Modul 13 - CRUD Database MySQL dengan PHP

TEORI SINGKAT

Apa itu CRUD?

CRUD adalah singkatan dari create, read, update, and delete. Akronim CRUD mengidentifikasi semua fungsi utama yang melekat pada database relasional dan aplikasi yang digunakan untuk mengelolanya, termasuk Oracle Database, Microsoft SQL Server, MySQL, dan lainnya.

Fungsi create, read, update, dan delete merupakan fungsi yang secara konstan digunakan dan merupakan bagian yang tidak terpisahkan dari pekerjaan seorang programmer. Ini karena hampir sebagian besar pemograman komputer modern menggunakan fungsi CRUD.

• Create = Fungsi ini memungkinkanmu membuat record baru dalam database.

• Read = Fungsi ini memungkinkan kamu untuk mencari dan mengambil data tertentu dalam tabel dan membaca nilainya.

• Update = Untuk memodifikasi record yang telah tersimpan di database.

• Delete = Menghapus record yang telah tersimpan di database.

Web Service

Web service merupakan aplikasi yang berisi sekumpulan basis data (database) dan perangkat lunak (software) atau bagian dari program perangkat lunak yang diakses secara remote oleh piranti dengan perantara tertentu.

Web service mampu menukar data tanpa memandang sumber database, bahasa yang digunakan, dan pada platform apa data tersebut dikonsumsi. Kemampuan itulah yang memungkinkan web service menjadi jembatan penghubung untuk berbagai sistem.

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PRAKTIKUM

Pertama - tama jalankan aplikasi android studio dan buat projek baru.

Lalu ketikkan kode program dibawah ini pada activity_main :

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    android:paddingLeft="16dp"
    android:paddingRight="16dp"
    android:paddingTop="16dp"
    android:paddingBottom="16dp"
    tools:context=".MainActivity">
    <TextView
      android:layout_width="match_parent"
      android:layout_height="wrap_content"
      android:text="Nama Mahasiswa : "
        android:textSize="18dp"/>

    <EditText
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:id="@+id/editTextName"
        android:hint="Masukan Nama Anda"
        android:inputType="text" />

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="N R P : "
        android:textSize="18dp" />

    <EditText
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:id="@+id/editTextNRP"
        android:inputType="number" />

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Kelas : "
        android:textSize="18dp" />

    <Spinner
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:id="@+id/spinnerkelas"
        android:spinnerMode="dropdown" />

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Blog URL : "
        android:textSize="18dp"/>

    <EditText
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:id="@+id/editTextBlog"
        android:hint="Input Link URL Blog"
        android:inputType="text" />

    <Button
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="Tambah Data Mahasiswa"
        android:id="@+id/buttonAdd" />

    <Button
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="Daftar Mahasiswa"
        android:id="@+id/buttonView" />

  </LinearLayout>

Juga ketikkan kode berikut ini pada MainActivity.java

package com.example.tugas13;

import androidx.appcompat.app.AppCompatActivity;

import android.app.ProgressDialog;
import android.content.Intent;
import android.os.AsyncTask;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Spinner;
import android.widget.Toast;

import java.nio.channels.AsynchronousChannelGroup;
import java.util.HashMap;

public class MainActivity extends AppCompatActivity implements View.OnClickListener {
    private EditText editTextName;
    private EditText editTextNRP;
    private EditText editTextBlog;
    private Button buttonAdd;
    private Button buttonView;
    private Spinner spinnerKelas;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        editTextName = findViewById(R.id.editTextName);
        editTextNRP = findViewById(R.id.editTextNRP);
        editTextBlog = findViewById(R.id.editTextBlog);

        buttonAdd = findViewById(R.id.buttonAdd);
        buttonView = findViewById(R.id.buttonView);

        spinnerKelas = findViewById(R.id.spinnerkelas);

        String[] spinnerItem = new String[] {"TI-1","TI-2","TI-3","TI-Malam"};
        ArrayAdapter<String> adapter = new ArrayAdapter<>(this, android.R.layout.simple_spinner_dropdown_item,spinnerItem);
        spinnerKelas.setAdapter(adapter);

        buttonAdd.setOnClickListener(this);
        buttonView.setOnClickListener(this);
    }

    private void addMhs(){
        final String name = editTextName.getText().toString().trim();
        final String nrp = editTextNRP.getText().toString().trim();
        final String blog = editTextBlog.getText().toString().trim();
        final String kelas = (String) spinnerKelas.getSelectedItem();
        Log.d("kelas",kelas);

        class AddMhs extends AsyncTask <Void,Void,String>{
            ProgressDialog loading;
            @Override protected void onPreExecute() {
                super.onPreExecute();
                loading = ProgressDialog.show(MainActivity.this, "Menambahkan . . .",
                        "Tunggu . . . ",false, false);
            }

