单击 ListView 项目时如何从数据库 mysql &Screen 中删除记录？答案

【问题标题】：How to Delete a record from the DataBase mysql &Screen while Clicked on ListView item?单击 ListView 项目时如何从数据库 mysql &Screen 中删除记录？
【发布时间】：2017-04-13 00:59:35
【问题描述】：

当我点击按钮时，我想从数据库中删除一条记录。

我在 listView 中设置的 Button。

我想在 ListView 上执行此操作在这里我尝试了以下方式但它不起作用..

这里是我的 API

<?php
include("connection.php");
$tbl = "abc";   
$idToDelete = $_GET["id"]; 
$delete_row = mysql_query("DELETE FROM $tbl WHERE o_id=".$idToDelete);
$response["delete"] = array();
$response["success"]=1;
// push single product into final response array
echo json_encode($response);
?>

ListviewAdapter.java

     package com.example.sachin.alertbox;

import android.app.ProgressDialog;
import android.content.Context;
import android.content.DialogInterface;
import android.os.AsyncTask;
import android.os.Bundle;
import android.support.v7.app.AlertDialog;
import android.support.v7.app.AppCompatActivity;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.widget.ActionMenuView;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.EditText;
import android.widget.LinearLayout;
import android.widget.ListView;
import android.widget.PopupWindow;
import android.widget.Spinner;
import android.widget.Toast;

import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.NameValuePair;
import org.apache.http.client.HttpClient;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.impl.client.DefaultHttpClient;
import org.json.JSONArray;
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.util.ArrayList;
import java.util.HashMap;
import java.util.List;

public class MainActivity extends AppCompatActivity {
    Button add;
    Spinner spinner;
    ListView listview;
    LinearLayout linearlayout;
    JSONObject jsonobject;
    private static String url_addevent = "http  ://10.0.2.2/portal/order_product.php";
    public static String url_visitor= "http://10.0.2.2/portal/fetchorder_of_user.php";
    JSONParser jParser = new JSONParser();
    JSONArray ownerObj;
    ArrayList<HashMap<String, String>> arraylist;
    ArrayList<String> delivery_fetch = new ArrayList<String>();
    ListViewAdapterorder listadapter;
    EditText qty;
    LinearLayout layout;
    ActionMenuView.LayoutParams params;
    LinearLayout mainLayout;
    PopupWindow popUp;
    final Context context = this;
    ArrayAdapter<String> adapter;
    Button Delete;
    ArrayList<String> listItems = new ArrayList<>();



    String stringqty,stringspinner;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        add = (Button) findViewById(R.id.clickme);
        popUp = new PopupWindow(this);
        layout = new LinearLayout(this);
        mainLayout = new LinearLayout(this);
        listview = (ListView)findViewById(R.id.listview);
        Delete=(Button)findViewById(R.id.delete);
        add.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {

                LayoutInflater li = LayoutInflater.from(context);
                View promptsView = li.inflate(R.layout.prompts, null);
                AlertDialog.Builder alertDialogBuilder = new AlertDialog.Builder(context);

                // set prompts.xml to alertdialog builder
                alertDialogBuilder.setView(promptsView);

                spinner=(Spinner)promptsView.findViewById(R.id.spinner);
                adapter = new ArrayAdapter<String>(getApplication(), R.layout.spinner_layout, R.id.txt, listItems);
                spinner.setAdapter(adapter);
                spinner.setSelection(0);

                qty=(EditText)promptsView.findViewById(R.id.qty);

                // set dialog message
                alertDialogBuilder
                        .setCancelable(false)
                        .setPositiveButton("OK", new DialogInterface.OnClickListener() {
                            public void onClick(DialogInterface dialog, int id) {
                                // get user input and set it to result
                                // edit text
                                stringqty=qty.getText().toString();
                                stringspinner=spinner.getSelectedItem().toString();
                                addvisitor();
                                new fetchorder().execute();
                                Toast.makeText(getApplicationContext(), "qty :  " + stringqty +stringspinner, Toast.LENGTH_SHORT).show();
                            }
                        })
                        .setNegativeButton("Cancel",
                                new DialogInterface.OnClickListener() {
                                    public void onClick(DialogInterface dialog, int id) {
                                        dialog.cancel();
                                    }
                                });

                // create alert dialog
                AlertDialog alertDialog = alertDialogBuilder.create();
                // show it
                alertDialog.show();
            }
        });
    }
    private void addvisitor() {
        service(stringqty,stringspinner);
    }
    private void service(String qty,String sp) {

        class AddVisitclass extends AsyncTask<String, Void, String> {
            ProgressDialog loading;
            RegisterUserClass ruc = new RegisterUserClass();

