在本教程中，我们将了解Android SQLite数据库CRUD示例。

Android SQLite是开源关系数据库，可用于执行CRUD操作。

我们不必为此进行显式安装。
它可在Android中默认提供。

让我们从简单的例子开始：

在此示例中，我们将创建列表查看以显示Country列表，并在SQLite数据库的帮助下支持所有CRUD操作。
当我们将新的国家添加到列表或者删除任何现有国家/地区时，它将反映在数据库中。

数据库表结构：

表名称：Country

第1步：创建项目

创建Android应用程序项目"SQLitedatabasecrudexample"。

第2步：创建布局

更改RES - >布局 - > Activity_main.xml如下所示：

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/activity_main"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context="com.theitroad.sqlitedatabasecrudexample.MainActivity">
    <Button
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="Add Country"
        android:id="@+id/btnSubmit"
        
    <ListView
        android:id="@+id/android:list"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_below="@id/btnSubmit"
        
</RelativeLayout>

我们将在设计视图中看到以下屏幕。

第3步：创建国家类

创建一个Country类，该类将与SQLite数据库中的Country表对应。

package com.theitroad.sqlitedatabasecrudexample;
/*
 * This is our model class and it corresponds to Country table in database
 */
 
import static android.R.attr.name;
 
public class Country{
 
    int id;
    String countryName;
    long population;
 
    public Country() {
        super();
    }
    public Country(int i, String countryName,long population) {
        super();
        this.id = i;
        this.countryName = countryName;
        this.population=population;
    }
 
    //constructor
    public Country(String countryName, long population){
        this.countryName = countryName;
        this.population = population;
    }
    public int getId() {
        return id;
    }
    public void setId(int id) {
        this.id = id;
    }
    public String getCountryName() {
        return countryName;
    }
    public void setCountryName(String countryName) {
        this.countryName = countryName;
    }
    public long getPopulation() {
        return population;
    }
    public void setPopulation(long population) {
        this.population = population;
    }
 
}

步骤4：创建SQLitedatabaseHandler以定义数据库操作。

我们将创建一个名为SqlitedatabaseHandler的类，它将扩展SQLiteopenHelper并覆盖OnCreate和OnUpdate方法。
我们还将添加一些CRUD方法。

• addcountry
• getcountry
• GetAllCountries.
• Updatecountry.
• deletecountry
• delelteallcountries

以上所有方法都将与SQLite数据库交互并执行CRUD操作。

package com.theitroad.sqlitedatabasecrudexample;
import android.content.ContentValues;
import android.database.Cursor;
import android.database.sqlite.SQLiteOpenHelper;
import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
 
import java.util.ArrayList;
import java.util.List;
 
public class SQLiteDatabaseHandler extends SQLiteOpenHelper {
 
    //All Static variables
    //Database Version
    private static final int DATABASE_VERSION = 1;
 
    //Database Name
    private static final String DATABASE_NAME = "countryData";
 
    //Country table name
    private static final String TABLE_COUNTRY= "Country";
 
    //Country Table Columns names
    private static final String KEY_ID = "id";
    private static final String COUNTRY_NAME = "CountryName";
    private static final String POPULATION = "Population";
 
    public SQLiteDatabaseHandler(Context context) {
        super(context, DATABASE_NAME, null, DATABASE_VERSION);
    }
 
    //Creating Tables
    @Override
    public void onCreate(SQLiteDatabase db) {
        String CREATE_COUNTRY_TABLE = "CREATE TABLE " + TABLE_COUNTRY + "("
                + KEY_ID + " INTEGER PRIMARY KEY," + COUNTRY_NAME + " TEXT,"
                + COUNTRY_NAME + " LONG" + ")";
        db.execSQL(CREATE_COUNTRY_TABLE);
    }
 
    //Upgrading database
    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        //Drop older table if existed
        db.execSQL("DROP TABLE IF EXISTS " + TABLE_COUNTRY);
        //Create tables again
        onCreate(db);
    }
 
    /**
     * All CRUD(Create, Read, Update, Delete) Operations
     */
 
    //Adding new country
    void addCountry(Country country) {
        SQLiteDatabase db = this.getWritableDatabase();
 
