Trying to convert this activity into a fragment in android studio, no luck till now

问题

This is my test activity and I want to convert this into a fragment. Please guide me how to convert this activity into a fragment which is inside a tabview. I am new bee in android app development and this is beyond my reach for now. Any help or suggestion is appreciated.

package in.catking.catking;

import android.content.Intent;
import android.os.AsyncTask;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.AdapterView;
import android.widget.ListView;
import android.widget.ProgressBar;
import android.widget.Toast;

import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;

import java.util.ArrayList;
import java.util.HashMap;

public class test2 extends AppCompatActivity {

    String API_KEY = "ABA"; // API owner  XYX
    String NEWS_SOURCE = "in";
    public ListView listNews;
    ProgressBar loader;

    public ArrayList<HashMap<String, String>> dataList = new ArrayList<HashMap<String, String>>();
    static final String KEY_AUTHOR = "author";
    static final String KEY_TITLE = "title";
    static final String KEY_DESCRIPTION = "description";
    static final String KEY_URL = "url";
    static final String KEY_URLTOIMAGE = "urlToImage";
    static final String KEY_PUBLISHEDAT = "publishedAt";
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_test2);

        listNews = (ListView) findViewById(R.id.listNews);
        loader = (ProgressBar) findViewById(R.id.loader);
        listNews.setEmptyView(loader);



        if(Function.isNetworkAvailable(getApplicationContext()))
        {
            DownloadNews newsTask = new DownloadNews();
            newsTask.execute();
        }else{
            Toast.makeText(getApplicationContext(), "No Internet Connection", Toast.LENGTH_LONG).show();
        }

    }


    class DownloadNews extends AsyncTask<String, Void, String> {
        @Override
        protected void onPreExecute() {
            super.onPreExecute();

        }
        protected String doInBackground(String... args) {
            String xml = "";

            String urlParameters = "";//xml = Function.excuteGet("https://newsapi.org/v2/top-headlines?country="+NEWS_SOURCE+"&apiKey="+API_KEY, urlParameters);
            xml = Function.excuteGet("https://newsapi.org/v2/top-headlines?country="+NEWS_SOURCE+"&apiKey="+API_KEY, urlParameters);
            return  xml;
        }
        @Override
        protected void onPostExecute(String xml) {

            if(xml.length()>10){ // Just checking if not empty

                try {
                    JSONObject jsonResponse = new JSONObject(xml);
                    JSONArray jsonArray = jsonResponse.optJSONArray("articles");

                    for (int i = 0; i < jsonArray.length(); i++) {
                        JSONObject jsonObject = jsonArray.getJSONObject(i);
                        HashMap<String, String> map = new HashMap<String, String>();
                        map.put(KEY_AUTHOR, jsonObject.optString(KEY_AUTHOR).toString());
                        map.put(KEY_TITLE, jsonObject.optString(KEY_TITLE).toString());
                        map.put(KEY_DESCRIPTION, jsonObject.optString(KEY_DESCRIPTION).toString());
                        map.put(KEY_URL, jsonObject.optString(KEY_URL).toString());
                        map.put(KEY_URLTOIMAGE, jsonObject.optString(KEY_URLTOIMAGE).toString());
                        map.put(KEY_PUBLISHEDAT, jsonObject.optString(KEY_PUBLISHEDAT).toString());
                        dataList.add(map);
                    }
                } catch (JSONException e) {
                    Toast.makeText(getApplicationContext(), "Unexpected error", Toast.LENGTH_SHORT).show();
                }

                ListNewsAdapter adapter = new ListNewsAdapter(test2.this, dataList);
                listNews.setAdapter(adapter);

                listNews.setOnItemClickListener(new AdapterView.OnItemClickListener() {
                    public void onItemClick(AdapterView<?> parent, View view,
                                            int position, long id) {
                        Intent i = new Intent(test2.this, DetailsActivity.class);
                        i.putExtra("url", dataList.get(+position).get(KEY_URL));
                        startActivity(i);
                    }
                });

            }else{
                Toast.makeText(getApplicationContext(), "No news found", Toast.LENGTH_SHORT).show();
            }
        }



