Android Web视图变为空

我有一个显示网络视图的片段，为了保留正在显示的网站，我保存如下状态：

@Override
public void onSaveInstanceState(Bundle outState) {
    super.onSaveInstanceState(outState);
    /*Saves the currently displayed webpage and the browser history*/
    webView.saveState(outState);        
}

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
        Bundle savedInstanceState) {
    rootView = inflater.inflate(R.layout.fragment_page_detail,
            container, false);
    webView = (WebView) rootView.findViewById(R.id.page_detail_webview);

    progressBar = (ProgressBar) rootView.findViewById(R.id.op_progress);

    webView.setWebChromeClient(new WebChromeClient() {
        public void onProgressChanged(WebView view, int progress) {

            progressBar.setVisibility(View.VISIBLE);
            progressBar.setProgress(progress);
            if (progress == 100) {

                progressBar.setVisibility(View.GONE);
            }
        }
    });
    webView.setWebViewClient(new StockStreamWebViewClient());
    webView.getSettings().setBuiltInZoomControls(true);
    /*Restores the saved browser history if there is any*/
    if (savedInstanceState != null) {
        webView.restoreState(savedInstanceState);

    } else if (mItem != null) {
        webView.loadUrl(mItem.content);

    }
    return rootView;
}

然后我恢复它如下：

@Override
public void onSaveInstanceState(Bundle outState) {
    super.onSaveInstanceState(outState);
    /*Saves the currently displayed webpage and the browser history*/
    webView.saveState(outState);        
}

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
        Bundle savedInstanceState) {
    rootView = inflater.inflate(R.layout.fragment_page_detail,
            container, false);
    webView = (WebView) rootView.findViewById(R.id.page_detail_webview);

    progressBar = (ProgressBar) rootView.findViewById(R.id.op_progress);

    webView.setWebChromeClient(new WebChromeClient() {
        public void onProgressChanged(WebView view, int progress) {

            progressBar.setVisibility(View.VISIBLE);
            progressBar.setProgress(progress);
            if (progress == 100) {

                progressBar.setVisibility(View.GONE);
            }
        }
    });
    webView.setWebViewClient(new StockStreamWebViewClient());
    webView.getSettings().setBuiltInZoomControls(true);
    /*Restores the saved browser history if there is any*/
    if (savedInstanceState != null) {
        webView.restoreState(savedInstanceState);

    } else if (mItem != null) {
        webView.loadUrl(mItem.content);

    }
    return rootView;
}

要允许用户返回WebView，我的活动中有以下代码：

@Override
public void onBackPressed() {

    if (!clientFragment.onBackPressed()) {
        super.onBackPressed();
    }
  }
}

这段代码在我的片段中：

public boolean onBackPressed() {
    if (webView != null && webView.canGoBack()) {
        webView.goBack();
        return true;
    } else {
        return false;
    }
}

@Override
public void onSaveInstanceState(Bundle outState) {
    super.onSaveInstanceState(outState);
    if (clientFragment != null) {
        outState.putInt(CLIENT_FRAGMENT_ID, clientFragment.getId());
    }
}

if (savedInstanceState != null
            && savedInstanceState.containsKey(CLIENT_FRAGMENT_ID)) {
        clientFragment = (PageDetailFragment) getSupportFragmentManager()
                .findFragmentById(savedInstanceState.getInt(CLIENT_FRAGMENT_ID));
    }

当我旋转设备时，屏幕将正确绘制，WebView将恢复上一页，但当我按下back时，WebView为空

为什么会这样

谢谢， 安卓开发中的ANkh

SimonVT正确地指出，我可能正在调用活动中的空片段或新片段

因此，我将此代码添加到我的活动中，以保存片段的ID：

public boolean onBackPressed() {
    if (webView != null && webView.canGoBack()) {
        webView.goBack();
        return true;
    } else {
        return false;
    }
}

@Override
public void onSaveInstanceState(Bundle outState) {
    super.onSaveInstanceState(outState);
    if (clientFragment != null) {
        outState.putInt(CLIENT_FRAGMENT_ID, clientFragment.getId());
    }
}

if (savedInstanceState != null
            && savedInstanceState.containsKey(CLIENT_FRAGMENT_ID)) {
        clientFragment = (PageDetailFragment) getSupportFragmentManager()
                .findFragmentById(savedInstanceState.getInt(CLIENT_FRAGMENT_ID));
    }

此代码用于将引用还原到正确的片段：

public boolean onBackPressed() {
    if (webView != null && webView.canGoBack()) {
        webView.goBack();
        return true;
    } else {
        return false;
    }
}

@Override
public void onSaveInstanceState(Bundle outState) {
    super.onSaveInstanceState(outState);
    if (clientFragment != null) {
        outState.putInt(CLIENT_FRAGMENT_ID, clientFragment.getId());
    }
}

if (savedInstanceState != null
            && savedInstanceState.containsKey(CLIENT_FRAGMENT_ID)) {
        clientFragment = (PageDetailFragment) getSupportFragmentManager()
                .findFragmentById(savedInstanceState.getInt(CLIENT_FRAGMENT_ID));
    }

PageDetailFragment是我的扩展片段

谢谢， 安卡