        ContentValues values = new ContentValues();
        values.put(COUNTRY_NAME, country.getCountryName()); //Country Name
        values.put(POPULATION, country.getPopulation()); //Country Population
 
        //Inserting Row
        db.insert(TABLE_COUNTRY, null, values);
        db.close(); //Closing database connection
    }
 
    //Getting single country
    Country getCountry(int id) {
        SQLiteDatabase db = this.getReadableDatabase();
 
        Cursor cursor = db.query(TABLE_COUNTRY, new String[] { KEY_ID,
                        COUNTRY_NAME, POPULATION }, KEY_ID + "=?",
                new String[] { String.valueOf(id) }, null, null, null, null);
        if (cursor != null)
            cursor.moveToFirst();
 
        Country country = new Country(Integer.parseInt(cursor.getString(0)),
                cursor.getString(1), cursor.getLong(2));
        //return country
        return country;
    }
 
    //Getting All Countries
    public List getAllCountries() {
        List countryList = new ArrayList();
        //Select All Query
        String selectQuery = "SELECT  * FROM " + TABLE_COUNTRY;
 
        SQLiteDatabase db = this.getWritableDatabase();
        Cursor cursor = db.rawQuery(selectQuery, null);
 
        //looping through all rows and adding to list
        if (cursor.moveToFirst()) {
            do {
                Country country = new Country();
                country.setId(Integer.parseInt(cursor.getString(0)));
                country.setCountryName(cursor.getString(1));
                country.setPopulation(cursor.getLong(2));
                //Adding country to list
                countryList.add(country);
            } while (cursor.moveToNext());
        }
 
        //return country list
        return countryList;
    }
 
    //Updating single country
    public int updateCountry(Country country) {
        SQLiteDatabase db = this.getWritableDatabase();
 
        ContentValues values = new ContentValues();
        values.put(COUNTRY_NAME, country.getCountryName());
        values.put(POPULATION, country.getPopulation());
 
        //updating row
        return db.update(TABLE_COUNTRY, values, KEY_ID + " = ?",
                new String[] { String.valueOf(country.getId()) });
    }
 
    //Deleting single country
    public void deleteCountry(Country country) {
        SQLiteDatabase db = this.getWritableDatabase();
        db.delete(TABLE_COUNTRY, KEY_ID + " = ?",
                new String[] { String.valueOf(country.getId()) });
        db.close();
    }
 
    //Deleting all countries
    public void deleteAllCountries() {
        SQLiteDatabase db = this.getWritableDatabase();
        db.delete(TABLE_COUNTRY,null,null);
        db.close();
    }
 
    //Getting countries Count
    public int getCountriesCount() {
        String countQuery = "SELECT  * FROM " + TABLE_COUNTRY;
        SQLiteDatabase db = this.getReadableDatabase();
        Cursor cursor = db.rawQuery(countQuery, null);
        cursor.close();
 
        //return count
        return cursor.getCount();
    }
}

步骤5：为行创建布局

正如我们在Activity_main.xml中声明listview小部件。
现在我们需要为单个行提供布局。

• 转到res - >布局
• 右键单击布局
• 单击"新建 - >文件"。
• 创建名为"row_item.xml"的文件，并在row_item.xml中粘贴以下代码。

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout 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:layout_columnWeight="1"
        android:layout_marginLeft="10dp"
        android:textSize="30dp"
        android:textColor="#1E90FF"
        android:id="@+id/textViewId"
        android:layout_row="0"
        android:layout_column="1" 
    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_columnWeight="1"
        android:layout_marginLeft="10dp"
        android:textSize="20dp"
        android:textColor="#4B0082"
        android:layout_below="@+id/textViewId"
        android:id="@+id/textViewCountry"
        android:layout_row="1"
        android:layout_column="1" 
 
    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_columnWeight="1"
        android:layout_marginLeft="10dp"
        android:textSize="20dp"
        android:textColor="#4B0082"
        android:layout_below="@+id/textViewCountry"
        android:id="@+id/textViewPopulation"
        android:layout_row="1"
        android:layout_column="2" 
 
    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_columnWeight="1"
        android:layout_marginRight="10dp"
        android:layout_marginLeft="100dp"
        android:layout_marginTop="30dp"
        android:id="@+id/edit"
        android:text="Edit"
        android:layout_toRightOf="@+id/textViewId"
        
