android - 执行FragmentTransaction后，WebViewFragment webView为null

目前，我的应用程序在左侧设置了一个ListFragment，在右侧设置了一个DetailsFragment（类似于下面平板电脑上的布局）。
在details片段（列表旁边的片段）上，我有一个goto deal按钮，当按下该按钮时，应该用WebViewFragment替换detailsFragment。
我遇到的问题是，当试图在webviewfragment中加载url时，WebView为空。

WebViewFragment webViewFragment = new WebViewFragment();

FragmentTransaction transaction = getFragmentManager().beginTransaction();

// Replace whatever is in the fragment_container view with this fragment,
// and add the transaction to the back stack
transaction.replace(R.id.deal_details_fragment, webViewFragment);
transaction.addToBackStack(null);

// Commit the transaction
transaction.commit();

// Set the url
if (webViewFragment.getWebView()==null)
    Log.d("webviewfragment", "is null");
webViewFragment.getWebView().loadUrl("http://www.google.com");

下面是我的主布局，它定义了最初的两个片段。

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
          android:id="@+id/main_activity_layout"

    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:orientation="horizontal" >

  <fragment
      android:name="com.bencallis.dealpad.DealListFragment"
      android:id="@+id/deal_list_fragment"
      android:layout_weight="1"
      android:layout_width="0px"
      android:layout_height="match_parent" >
      <!-- Preview: layout=@layout/deal_list_fragment -->
  </fragment>
  <fragment
      android:name="com.bencallis.dealpad.DealDetailsFragment"
      android:id="@+id/deal_details_fragment"
      android:layout_weight="2"
      android:layout_width="0px"
      android:layout_height="match_parent" >
      <!-- Preview: layout=@layout/deal_details_fragment -->
  </fragment>

</LinearLayout>

似乎没有完全创建webviewfragment，因为WebView尚未初始化。我在网上查过，但关于WebViewFragment的信息很少。
如何确保WebView在WebViewFragment中初始化？

最佳答案

在espiandev的大力帮助下，我成功地获得了一个工作的webview。为了确保在片段中而不是在web浏览器应用程序中打开链接，我创建了一个扩展webviewclinet的简单innerwebview客户端。

public class DealWebViewFragment extends Fragment {

    private WebView mWebView;
    private boolean mIsWebViewAvailable;
    private String mUrl = null;

    /**
     * Creates a new fragment which loads the supplied url as soon as it can
     * @param url the url to load once initialised
     */
    public DealWebViewFragment(String url) {
        super();
        mUrl = url;
    }

    /**
     * Called to instantiate the view. Creates and returns the WebView.
     */
    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
            Bundle savedInstanceState) {

        if (mWebView != null) {
            mWebView.destroy();
        }
        mWebView = new WebView(getActivity());
        mWebView.setOnKeyListener(new OnKeyListener(){


            @Override
            public boolean onKey(View v, int keyCode, KeyEvent event) {
                  if ((keyCode == KeyEvent.KEYCODE_BACK) && mWebView.canGoBack()) {
                        mWebView.goBack();
                        return true;
                    }
                    return false;
            }

        });
        mWebView.setWebViewClient(new InnerWebViewClient()); // forces it to open in app
        mWebView.loadUrl(mUrl);
        mIsWebViewAvailable = true;
        WebSettings settings = mWebView.getSettings();
        settings.setJavaScriptEnabled(true);
        return mWebView;
    }

    /**
     * Convenience method for loading a url. Will fail if {@link View} is not initialised (but won't throw an {@link Exception})
     * @param url
     */
    public void loadUrl(String url) {
        if (mIsWebViewAvailable) getWebView().loadUrl(mUrl = url);
        else Log.w("ImprovedWebViewFragment", "WebView cannot be found. Check the view and fragment have been loaded.");
    }

    /**
     * Called when the fragment is visible to the user and actively running. Resumes the WebView.
     */
    @Override
    public void onPause() {
        super.onPause();
        mWebView.onPause();
    }

    /**
     * Called when the fragment is no longer resumed. Pauses the WebView.
     */
    @Override
    public void onResume() {
        mWebView.onResume();
        super.onResume();
    }

    /**
     * Called when the WebView has been detached from the fragment.
     * The WebView is no longer available after this time.
     */
    @Override
    public void onDestroyView() {
        mIsWebViewAvailable = false;
        super.onDestroyView();
    }

    /**
     * Called when the fragment is no longer in use. Destroys the internal state of the WebView.
     */
    @Override
    public void onDestroy() {
        if (mWebView != null) {
            mWebView.destroy();
            mWebView = null;
        }
        super.onDestroy();
    }

    /**
     * Gets the WebView.
     */
    public WebView getWebView() {
        return mIsWebViewAvailable ? mWebView : null;
    }

    /* To ensure links open within the application */
    private class InnerWebViewClient extends WebViewClient {
        @Override
        public boolean shouldOverrideUrlLoading(WebView view, String url) {
            view.loadUrl(url);
            return true;
        }


    }

希望这对将来的人有用。