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--- android_learning:headfirst_android_development_notes:chapter_11 [2016/03/16 22:25] – [Chapter 11] mithat
+++ android_learning:headfirst_android_development_notes:chapter_11 [2016/04/23 22:23] (current) – [p. 444: Code block] mithat
@@ Line 1: / Line 1: @@
 ====== Chapter 11 ======
-<WRAP center round info 60%>
+===== Foreword =====
-Under development.
+If you are not familiar with the term CRUD as applied to databases, it is an acronym for **C**reate (or Insert), **R**ead, **U**pdate, and **D**elete---the four main operations that are done on database records. It's often helpful to approach learning database stuff with these four primary operations in mind.
-</WRAP>
-You may hear the term "CRUD" used in relation to databases. And if you haven't, you have now. CRUD is a acronym for **C**reate (or Insert), **R**ead, **U**pdate, and **D**elete---the four main operations that are done on database records. It's also helpful to think in terms of database //schema//---the plan or layout of the database table(s).
+It's also helpful to think in terms of database //schema//---the plan or layout of the database table(s).
-The book consistently uses "a" as the indefinite article ahead of "SQLite"---most probably because they assume a pronunciation of "sequel lite." The primary author of "SQLite" [[https://youtu.be/jN_YdMdjVpU?t=1m7s|sees things differently]], so the indefinite article should be "an".
+The book consistently uses "a" as the indefinite article ahead of "SQLite"---most probably because they assume a pronunciation of "sequel lite." The primary author of SQLite [[https://youtu.be/jN_YdMdjVpU?t=1m7s|sees things differently]], so the indefinite article should be "an".
 ===== p. 444: Code block =====
@@ Line 33: / Line 32: @@
 }
 </file>
-Note that the constructor in the above class definition creates compiler rage. It gets fixed on the following page.
+The constructor in the above class definition will create compiler rage---which is fixed on the following page. But if you're impatient, the solution is to invoke to parent class' ctor:<code java>
+    StarbuzzDatabaseHelper(Context context) {
+        super(context, DB_NAME, null, DB_VERSION);
+    }</code>
-===== p. 447 =====
-You create the schema for your database in the ''SQLiteOpenHelper'''s ''onCreate'' method using plain old SQL on the SQLite database that's passed in.
+===== p. 447: Schema definition =====
+You create the schema for your database in the ''SQLiteOpenHelper'''s ''onCreate'' method using plain old SQL on the SQLite database that's passed in. (If you've not seen SQL before, don't worry. It's the "standard" language used by databases for conducting transactions, and the basics are explained by example in the book.)
 <code java>
-/**
- * Create a DRINK table with an _id PK,
- * and fields for NAME, DESCRIPTION, and
- * IMAGE_RESOURCE_ID.
- * @param db
- */
 @Override
 public void onCreate(SQLiteDatabase db) {
+	/**
+	 * Create a DRINK table with an _id PK,
+	 * and fields for NAME, DESCRIPTION, and
+	 * IMAGE_RESOURCE_ID.
+	 */
 	db.execSQL("CREATE TABLE DRINK ("
 			+ "_id INTEGER PRIMARY KEY AUTOINCREMENT, "
@@ Line 55: / Line 57: @@
 </code>
+===== p. 448: Create =====
+Use a ''ContentValues'' object to accumulate data for the new record and then use ''SQLiteDatabase'''s ''insert'' method to do the new record creation/insertion. Here it's being done in a private method:
+<code java>
+/**
+ * Create a new drink record in the DRINK table.
+ */
+private static void insertDrink(SQLiteDatabase db, String name,
+				String description, int resourceId) {
+	ContentValues drinkValues = new ContentValues();
+	drinkValues.put("NAME", name);
+	drinkValues.put("DESCRIPTION", description);
+	drinkValues.put("IMAGE_RESOURCE_ID", resourceId);
+	db.insert("DRINK", null, drinkValues);
+}
+</code>
+===== p. 449: Update =====
+Update existing records in a table with ''SQLiteDatabase'''s ''update'' method:
+<code java>
+public int update (String table,
+                   ContentValues values,
+                   String whereClause,
+                   String[] whereArgs)
+</code>
+===== p. 450: Delete =====
+Delete records in a table with ''SQLiteDatabase'''s ''delete'' method:
+<code java>
+public int delete(String table,
+                   String whereClause,
+                   String[] whereArgs)
+</code>
+<WRAP center round important 90%>
+Calling ''delete()'' with null ''whereClause'' and ''whereArgs'' arguments will delete all the records in the database.