            @Override
            protected void onPostExecute(String s){
                super.onPostExecute(s);
                loading.dismiss();
                Toast.makeText(MainActivity.this, s, Toast.LENGTH_LONG).show();
            }

            @Override
            protected String doInBackground(Void... v){
                HashMap<String,String> params = new HashMap<>();
                params.put(konfigurasi.KEY_MHS_NAMA, name);
                params.put(konfigurasi.KEY_MHS_NRP, nrp);
                params.put(konfigurasi.KEY_MHS_KELAS, kelas);
                params.put(konfigurasi.KEY_MHS_BLOG, blog);

                RequestHandler rh = new RequestHandler();
                String res = rh.sendPostRequest(konfigurasi.URL_ADD, params);
                Log.d("res", res);
                return res;
            }
        }
        AddMhs ae = new AddMhs();
        ae.execute();
    }
    @Override
    public void onClick (View v){
        if (v==buttonAdd){
            addMhs();
        }
        if (v==buttonView){
            startActivity(new Intent(this,TampilSemuaMhs.class));
        }
    }
}

Akan nampak banyak error, itu karena kita belum menambahkan class lainnya.

Buat 2 class baru yaitu "konfigurasi" dan "RequestHandler" (tanpa tanda "") dengan cara klik kanan pada direktori nama package lalu pilih new class.

Pertama ketikkan kode berikut kedalam file konfigurasi.java

package com.example.tugas13;

public class konfigurasi {
    public static final String URL_ADD = "http://android.unggasid.com/mhs/tambahMhs.php";
    public static final String URL_GET_ALL = "http://android.unggasid.com/mhs/tampilSemuaMhs.php";
    public static final String URL_GET_EMP = "http://android.unggasid.com/mhs/tampilMhs.php?id=";
    public static final String URL_UPDATE_EMP = "http://android.unggasid.com/mhs/updateMhs.php";
    public static final String URL_DELETE_EMP = "http://android.unggasid.com/mhs/hapusMhs.php?id=";

    public static final String KEY_MHS_ID = "id";
    public static final String KEY_MHS_NAMA = "name";
    public static final String KEY_MHS_NRP = "nrp";
    public static final String KEY_MHS_KELAS = "kelas";
    public static final String KEY_MHS_BLOG = "blog";

    public static final String TAG_JSON_ARRAY = "result";
    public static final String TAG_ID = "id";
    public static final String TAG_NAMA = "name";
    public static final String TAG_NRP = "nrp";
    public static final String TAG_KELAS = "kelas";
    public static final String TAG_BLOG = "blog";


    public static final String MHS_ID = "mhs_id";
}

Dan ketikkan kode dibawah ini pada file RequestHandler.java

package com.example.tugas13;

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.OutputStreamWriter;
import java.io.UnsupportedEncodingException;
import java.net.HttpURLConnection;
import java.net.URL;
import java.net.URLEncoder;
import java.util.HashMap;
import java.util.Map;

import javax.net.ssl.HttpsURLConnection;

public class RequestHandler {

    //metode yang digunakan mengirim httpPostRequest
    public String sendPostRequest (String requestURL, HashMap<String,String>postDataParams){
        URL url;
        StringBuilder sb = new StringBuilder();
        try{
            url = new URL(requestURL);
            HttpURLConnection conn = (HttpURLConnection) url.openConnection();
            conn.setReadTimeout(15000);
            conn.setConnectTimeout(15000);
            conn.setRequestMethod("POST");
            conn.setDoInput(true);
            conn.setDoOutput(true);

