java - 将 Activity 类更改为 Fragment

Question

我是一个相当新的 Android 开发者。我有一个扩展 Activity 的类，我想更改为 Fragment。我知道作为一个 fragment 它会使用 onCreateView(LayoutInflater, ViewGroup, Bundle)但我不知道如何将我的工作 Activity 更改为 fragment 。

编辑:我已经开始工作了。现在的问题是我的 RSS 提要列表没有显示。我收到加载指示器，完成后它就会停止，但列表不显示。

编辑:实际上列表正在显示，但文本与背景颜色相同，所以我看不到它。

这是我现有的 Activity :

import java.io.IOException;
import java.net.MalformedURLException;
import java.net.URL;

import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.ParserConfigurationException;

import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.Node;
import org.w3c.dom.NodeList;
import org.xml.sax.InputSource;
import org.xml.sax.SAXException;


import android.app.Activity;
import android.content.Intent;
import android.content.res.Configuration;
import android.graphics.Color;
import android.graphics.drawable.ColorDrawable;
import android.net.Uri;
import android.os.AsyncTask;
import android.os.Bundle;
import android.view.View;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemClickListener;
import android.widget.ImageView;
import android.widget.ListView;
import android.widget.ProgressBar;
import android.widget.TextView;

public class ActionAlerts extends Activity {

    ListView listFeed;
    ProgressBar prgLoading;
    TextView txtAlert;

    ActionAlertsAdapter la;

    static String[] title;
    static String[] pubDate;
    static String[] link;

    String URLFeed;

    URL Feed;
    DocumentBuilder db;
    Document doc;
    NodeList nodeList;
    Bundle rssBundle = new Bundle();


    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.actionalerts);

        Bundle b = getIntent().getExtras();

        URLFeed = b.getString("url");



        la = new ActionAlertsAdapter(this);

        listFeed = (ListView) findViewById(R.id.listFeed);
        prgLoading = (ProgressBar) findViewById(R.id.prgLoading);
        txtAlert = (TextView) findViewById(R.id.txtAlert);

        // ColorDrawable whiteColor = new ColorDrawable(Color.WHITE);
        ColorDrawable blackColor = new ColorDrawable(Color.BLACK);
        listFeed.setDivider(blackColor);
        listFeed.setDividerHeight(3);


        new getDataTask().execute();


        listFeed.setOnItemClickListener(new OnItemClickListener() {

            public void onItemClick(AdapterView<?> arg0, View arg1, int position,
                    long arg3) {
                // TODO Auto-generated method stub


                Intent web = new Intent(ActionAlerts.this, WebBrowser.class);
                rssBundle.putString("myURL", link[position]);
                web.putExtras(rssBundle);
                startActivity(web);

            }
        });
    }


    /** this class is used to handle thread */
    public class getDataTask extends AsyncTask<Void, Void, Void>{


        @Override
         protected void onPreExecute() {
          // TODO Auto-generated method stub

        }

        @Override
        protected Void doInBackground(Void... arg0) {
            // TODO Auto-generated method stub
            getDataFromFeed();

            return null;
        }

        @Override
        protected void onPostExecute(Void result) {
            // TODO Auto-generated method stub
            //dialog.dismiss();
            prgLoading.setVisibility(8);
            if(title != null){
                listFeed.setVisibility(0);
                listFeed.setAdapter(la);
            }else{
                txtAlert.setVisibility(0);
            }
        }
    }

    /*
     * This code is used to get data from feed and store them
     * to array attributes
     */
    public void getDataFromFeed(){

        try {
            Feed = new URL(URLFeed);
            DocumentBuilderFactory dbf= DocumentBuilderFactory.newInstance();
            db = dbf.newDocumentBuilder();
            doc = db.parse(new InputSource(Feed.openStream()));
            doc.getDocumentElement().normalize();
            nodeList = doc.getElementsByTagName("item");

            title = new String[nodeList.getLength()];
            pubDate = new String[nodeList.getLength()];
            link = new String[nodeList.getLength()];

            for(int i=0;i<nodeList.getLength();i++){
                Node node = nodeList.item(i);

                Element fstElmnt = (Element) node;

                NodeList titleList = fstElmnt.getElementsByTagName("title");
                Element titleElement = (Element) titleList.item(0);
                titleList = titleElement.getChildNodes();
                title[i] = ((Node) titleList.item(0)).getNodeValue();

