android webview抓坏网址

在我的应用程序中,我从Web服务接收URL作为字符串并将其加载到WebView.

mainContentText = (WebView) findViewById(R.id.mainContentText); 
mainContentText.getSettings().setJavaScriptEnabled(true);
mainContentText.setWebViewClient(new CustomWebClient());

mainContentText.loadUrl(url);

private class CustomWebClient extends WebViewClient{

        private static final String TAG = "WebWiewActivity";

        @Override
        public boolean shouldOverrideUrlLoading(WebView view, String url) {
            Log.d(TAG, "loading: " + url);
            return false;
        }

        @Override
        public void onReceivedError(WebView view, int errorCode, String description, String failingUrl) {
            super.onReceivedError(view, errorCode, description, failingUrl);
            Log.e(TAG, String.format("*ERROR*  Code: %d  Desc: %s  URL: %s", errorCode, description, failingUrl));
        }
    }

当测试的情况,当URL不好(一个随机字符串,url = "abc")我只是在收到默认的错误页面,但没有onReceivedError不shouldOverrideUrlLoading回调并没有异常
我如何能赶上这样的情况？