java - 后退按钮在 WebView 中无法正常运行 - Android

Question

我有 4 个 fragment ，它们使用查看寻呼机和选项卡在主要 Activity 中显示新闻。但是我的代码仅适用于第一个 fragment ，即选项卡 1

在我的主要 Activity 中

 @Override
    public void onBackPressed() {

        WebView mWebView = (WebView) findViewById(R.id.webview);
        if (mWebView.getVisibility() == View.VISIBLE) {
            mWebView.setVisibility(View.GONE);
            mWebView.loadUrl("about:blank");
        }
        else {

            super.onBackPressed();
        }

        return;
    }

因此，当按下后退按钮时，它会通过将用户带回主布局来隐藏 Web View 。它适用于选项卡 1

但是在 fragment 2、3、4 中——当我按下后退按钮时，它退出了应用程序。我使用与 fragment 1 中相同的代码

我发现 - mWebView.getVisibility() == View.VISIBLE 未变为真 - 即使网页 View 对于 fragment 2、3、4 可见

fragment 1 代码:

public class WSJFragment extends Fragment implements LoaderManager.LoaderCallbacks<List<News>> {


    .........


    public WSJFragment() {
        // Required empty public constructor
    }


    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        rootView = inflater.inflate(R.layout.newsview, container, false);

        ............

        NewsListView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
            @Override
            public void onItemClick(AdapterView<?> adapterView, View view, int position, long l) {
                // Find the current earthquake that was clicked on
                News currentNews = mAdapter.getItem(position);


                String newsUrl = currentNews.getUrl();

                progress.setVisibility(View.VISIBLE);

                mWebView.setVisibility(View.VISIBLE);

                mWebView.loadUrl(newsUrl);

                mWebView.setWebViewClient(new WebViewClient() {
                    @Override
                    public void onPageFinished(WebView view, String url) {
                        super.onPageFinished(mWebView, url);
                        progress.setVisibility(View.GONE);

                    }

                });


            }


        });


        return rootView;
    }


    ........

}

https://github.com/mrafz/W3News

Answer 1

我已 checkin 您的代码，进行此更改。

在 MainActivity 中用这个替换

@Override
public void onBackPressed() {

    if(mWebView != null){
        if (mWebView.getVisibility() == View.VISIBLE) {
            mWebView.setVisibility(View.GONE);
            mWebView.loadUrl("about:blank");
        }else {
            finish();
        }
    }else{ //if webview is null do something... here
    }
}

在所有 4 个 fragment 中替换为这个

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {
    rootView = inflater.inflate(R.layout.newsview, container, false);

    MainActivity.mWebView = (WebView) rootView.findViewById(R.id.webview);
    MainActivity.mWebView.setVisibility(View.GONE);

   //your remaining code here

 return rootView;
}

并且在您找到“mWebView” 对象的每个 fragment 中将其替换为MainActivity.mWebView