带有 Webview 的片段利用硬件后退按钮转到上一个网页

Posted 2023-05-07

【中文标题】带有 Webview 的片段利用硬件后退按钮转到上一个网页

【英文标题】：Fragment with Webview utilize harware back button to go to previous webpage

【发布时间】：2015-07-09 22:33:51

【问题描述】：

这似乎在堆栈溢出时被问了很多，但随着 SDK 的更改似乎不再可以实现答案（我可能错了！）。

我一直在尝试允许 MainActivity 中的片段使用硬件按钮返回片段中 web 视图中的上一页。

我尝试过使用 return super.onKeyDown(keyCode, event); 作为函数的一部分，但 onKeyDown 在我的项目中无效。

这是我的包含 web 视图的 BlogFragment：

public class BlogFragment extends Fragment 
// TODO: Rename parameter arguments, choose names that match
// the fragment initialization parameters, e.g. ARG_ITEM_NUMBER
private static final String ARG_PARAM1 = "param1";
private static final String ARG_PARAM2 = "param2";

// TODO: Rename and change types of parameters
private String mParam1;
private String mParam2;

WebView wv;
private OnFragmentInteractionListener mListener;

/**
 * Use this factory method to create a new instance of
 * this fragment using the provided parameters.
 *
 * @param param1 Parameter 1.
 * @param param2 Parameter 2.
 * @return A new instance of fragment blog.
 */
// TODO: Rename and change types and number of parameters
public static BlogFragment newInstance(String param1, String param2) 
    BlogFragment fragment = new BlogFragment();
    Bundle args = new Bundle();
    args.putString(ARG_PARAM1, param1);
    args.putString(ARG_PARAM2, param2);
    fragment.setArguments(args);
    return fragment;



public static boolean canGoBack()
    return wv.canGoBack();


public static void goBack()
    wv.goBack();


public BlogFragment() 
    // Required empty public constructor


@Override
public void onCreate(Bundle savedInstanceState) 
    super.onCreate(savedInstanceState);
    if (getArguments() != null) 
        mParam1 = getArguments().getString(ARG_PARAM1);
        mParam2 = getArguments().getString(ARG_PARAM2);
    


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


    View view=inflater.inflate(R.layout.fragment_blog, null);

    wv = (WebView) view.findViewById(R.id.webview);
    WebSettings settings = wv.getSettings();
    wv.setWebChromeClient(new WebChromeClient() 
    );
    final String mimeType = "text/html";
    final String encoding = "UTF-8";
    String html = getHTML();
    settings.setjavascriptEnabled(true);
    wv.loadDataWithBaseURL("http://www.bbc.co.uk", html, mimeType, encoding, "");

    return view;



// TODO: Rename method, update argument and hook method into UI event
public void onButtonPressed(Uri uri) 
    if (mListener != null) 
        mListener.onFragmentInteraction(uri);
    


@Override
public void onAttach(Activity activity) 
    super.onAttach(activity);
    try 
        mListener = (OnFragmentInteractionListener) activity;
     catch (ClassCastException e) 
        throw new ClassCastException(activity.toString()
                + " must implement OnFragmentInteractionListener");
    



@Override
public void onDetach() 
    super.onDetach();
    mListener = null;


public String getHTML() 
    String html = "<iframe width=\"100%\" height=\"100%\" src=\"http://blog.mrgyro.co.uk\" frameborder=\"0\" allowfullscreen></iframe>";
    return html;



/**
 * This interface must be implemented by activities that contain this
 * fragment to allow an interaction in this fragment to be communicated
 * to the activity and potentially other fragments contained in that
 * activity.
 * <p/>
 * See the android Training lesson <a href=
 * "http://developer.android.com/training/basics/fragments/communicating.html"
 * >Communicating with Other Fragments</a> for more information.
 */
public interface OnFragmentInteractionListener 
    // TODO: Update argument type and name
    public void onFragmentInteraction(Uri uri);

活动：

public class MainActivity extends ActionBarActivity
    implements NavigationDrawerFragment.NavigationDrawerCallbacks, BlogFragment.OnFragmentInteractionListener, HomeFragment.OnFragmentInteractionListener 


/**
 * Fragment managing the behaviors, interactions and presentation of the navigation drawer.
 */
private NavigationDrawerFragment mNavigationDrawerFragment;

/**
 * Used to store the last screen title. For use in @link #restoreActionBar().
 */
private CharSequence mTitle;

@Override
protected void onCreate(Bundle savedInstanceState) 
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    mNavigationDrawerFragment = (NavigationDrawerFragment)
            getSupportFragmentManager().findFragmentById(R.id.navigation_drawer);
    mTitle = getTitle();

    // Set up the drawer.
    mNavigationDrawerFragment.setUp(
            R.id.navigation_drawer,
            (DrawerLayout) findViewById(R.id.drawer_layout));



@Override
public void onBackPressed() 
    if(BlogFragment.canGoBack())
        BlogFragment.goBack();
    else
        super.onBackPressed();
    



@Override
public void onNavigationDrawerItemSelected(int position) 
    android.support.v4.app.FragmentManager fragmentManager = getSupportFragmentManager();
    android.support.v4.app.FragmentTransaction transaction = fragmentManager.beginTransaction();

    switch (position) 
        case 0:
            HomeFragment homeFragment = new HomeFragment();
            transaction.replace(R.id.container, homeFragment);
            break;
        case 1:
            BlogFragment blogFragment = new BlogFragment();
            transaction.replace(R.id.container, blogFragment);
            break;

    
    transaction.commit();


public void onSectionAttached(int number) 
    switch (number) 
        case 1:
            mTitle = getString(R.string.title_section1);
            break;
        case 2:
            mTitle = getString(R.string.title_section2);
            break;
        case 3:
            mTitle = getString(R.string.title_section3);
            break;
        case 4:
            mTitle = getString(R.string.title_section4);
            break;
    


public void restoreActionBar() 
    ActionBar actionBar = getSupportActionBar();
    actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_STANDARD);
    actionBar.setDisplayShowTitleEnabled(true);
    actionBar.setTitle(mTitle);



