Kotlin 데이터 저장,관리 : SQLite
- 이름과 영어 성적을 입력하고, 저장을 클릭하면 성적이 저장된다.
- 이름을 입력하고, 읽기 버튼을 클릭하면 하면 성적을 알 수 있다.
- 모두 삭제하면 저장한 입력한 모든 내용을 삭제한다.

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

        <TextView
            android:id="@+id/textVIEW"
            android:hint="상태 메시지"
            android:layout_width="match_parent"
            android:layout_height="50dp"
            android:layout_margin="10dp"/>
    </LinearLayout>

    <LinearLayout
        android:orientation="horizontal"
        android:layout_width="match_parent"
        android:layout_height="wrap_content">

        <Button
            android:id="@+id/writeBT"
            android:text="저장"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:background="@drawable/confirm_botton"
            android:layout_weight="1"
            android:layout_marginTop="30dp"
            android:layout_marginLeft="20dp" />
        <Button
            android:id="@+id/readBT"
            android:text="읽기"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:background="@drawable/confirm_botton"
            android:layout_weight="1"
            android:layout_marginTop="30dp"
            android:layout_marginLeft="10dp" />
        <Button
            android:id="@+id/deleteBT"
            android:text="모두 삭제"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:background="@drawable/confirm_botton"
            android:layout_weight="1"
            android:layout_marginTop="30dp"
            android:layout_marginLeft="10dp"
            android:layout_marginRight="20dp" />

    </LinearLayout>

    <LinearLayout
        android:orientation="horizontal"
        android:layout_width="match_parent"
        android:layout_height="wrap_content">

    <EditText
        android:id="@+id/nameET"
        android:hint="Name"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_weight="1"
        android:layout_marginTop="10dp"
        android:layout_marginLeft="10dp"/>

    <EditText
        android:id="@+id/scoreET"
        android:hint="Score"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_weight="1"
        android:layout_marginTop="10dp"
        android:layout_marginLeft="10dp"
        android:layout_marginRight="10dp"/>
    </LinearLayout>
</LinearLayout>

------------------------------------------------------------------------------------
    botton_true.xml
-- res/drawable
-- New --> Drawable Resource File
-- File Name : button_true  , Root Element : shape
-----------------------------------------------------------------------------------
<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android"
    android:padding="10dp"
    android:shape="rectangle" >
    <solid android:color="#8EC7F4" />
    <stroke android:color="#ff0000ff" android:width="5dp" />
    <padding android:left="7dp" android:top="7dp"
        android:right="7dp" android:bottom="7dp" />
    <corners
        android:radius="30dp"
        android:bottomLeftRadius="100dp"
        android:bottomRightRadius="100dp"
        android:topLeftRadius="100dp"
        android:topRightRadius="100dp" />
</shape>

------------------------------------------------------------------------------------
    botton_false.xml
-- res/drawable
-- New --> Drawable Resource File
-- File Name : button_farse  , Root Element : shape
------------------------------------------------------------------------------------
<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android"
    android:padding="10dp"
    android:shape="rectangle" >
    <solid android:color="#F4DB8E" />
    <stroke android:color="#ff0000ff" android:width="5dp" />
    <padding android:left="7dp" android:top="7dp"
        android:right="7dp" android:bottom="7dp" />
    <corners
        android:radius="30dp"
        android:bottomLeftRadius="100dp"
        android:bottomRightRadius="100dp"
        android:topLeftRadius="100dp"
        android:topRightRadius="100dp" />
</shape>

------------------------------------------------------------------------------------
    confirm_botton.xml
-- res/drawable
-- New --> Drawable Resource File
-- File Name : confirm_botton  , Root Element : selector
------------------------------------------------------------------------------------
<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android">
    <item android:state_pressed="true" android:drawable="@drawable/button_farse"></item>
    <item android:state_pressed="false" android:drawable="@drawable/botton_true"></item>
</selector>

------------------------------------------------------------------------------------
    MainActivity.kt
------------------------------------------------------------------------------------
private lateinit var statusTV : TextView

class MainActivity : AppCompatActivity() {
    val TAG = MainActivity::class.java.simpleName
    private lateinit var myEngScoreDatabase : EKownDbHelper
    private lateinit var readEngDb: SQLiteDatabase
    private lateinit var writeEngDb: SQLiteDatabase
    private lateinit var editName  : EditText
    private lateinit var editScore : EditText


