如何从数据库中获取数据以PHP形式发送回响应？

Question

Need to take the subject provided by the user via android app and then use it to search database to find a teacher name and email for that subject and then send their email , name to android list view.

PHP Code:

 if ( !empty($_GET['subject']) ) {

    $SUBJECT=$_GET['subject'];
    $sql="SELECT IFF(sub== Name,Email,subjects_known FROM teacher_registration";
    $res=$con->query($sql);
    $result["Email"] = array();
    $result["Name"] = array();
    $result["Sub"] = array();
    $row=array();
    if($res->num_rows>0){
    while($row=$res->fetch_assoc())
    {
        //$Name= array();
        $Name= $row['Name'];
        //array_push($result["Name"], $Name);
       // $Email=array();
        $Email= $row['Email'];
        $Sub=$row['subjects_known'];
        array_push($result["Email"],$Email);
        array_push($result["Name"], $Name);
        array_push($result["Sub"],$Sub);

            // $result[] = $row;
     }
    // $r1=array();
    // $r1['TEACHER']=$result;
     echo json_encode($result,JSON_FORCE_OBJECT);
     mysqli_close($con);
  }
  else
  {
      echo "Give the info";
      mysqli_close($con);
  }

adapter

import android.content.Context;
import android.support.annotation.NonNull;
import android.support.annotation.Nullable;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;

import android.widget.TextView;



public class CustomListView extends BaseAdapter {


    public String[] profilename;
    public String[] Email;


    LayoutInflater li;


    public CustomListView(String[] p,String[] e,Teacher_searching ref) {
        Context context = ref;
        li=LayoutInflater.from(context);
        this.profilename=p;
        this.Email=e;


    }

    @Override
    public int getCount() {
        return Email.length;

    }

    @Override
    public Object getItem(int position) {
        return (position);
    }

    @Override
    public long getItemId(int position) {
        return position;
    }

    @NonNull
    @Override

    public View getView(int position, @Nullable View convertView, @NonNull ViewGroup parent){
        ViewHolder v=null;
        if(convertView==null){
            convertView = li.inflate(R.layout.layout, null);
            v=new ViewHolder(convertView);
            convertView.setTag(v);
        }
        else {
            v=(ViewHolder)convertView.getTag();

        }

        v.tvw1.setText(profilename[position]);
        v.tvw2.setText(Email[position]);



        return convertView;
    }

    class ViewHolder{

        TextView tvw1;
        TextView tvw2;


        ViewHolder(View v){
            tvw1=v.findViewById(R.id.tvprofilename);
            tvw2=v.findViewById(R.id.tvemail);

        }

    }


}

search initiator:

public class Teacher_searching extends AppCompatActivity {
    String urladdress="https://light-headed-nests.000webhostapp.com/proed/searching1.php";
    String[] name;
    String[] Email;
    String SUBJECT_SEARCH;
    ListView listView;
    BufferedInputStream is;
    JsonObjectRequest jsonObjectRequest;
    String subject_Search;
    String line;
    String result=null;
    Bundle b=new Bundle();

    JSONObject jsonObj = new JSONObject();
    RequestQueue mqueue;
    StringRequest s;
    Integer i;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_teacher_searching);
        listView=(ListView) findViewById(R.id.lview);
        SUBJECT_SEARCH=b.getString("Teacher");
    //    collectData();
        mqueue= Volley.newRequestQueue(getApplicationContext());
      jsonParse();
      //  onlyvolley();
        Toast.makeText(getApplicationContext(),Email.length,Toast.LENGTH_SHORT).show();
        /*CustomListView customListView=new CustomListView(name,Email,Teacher_searching.this);
        listView.setAdapter(customListView);*/
    }

   /* private void onlyvolley() {
        s=new StringRequest(Request.Method.POST, urladdress,
                new Response.Listener<String>() {
                    @Override
                    public void onResponse(String response) {

                    }
                },
                new Response.ErrorListener() {
                    @Override
                    public void onErrorResponse(VolleyError error) {
                        showMsg("Server Response","Page not reachable");
                    }
        )

    }*/

   private void jsonParse() {
        jsonObjectRequest=new JsonObjectRequest(Request.Method.GET, urladdress, null,
                new Response.Listener<JSONObject>() {
                    @Override
                    public void onResponse(JSONObject response) {
                        try {
                            JSONArray jsonArray=response.getJSONArray("TEACHER");
                            jsonObj=null;
                            name=new String[jsonArray.length()];
                            Email=new String[jsonArray.length()];
                            for (int i=0;i<=jsonArray.length();i++)
                            {
                                jsonObj=jsonArray.getJSONObject(i);
                                name[i]=jsonObj.getString("Name");
                                Email[i]=jsonObj.getString("Email");
                            }
                        } catch (JSONException e) {
                            e.printStackTrace();
                        }