@Override
public boolean onCreateOptionsMenu(Menu menu) 
    if (!mNavigationDrawerFragment.isDrawerOpen()) 
        // Only show items in the action bar relevant to this screen
        // if the drawer is not showing. Otherwise, let the drawer
        // decide what to show in the action bar.
        getMenuInflater().inflate(R.menu.main, menu);
        restoreActionBar();
        return true;
    
    return super.onCreateOptionsMenu(menu);


@Override
public boolean onOptionsItemSelected(MenuItem item) 
    // Handle action bar item clicks here. The action bar will
    // automatically handle clicks on the Home/Up button, so long
    // as you specify a parent activity in AndroidManifest.xml.
    int id = item.getItemId();

    //noinspection SimplifiableIfStatement
    //if (id == R.id.action_settings) 
   //     return true;
   // 

    return super.onOptionsItemSelected(item);


@Override
public void onFragmentInteraction(Uri uri) 



/**
 * A placeholder fragment containing a simple view.
 */
public static class PlaceholderFragment extends Fragment 
    /**
     * The fragment argument representing the section number for this
     * fragment.
     */
    private static final String ARG_SECTION_NUMBER = "section_number";

    /**
     * Returns a new instance of this fragment for the given section
     * number.
     */
    public static PlaceholderFragment newInstance(int sectionNumber) 
        PlaceholderFragment fragment = new PlaceholderFragment();
        Bundle args = new Bundle();
        args.putInt(ARG_SECTION_NUMBER, sectionNumber);
        fragment.setArguments(args);
        return fragment;
    

    public PlaceholderFragment() 
    

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) 
        View rootView = null;
        rootView = inflater.inflate(R.layout.fragment_home, container, false);
        switch(getArguments().getInt(ARG_SECTION_NUMBER)) 
            case 1:
                rootView = inflater.inflate(R.layout.fragment_home, container, false);
                break;
            case 2:
                rootView = inflater.inflate(R.layout.fragment_blog, container, false);
                break;
            case 3:
               // rootView = inflater.inflate(R.layout.fragment_test, container, false);
                break;
            case 4:
                //rootView = inflater.inflate(R.layout.fragment_info, container, false);
                break;
            default:
                Log.e("TAG", "Unrecognized section: " + getArguments().getInt(ARG_SECTION_NUMBER));

        
        return rootView;
    

    @Override
    public void onAttach(Activity activity) 
        super.onAttach(activity);
        ((MainActivity) activity).onSectionAttached(
                getArguments().getInt(ARG_SECTION_NUMBER));
    

提前致谢。

编辑：我已经用我最近的尝试更新了博客片段，但是当尝试静态 wv.canGoBack() 和 wv.goBack() 时都返回错误“非静态字段 'wv' 不能从静态上下文

【参考方案1】：

尝试在您的Activity 中覆盖onBackPressed() 并使其戳WebView。

顺便说一句 - 您也可以发布包含 onKeyDown 方法的 Activity。

编辑：首先实例化片段：

BlogFragment blogFragment = new BlogFragment();
blogFragment.canGoBack();

然后从您的方法中删除static。 :)

OPs 实施（感谢 Klotor） 在 MainActivity 实现的头部：

BlogFragment blogFragment = new BlogFragment();

然后执行：

public void onBackPressed() 

    blogFragment.canGoBack();
    if(blogFragment.canGoBack())
        blogFragment.goBack();
    else
        super.onBackPressed();
    

片段在 onBackPressed 之外实例化，以防止在使用方法在片段之间导航时崩溃。 在这种情况下，您需要实例化片段的新实例，而不是一个全新的片段。

【讨论】：

你好@Klotor，我已经尝试过这个，我遇到了我作为编辑添加到我原来的帖子中的错误。我也包括了这个活动。

@Lister 好吧，要么删除 static，要么在你的 canGoBack 和 goBack 方法中添加一个参数，我会编辑我的答案

我已经删除了静态，但是现在当调用 BlogFragment.CanGoBack() 和 goBack 时，我得到一个“非静态方法 .goBack() 不能从静态上下文中引用。工作室建议的修复是读取静态，但这又会导致原来的问题。

在你调用它之前把我添加到答案中的代码放在你调用方法的行上，将大写 B 更改为一个小写 ;)

放在Activity中的onBackPressed() :)

【参考方案2】：

** 在 OnCreateView 内的 Fragment 类中放入以下代码**

 @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) 
        // Inflate the layout for this fragment
        view = inflater.inflate(R.layout.your_layout, container, false);

      mWebView = (WebView) view.findViewById(R.id.webView);
        mWebView.getSettings().setJavaScriptEnabled(true);
        mWebView.setWebViewClient(new MyWebViewClient());
        mWebView.loadUrl(expertsUrl);

        return view;
    


private class MyWebViewClient extends WebViewClient 
        @Override
        public boolean shouldOverrideUrlLoading(WebView view, String url) 
            view.loadUrl(url);
            return true;
        
    

**在 MainActivity 类中放下面的代码 **

@Override
public void onBackPressed() 
    if (WebViewFragment.mWebView!=null) 
        if (WebViewFragment.mWebView.canGoBack()) 
            WebViewFragment.mWebView.goBack();
        
        else 
            super.onBackPressed();
        
        
    

用你的 Fragment 替换 WebViewFragment -> mWebView -> 与您的网络视图

希望对你有帮助！！！！