android 中使用返回按钮不能退出 web 视图

我从 http://developer.android.com/guide/webapps/webview.html. 中找的这段代码。使用这段代码进入web 视图后,但是不能退出web 视图,除非我快速的点击两次返回按钮。有办法可以点击返回按钮一次就退出web视图?

@Override
 public boolean onKeyDown(int keyCode, KeyEvent event) {
     // Check if the key event was the BACK key and if there's history
     if ((keyCode == KeyEvent.KEYCODE_BACK) && myWebView.canGoBack() {
         myWebView.goBack();
         return true;
     }
     // If it wasn't the BACK key or there's no web page history, bubble up to the default
     // system behavior (probably exit the activity)
    return super.onKeyDown(keyCode, event);
 }

在 WebViewClient 中的 onPageFinished 方法中,你要清除历史,然后点击一次就可以:

 @Override
    public void onPageFinished(WebView view, String url) {
        // TODO Auto-generated method stub
        super.onPageFinished(view, url);

        if (url.equals("http://www.yourcurrenturl.com")) {              
            view.clearHistory();
        }
    }