Android开发系列之数据存储（一）

  Android开发中，数据存储主要有五种：网络、数据库、SharePreferences、文件以及Content Provider.

  . 数据库

   Android中的数据库最常用的是Sqlite. 使用Sqlite进行数据存储，可分为以下几步：

   . 继承SqliteOpenHelper

   . 整理4个构造方法

   . 重写onCreate与onUpgrade

public class DownDBHelper extends SQLiteOpenHelper {

    public static final String DATABASE_NAME = "download.db";
    public static final int DATABASE_VERSION = 1;

    public static final String TABLE_NAME = "down_info";

    // /////////////////// TABLE COLUMN

    public static final String COLUMN_ID = "_id";
    public static final String COLUMN_THREAD_ID = "thread_id";
    public static final String COLUMN_URL = "url";
    public static final String COLUMN_START = "start";
    public static final String COLUMN_END = "end";
    public static final String COLUMN_PROGRESS = "progress";

    // ///////////////////// CONTRUCTOR

    public DownDBHelper(Context context, String name, CursorFactory factory,
            int version) {
        super(context, name, factory, version);
    }

    public DownDBHelper(Context context, String name, int version) {
        this(context, name, null, version);
    }

    public DownDBHelper(Context context, String name) {
        this(context, name, DATABASE_VERSION);
    }

    public DownDBHelper(Context context) {
        this(context, DATABASE_NAME);
    }

    // ////////////// OVERRIDE

    @Override
    public void onCreate(SQLiteDatabase db) {

        String creSQL = "CREATE TABLE IF NOT EXISTS" + TABLE_NAME + "("
                + COLUMN_ID + " INTEGER PRIMARY KEY AUTOINCREMENT,"
                + COLUMN_THREAD_ID + "INTEGER," + COLUMN_URL + " CHAR,"
                + COLUMN_START + " INTEGER," + COLUMN_END + "INTEGER,"
                + COLUMN_PROGRESS + "INTEGER)";

        db.execSQL(creSQL);
    }

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

        String dropSQL = "DROP TABLE IF EXISTS " + TABLE_NAME;
        db.execSQL(dropSQL);

        this.onCreate(db);
    }

}