sql 샘플코드 추가

sql_db/.gitignore

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+# Miscellaneous
+*.class
+*.log
+*.pyc
+*.swp
+.DS_Store
+.atom/
+.buildlog/
+.history
+.svn/
+
+# IntelliJ related
+*.iml
+*.ipr
+*.iws
+.idea/
+
+# The .vscode folder contains launch configuration and tasks you configure in
+# VS Code which you may wish to be included in version control, so this line
+# is commented out by default.
+#.vscode/
+
+# Flutter/Dart/Pub related
+**/doc/api/
+**/ios/Flutter/.last_build_id
+.dart_tool/
+.flutter-plugins
+.flutter-plugins-dependencies
+.packages
+.pub-cache/
+.pub/
+/build/
+
+# Web related
+lib/generated_plugin_registrant.dart
+
+# Symbolication related
+app.*.symbols
+
+# Obfuscation related
+app.*.map.json
+
+# Android Studio will place build artifacts here
+/android/app/debug
+/android/app/profile
+/android/app/release

sql_db/.metadata

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+# This file tracks properties of this Flutter project.
+# Used by Flutter tool to assess capabilities and perform upgrades etc.
+#
+# This file should be version controlled and should not be manually edited.
+
+version:
+  revision: 8328b56ef37c511097545f24a054b6abe7631b0b
+  channel: master
+
+project_type: app

sql_db/README.md

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+# sql_db
+
+flutter에서 sqldb 사용법을 배운다.
+예제는 구글링에서 찾은 [블로그](https://suragch.medium.com/simple-sqflite-database-example-in-flutter-e56a5aaa3f91)를 기본으로 한다.
+
+## 의존성
+sqflite와 path_provider가 필요하다.
+sql이 아니고 sqf이다. 파일db라서 그런것인가??
+path_provider는 문서 디렉토리를 찾기 위해 사용된다.
+```
+sqflite: ^1.2.0
+path_provider: ^1.5.1
+```
+
+## 데이터베이스 헬퍼 클래스
+우선 눈에 띄는 부분이 싱클톤 객체로 만드는 부분이다.
+코드와 주석은 이해가 되는데, _privateConstructor();이게 공식적인 문법인지 애매하다.
+구글링을 해봐도 명확하게 나오지는 않는데, 코드 실행상 이상이 없으니 맞겠죠??
+```
+  // make this a singleton class
+  DatabaseHelper._privateConstructor();
+  static final DatabaseHelper instance = DatabaseHelper._privateConstructor();
+```
+
+실제 instance부분은 싱글톤 객체로 유일한 데이터접근 경로인것이고,
+실제 데이터베이스 객체는 아래와 같이 선언되어 있다.
+
+역시 static으로 선언되어 있고, get을 할때 최초 한번 초기화를 수행한다.
+초기화에는 데이터베이스 생성을 위한 ddl도 포함되어 있다.
+테이블 구조는 목적에 맞게 정의하되, app이기때문에 너무 복잡한 구조는 피하게 좋을듯 하다.
+```
+  // only have a single app-wide reference to the database
+  static Database _database;
+  Future<Database> get database async {
+    if (_database != null) return _database;
+    // lazily instantiate the db the first time it is accessed
+    _database = await _initDatabase();
+    return _database;
+  }
+
+  // this opens the database (and creates it if it doesn't exist)
+  _initDatabase() async {
+    Directory documentsDirectory = await getApplicationDocumentsDirectory();
+    String path = join(documentsDirectory.path, _databaseName);
+    return await openDatabase(path,
+        version: _databaseVersion, onCreate: _onCreate);
+  }
+
+  // SQL code to create the database table
+  Future _onCreate(Database db, int version) async {
+    await db.execute('''
+          CREATE TABLE $table (
+            $columnId INTEGER PRIMARY KEY,
+            $columnName TEXT NOT NULL,
+            $columnAge INTEGER NOT NULL
+          )
+          ''');
+  }
+```
+
+## 데이터베이스 CRUD
+실제 sql과는 조금 다르다.
+orm같은 느낌이 더 강하다.
+간단한 코드저장/select 용도이기 때문에 크게 문제가 없을것 같다.
+실제 SQL도 되는것 같지만, 코드 샘플상 sql보다는 프로그램코드를 권장하는 느낌이다.
+(당연히 app개발 영역이니 복잡한 sql보다 심플한 코드가 선호되는게 맞다고 본다.)
+```
+  // All of the rows are returned as a list of maps, where each map is
+  // a key-value list of columns.
+  Future<List<Map<String, dynamic>>> queryAllRows() async {
+    Database db = await instance.database;
+    return await db.query(table);
+  }
+
+  // All of the methods (insert, query, update, delete) can also be done using
+  // raw SQL commands. This method uses a raw query to give the row count.
+  Future<int> queryRowCount() async {
+    Database db = await instance.database;
+    return Sqflite.firstIntValue(
+        await db.rawQuery('SELECT COUNT(*) FROM $table'));
+  }
+
+  // We are assuming here that the id column in the map is set. The other
+  // column values will be used to update the row.
+  Future<int> update(Map<String, dynamic> row) async {
+    Database db = await instance.database;
+    int id = row[columnId];
+    return await db.update(table, row, where: '$columnId = ?', whereArgs: [id]);
+  }
+```
+
+
+## 데이터 베이스 사용
+싱글턴객체를 통해서 일단 데이터베이스 객체를 구한다.
+그리고, 선언된 crud 메소드를 통해 실제 database객체로 접근하도록 가이드 되고 있다.
+```
+  // reference to our single class that manages the database
+  final dbHelper = DatabaseHelper.instance;
+
+...
+...
+
+  void _insert() async {
+    // row to insert
+    Map<String, dynamic> row = {
+      DatabaseHelper.columnName: 'Bob',
+      DatabaseHelper.columnAge: 23
+    };
+    final id = await dbHelper.insert(row);
+    print('inserted row id: $id');
+  }
+
+```