    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_columnWeight="1"
        android:layout_marginRight="10dp"
        android:layout_marginTop="30dp"
        android:layout_marginLeft="10dp"
        android:id="@+id/delete"
        android:text="Delete"
        android:layout_toRightOf="@+id/edit"
        
</RelativeLayout>

步骤6：为ListView创建ArrayAdapter

在创建捕获期之前，我们需要为自定义ListView行创建CustomCountrylist类。

package com.theitroad.sqlitedatabasecrudexample;
 
import android.app.Activity;
import android.util.Log;
import android.view.Gravity;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.Button;
import android.widget.EditText;
import android.widget.PopupWindow;
import android.widget.TextView;
import java.util.ArrayList;
 
public class CustomCountryList extends BaseAdapter {
    private Activity context;
    ArrayList countries;
    private PopupWindow pwindo;
    SQLiteDatabaseHandler db;
    BaseAdapter ba;
 
    public CustomCountryList(Activity context, ArrayList countries,SQLiteDatabaseHandler db) {
        this.context = context;
        this.countries=countries;
        this.db=db;
    }
 
    public static class ViewHolder
    {
        TextView textViewId;
        TextView textViewCountry;
        TextView textViewPopulation;
        Button editButton;
        Button deleteButton;
    }
    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        View row = convertView;
            LayoutInflater inflater = context.getLayoutInflater();
            ViewHolder vh;
            if (convertView == null) {
                vh = new ViewHolder();
                row = inflater.inflate(R.layout.row_item, null, true);
 
                        vh.textViewId = (TextView) row.findViewById(R.id.textViewId);
                        vh.textViewCountry = (TextView) row.findViewById(R.id.textViewCountry);
                        vh.textViewPopulation = (TextView) row.findViewById(R.id.textViewPopulation);
                        vh.editButton = (Button) row.findViewById(R.id.edit);
                        vh.deleteButton = (Button) row.findViewById(R.id.delete);
 
                //store the holder with the view.
                row.setTag(vh);
            } else {
 
                    vh = (ViewHolder) convertView.getTag();
 
            }
 
            vh.textViewCountry.setText(countries.get(position).getCountryName());
            vh.textViewId.setText("" + countries.get(position).getId());
            vh.textViewPopulation.setText("" + countries.get(position).getPopulation());
            final int positionPopup = position;
            vh.editButton.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View view) {
 
                    Log.d("Save: ", "" + positionPopup);
                    editPopup(positionPopup);
 
                }
            });
            vh.deleteButton.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View view) {
                    Log.d("Last Index", "" + positionPopup);
                    //    Integer index = (Integer) view.getTag();
                    db.deleteCountry(countries.get(positionPopup));
 
                    //     countries.remove(index.intValue());
                    countries = (ArrayList) db.getAllCountries();
                    Log.d("Country size", "" + countries.size());
                    notifyDataSetChanged();
                }
            });
        return  row;
    }
 
    public long getItemId(int position) {
        return position;
    }
 
    public Object getItem(int position) {
        return position;
    }
 
    public int getCount() {
        return countries.size();
    }
 
  public void editPopup(final int positionPopup)
  {
      LayoutInflater inflater = context.getLayoutInflater();
      View layout = inflater.inflate(R.layout.edit_popup,
              (ViewGroup) context.findViewById(R.id.popup_element));
      pwindo = new PopupWindow(layout, 600, 670, true);
      pwindo.showAtLocation(layout, Gravity.CENTER, 0, 0);
      final EditText countryEdit = (EditText) layout.findViewById(R.id.editTextCountry);
      final EditText populationEdit = (EditText) layout.findViewById(R.id.editTextPopulation);
      countryEdit.setText(countries.get(positionPopup).getCountryName());
      populationEdit.setText("" + countries.get(positionPopup).getPopulation());
      Log.d("Name: ", "" + countries.get(positionPopup).getPopulation());
      Button save = (Button) layout.findViewById(R.id.save_popup);
      save.setOnClickListener(new View.OnClickListener() {
          @Override
          public void onClick(View view) {
              String countryStr = countryEdit.getText().toString();
              String population = populationEdit.getText().toString();
              Country country = countries.get(positionPopup);
              country.setCountryName(countryStr);
              country.setPopulation(Long.parseLong(population));
              db.updateCountry(country);
              countries = (ArrayList) db.getAllCountries();
              notifyDataSetChanged();
              for (Country country1 : countries) {
                  String log = "Id: " + country1.getId() + " ,Name: " + country1.getCountryName() + " ,Population: " + country1.getPopulation();
                  //Writing Countries to log
                  Log.d("Name: ", log);
              }
              pwindo.dismiss();
          }
      });
  }
}

