java - 关闭android程序立即运行json中的应用程序

Question

大家好，我编写了一个程序来从服务器获取数据并使用 json 在 ListView 中显示数据但是当我启动应用程序时，应用程序立即关闭。我检查了我的 list ，没问题，不知道该怎么办，请帮助我!

主要 Activity 代码:

package com.example.delta.travel;

import android.app.ListActivity;
import android.app.ProgressDialog;
import android.os.AsyncTask;
import android.os.Bundle;
import android.support.design.widget.FloatingActionButton;
import android.support.design.widget.Snackbar;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.Toolbar;
import android.view.View;
import android.view.Menu;
import android.view.MenuItem;
import android.widget.ListAdapter;
import android.widget.SimpleAdapter;
import android.widget.Toast;

import org.apache.http.NameValuePair;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;

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

public class MainActivity extends ListActivity {

private ProgressDialog pd;
JSONParser jParser=new JSONParser();
ArrayList<HashMap<String,String>> P;
JSONArray s=null;
private final String url="http://192.168.1.4/upload/travel.php";

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    new travel().execute();

}

class travel extends AsyncTask<String,String,String>{

    @Override
    protected void onPreExecute() {
        super.onPreExecute();
        pd=new ProgressDialog(MainActivity.this);
        pd.setMessage("login");
        pd.show();
    }

    @Override
    protected String doInBackground(String... params) {

        List<NameValuePair> parms=new ArrayList<>();
        JSONObject json=jParser.makeHTTPRequest(url,"GET",parms);
        try {
            int t=json.getInt("t");
            if(t==1){
                s=json.getJSONArray("travel");
                for(int i=0;i<s.length();i++){
                    JSONObject c=s.getJSONObject(i);
                    String companyname=c.getString("companyname");
                    String cod=c.getString("cod");
                    String bign=c.getString("bign");
                    String stop=c.getString("stop");
                    String date=c.getString("date");
                    String time=c.getString("time");
                    String price=c.getString("price");

                    HashMap<String,String>map=new HashMap<String,String>();
                    map.put("companyname",companyname);
                    map.put("cod",cod);
                    map.put("bign",bign);
                    map.put("stop",stop);
                    map.put("date",date);
                    map.put("time",time);
                    map.put("price",price);

                    P.add(map);

                }
            }else {
                Toast.makeText(MainActivity.this,"No                DataFound",Toast.LENGTH_SHORT).show();
            }


        } catch (JSONException e) {
            e.printStackTrace();
        }

        return null;
    }

    @Override
    protected void onPostExecute(String s) {
        super.onPostExecute(s);
        pd.dismiss();
        runOnUiThread(new Runnable() {
            @Override
            public void run() {
                ListAdapter adapter = new SimpleAdapter(MainActivity.this, P, R.layout.item_list,
                        new String[]{"companyname", "cod", "bign", "stop", "date", "time", "price"},
                        new int[]{R.id.companyname, R.id.cod, R.id.bign,   R.id.stop, R.id.date, R.id.time1, R.id.price});
                setListAdapter(adapter);
            }
        });

    }
}
}

我的 JSONParser 代码:

package com.example.delta.travel;

import android.net.http.HttpResponseCache;
import android.util.Log;

import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.NameValuePair;
import org.apache.http.client.ClientProtocolException;
import org.apache.http.client.entity.UrlEncodedFormEntity;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.client.utils.URLEncodedUtils;
import org.apache.http.impl.client.DefaultHttpClient;
import org.json.JSONException;
import org.json.JSONObject;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.UnsupportedEncodingException;
import java.net.URL;
import java.util.Date;
import java.util.List;

/**
 * Created by delta on 5/28/2016.
 */
public class JSONParser {

static InputStream is=null;
static JSONObject jObj=null;
static String json="";

// constructor
public JSONParser(){

}

// function get json from url
// by making HTTP POST or GET method
public JSONObject makeHTTPRequest(String url,String method,
                                  List<NameValuePair> params){