sql_db/android/.gitignore

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+gradle-wrapper.jar
+/.gradle
+/captures/
+/gradlew
+/gradlew.bat
+/local.properties
+GeneratedPluginRegistrant.java
+
+# Remember to never publicly share your keystore.
+# See https://flutter.dev/docs/deployment/android#reference-the-keystore-from-the-app
+key.properties

sql_db/android/app/build.gradle

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+def localProperties = new Properties()
+def localPropertiesFile = rootProject.file('local.properties')
+if (localPropertiesFile.exists()) {
+    localPropertiesFile.withReader('UTF-8') { reader ->
+        localProperties.load(reader)
+    }
+}
+
+def flutterRoot = localProperties.getProperty('flutter.sdk')
+if (flutterRoot == null) {
+    throw new GradleException("Flutter SDK not found. Define location with flutter.sdk in the local.properties file.")
+}
+
+def flutterVersionCode = localProperties.getProperty('flutter.versionCode')
+if (flutterVersionCode == null) {
+    flutterVersionCode = '1'
+}
+
+def flutterVersionName = localProperties.getProperty('flutter.versionName')
+if (flutterVersionName == null) {
+    flutterVersionName = '1.0'
+}
+
+apply plugin: 'com.android.application'
+apply plugin: 'kotlin-android'
+apply from: "$flutterRoot/packages/flutter_tools/gradle/flutter.gradle"
+
+android {
+    compileSdkVersion 29
+
+    sourceSets {
+        main.java.srcDirs += 'src/main/kotlin'
+    }
+
+    lintOptions {
+        disable 'InvalidPackage'
+    }
+
+    defaultConfig {
+        // TODO: Specify your own unique Application ID (https://developer.android.com/studio/build/application-id.html).
+        applicationId "com.example.sql_db"
+        minSdkVersion 16
+        targetSdkVersion 29
+        versionCode flutterVersionCode.toInteger()
+        versionName flutterVersionName
+    }
+
+    buildTypes {
+        release {
+            // TODO: Add your own signing config for the release build.
+            // Signing with the debug keys for now, so `flutter run --release` works.
+            signingConfig signingConfigs.debug
+        }
+    }
+}
+
+flutter {
+    source '../..'
+}
+
+dependencies {
+    implementation "org.jetbrains.kotlin:kotlin-stdlib-jdk7:$kotlin_version"
+}

sql_db/android/app/src/debug/AndroidManifest.xml

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+<manifest xmlns:android="http://schemas.android.com/apk/res/android"
+    package="com.example.sql_db">
+    <!-- Flutter needs it to communicate with the running application
+         to allow setting breakpoints, to provide hot reload, etc.
+    -->
+    <uses-permission android:name="android.permission.INTERNET"/>
+</manifest>