此类用于填充ListView的数据。
GetView方法被调用用于绘制每一行。
当我们单击编辑时，我们将看到一个弹出窗口以编辑国家/地区名称和人口。
如果单击"删除"，则将从ListView和SQLite数据库中删除国家/地区。

第7步：创建MainActivity

更改src/main/packageName/mainActivity.java如下：

package com.theitroad.sqlitedatabasecrudexample;
 
import android.app.Activity;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.Gravity;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.AdapterView;
import android.widget.BaseAdapter;
import android.widget.Button;
import android.widget.EditText;
import android.widget.ListView;
import android.widget.PopupWindow;
import android.widget.Toast;
import java.util.ArrayList;
 
public class MainActivity extends AppCompatActivity {
 
    ArrayList countries;
    SQLiteDatabaseHandler db;
    Button btnSubmit;
    PopupWindow pwindo;
    Activity activity;
    ListView listView;
    CustomCountryList customCountryList;
 
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        activity=this;
        db= new SQLiteDatabaseHandler(this);
        listView = (ListView) findViewById(android.R.id.list);
        btnSubmit = (Button) findViewById(R.id.btnSubmit);
        btnSubmit.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                addPopUp();
                    }
                });
        Log.d("MainActivity: ", "Before reading mainactivity");
        countries = (ArrayList) db.getAllCountries();
 
            for (Country country : countries) {
                String log = "Id: " + country.getId() + " ,Name: " + country.getCountryName() + " ,Population: " + country.getPopulation();
                //Writing Countries to log
                Log.d("Name: ", log);
            }
 
                CustomCountryList customCountryList = new CustomCountryList(this, countries, db);
                listView.setAdapter(customCountryList);
 
                listView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
                    @Override
                    public void onItemClick(AdapterView<?> adapterView, View view, int position, long l) {
                        Toast.makeText(getApplicationContext(), "You Selected " + countries.get(position).getCountryName() + " as Country", Toast.LENGTH_SHORT).show();
                    }
                });
    }
 
    public void addPopUp() {
        LayoutInflater inflater = activity.getLayoutInflater();
        View layout = inflater.inflate(R.layout.edit_popup,
                (ViewGroup) activity.findViewById(R.id.popup_element));
        pwindo = new PopupWindow(layout, 600, 670, true);
        pwindo.showAtLocation(layout, Gravity.CENTER, 0, 0);
        final EditText countryEdit = (EditText) layout.findViewById(R.id.editTextCountry);
        final EditText populationEdit = (EditText) layout.findViewById(R.id.editTextPopulation);
 
        Button save = (Button) layout.findViewById(R.id.save_popup);
        save.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                String countryStr = countryEdit.getText().toString();
                String population = populationEdit.getText().toString();
                Country country = new Country(countryStr, Long.parseLong(population));
                db.addCountry(country);
                if(customCountryList==null)
                {
                    customCountryList = new CustomCountryList(activity, countries, db);
                    listView.setAdapter(customCountryList);
                }
                customCountryList.countries = (ArrayList) db.getAllCountries();
                ((BaseAdapter)listView.getAdapter()).notifyDataSetChanged();
                for (Country country1 : countries) {
                    String log = "Id: " + country1.getId() + " ,Name: " + country1.getCountryName() + " ,Population: " + country1.getPopulation();
                    //Writing Countries to log
                    Log.d("Name: ", log);
                }
                pwindo.dismiss();
            }
        });
    }
}

当我们单击"添加国家"按钮时，我们将获得一个popup.you put国家名称和人口和国家将添加到列表中。

第8步：运行应用程序

运行应用程序时，单击"添加国家"按钮
我将国家名称放在丹麦和人口为10000。

单击"保存"时，将保存到数据库。