            //@Override
            protected void onPreExecute() {
                // Create a progressdialog
                super.onPreExecute();
                //loading = ProgressDialog.show(getApplicationContext(), "Please Wait...!!!", null, true, true);
            }

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

                HashMap<String, String> param = new HashMap<String, String>();

                param.put("quantity", params[0]);
                param.put("model", params[1]);


                String result = ruc.sendPostRequest(url_addevent, param);
                Log.d("Result", result);
                Log.d("Data", param.toString());
                return result;
            }

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

                //loading.dismiss();
                Toast.makeText(getApplicationContext(), "Service Added Successfully...!!!", Toast.LENGTH_LONG).show();
                      /*  Intent i1 = new Intent(getApplicationContext(), HomeActivity.class);
                        startActivity(i1);*/
            }
        }
        AddVisitclass regi = new AddVisitclass();
        regi.execute(qty,sp);

    }

    ArrayList<String> o_aid= new ArrayList<String>();
    ArrayList<String> o_aproduct= new ArrayList<String>();
    ArrayList<String> o_aqty= new ArrayList<String>();
    ArrayList<String> o_atotal= new ArrayList<String>();

    private class fetchorder extends AsyncTask<Void, Void, Void> {
        @Override
        protected void onPreExecute() {
            super.onPreExecute();
        }
        @Override
        protected Void doInBackground(Void... args) {
            try {
                arraylist = new ArrayList<HashMap<String, String>>();

                List<NameValuePair> params = new ArrayList<NameValuePair>();
//              params.add(new BasicNameValuePair("v_username", uid));
                JSONObject json = jParser.makeHttpRequest(url_visitor, "GET", params);
                int success1 = Integer.parseInt(json.getString("success4"));
                Log.d("success4", json.toString());
                if (success1 == 0) {}
                if (success1 == 1) {
                    o_aid.clear();
                    o_aproduct.clear();
                    o_aqty.clear();
                    o_atotal.clear();
                    ownerObj = json.getJSONArray("visit");
                    for (int i = 0; i < ownerObj.length(); i++) {
                        jsonobject = ownerObj.getJSONObject(i);
                        o_aid.add(jsonobject.getString("o_id"));
                        o_aproduct.add(jsonobject.getString("o_product"));
                        o_aqty.add(jsonobject.getString("o_qty"));
                        o_atotal.add(jsonobject.getString("o_total"));
                    }
                }
            } catch (Exception e) {
            }
            return null;
        }
        @Override
        protected void onPostExecute(Void args) {
            // Locate the listview in listview_main.xml
            if (listadapter == null) {
                listadapter = new ListViewAdapterorder(getApplicationContext(), o_aid, o_aproduct, o_aqty, o_atotal);
                listview.setAdapter(listadapter);
            } else {
                listadapter.notifyDataSetChanged();
            }
        }
    }
    public void onStart() {
        super.onStart();
        BackTask bt = new BackTask();
        bt.execute();
    }
    private class BackTask extends AsyncTask<Void, Void, Void> {
        ArrayList<String> list;
        protected void onPreExecute() {
            super.onPreExecute();
            list = new ArrayList<>();
        }
        protected Void doInBackground(Void... params) {
            InputStream is = null;
            String result = "";
            try {
                HttpClient httpclient = new DefaultHttpClient();
                HttpPost httppost = new HttpPost("http://10.0.2.2/portal/spinner.php");
                HttpResponse response = httpclient.execute(httppost);
                HttpEntity entity = response.getEntity();
                // Get our response as a String.
                is = entity.getContent();
            } catch (IOException e) {
                e.printStackTrace();
            }

            //convert response to string
            try {
                BufferedReader reader = new BufferedReader(new InputStreamReader(is, "utf-8"));
                String line = null;
                while ((line = reader.readLine()) != null) {
                    result += line;
                }
                is.close();
                //result=sb.toString();
            } catch (Exception e) {
                e.printStackTrace();
            }
            // parse json data
            try {
                JSONArray jArray = new JSONArray(result);
                list.add("Please Select Model");
                for (int i = 0; i < jArray.length(); i++) {
                    JSONObject jsonObject = jArray.getJSONObject(i);
                    // add interviewee name to arraylist
                    list.add(jsonObject.getString("m_model"));
                }
            } catch (JSONException e) {
                e.printStackTrace();
            }
            return null;
        }

        protected void onPostExecute(Void result) {
            listItems.addAll(list);