                NodeList pubDateList = fstElmnt.getElementsByTagName("pubDate");
                Element pubDateElement = (Element) pubDateList.item(0);
                pubDateList = pubDateElement.getChildNodes();
                pubDate[i] = ((Node) pubDateList.item(0)).getNodeValue();
                // chops off the " +0000" on date
                pubDate[i] = pubDate[i].substring(0, pubDate[i].length()-14);

                NodeList linkList = fstElmnt.getElementsByTagName("link");
                Element linkElement = (Element) linkList.item(0);
                linkList = linkElement.getChildNodes();
                link[i] = ((Node) linkList.item(0)).getNodeValue();
            }

        } catch (MalformedURLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }catch (ParserConfigurationException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (SAXException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }   
    }

    @Override
    public void onConfigurationChanged(final Configuration newConfig)
    {
        // Ignore orientation change to keep activity from restarting
        super.onConfigurationChanged(newConfig);
    }
}

这是我的适配器类:

package kyfb.android.kyfb.com.kyfb;

import android.content.Context;
import android.graphics.Color;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.RelativeLayout;
import android.widget.TextView;

class ActionAlertsAdapter extends BaseAdapter {
    private LayoutInflater inflater;

    public ActionAlertsAdapter(Context context) {

        inflater = LayoutInflater.from(context);
    }

    public int getCount() {
        // TODO Auto-generated method stub

        return ActionAlertsFragment.title.length;
    }

    public Object getItem(int position) {
        // TODO Auto-generated method stub
        return position;
    }

    public long getItemId(int position) {
        // TODO Auto-generated method stub
        return position;
    }

    public View getView(int position, View convertView, ViewGroup parent) {
        // TODO Auto-generated method stub
        ViewHolder holder;

        if(convertView == null){
            convertView = inflater.inflate(R.layout.item_feed, null);
            holder = new ViewHolder();
            holder.lytItemFeed = (RelativeLayout) convertView.findViewById(R.id.lytItemFeed);
            holder.txtTitle= (TextView) convertView.findViewById(R.id.txtTitle);
            holder.txtPubDate = (TextView) convertView.findViewById(R.id.txtPubDate);

            convertView.setTag(holder);
        }else{
            holder = (ViewHolder) convertView.getTag();
        }

        if((position%2)!=0){
            // holder.lytItemFeed.setBackgroundResource(R.drawable.row_1);
            holder.lytItemFeed.setBackgroundColor(Color.TRANSPARENT);
        }else{
            // holder.lytItemFeed.setBackgroundResource(R.drawable.row_2);
            holder.lytItemFeed.setBackgroundColor(Color.TRANSPARENT);
        }

        holder.txtTitle.setText(ActionAlertsFragment.title[position]);
        holder.txtPubDate.setText(ActionAlertsFragment.pubDate[position]);

        holder.txtTitle.setTextColor(Color.BLACK);
        holder.txtPubDate.setTextColor(Color.BLACK);

        return convertView;
    }

    static class ViewHolder {
        TextView txtTitle, txtPubDate;
        RelativeLayout lytItemFeed;
    }
}

这是我试图从上面的 Activity 类中创建的 Fragment 类:

   package kyfb.android.kyfb.com.kyfb;

import android.app.Fragment;
import android.app.ListFragment;
import android.content.Context;
import android.content.Intent;
import android.content.res.Configuration;
import android.graphics.Color;
import android.graphics.drawable.ColorDrawable;
import android.os.AsyncTask;
import android.os.Bundle;
import android.support.v4.app.FragmentActivity;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemClickListener;
import android.widget.ListView;
import android.widget.ProgressBar;
import android.widget.TextView;

import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.Node;
import org.w3c.dom.NodeList;
import org.xml.sax.InputSource;
import org.xml.sax.SAXException;

import java.io.IOException;
import java.net.MalformedURLException;
import java.net.URL;

import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.ParserConfigurationException;

public class ActionAlertsFragment extends Fragment {

    ListView listFeed;
    ProgressBar prgLoading;
    TextView txtAlert;

    ActionAlertsAdapter la;

    static String[] title;
    static String[] pubDate;
    static String[] link;

    String URLFeed;