    }


}

this is my ListNewsAdapter

package in.catking.catking;


import android.app.Activity;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.ImageView;
import android.widget.TextView;

import com.squareup.picasso.Picasso;

import java.util.ArrayList;
import java.util.HashMap;

/**
 * vvklr
 */

class ListNewsAdapter extends BaseAdapter {
    private Activity activity;
    private ArrayList<HashMap<String, String>> data;

    public ListNewsAdapter(Activity a, ArrayList<HashMap<String, String>> d) {
        activity = a;
        data=d;
    }
    public int getCount() {
        return data.size();
    }
    public Object getItem(int position) {
        return position;
    }
    public long getItemId(int position) {
        return position;
    }
    public View getView(int position, View convertView, ViewGroup parent) {
        ListNewsViewHolder holder = null;
        if (convertView == null) {
            holder = new ListNewsViewHolder();
            convertView = LayoutInflater.from(activity).inflate(
                    R.layout.list_row, parent, false);
            holder.galleryImage = (ImageView) convertView.findViewById(R.id.galleryImage);
            holder.author = (TextView) convertView.findViewById(R.id.author);
            holder.title = (TextView) convertView.findViewById(R.id.title);
            holder.sdetails = (TextView) convertView.findViewById(R.id.sdetails);
            holder.time = (TextView) convertView.findViewById(R.id.time);
            convertView.setTag(holder);
        } else {
            holder = (ListNewsViewHolder) convertView.getTag();
        }
        holder.galleryImage.setId(position);
        holder.author.setId(position);
        holder.title.setId(position);
        holder.sdetails.setId(position);
        holder.time.setId(position);

        HashMap<String, String> song = new HashMap<String, String>();
        song = data.get(position);

        try{
            holder.author.setText(song.get(test2.KEY_AUTHOR));
            holder.title.setText(song.get(test2.KEY_TITLE));
            holder.time.setText(song.get(test2.KEY_PUBLISHEDAT));
            holder.sdetails.setText(song.get(test2.KEY_DESCRIPTION));

            if(song.get(test2.KEY_URLTOIMAGE).toString().length() < 5)
            {
                holder.galleryImage.setVisibility(View.GONE);
            }else{
                Picasso.with(activity)
                        .load(song.get(test2.KEY_URLTOIMAGE).toString())
                        .resize(300, 200)
                        .into(holder.galleryImage);
            }
        }catch(Exception e) {}
        return convertView;
    }
}

class ListNewsViewHolder {
    ImageView galleryImage;
    TextView author, title, sdetails, time;
}

I am trying to convert this activity into a fragment FragmentA but I am not able to do it. Anyone please help or suggest.

回答1:

Generally speaking, to convert an Activity to a Fragment, usually needs to do following things:

Move the layout from activity_test2.xml to fragment_a.xml. If the Fragment should appear below a Toolbar in its parent Activity, add the attribute app:layout_behavior="@string/appbar_scrolling_view_behavior"> to the root Layout of the Fragment XML.
Move the onCreate code from the Activity to the onCreateView method inside the Fragment. Your own methods can simply be copied into the Fragment class.

To keep findViewById() working inside the Fragment, do it like this:

public ListView listNews; 
ProgressBar loader;

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

    listNews = rootView.findViewById(R.id.listNews);
    loader = rootView.findViewById(R.id.loader);

    return rootView;
}

Replace all getApplicationContext() calls with getActivity()
If you have overridden any activity specific lifecycle methods, the code may need to be moved into the corresponding Fragment lifecycle method. For example, the code from onDestroy inside the Activity is moved to onDestroyView inside the Fragment. The Activity and Fragment lifecycle and how they are related can be found here.

The AsyncTask inner class can simply be moved inside the Fragment class. As far as I can see right now, the Adapter also can stay the same. You may (not totally sure) only need to replace private Activity activity; with private Context context.

Hope this helps you.

来源：https://stackoverflow.com/questions/54069248/trying-to-convert-this-activity-into-a-fragment-in-android-studio-no-luck-till

标签

android-activity

fragment