Android - NPE in BrowserFrame

Question

I get this exception triggered by users occasionally that I cannot reproduce. Since it's issued from looper I suppose it is result of Handler-type callback. I found similar bug on Google code but putting the solution into code didn't solve it. The problem is at this line of code in BrowserFrame:

WebAddress uri = new WebAddress(
    mCallbackProxy.getBackForwardList().getCurrentItem()
   .getUrl());

Which throws this Exception because I suppose mCallbackProxy is null

java.lang.NullPointerException
at android.webkit.BrowserFrame.handleMessage(BrowserFrame.java:348)
at android.os.Handler.dispatchMessage(Handler.java:99)
at android.os.Looper.loop(Looper.java:123)
at android.webkit.WebViewCore$WebCoreThread.run(WebViewCore.java:471)
at java.lang.Thread.run(Thread.java:1060)

And the questions are - will this forclose the app? And how do I work around this bug?

link text

Answer 1

So I invested some time into investigating this problem. The error comes from this code in BrowserFrame:

        case FRAME_COMPLETED: {
            if (mSettings.getSavePassword() && hasPasswordField()) {
                if (WebView.DEBUG) {
                    Assert.assertNotNull(mCallbackProxy.getBackForwardList()
                            .getCurrentItem());
                }
                WebAddress uri = new WebAddress(
                        mCallbackProxy.getBackForwardList().getCurrentItem()
                        .getUrl());
                String schemePlusHost = uri.mScheme + uri.mHost;
                String[] up = mDatabase.getUsernamePassword(schemePlusHost);
                if (up != null && up[0] != null) {
                    setUsernamePassword(up[0], up[1]);
                }
            }
            CacheManager.trimCacheIfNeeded();
            break;
        }

Specifically from this line

  WebAddress uri = new WebAddress(
                        mCallbackProxy.getBackForwardList().getCurrentItem()

The only place where mCallbackProxy is set is in BrowserFrame constructor which gets null for CallbackProxy parameter for whatever reason. Since I cannot try/catch this code (It is called from Looper) the only way I can deal with this error is to set WebSettings#setSavePassword(false) when I initialize WebView in my code. In which case IF statement fails and offending code is never executed