        }
    }




}

这里MainActivity.java ListView 类

 ArrayList<String> o_aid= new ArrayList<String>();
    ArrayList<String> o_aproduct= new ArrayList<String>();
    ArrayList<String> o_aqty= new ArrayList<String>();
    ArrayList<String> o_atotal= new ArrayList<String>();

    private class fetchorder extends AsyncTask<Void, Void, Void> {
        @Override
        protected void onPreExecute() {
            super.onPreExecute();
        }
        @Override
        protected Void doInBackground(Void... args) {
            try {
                arraylist = new ArrayList<HashMap<String, String>>();

                List<NameValuePair> params = new ArrayList<NameValuePair>();
//              params.add(new BasicNameValuePair("v_username", uid));
                JSONObject json = jParser.makeHttpRequest(url_visitor, "GET", params);
                int success1 = Integer.parseInt(json.getString("success4"));
                Log.d("success4", json.toString());
                if (success1 == 0) {}
                if (success1 == 1) {
                    o_aid.clear();
                    o_aproduct.clear();
                    o_aqty.clear();
                    o_atotal.clear();
                    ownerObj = json.getJSONArray("visit");
                    for (int i = 0; i < ownerObj.length(); i++) {
                        jsonobject = ownerObj.getJSONObject(i);
                        o_aid.add(jsonobject.getString("o_id"));
                        o_aproduct.add(jsonobject.getString("o_product"));
                        o_aqty.add(jsonobject.getString("o_qty"));
                        o_atotal.add(jsonobject.getString("o_total"));
                    }
                }
            } catch (Exception e) {
            }
            return null;
        }
        @Override
        protected void onPostExecute(Void args) {
            // Locate the listview in listview_main.xml
            if (listadapter == null) {
                listadapter = new ListViewAdapterorder(getApplicationContext(), o_aid, o_aproduct, o_aqty, o_atotal);
                listview.setAdapter(listadapter);
            } else {
                listadapter.notifyDataSetChanged();
            }
        }
   }

我尝试过这种方式，但没有删除。请为此建议我一些 coede。

【问题讨论】：

您没有在任何地方初始化 datlist arraylist 并且在删除单击时从该列表中删除，这是没有意义的。您应该遵循 Rujul 给出的答案。

标签： android mysql json

【解决方案1】：

试试这个。

  Delete.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {

                datlist.remove(position);

                o_aid.remove(position);
                o_aproduct.remove(position);
                o_aqty.remove(position);
                o_atotal.remove(position);

                Snackbar.make(view, "Record Delete Succesfully", Snackbar.LENGTH_LONG).show();
                notifyDataSetChanged();
            }
        });

【讨论】：

给出类似 java.lang.NullPointerException 的错误：尝试在 com.example.sachin 的空对象引用上调用虚拟方法 'int android.widget.ListView.getPositionForView(android.view.View)' .alertbox.ListViewAdapterorder$1.onClick(ListViewAdapterorder.java:96)
请删除行 final int position = listview.getPositionForView((View) view.getParent());
它正在从屏幕上移除...但它在 db 中不起作用..？我也想从数据库中删除它
我认为您必须调用一些 api，但目前它丢失了。所以请检查一下。如果答案正确，则标记为正确。
你能帮我解决这个问题吗？我应该上传我的 api 吗？

【解决方案2】：

如有任何问题，请致电我：85110 51548 您的 connection.php 有问题 请检查我已经检查过，但不是来自 php 查询的问题，但如果 connection.php 有问题，您将找不到，因为如果记录被删除，它会返回 1，如果它返回任何问题代码中的 0 返回 0 表示记录未成功删除。 在你的 php 中编写以下代码，并将其更改为 connection.php

   /*connection.php */
$host="your host";
    $username="your user name";
    $password="your password";
    $dbname="your database name";
   $con = new mysqli($host, $username, $password,$dbname);

  // Check connection
  if ($con->connect_error) {
      die("Connection failed: " . $con->connect_error);
  }
  /*code.php */
    include('connection.php');

    $tbl = "abc";   
$idToDelete = $_GET["id"]; 
 $sql="DELETE FROM $tbl WHERE o_id=".$idToDelete;
 $delete_row = $con->query($sql);


 $response["delete"] = array();
$response["success"]=1;
/// push single product into final response array
echo json_encode($response);
 ** In short there is a problem in connection file thats why not deleted that record **

【讨论】：

你真的想要你的电话号码吗？ :-/
当我试图从浏览器中删除记录时，记录正在删除。