1

我是安卓新手。我想要一个 ListView 并从 json 获取数据。我发现了很多教程，但他们没有 AsyncTask。我不知道，我如何将 AsyncTask 添加到该代码中！？

package de.test.ListView;

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

import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;
import android.app.ListActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemClickListener;
import android.widget.ListAdapter;
import android.widget.ListView;
import android.widget.SimpleAdapter;
import android.widget.Toast;

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

        ArrayList<HashMap<String, String>> mylist = new ArrayList<HashMap<String, String>>();


        JSONObject json = jsonFunctions.getJSONfromURL("http://api.geonames.org/earthquakesJSON?north=44.1&south=-9.9&east=-22.4&west=55.2&username=demo");

        try{

            JSONArray  earthquakes = json.getJSONArray("earthquakes");

            for(int i=0;i<earthquakes.length();i++){                        
                HashMap<String, String> map = new HashMap<String, String>();    
                JSONObject e = earthquakes.getJSONObject(i);

                map.put("id",  String.valueOf(i));
                map.put("name", "Earthquake name:" + e.getString("eqid"));
                map.put("magnitude", "Magnitude: " +  e.getString("magnitude"));
                mylist.add(map);            
            }       
        }catch(JSONException e)        {
             Log.e("log_tag", "Error parsing data "+e.toString());
        }

        ListAdapter adapter = new SimpleAdapter(this, mylist , R.layout.main, 
                        new String[] { "name", "magnitude" }, 
                        new int[] { R.id.item_title, R.id.item_subtitle });

        setListAdapter(adapter);

        final ListView lv = getListView();
        lv.setTextFilterEnabled(true);  
        lv.setOnItemClickListener(new OnItemClickListener() {
            public void onItemClick(AdapterView<?> parent, View view, int position, long id) {              
                @SuppressWarnings("unchecked")
                HashMap<String, String> o = (HashMap<String, String>) lv.getItemAtPosition(position);                   
                Toast.makeText(MeinListViewActivity.this, "ID '" + o.get("id") + "' was clicked.", Toast.LENGTH_SHORT).show(); 

            }
        });
    }
}

和 jsonFunctions

package de.test.ListView;

import java.io.BufferedReader;
import java.io.InputStream;
import java.io.InputStreamReader;
import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.client.HttpClient;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.impl.client.DefaultHttpClient;
import org.json.JSONException;
import org.json.JSONObject;

import android.util.Log;

public class jsonFunctions {


    public static JSONObject getJSONfromURL(String url){
        InputStream is = null;
        String result = "";
        JSONObject jArray = null;

        //http post
        try{
                HttpClient httpclient = new DefaultHttpClient();
                HttpPost httppost = new HttpPost(url);
                HttpResponse response = httpclient.execute(httppost);
                HttpEntity entity = response.getEntity();
                is = entity.getContent();

        }catch(Exception e){
                Log.e("log_tag", "Error in http connection "+e.toString());
        }

      //convert response to string
        try{
                BufferedReader reader = new BufferedReader(new InputStreamReader(is,"iso-8859-1"),8);
                StringBuilder sb = new StringBuilder();
                String line = null;
                while ((line = reader.readLine()) != null) {
                        sb.append(line + "\n");
                }
                is.close();
                result=sb.toString();
        }catch(Exception e){
                Log.e("log_tag", "Error converting result "+e.toString());
        }

        try{

            jArray = new JSONObject(result);            
        }catch(JSONException e){
                Log.e("log_tag", "Error parsing data "+e.toString());
        }

        return jArray;
    }
}
4

1 回答 1

1

你可以使用我的代码来获取 Gson 的东西

public void executeHttpGet() throws Exception {

    BufferedReader in = null;
    try {
        HttpClient client = new DefaultHttpClient();
        HttpGet request = new HttpGet();
        request.setURI(new URI(
                "http://cardsplatform.appspot.com/cardeckplatform_details"));
        HttpResponse response = client.execute(request);
        in = new BufferedReader(new InputStreamReader(response.getEntity()
                .getContent()));
        StringBuffer sb = new StringBuffer("");
        String line = "";
        String NL = System.getProperty("line.separator");
        while ((line = in.readLine()) != null) {
            sb.append(line + NL);
        }
        in.close();
        String json = sb.toString();
        System.out.println(json);
        Gson gson = new Gson();
        Type collectionType = new TypeToken<MyClass>() {
        }.getType();
        MyClass myclass= gson.fromJson(json, collectionType);
        GameEnvironment.get().getHandler().post(new Runnable() {

            @Override
            public void run() {
                addElementsToTableLayout();                 
            }
        });
    } finally {
        if (in != null) {
            try {
                in.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }
}

现在，如果您希望使用异步任务来完成它，您应该做的就是将它放在 onBackground 方法上

例如

private class DownloadFile extends
        AsyncTask<PluginDetails, Integer, MyBoolean> {
    MyBoolean downloaded;
    ProgressDialog mProgressDialog;
    boolean canceled=false;
    public DownloadFile(MyBoolean downloaded) {
        this.downloaded=downloaded;
    }
    @Override
    protected MyBoolean doInBackground(PluginDetails... pluginDetail) {
        try {

            URL url = new URL("http://cardsplatform.appspot.com"
                    );
            URLConnection connection = url.openConnection();
            connection.connect();
            // this will be useful so that you can show a typical 0-100%
            // progress bar
            long fileLength = getSize();

            // download the file
            InputStream input = new BufferedInputStream(
                    connection.getInputStream());
            FileOutputStream output = StaticFunctions
                    .getPluginOutputStream(pluginDetail[0].getFilename());

            byte data[] = new byte[4096];
            long total = 0;
            int count;
            while ((count = input.read(data)) != -1 && !canceled) {
                total += count;
                System.out.println((int) (total * 100 / fileLength));
                // publishing the progress....
                publishProgress((int) (total * 100 / fileLength));
                output.write(data, 0, count);
            }
            output.flush();
            output.close();
            input.close();
            if(!canceled)
                downloaded.setFlag(true);
            else{//case its was canceled

            }
        } catch (Exception e) {
            cannotMakeConnection();
            e.printStackTrace();
        }
        return null;
    }
enter code here
于 2012-10-06T18:57:59.803 回答