java - 检索数据只给我数据库的第一行，我只想将最后一行插入数据库

Question

我正在使用 JSON 结构从数据库中检索数据。检索它只会给我数据库的第一行，而我只想将最后一行插入到数据库中。

这是我的 java 类 RetrieveInfo.java

public class RetrieveInfo extends AppCompatActivity implements View.OnClickListener {

    public static final String DATA_URL = "http://ksvira.edu.in/getBusinessDetails.php";
    public static final String KEY_NAME = "name";
    public static final String KEY_EMAIL = "email";
    public static final String KEY_PHONENUM = "phone";
    public static final String KEY_ADDRESS = "address";
    public static final String KEY_FAX = "fax";
    public static final String KEY_MAILADDRESS = "mailaddress";
    public static final String KEY_OPENDATE = "opendate";

    public static final String JSON_ARRAY = "result";



    private Button buttonGet;
    private TextView textViewResult;

    private ProgressDialog loading;


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


        buttonGet = (Button) findViewById(R.id.buttonGet);
        textViewResult = (TextView) findViewById(R.id.textView);
        buttonGet.setOnClickListener(this);
    }

    private void getData() {

        loading = ProgressDialog.show(this,"Please wait...","Fetching...",false,false);

        //String url = DATA_URL+editTextId.getText().toString().trim();
        String url=DATA_URL;
        StringRequest stringRequest = new StringRequest(url, new Response.Listener<String>() {
            @Override
            public void onResponse(String response) {
                loading.dismiss();
                showJSON(response);
            }
        },
                new Response.ErrorListener() {
                    @Override
                    public void onErrorResponse(VolleyError error) {
                        Toast.makeText(RetrieveInfo.this,error.getMessage().toString(),Toast.LENGTH_LONG).show();
                    }
                });

        RequestQueue requestQueue = Volley.newRequestQueue(this);
        requestQueue.add(stringRequest);
    }

    private void showJSON(String response){
        String name="";
        String email="";
        String phonenum ="";
        String fax = "";
        String address="";
        String mailaddress = "";
        String opendate = "";

        try {
            JSONObject jsonObject = new JSONObject(response);
            JSONArray result = jsonObject.getJSONArray(JSON_ARRAY);

            int size = jsonObject.length();
            JSONObject collegeData = result.getJSONObject(size);
            name = collegeData.getString(KEY_NAME);
            email=collegeData.getString(KEY_EMAIL);
            phonenum=collegeData.getString(KEY_PHONENUM);
            fax=collegeData.getString(KEY_FAX);
            address = collegeData.getString(KEY_ADDRESS);
            mailaddress =collegeData.getString(KEY_MAILADDRESS);
            opendate = collegeData.getString(KEY_OPENDATE);

        } catch (JSONException e) {
            e.printStackTrace();
        }
        textViewResult.setText("Name:\t"+name+"\nEmail:\t"+email+"\nPhone:\t"+phonenum+"\nFax:\t"+fax+"\nAddress:\t" +address+"\nMailAddress:\t"+mailaddress
                +"\nOpenDate\t"+opendate);
    }

    @Override
    public void onClick(View v) {

        getData();
    }
}

activity_retrieveinfo.xml

<Button
    android:text="View Information"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:id="@+id/button_View1"
    android:layout_alignParentTop="true"
    android:layout_centerHorizontal="true" />

<TextView
    android:layout_width="wrap_content"
    android:layout_height="30sp"
    android:id="@+id/textView2"
    android:layout_below="@+id/button_View1"
    android:layout_alignParentRight="true"
    android:layout_alignParentEnd="true"
    android:layout_alignParentLeft="true"
    android:layout_alignParentStart="true"
    android:layout_alignParentBottom="true" />

getBusinessDetails.php

<?php 

 //if($_SERVER['REQUEST_METHOD']=='GET'){

 //$id  = $_GET['id'];

 require_once('dbConnect.php');

 $sql = "SELECT * from business_info";

 $r = mysqli_query($con,$sql);

// $res = mysqli_fetch_array($r);


 $result = array();

while($res = mysqli_fetch_array($r))
        { 
        $result[] = $res;    
        //array_push($result,array("name"=>$res[0],"email"=>$res[1],"phonenum"=>$res[2],"fax"=>$res[3],"address"=>$res[4],"mailaddress"=>$res[5],"opendate"=>$res[6]));            

        }

 //array_push($result,array("content"=>$res['content']));

 echo json_encode(array("result"=>$result));


 mysqli_close($con);

// }
?>

Answer 1

纠正您的服务器端查询 $sql =

 SELECT * FROM business_info  ORDER BY column_name DESC LIMIT 1

仅供引用

column_name should be Primary Key . The ORDER BY keyword is used to sort the result-set in ascending or descending order. DESC LIMIT 1 fetching Last Element .