    URL Feed;
    DocumentBuilder db;
    Document doc;
    NodeList nodeList;
    Bundle rssBundle = new Bundle();

    public ActionAlertsFragment(){}

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

        super.onCreateView(inflater, container, savedInstanceState);
        // View rootView = inflater.inflate(R.layout.fragment_actionalerts, container, false);
        View rootView = inflater.inflate(R.layout.fragment_actionalerts, null);

        URLFeed = "http://kyfbnewsroom.com/category/notifications/feed";

        Context ctx = rootView.getContext();

        la = new ActionAlertsAdapter(ctx);

        listFeed = (ListView) rootView.findViewById(R.id.listFeed);
        prgLoading = (ProgressBar) rootView.findViewById(R.id.prgLoading);
        txtAlert = (TextView) rootView.findViewById(R.id.txtAlert);

        // ColorDrawable whiteColor = new ColorDrawable(Color.WHITE);
        ColorDrawable blackColor = new ColorDrawable(Color.BLACK);
        listFeed.setDivider(blackColor);
        listFeed.setDividerHeight(3);

        new getDataTask().execute();

        listFeed.setOnItemClickListener(new OnItemClickListener() {

            public void onItemClick(AdapterView<?> arg0, View arg1, int position,
                                    long arg3) {
                // TODO Auto-generated method stub

                // Intent web = new Intent(ActionAlertsFragment.this, WebBrowser.class);
                // rssBundle.putString("myURL", link[position]);
                // web.putExtras(rssBundle);
                // startActivity(web);
            }
        });

        return rootView;
    }

    /** this class is used to handle thread */
    public class getDataTask extends AsyncTask<Void, Void, Void> {

        @Override
        protected void onPreExecute() {
            // TODO Auto-generated method stub
        }

        @Override
        protected Void doInBackground(Void... arg0) {
            // TODO Auto-generated method stub
            getDataFromFeed();

            return null;
        }

        @Override
        protected void onPostExecute(Void result) {
            // TODO Auto-generated method stub
            //dialog.dismiss();
            prgLoading.setVisibility(8);
            if(title != null){
                listFeed.setVisibility(0);
                listFeed.setAdapter(la);
            }else{
                txtAlert.setVisibility(0);
            }
        }
    }

    /*
     * This code is used to get data from feed and store them
     * to array attributes
     */
    public void getDataFromFeed(){

        try {
            Feed = new URL(URLFeed);
            DocumentBuilderFactory dbf= DocumentBuilderFactory.newInstance();
            db = dbf.newDocumentBuilder();
            doc = db.parse(new InputSource(Feed.openStream()));
            doc.getDocumentElement().normalize();
            nodeList = doc.getElementsByTagName("item");

            title = new String[nodeList.getLength()];
            pubDate = new String[nodeList.getLength()];
            link = new String[nodeList.getLength()];

            for(int i=0;i<nodeList.getLength();i++){
                Node node = nodeList.item(i);

                Element fstElmnt = (Element) node;

                NodeList titleList = fstElmnt.getElementsByTagName("title");
                Element titleElement = (Element) titleList.item(0);
                titleList = titleElement.getChildNodes();
                title[i] = ((Node) titleList.item(0)).getNodeValue();

                NodeList pubDateList = fstElmnt.getElementsByTagName("pubDate");
                Element pubDateElement = (Element) pubDateList.item(0);
                pubDateList = pubDateElement.getChildNodes();
                pubDate[i] = ((Node) pubDateList.item(0)).getNodeValue();
                // chops off the " +0000" on date
                pubDate[i] = pubDate[i].substring(0, pubDate[i].length()-14);

                NodeList linkList = fstElmnt.getElementsByTagName("link");
                Element linkElement = (Element) linkList.item(0);
                linkList = linkElement.getChildNodes();
                link[i] = ((Node) linkList.item(0)).getNodeValue();
            }

        } catch (MalformedURLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }catch (ParserConfigurationException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (SAXException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }

    @Override
    public void onConfigurationChanged(final Configuration newConfig)
    {
        // Ignore orientation change to keep activity from restarting
        super.onConfigurationChanged(newConfig);
    }
}

Answer 1

首先更改此设置。

View rootView = inflater.inflate(R.layout.fragment_actionalerts, null);

至

View rootView = inflater.inflate(R.layout.fragment_actionalerts, container, false);

并使用Fragment Context作为getActivity()。