Question

我有一个包含2个页面的android应用程序，一个用于登录，另一个用于列表视图。

登录很好，当PHP JSON结果在网络上很好但是当我点击按钮时我无法在列表视图中查看我的项目时出现错误＆＃34;不幸的是该应用程序已停止＆＃34;并重新启动应用程序。

这是PHP代码：

<?php
    include 'DatabaseConfig.php';

    // Create connection
    $conn = new mysqli($HostName, $HostUser, $HostPass, $DatabaseName);

    if ($conn->connect_error) {

     die("Connection failed: " . $conn->connect_error);
    } 

    $sql = "SELECT * FROM products";

    $result = $conn->query($sql);

    if ($result->num_rows >0) {


     while($row[] = $result->fetch_assoc()) {

     $tem = $row;

     $json = json_encode($tem);


     }

    } else {
     echo "No Results Found.";
    }
     echo $json;
    $conn->close();
    ?>

对于android：

MainPageActivity.java

package com.example.dell.apptest;

import android.os.Bundle;
import android.support.design.widget.FloatingActionButton;
import android.support.design.widget.Snackbar;
import android.view.View;
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.ListView;
import android.support.design.widget.NavigationView;
import android.support.v7.app.ActionBarDrawerToggle;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.Toolbar;
import android.view.Menu;
import android.view.MenuItem;

public class MainPageActivity extends AppCompatActivity
{
    String url="http://187.241.2.32:8089/AppTest/JSonTextView.php";


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main_page);
        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);

        final ListView lv= (ListView) findViewById(R.id.lv);
        final Downloader d=new Downloader(this,url,lv);

        FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab);
        fab.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                //EXECUTE DOWNLOAD
                d.execute();
            }
        });
    }



}

它提供了这个JSON：

[{"Id":"7","Name":" test","Position":"description"},{"Id":"1","Name":"zerty","Position":"feztez"}]

Parser.java

package com.example.dell.apptest;

import android.app.ProgressDialog;
import android.content.Context;
import android.os.AsyncTask;
import android.support.design.widget.Snackbar;
import android.view.View;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.ListView;
import android.widget.Toast;

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

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

public class Parser extends AsyncTask<Void,Integer,Integer> {

    Context c;
    ListView lv;
    String data;

    ArrayList<String> products=new ArrayList<>();
    ProgressDialog pd;

    public Parser(Context c, String data, ListView lv) {
        this.c = c;
        this.data = data;
        this.lv = lv;
    }

    @Override
    protected void onPreExecute() {
        super.onPreExecute();

        pd=new ProgressDialog(c);
        pd.setTitle("Parser");
        pd.setMessage("Parsing ....Please wait");
        pd.show();
    }

    @Override
    protected Integer doInBackground(Void... params) {

        return this.parse();
    }

    @Override
    protected void onPostExecute(Integer integer) {
        super.onPostExecute(integer);

        if(integer == 1)
        {
            //ADAPTER
            ArrayAdapter<String> adapter=new ArrayAdapter<String>(c,android.R.layout.simple_list_item_1,products);

            //ADAPT TO LISTVIEW
            lv.setAdapter(adapter);

            //LISTENET
            lv.setOnItemClickListener(new AdapterView.OnItemClickListener() {
                @Override
                public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
                    Snackbar.make(view,products.get(position),Snackbar.LENGTH_SHORT).show();;
                }
            });

        }else
        {
            Toast.makeText(c,"Unable to Parse",Toast.LENGTH_SHORT).show();
        }

        pd.dismiss();
    }

    //PARSE RECEIVED DATA
    private int parse()
    {
        try
        {
            //ADD THAT DATA TO JSON ARRAY FIRST
            JSONArray ja=new JSONArray(data);

            //CREATE JO OBJ TO HOLD A SINGLE ITEM
            JSONObject jo=null;

            products.clear();

            //LOOP THRU ARRAY
            for(int i=0;i<ja.length();i++)
            {
                jo=ja.getJSONObject(i);

                //RETRIOEVE NAME
                String name=jo.getString("Name");

                //ADD IT TO OUR ARRAYLIST
                products.add(name);
            }

            return 1;

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

        return 0;
    }
}

Downloader.java

   package com.example.dell.apptest;

import android.app.ProgressDialog;
import android.content.Context;
import android.os.AsyncTask;
import android.widget.ListView;
import android.widget.Toast;

import java.io.BufferedInputStream;
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;

public class Downloader extends AsyncTask<Void,Integer,String> {

    Context c;
    String address;
    ListView lv;

    ProgressDialog pd;

    public Downloader(Context c, String address, ListView lv) {
        this.c = c;
        this.address = address;
        this.lv = lv;
    }

    //B4 JOB STARTS
    @Override
    protected void onPreExecute() {
        super.onPreExecute();

        pd=new ProgressDialog(c);
        pd.setTitle("Fetch Data");
        pd.setMessage("Fetching Data...Please wait");
        pd.show();
    }

    @Override
    protected String doInBackground(Void... params) {
        String data=downloadData();
        return data;
    }

    @Override
    protected void onPostExecute(String s) {
        super.onPostExecute(s);

        pd.dismiss();;

        if(s != null)
        {
            Parser p=new Parser(c,s,lv);
            p.execute();

        }else
        {
            Toast.makeText(c,"Unable to download data",Toast.LENGTH_SHORT).show();
        }
    }

    private String downloadData()
    {
        //connect and get a stream
        InputStream is=null;
        String line =null;

        try {
            URL url=new URL(address);
            HttpURLConnection con= (HttpURLConnection) url.openConnection();
            is=new BufferedInputStream(con.getInputStream());

            BufferedReader br=new BufferedReader(new InputStreamReader(is));

            StringBuffer sb=new StringBuffer();

            if(br != null) {

                while ((line=br.readLine()) != null) {
                    sb.append(line+"\n");
                }

            }else {
                return null;
            }

            return sb.toString();

        } catch (MalformedURLException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }finally {
            if(is != null)
            {
                try {
                    is.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
        return null;
    }
}

如何从mysql数据库中获取数据到android

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