sql_db/android/app/src/main/AndroidManifest.xml

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+<manifest xmlns:android="http://schemas.android.com/apk/res/android"
+    package="com.example.sql_db">
+   <application
+        android:label="sql_db"
+        android:icon="@mipmap/ic_launcher">
+        <activity
+            android:name=".MainActivity"
+            android:launchMode="singleTop"
+            android:theme="@style/LaunchTheme"
+            android:configChanges="orientation|keyboardHidden|keyboard|screenSize|smallestScreenSize|locale|layoutDirection|fontScale|screenLayout|density|uiMode"
+            android:hardwareAccelerated="true"
+            android:windowSoftInputMode="adjustResize">
+            <!-- Specifies an Android theme to apply to this Activity as soon as
+                 the Android process has started. This theme is visible to the user
+                 while the Flutter UI initializes. After that, this theme continues
+                 to determine the Window background behind the Flutter UI. -->
+            <meta-data
+              android:name="io.flutter.embedding.android.NormalTheme"
+              android:resource="@style/NormalTheme"
+              />
+            <!-- Displays an Android View that continues showing the launch screen
+                 Drawable until Flutter paints its first frame, then this splash
+                 screen fades out. A splash screen is useful to avoid any visual
+                 gap between the end of Android's launch screen and the painting of
+                 Flutter's first frame. -->
+            <meta-data
+              android:name="io.flutter.embedding.android.SplashScreenDrawable"
+              android:resource="@drawable/launch_background"
+              />
+            <intent-filter>
+                <action android:name="android.intent.action.MAIN"/>
+                <category android:name="android.intent.category.LAUNCHER"/>
+            </intent-filter>
+        </activity>
+        <!-- Don't delete the meta-data below.
+             This is used by the Flutter tool to generate GeneratedPluginRegistrant.java -->
+        <meta-data
+            android:name="flutterEmbedding"
+            android:value="2" />
+    </application>
+</manifest>

sql_db/android/app/src/main/kotlin/com/example/sql_db/MainActivity.kt

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+package com.example.sql_db
+
+import io.flutter.embedding.android.FlutterActivity
+
+class MainActivity: FlutterActivity() {
+}

sql_db/android/app/src/main/res/drawable/launch_background.xml

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+<?xml version="1.0" encoding="utf-8"?>
+<!-- Modify this file to customize your launch splash screen -->
+<layer-list xmlns:android="http://schemas.android.com/apk/res/android">
+    <item android:drawable="?android:colorBackground" />
+
+    <!-- You can insert your own image assets here -->
+    <!-- <item>
+        <bitmap
+            android:gravity="center"
+            android:src="@mipmap/launch_image" />
+    </item> -->
+</layer-list>

sql_db/android/app/src/main/res/values-night/styles.xml

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+<?xml version="1.0" encoding="utf-8"?>
+<resources>
+    <!-- Theme applied to the Android Window while the process is starting when the OS's Dark Mode setting is on -->
+    <style name="LaunchTheme" parent="@android:style/Theme.Black.NoTitleBar">
+        <!-- Show a splash screen on the activity. Automatically removed when
+             Flutter draws its first frame -->
+        <item name="android:windowBackground">@drawable/launch_background</item>
+    </style>
+    <!-- Theme applied to the Android Window as soon as the process has started.
+         This theme determines the color of the Android Window while your
+         Flutter UI initializes, as well as behind your Flutter UI while its
+         running.
+         
+         This Theme is only used starting with V2 of Flutter's Android embedding. -->
+    <style name="NormalTheme" parent="@android:style/Theme.Black.NoTitleBar">
+        <item name="android:windowBackground">?android:colorBackground</item>
+    </style>
+</resources>

sql_db/android/app/src/main/res/values/styles.xml

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+<?xml version="1.0" encoding="utf-8"?>
+<resources>
+    <!-- Theme applied to the Android Window while the process is starting when the OS's Dark Mode setting is off -->
+    <style name="LaunchTheme" parent="@android:style/Theme.Light.NoTitleBar">
+        <!-- Show a splash screen on the activity. Automatically removed when
+             Flutter draws its first frame -->
+        <item name="android:windowBackground">@drawable/launch_background</item>
+    </style>
+    <!-- Theme applied to the Android Window as soon as the process has started.
+         This theme determines the color of the Android Window while your
+         Flutter UI initializes, as well as behind your Flutter UI while its
+         running.
+
+         This Theme is only used starting with V2 of Flutter's Android embedding. -->
+    <style name="NormalTheme" parent="@android:style/Theme.Light.NoTitleBar">
+        <item name="android:windowBackground">?android:colorBackground</item>
+    </style>
+</resources>

sql_db/android/app/src/profile/AndroidManifest.xml

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+<manifest xmlns:android="http://schemas.android.com/apk/res/android"
+    package="com.example.sql_db">
+    <!-- Flutter needs it to communicate with the running application
+         to allow setting breakpoints, to provide hot reload, etc.
+    -->
+    <uses-permission android:name="android.permission.INTERNET"/>
+</manifest>

sql_db/android/build.gradle

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+buildscript {
+    ext.kotlin_version = '1.3.50'
+    repositories {
+        google()
+        jcenter()
+    }
+
+    dependencies {
+        classpath 'com.android.tools.build:gradle:3.5.0'
+        classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version"
+    }
+}
+
+allprojects {
+    repositories {
+        google()
+        jcenter()
+    }
+}
+
+rootProject.buildDir = '../build'
+subprojects {
+    project.buildDir = "${rootProject.buildDir}/${project.name}"
+}
+subprojects {
+    project.evaluationDependsOn(':app')
+}
+
+task clean(type: Delete) {
+    delete rootProject.buildDir
+}