            OutputStream os = conn.getOutputStream();
            BufferedWriter writer = new BufferedWriter(new OutputStreamWriter(os,"UTF-8"));
            writer.write(getPostDataString(postDataParams));
            writer.flush();
            writer.close();
            os.close();
            int responseCode = conn.getResponseCode();
            if(responseCode== HttpsURLConnection.HTTP_OK){
                BufferedReader br = new BufferedReader(new InputStreamReader(conn.getInputStream()));
                sb = new StringBuilder();
                String response;
                while ((response = br.readLine())!= null){
                    sb.append(response);
                }
            }
        }
        catch (Exception e){
            e.printStackTrace();
        }
        return sb.toString();
    }

    public String sendGetRequest(String requestURL){
        StringBuilder sb = new StringBuilder();
        try {
            URL url = new URL(requestURL);
            HttpURLConnection con = (HttpURLConnection) url.openConnection();
            BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(con.getInputStream()));
            String s;
            while((s=bufferedReader.readLine())!=null){
                sb.append(s+"\n");
            }
        }
        catch (Exception e){
        }
        return sb.toString();
    }
    public String sendGetRequestParam (String requestURL, String id){
        StringBuilder sb = new StringBuilder();
        try{
            URL url = new URL(requestURL+id);
            HttpURLConnection con = (HttpURLConnection) url.openConnection();
            BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(con.getInputStream()));
            String s;
            while ((s=bufferedReader.readLine())!=null){
                sb.append(s+"\n");
            }
        }
        catch (Exception e ){ }
        return sb.toString();
    }

    private String getPostDataString (HashMap<String,String>params) throws UnsupportedEncodingException {
        StringBuilder result = new StringBuilder();
        boolean first = true;
        for (Map.Entry<String,String> entry : params.entrySet()){
            if(first)
                first = false;
            else
                result.append("&");
            result.append(URLEncoder.encode(entry.getKey(),"UTF-8"));
            result.append("=");
            result.append(URLEncoder.encode(entry.getValue(),"UTF-8"));
        }
        return result.toString();
    }
}

Membuat Layout baru

Buat 3 activity baru dengan cara klik kanan pada folder dengan nama package lalu pilih new activity > empty activity

Activity baru yang pertama :

Activity baru yang kedua :

Acitivity baru yang ketiga :

KODE UNTUK 3 LAYOUT BARU

Setelah membuat 3 activity baru, selanjutnya ketikkan kode berikut ke layout di activity baru yang pertama, yaitu activty_tampil_semua_mhs.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    android:paddingLeft="16dp"
    android:paddingRight="16dp"
    android:paddingTop="16dp"
    android:paddingBottom="16dp"
    tools:context=".TampilSemuaMhs">

    <ListView
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:id="@+id/listView" />

</LinearLayout>

Lalu ketikkan lagi kode berikut di activity_tampil_mhs.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    android:paddingLeft="16dp"
    android:paddingRight="16dp"
    android:paddingTop="16dp"
    android:paddingBottom="16dp"
    tools:context=".MainActivity">

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="ID Mahasiswa : " />

    <EditText
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:id="@+id/editTextId" />

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Nama Mahasiswa :" />

    <EditText
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:id="@+id/editTextName" />

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="N R P :" />

    <EditText
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:id="@+id/editTextNRP" />

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Kelas :" />

    <EditText
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:id="@+id/editTextKelas" />

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Blog URL :" />

    <EditText
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:id="@+id/editTextBlog" />

    <Button
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="Update Data Mahasiswa"
        android:id="@+id/buttonUpdate" />

    <Button
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="Hapus Data"
        android:id="@+id/buttonDelete" />

</LinearLayout>

dan layout yang terakhir adalah list_item.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:id="@+id/id" />

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:id="@+id/name" />

</LinearLayout>

KODE UNTUK CLASS BARU

TampilSemuaMhs.java kode :

package com.example.tugas13;

import androidx.appcompat.app.AppCompatActivity;

import android.app.ProgressDialog;
import android.content.Intent;
import android.os.AsyncTask;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.AdapterView;
import android.widget.ListAdapter;
import android.widget.ListView;
import android.widget.SimpleAdapter;

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

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

public class TampilSemuaMhs extends AppCompatActivity implements ListView.OnItemClickListener {
    private ListView listView;
    private String JSON_STRING;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_tampil_semua_mhs);
        listView = findViewById(R.id.listView);
        listView.setOnItemClickListener(this);
        getJSON();
    }

    private void showMhs(){
        JSONObject jsonObject = null;
        ArrayList <HashMap<String,String>> list = new ArrayList<HashMap<String, String>>();
        try {
            jsonObject = new JSONObject(JSON_STRING);
            JSONArray result = jsonObject.getJSONArray(konfigurasi.TAG_JSON_ARRAY);
            for (int i = 0; i<result.length();i++){
                JSONObject jo = result.getJSONObject(i);
                String id = jo.getString(konfigurasi.TAG_ID);