+</WRAP>
+===== What about Read? =====
+It's covered in Chapter 12.
+===== p. 452: Code block =====
+<file java StarbuzzDatabaseHelper.java>
+package com.hfad.starbuzz;
+import android.content.ContentValues;
+import android.database.sqlite.SQLiteOpenHelper;
+import android.content.Context;
+import android.database.sqlite.SQLiteDatabase;
+class StarbuzzDatabaseHelper extends SQLiteOpenHelper {
+    private static final String DB_NAME = "starbuzz";   // the name of the DB
+    private static final int DB_VERSION = 1;    // the version of the DB
+    StarbuzzDatabaseHelper(Context context) {
+        super(context, DB_NAME, null, DB_VERSION);
+    }
+    @Override
+    public void onCreate(SQLiteDatabase db) {
+        /**
+         * Create a DRINK table with an _id PK,
+         * and fields for NAME, DESCRIPTION, and
+         * IMAGE_RESOURCE_ID.
+         */
+        db.execSQL("CREATE TABLE DRINK ("
+                + "_id INTEGER PRIMARY KEY AUTOINCREMENT, "
+                + "NAME TEXT, "
+                + "DESCRIPTION TEXT, "
+                + "IMAGE_RESOURCE_ID INTEGER);");
+        // Insert some drinks into the DRINKS table:
+        insertDrink(db, "Latte", "Espresso and steamed milk", R.drawable.latte);
+        insertDrink(db, "Cappuccino", "Espresso, hot milk and steamed-milk foam",
+                R.drawable.cappuccino);
+        insertDrink(db, "Filter", "Our best drip coffee", R.drawable.filter);
+    }
+    @Override
+    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
+    }
+    private static void insertDrink(SQLiteDatabase db, String name,
+                                    String description, int resourceId) {
+        ContentValues drinkValues = new ContentValues();
+        drinkValues.put("NAME", name);
+        drinkValues.put("DESCRIPTION", description);
+        drinkValues.put("IMAGE_RESOURCE_ID", resourceId);
+        db.insert("DRINK", null, drinkValues);
+    }
+}
+</file>
+===== p. 467-468: Code block =====
+<file java StarbuzzDatabaseHelper.java>
+package com.hfad.starbuzz;
+import android.content.ContentValues;
+import android.content.Context;
+import android.database.sqlite.SQLiteDatabase;
+import android.database.sqlite.SQLiteOpenHelper;
+class StarbuzzDatabaseHelper extends SQLiteOpenHelper{
+    private static final String DB_NAME = "starbuzz"; // the name of our database
+    private static final int DB_VERSION = 2; // the version of the database
+    StarbuzzDatabaseHelper(Context context){
+        super(context, DB_NAME, null, DB_VERSION);
+    }
+    @Override
+    public void onCreate(SQLiteDatabase db){
+        updateMyDatabase(db, 0, DB_VERSION);
+    }
+    @Override
+    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
+        updateMyDatabase(db, oldVersion, newVersion);
+    }
+    private void updateMyDatabase(SQLiteDatabase db, int oldVersion, int newVersion) {
+        if (oldVersion < 1) {
+            /**
+             * Create a DRINK table with an _id PK,
+             * and fields for NAME, DESCRIPTION, and
+             * IMAGE_RESOURCE_ID.
+             */
+            db.execSQL("CREATE TABLE DRINK (_id INTEGER PRIMARY KEY AUTOINCREMENT, "
+                    + "NAME TEXT, "
+                    + "DESCRIPTION TEXT, "
+                    + "IMAGE_RESOURCE_ID INTEGER);");
+            // Insert drinks into the DRINKS table:
+            insertDrink(db, "Latte", "Espresso and steamed milk", R.drawable.latte);
+            insertDrink(db, "Cappuccino", "Espresso, hot milk and steamed-milk foam",
+                    R.drawable.cappuccino);
+            insertDrink(db, "Filter", "Our best drip coffee", R.drawable.filter);
+        }
+        if (oldVersion < 2) {
+            // Add a FAVORITE column.
+            db.execSQL("ALTER TABLE DRINK ADD COLUMN FAVORITE NUMERIC;");
+        }
+    }
+    private static void insertDrink(SQLiteDatabase db, String name,
+                                    String description, int resourceId) {
+        ContentValues drinkValues = new ContentValues();
+        drinkValues.put("NAME", name);
+        drinkValues.put("DESCRIPTION", description);
+        drinkValues.put("IMAGE_RESOURCE_ID", resourceId);
+        db.insert("DRINK", null, drinkValues);
+    }
+}
+</file>