AsyncTask的使用

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package com.lbp.mode4;import android.os.AsyncTask;import android.os.Bundle;import android.support.v7.app.AppCompatActivity;import android.view.View;import android.view.ViewGroup;import android.widget.BaseAdapter;import android.widget.ListView;import android.widget.TextView;import com.google.gson.Gson;import com.lbp.mode4.bean.MyBean;import com.lbp.mode4.util.GetJsonUtil;import java.util.ArrayList;import java.util.List;public class MainActivity extends AppCompatActivity {    public String urstring="http://api.expoon.com/AppNews/getNewsList/type/1/p/1";    List<MyBean.DataBean> Beanlist = new ArrayList<MyBean.DataBean>();    private MyAdapter adapter;    private ListView lv;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        lv = (ListView) findViewById(R.id.lv);        adapter = new MyAdapter();        lv.setAdapter(adapter);        new MAsyncTask().execute(urstring);    }    private class MAsyncTask extends AsyncTask<String,Void,String>{        @Override        protected String doInBackground(String... strings) {            String str = strings[0];            String getjson = GetJsonUtil.getjson(str);            return getjson;        }        @Override        protected void onPostExecute(String s) {            super.onPostExecute(s);            Gson gson = new Gson();            MyBean json = gson.fromJson(s,MyBean.class);            List<MyBean.DataBean> data = json.getData();            Beanlist.addAll(data);            adapter.notifyDataSetChanged();        }    }    class MyAdapter extends BaseAdapter{        @Override        public int getCount() {            return Beanlist.size();        }        @Override        public Object getItem(int i) {            return Beanlist.get(i);        }        @Override        public long getItemId(int i) {            return i;        }        @Override        public View getView(int i, View view, ViewGroup viewGroup) {            if(view==null){                view = View.inflate(MainActivity.this, R.layout.item, null);            }            TextView tv1 = view.findViewById(R.id.tv1);            TextView tv2 = view.findViewById(R.id.tv2);            TextView tv3 = view.findViewById(R.id.tv3);            TextView tv4 = view.findViewById(R.id.tv4);            tv1.setText(Beanlist.get(i).getPic_url());            tv2.setText(Beanlist.get(i).getNews_id());            tv3.setText(Beanlist.get(i).getNews_summary());            tv4.setText(Beanlist.get(i).getNews_title());            return view;        }    }}

package com.lbp.mode4.util;import java.io.BufferedReader;import java.io.IOException;import java.io.InputStream;import java.io.InputStreamReader;import java.net.HttpURLConnection;import java.net.MalformedURLException;import java.net.URL;/** * author:Created by WangZhiQiang on 17/11/2. */public class GetJsonUtil {    public static  String getjson(String urlstring){        try {            URL url = new URL(urlstring);            HttpURLConnection urlConnection = (HttpURLConnection) url.openConnection();            InputStream stream = urlConnection.getInputStream();            BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(stream));            StringBuilder stringBuilder = new StringBuilder();            String line="";            while((line=bufferedReader.readLine())!=null){                stringBuilder.append(line);            }            String s = stringBuilder.toString();            return s;        } catch (MalformedURLException e) {            e.printStackTrace();        } catch (IOException e) {            e.printStackTrace();        }        return "";    }}

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