                String name = jo.getString(konfigurasi.TAG_NAMA);
                HashMap<String,String> mhs = new HashMap<>();
                mhs.put(konfigurasi.TAG_ID, id);
                mhs.put(konfigurasi.TAG_NAMA, name);
                list.add(mhs);
            }
        }
        catch (JSONException e) {
            e.printStackTrace();
        }

        ListAdapter adapter = new SimpleAdapter(TampilSemuaMhs.this, list,
                R.layout.list_item, new String[]{konfigurasi.TAG_ID, konfigurasi.TAG_NAMA},
                new int[]{R.id.id, R.id.name});
        listView.setAdapter(adapter);
    }

    private void getJSON(){
        class GetJSON extends AsyncTask <Void, Void, String>{
            ProgressDialog loading;
            @Override
            protected void onPreExecute(){
                super.onPreExecute();
                loading = ProgressDialog.show(TampilSemuaMhs.this,"Mengambil data","Mohon Tunggu",false,false);
            }

            @Override
            protected void onPostExecute(String s){
                super.onPostExecute(s);
                loading.dismiss();
                JSON_STRING = s;
                showMhs();
            }

            @Override
            protected String doInBackground(Void... params){
                RequestHandler rh = new RequestHandler();
                Log.d("Testing","Test");
                String s = rh.sendGetRequest(konfigurasi.URL_GET_ALL);
                Log.d("response",s);

                return  s;
            }
        }
        GetJSON gj = new GetJSON();
        gj.execute();
    }

    @Override
    public void onItemClick(AdapterView<?> parent, View view, int position, long id){
        Intent intent = new Intent(this, TampilMhs.class);
        HashMap<String,String> map = (HashMap)parent.getItemAtPosition(position);
        String mhsID = map.get(konfigurasi.TAG_ID).toString();
        intent.putExtra(konfigurasi.MHS_ID,mhsID);
        startActivity(intent);
    }
}

Kode untuk TampilMhs.java

package com.example.tugas13;

import androidx.appcompat.app.AppCompatActivity;

import android.app.AlertDialog;
import android.app.DownloadManager;
import android.app.ProgressDialog;
import android.content.DialogInterface;
import android.content.Intent;
import android.os.AsyncTask;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;

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

import java.util.HashMap;

public class TampilMhs extends AppCompatActivity implements View.OnClickListener {
    private EditText editTextId;
    private EditText editTextName;
    private EditText editTextNRP;
    private EditText editTextKelas;
    private EditText editTextBlog;

    private Button buttonUpdate;
    private Button buttonDelete;

    private String id;


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_tampil_mhs);
        Intent intent = getIntent();
        id = intent.getStringExtra(konfigurasi.MHS_ID);
        editTextId = findViewById(R.id.editTextId);
        editTextName = findViewById(R.id.editTextName);
        editTextNRP = findViewById(R.id.editTextNRP);
        editTextKelas = findViewById(R.id.editTextKelas);
        editTextBlog = findViewById(R.id.editTextBlog);

        buttonUpdate = findViewById(R.id.buttonUpdate);
        buttonDelete = findViewById(R.id.buttonDelete);
        buttonDelete.setOnClickListener(this);
        buttonUpdate.setOnClickListener(this);
        editTextId.setText(id);
        getMhs();
    }

    private void getMhs(){
        class GetMhs extends AsyncTask<Void,Void,String>{
            ProgressDialog loading;

            @Override
            protected void onPreExecute(){
                super.onPreExecute();
                loading = ProgressDialog.show(TampilMhs.this,"Fetching . . .","Wait. . .",false,false);
            }

            @Override
            protected void onPostExecute (String s){
                super.onPostExecute(s);
                loading.dismiss();
                showMhs(s);
            }

