返回不在SherlockFragment中的WebView中工作

Question

尝试在SherlockFragment中使用WebView创建应用程序但是当我在WebView中单击某个链接后按回来时我希望它返回到上一页，但所有发生的事情是它关闭了应用程序。我想要的是回到上一页，如果它不能再回去，那么关闭应用程序。任何帮助都会很棒！

代码：

WebView myWebView;

public View onCreateView(LayoutInflater inflater, ViewGroup container,
        Bundle savedInstanceState) {

    return inflater.inflate(R.layout.fragment_4, container, false);
}

String mURL = "http://www.facebook.com";

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    Log.v("DetailFragment", "onCreate()");

}

@Override
public void onActivityCreated(Bundle savedInstanceState) {
    super.onActivityCreated(savedInstanceState);
    Log.v("DetailFragment", "onActivityCreated()");
    if (savedInstanceState != null) {
        mURL = savedInstanceState.getString("currentURL", "");
    }

    if (!mURL.trim().equalsIgnoreCase("")) {
        myWebView = (WebView) getView().findViewById(R.id.webView);
        myWebView.loadUrl(mURL.trim());
        myWebView.getSettings().setJavaScriptEnabled(true);
        myWebView.setWebViewClient(new WebViewClient());
        myWebView.getSettings().setBuiltInZoomControls(true);
        myWebView.getSettings().setSupportZoom(true);
        myWebView.getSettings().setUseWideViewPort(true);
        myWebView.getSettings().setLoadWithOverviewMode(true);
        getView().setOnKeyListener( new OnKeyListener()
        {
            @Override
            public boolean onKey( View v, int keyCode, KeyEvent event )  {
               return  myOnKeyDown(keyCode);
            }
        } );
    }

}

@Override
public void onSaveInstanceState(Bundle outState) {
    super.onSaveInstanceState(outState);
    outState.putString("currentURL", mURL);
}

public void setURLContent(String URL) {
    mURL = URL;
}

public void updateURLContent(String URL) {
    mURL = URL;
    myWebView.getSettings().setJavaScriptEnabled(true);
    myWebView.loadUrl(mURL.trim());
    myWebView.setWebViewClient(new WebViewClient());
    myWebView.getSettings().setBuiltInZoomControls(true);
    myWebView.getSettings().setSupportZoom(true);
    myWebView.getSettings().setUseWideViewPort(true);
    myWebView.getSettings().setLoadWithOverviewMode(true);
}

public class WebAppInterface {
    Context mContext;

    /** Instantiate the interface and set the context */
    WebAppInterface(Context fragment_4) {
        mContext = fragment_4;
    }

    /** Show a toast from the web page */
    @JavascriptInterface
    public void showToast(String toast) {
        Toast.makeText(mContext, toast, Toast.LENGTH_SHORT).show();
    }

    private class MyWebViewClient extends WebViewClient {
        @Override
        public boolean shouldOverrideUrlLoading(WebView view, String url) {
            if (Uri.parse(url).getHost().equals("http://www.facebook.com")) {
                // This is my web site, so do not override; let my WebView
                // load the page
                return false;
            }
            return false;
        }
    }
}
 public boolean myOnKeyDown(int key_code) {
        if ((key_code == KeyEvent.KEYCODE_BACK)
                && myWebView.canGoBack()) {
            myWebView.goBack();
            return true;
        }
        return false;
    }


@Override
public void onCreateOptionsMenu(Menu menu, MenuInflater inflater) {
    inflater.inflate(R.menu.fragment_4, menu);
    return;
}

}

XML：

 <WebView xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:id="@+id/webView"
   android:layout_width="fill_parent"
   android:layout_height="fill_parent" />