/dyld.h>
#import <objc/runtime.h>
#import <WebKit/WebKit.h>

// Work around <https://webkit.org/b/136140> WKScriptMessage leaks its body

@interface WKScriptMessage (WKScriptMessageLeakFix)
@end

@implementation WKScriptMessage (WKScriptMessageLeakFix)

+ (void)load
{
    // <https://webkit.org/b/136140> was fixed in WebKit trunk prior to the first v601 build being released.
    // Enable the workaround in WebKit versions < 601. In the unlikely event that the fix is backported, this
    // version check will need to be updated.
    int32_t version = NSVersionOfRunTimeLibrary("WebKit");
    int32_t majorVersion = version >> 16;
    if (majorVersion > 600)
        return;

    // Add our -dealloc to WKScriptMessage. If -[WKScriptMessage dealloc] already existed
    // we'd need to swap implementations instead.
    Method fixedDealloc = class_getInstanceMethod(self, @selector(fixedDealloc));
    IMP fixedDeallocIMP = method_getImplementation(fixedDealloc);
    class_addMethod(self, @selector(dealloc), fixedDeallocIMP, method_getTypeEncoding(fixedDealloc));
}

- (void)fixedDealloc
{
    // Compensate for the over-retain in -[WKScriptMessage _initWithBody:webView:frameInfo:name:].
    [self.body release];

    // Call our WKScriptMessage's superclass -dealloc implementation.
    [super dealloc];
}

@end

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将它放在项目的Objective-C文件中,设置要包含的文件的编译器标志-fno-objc-arc,它应该为您处理泄漏.

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