            @Override
            protected String doInBackground(Void... params){
                RequestHandler rh = new RequestHandler();
                String s = rh.sendGetRequestParam(konfigurasi.URL_GET_EMP,id);
                return s;
            }
        }
        GetMhs ge = new GetMhs();
        ge.execute();
    }

    private void showMhs(String json){
        try {
            JSONObject jsonObject = new JSONObject(json);
            JSONArray result = jsonObject.getJSONArray(konfigurasi.TAG_JSON_ARRAY);
            JSONObject c = result.getJSONObject(0);
            String name = c.getString(konfigurasi.TAG_NAMA);
            String nrp = c.getString(konfigurasi.TAG_NRP);
            String kelas = c.getString(konfigurasi.TAG_KELAS);
            String blog = c.getString(konfigurasi.TAG_BLOG);
            editTextName.setText(name);
            editTextNRP.setText(nrp);
            editTextKelas.setText(kelas);
            editTextBlog.setText(blog);
        }
        catch (JSONException e){
            e.printStackTrace();
        }
    }
    private void updateMhs(){
        final String name = editTextName.getText().toString().trim();
        final String nrp = editTextNRP.getText().toString().trim();
        final String kelas = editTextKelas.getText().toString().trim();
        final String blog = editTextBlog.getText().toString().trim();

        class UpdateMhs extends AsyncTask<Void,Void,String>{
            ProgressDialog loading;
            @Override
            protected void onPreExecute(){
                super.onPreExecute();
                loading = ProgressDialog.show(TampilMhs.this, "Updating. . .","Wait. . .",false,false);
            }

            @Override
            protected void onPostExecute(String s){
                super.onPostExecute(s);
                loading.dismiss();
                Toast.makeText(TampilMhs.this,s,Toast.LENGTH_LONG).show();
            }

            @Override
            protected String doInBackground(Void... params){
                HashMap<String,String> hashMap = new HashMap<>();
                hashMap.put(konfigurasi.KEY_MHS_ID,id);
                hashMap.put(konfigurasi.KEY_MHS_NAMA,name);
                hashMap.put(konfigurasi.KEY_MHS_NRP,nrp);
                hashMap.put(konfigurasi.KEY_MHS_KELAS,kelas);
                hashMap.put(konfigurasi.KEY_MHS_BLOG,blog);
                RequestHandler rh = new RequestHandler();
                String s = rh.sendPostRequest(konfigurasi.URL_UPDATE_EMP, hashMap);
                return s;
            }
        }
        UpdateMhs ue = new UpdateMhs();
        ue.execute();
    }

    private void deleteMhs(){
        class DeleteMhs extends AsyncTask<Void,Void,String>{
            ProgressDialog loading;
            @Override
            protected void onPreExecute(){
                super.onPreExecute();
                loading = ProgressDialog.show(TampilMhs.this, "Updating. . .","Tunggu. . .",false,false);
            }

            @Override
            protected void onPostExecute(String s){
                super.onPostExecute(s);
                loading.dismiss();
                Toast.makeText(TampilMhs.this,s,Toast.LENGTH_LONG).show();
            }

            @Override
            protected String doInBackground(Void... params){
                RequestHandler rh = new RequestHandler();
                String s = rh.sendGetRequestParam(konfigurasi.URL_DELETE_EMP, id);
                return s;
            }
        }
        DeleteMhs de = new DeleteMhs();
        de.execute();
    }

    private void confirmDeleteMhs(){
        AlertDialog.Builder alertDialogBuilder = new AlertDialog.Builder(this);
        alertDialogBuilder.setMessage("Apakah kamu yakin ingin menghapus data ini ?");
        alertDialogBuilder.setPositiveButton("Ya", new DialogInterface.OnClickListener() {
            @Override
            public void onClick(DialogInterface arg0, int arg1) {
                deleteMhs();
                startActivity(new Intent(TampilMhs.this, TampilSemuaMhs.class));
            }
        });
        alertDialogBuilder.setNegativeButton("Tidak", new DialogInterface.OnClickListener() {
            @Override
            public void onClick(DialogInterface arg0, int arg1) {

            }
        });
        AlertDialog alertDialog = alertDialogBuilder.create();
        alertDialog.show();
    }

    @Override
    public void onClick (View v){
        if (v==buttonUpdate){
            updateMhs();
        }
        if (v==buttonDelete){
            confirmDeleteMhs();
        }
    }
}

Dan untuk class ListView.java, biarkan saja seperti itu. Coba jalankan di emulator ataupun HP android masing-masing.

https://www.youtube.com/watch?v=P6lnW6hh1B4