    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        title = "영어 점수 관리하기"

        myEngScoreDatabase = EKownDbHelper(this)
        readEngDb = myEngScoreDatabase.readableDatabase
        writeEngDb = myEngScoreDatabase.writableDatabase
        editName = findViewById<EditText>(R.id.nameET)
        editScore = findViewById<EditText>(R.id.scoreET)
        statusTV = findViewById(R.id.textVIEW)
        val btnReadDb = findViewById<Button>(R.id.readBT)
        val btnWriteDb = findViewById<Button>(R.id.writeBT)
        val btnDeleteAllColumns = findViewById<Button>(R.id.deleteBT)

        btnReadDb.setOnClickListener {
            Log.d(TAG,"read database")
            statusTV.text = " read database"
            var strName =  editName.text
            val projection = arrayOf(BaseColumns._ID,
                EKownDbHelper.MyContract.MyEntry.COLUMN_NAME_TITLE,
                EKownDbHelper.MyContract.MyEntry.COLUMN_NAME_SCORE )

            val selection = "${EKownDbHelper.MyContract.MyEntry.COLUMN_NAME_TITLE} = ?"

            val selectionArgs = arrayOf("${strName.toString()}")
            val cursor = readEngDb.query(
                EKownDbHelper.MyContract.MyEntry.TABLE_NAME,  // The table to query
                projection,            // The array of columns to return (pass null to get all)
                selection,              // The columns for the WHERE clause
                selectionArgs,          // The values for the WHERE clause
                null,                  // don't group the rows
                null,                  // don't filter by row groups
                null              // The sort order
            )

            with(cursor) {
                while (moveToNext()) {
                    val score = getInt(getColumnIndexOrThrow(EKownDbHelper.MyContract.MyEntry.COLUMN_NAME_SCORE))
                    Log.d(TAG,"score = $score")
                    editScore.setText(score.toString())
                }
            }
        }

        btnWriteDb.setOnClickListener {
            Log.d(TAG,"write database")
            statusTV.text = " write database"

            var strName =  editName.text
            val strScore = editScore.text

            // Create a new map of values , where column names are the keys
            val values = ContentValues().apply{
                put(EKownDbHelper.MyContract.MyEntry.COLUMN_NAME_TITLE, strName.toString())
                put(EKownDbHelper.MyContract.MyEntry.COLUMN_NAME_SCORE, strScore.toString().toInt())
            }

            // Insert the new row,  returning the primary key value of the new row
            val newRowId = writeEngDb.insert(EKownDbHelper.MyContract.MyEntry.TABLE_NAME, null,values)
            Log.d(TAG,"id = $newRowId")
            editName.setText(null)
            editScore.setText(null)
        }

        btnDeleteAllColumns.setOnClickListener {
            statusTV.text = statusTV.text.toString() + "\n Delete all columns."
            writeEngDb.delete( EKownDbHelper.MyContract.MyEntry.TABLE_NAME, null,null)
            editName.setText(null)
            editScore.setText(null)
        }

        editName.setOnClickListener  {
            editName.setText(null)
        }
        editScore.setOnClickListener  {
            editScore.setText(null)
        }
    }

    override fun onDestroy() {
        myEngScoreDatabase.close()
        super.onDestroy()
    }

}

class EKownDbHelper(context: Context) : SQLiteOpenHelper(context, DATABASE_NAME,null,DATABASE_VERSION) {

    private val TAG = EKownDbHelper::class.java.simpleName
    private val SQL_CREATE_ENTRIES =
        "CREATE TABLE ${MyContract.MyEntry.TABLE_NAME} (" +
                "${BaseColumns._ID} INTEGER PRIMARY KEY," +
                "${MyContract.MyEntry.COLUMN_NAME_TITLE} TEXT," +
                "${MyContract.MyEntry.COLUMN_NAME_SCORE} INT)"
    private val SQL_DELETE_ENTRIES = "DROP TABLE IF EXISTS ${MyContract.MyEntry.TABLE_NAME}"

    object MyContract {
        object MyEntry : BaseColumns {
            const val TABLE_NAME = "english"
            const val COLUMN_NAME_TITLE = "name"
            const val COLUMN_NAME_SCORE = "score"
        }
    }
    companion object{
        val DATABASE_NAME = "MyClassEnglishDb.db"
        val DATABASE_VERSION =1
    }

    override fun onCreate(p0: SQLiteDatabase?) {
        // CREATE TABLE tells the system to create a new database table keyword.
        Log.d(TAG,"onCreate() +")
        p0?.execSQL(SQL_CREATE_ENTRIES)
    }

    override fun onUpgrade(p0: SQLiteDatabase?, p1: Int, p2: Int) {
        // This database is only a cache for online data, so its upgrade policy is
        // to simply to discard the data and start over
        Log.d(TAG,"onUpgrade() +")
        p0?.execSQL(SQL_DELETE_ENTRIES)
        onCreate(p0)
    }
}

------------------------------------------------------------------------------------
    themes.xml
------------------------------------------------------------------------------------
<resources xmlns:tools="http://schemas.android.com/tools">
    <!-- Base application theme. -->
    <style name="Base.Theme.SQLiteWriteRead" parent="Theme.AppCompat.Light">
        <item name="colorPrimary">#FF7700</item>
        <item name="colorPrimaryDark">#FFC107</item>
    </style>

    <style name="Theme.SQLiteWriteRead" parent="Base.Theme.SQLiteWriteRead" />
</resources>