                    }
                }, new Response.ErrorListener() {
            @Override
            public void onErrorResponse(VolleyError error) {
                error.printStackTrace();
            }
        })
        {
            @Override
            protected Map<String, String> getParams() throws AuthFailureError {
                Map<String,String> params=new HashMap<String,String>();
                params.put("subject",SUBJECT_SEARCH);
                return params;
            }
        };
        mqueue.add(jsonObjectRequest);
    }

    /*private void collectData() {

        try{

            URL url=new URL(urladdress);
            HttpURLConnection con=(HttpURLConnection)url.openConnection();
            con.setRequestMethod("GET");
            subject_Search=b.getString("Teacher");
            jsonObj.put("subject",subject_Search);
            is=new BufferedInputStream(con.getInputStream());
        }
        catch (Exception ex) {}

        //content
        try{
            InputStreamReader read=new InputStreamReader(is);
            BufferedReader br=new BufferedReader(read);
            StringBuilder sb=new StringBuilder();
            while ((line=br.readLine())!=null){
                sb.append(line).append("\n");
            }
            is.close();
            result=sb.toString();

        }
        catch (Exception ex)
        {
            ex.printStackTrace();

        }

//JSON
        try{
            JSONArray ja=new JSONArray("TEACHER");
            JSONObject jo;
            name=new String[ja.length()];
            Email=new String[ja.length()];
            ArrayList<HashMap<String, String>> mylist =new ArrayList<HashMap<String, String>>();

            for(i=0;i<=ja.length();i++){
                HashMap<String, String> map = new HashMap<String, String>();
                jo=ja.getJSONObject(i);
                name[i]=jo.getString("Name");
                Email[i]=jo.getString("Email");

            }
        }
        catch (Exception ex)
        {

            ex.printStackTrace();
        }
    }*/
}

searchin for::

import android.content.Intent;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.Spinner;

public class Search_teacher extends AppCompatActivity {
    Spinner sub;
    Button btn;
    String sub_search[]={"Physics","Chemistry","Mathematics","Biology","English","Computer(C++)","Computer(Java)","History&Civics","Geography","Economics"};
    String Sub_stud;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_search_teacher);
        sub=findViewById(R.id.subject_search);
        btn=findViewById(R.id.btn);
        ArrayAdapter<String> adapter2=new ArrayAdapter<String>(getApplicationContext(),android.R.layout.simple_spinner_dropdown_item,sub_search);
        sub.setAdapter(adapter2);
        sub.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {
            @Override
            public void onItemSelected(AdapterView<?> adapterView, View view, int i, long l) {
                if(i==0)
                    Sub_stud="Physics";
                else if(i==1)
                    Sub_stud="Chemistry";
                else if(i==2)
                    Sub_stud="Mathematics";
                else if(i==3)
                    Sub_stud="Biology";
                else if(i==4)
                    Sub_stud="English";
                else if(i==5)
                    Sub_stud="Computer(C++)";
                else if(i==6)
                    Sub_stud="Computer(Java)";
                else if(i==7)
                    Sub_stud="History&Civics";
                else if(i==8)
                    Sub_stud="Geography";
                else if(i==9)
                    Sub_stud="Economics";
            }

            @Override
            public void onNothingSelected(AdapterView<?> adapterView) {

            }
        });
    }

    public void subject_teacher_search(View view) {
        Intent i=new Intent(getApplicationContext(),Teacher_searching.class);
        Bundle bundle=new Bundle();
        bundle.putString("Teacher",Sub_stud);
        i.putExtras(bundle);
        startActivity(i);

    }
}

stuff in list view:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
    xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="match_parent"
    android:layout_height="match_parent">
    <TextView
        android:id="@+id/tvprofilename"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentTop="true"
        android:layout_marginLeft="26dp"
        android:layout_marginStart="26dp"
        android:layout_marginTop="16dp"
        android:textColor="#333"
        android:textSize="22dp"
        />

    <TextView
        android:id="@+id/tvemail"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentTop="true"
        android:layout_marginLeft="26dp"
        android:layout_marginStart="26dp"
        android:layout_marginTop="50dp"
        android:textColor="#333"
        android:textSize="22dp"
        />

</LinearLayout>

the listview

<?xml version="1.

0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".Teacher_searching"
    android:orientation="vertical">



        <ListView
            android:id="@+id/lview"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:layout_alignParentTop="true"
            android:layout_centerHorizontal="true"/>




</RelativeLayout>

Answer 1

Seems like there is a " sql syntax error " in your php code, anyway first resolve it appropriately and start doing the following steps in the application

Step-1: Create a request queue using " Volley Library " to retrieve json response from server

Step-2: Add a "Custom_Listview" in your layout file

Step-3: Finally set the " Adapter Class " to the listview.. That's it

Follow the example

Happy Coding!!