Android使用SQLite数据库(1)

Android中使用SQLite数据库要通过SQLiteOpenHelper类。

首先，定义相关变量：

	// 数据库变量
	DatabaseHelper mDBH;
	SQLiteDatabase db;
	public static String strSql;

再定义SQLiteOpenHelper类：

	public static class DatabaseHelper extends SQLiteOpenHelper{

		public static final String DATABASE_NAME = "Call_db.db";
		public static final int DATABASE_VERSION = 1;
		public static final String TABLE_NAME = "Call";
		public static final String TABLE_NAME_2 = "Days";
		public static final String NAME = "Name";
		public static final String NUMBER = "Number";
		public static final String DATE = "Date";
		public static final String DATES = "Dates";
		public static final String YEAR = "Year";
		public static final String MONTH = "Month";
		public static final String DAY = "Day";
		public static final String HOUR = "Hour";
		public static final String MINUTE = "Minute";
		public static final String DOW = "Dow";
		public static final String TYPE = "Type";
		public static final String INC = "InC";
		public static final String OUTC = "OutC";
		public static final String TOTAL = "Total";

		DatabaseHelper(Context context){
			super(context, DATABASE_NAME, null, DATABASE_VERSION);
		}

		// 没有数据库时，建立数据库
		@Override
		public void onCreate(SQLiteDatabase db) {

			strSql = "CREATE TABLE " + TABLE_NAME + " (" + NAME
			+ " text not null, " + NUMBER + " text not null, " + DATE
			+ " text not null, " + DATES
			+ " text not null, "+ YEAR + " text not null, "
			+ MONTH + " text not null, " + DAY + " text not null, "
			+ HOUR + " text not null, " + MINUTE + " text not null, "
			+ DOW  + " text not null, " + TYPE + " text not null" + ");";
			db.execSQL(strSql);	

			strSql = "CREATE TABLE " + TABLE_NAME_2 + " (" + DATES
			+ " text not null, " + YEAR + " text not null, " + MONTH
			+ " text not null, " + DAY
			+ " text not null, "+ DOW + " text not null, "
			+ INC + " text not null, " + OUTC + " text not null, "
			+ TOTAL + " text not null);";
			db.execSQL(strSql);	

		}

		@Override
		public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
		}
	}

当数据库不存在时（如第一次运行时），调用onCreate(SQLiteDatabase db)建立数据库，建立的方法是定义SQL语句，再执行该语句。