    //making HTTP request
    try{
        //check for request method
        if(method=="POST"){
            // request method is POST
            //defaultHTTPClient
            DefaultHttpClient httpClient =new DefaultHttpClient();
            HttpPost httpPost=new HttpPost(url);
            httpPost.setEntity(new UrlEncodedFormEntity(params));

            HttpResponse httpResponse=httpClient.execute(httpPost);
            HttpEntity httpEntity=httpResponse.getEntity();
            is=httpEntity.getContent();
        }else if(method=="GET"){
            //request method is GET
            DefaultHttpClient httpClient=new DefaultHttpClient();
            String paramString = URLEncodedUtils.format(params,"utf-8");
            url+="?"+paramString;
            HttpGet httpGet=new HttpGet(url);

            HttpResponse httpResponse=httpClient.execute(httpGet);
            HttpEntity httpEntity=httpResponse.getEntity();
            is=httpEntity.getContent();



        }

    }catch (UnsupportedEncodingException e){
        e.printStackTrace();
    }catch (ClientProtocolException e){
        e.printStackTrace();
    }catch (IOException e){
        e.printStackTrace();
    }

    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();
        json=sb.toString();
    }catch (Exception e){
        Log.e("Buffer Error","Error Converting result"+e.toString());
    }

    //try parse the string to a JSON object

    try{
        jObj=new JSONObject(json);
    }catch (JSONException e){
        Log.e("JSON Parser","Error parsing data"+e.toString());
    }
    //return JSON String
    return jObj;


}


}

和我的travel.php代码:

 <?php

$con=mysqli_connect("localhost","root","","travels");
mysqli_set_charset($con,"utf8");
$response=array();


$result=mysqli_query($con,"select * from travel");

if(mysqli_num_rows($result)>0){
while($row=mysqli_fetch_array($result)){
    $temp=array();
    $temp["companyname"]=$row["companyname"];
    $temp["cod"]=$row["cod"];
    $temp["bign"]=$row["bign"];
    $temp["stop"]=$row["stop"];
    $temp["date"]=$row["date"];
    $temp["time"]=$row["time"];
    $temp["price"]=$row["price"];

    $response["travel"]=array();

    array_push($response["travel"],$temp);
    }

$response["t"]=1;
echo json_encode($response);

}
else{

$response["t"]=0;
$response["message"]="Not Found";
echo json_encode($response);

 }

 ?>

Answer 1

1) 使用此代码更改 JSONParser 类中的代码。仅使用此小说。

 public JSONObject makeHTTPRequest(String urlString, String method) {

    if(method.equals("POST")){

        URL url = null;
        try {
            url = new URL(urlString);
            HttpURLConnection conn = (HttpURLConnection) url.openConnection();
            conn.setRequestMethod("POST");
            conn.setRequestProperty("Accept", "application/json");

            BufferedReader br = new BufferedReader(new InputStreamReader(
                    (conn.getInputStream())));
            String output;
            StringBuilder sb = new StringBuilder();
            while ((output = br.readLine()) != null) {
                sb.append(output);
            }
            conn.disconnect();
            json = sb.toString();

        } catch (MalformedURLException e) {
            e.printStackTrace();
        } catch (ProtocolException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }

    }else if(method.equals("GET")){
        URL url = null;
        try {
            url = new URL(urlString);
            HttpURLConnection conn = (HttpURLConnection) url.openConnection();
            conn.setRequestMethod("GET");
            conn.setRequestProperty("Accept", "application/json");

            BufferedReader br = new BufferedReader(new InputStreamReader(
                    (conn.getInputStream())));
            String output;
            StringBuilder sb = new StringBuilder();
            while ((output = br.readLine()) != null) {
                sb.append(output);
            }
            conn.disconnect();
            json = sb.toString();

        } catch (MalformedURLException e) {
            e.printStackTrace();
        } catch (ProtocolException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    try {
        jObj = new JSONObject(json);
    } catch (JSONException e) {
        e.printStackTrace();
    }

    return jObj;
}

2) 在 MainActivity 中你必须添加 P = new ArrayList<>();在 onCreate() 方法中像这样。

 @Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    P = new ArrayList<>();
    new travel().execute();

}

这一切都在我身边完成。它肯定也适合你。