Question

我需要创建一个包含3个表的数据库，我这样做如下：

public class DatabaseUtils extends SQLiteOpenHelper {
      private final Context myContext;  
      private SQLiteDatabase DataBase; 

      // Database creation sql statement
      private static final String CREATE_TABLE_CS = "create table "+ TABLE_CS + "(" + COLUMN_CS + " TEXT NOT NULL, " + COLUMN_CE_CID + " INTEGER NOT NULL, "+ COLUMN_CE_PID +" INTEGER NOT NULL);";
      private static final String CREATE_TABLE_SS = "create table "+ TABLE_SS + "(" + COLUMN_SS + " TEXT NOT NULL, " + COLUMN_SUB_CID + " INTEGER NOT NULL, "+ COLUMN_SUB_PID +" INTEGER NOT NULL);";
      private static final String CREATE_TABLE_AS = "create table "+ TABLE_AS + "(" + COLUMN_AS + " TEXT NOT NULL, " + COLUMN_CID + " INTEGER NOT NULL, "+ COLUMN_AID +" INTEGER NOT NULL);";

      public DatabaseUtils(Context context) {
        super(context, DATABASE_NAME, null, DATABASE_VERSION);
        DATABASE_PATH =  Environment.getDataDirectory().getAbsolutePath() + "/" +"data/"+ context.getResources().getString(R.string.app_package);
        this.myContext = context;
      }

      @Override
      public void onCreate(SQLiteDatabase database) {
        database.execSQL(CREATE_TABLE_CS);
        database.execSQL(CREATE_TABLE_SS);
        database.execSQL(CREATE_TABLE_AS);
      }
      @Override
      public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        Log.w(DatabaseUtils.class.getName(),"Upgrading database from version " + oldVersion + " to "+ newVersion + ", which will destroy all old data");
        //db.execSQL("DROP TABLE IF EXISTS " + TABLE_COMMENTS);
        onCreate(db);
      }
}

在我的活动中，我在DatabaseUtils中拨打onCreate课程，如下所示：

DatabaseUtils db = new DatabaseUtils(this);

但数据库不是使用3个表创建的。我究竟做错了什么？顺便说一句，我正确地拥有所有字符串值。请帮我看看如何创建数据库。

Answer 1

我找到了解决方案。 DatabaseUtils onCreate()永远不会被调用，如果我实现如下：

 DatabaseUtils db = new DatabaseUtils(this);

{p} myActivity onCreate()方法中的

。我需要在myActivity中调用getWritableDatabase()，如下所示：

DatabaseUtils db = new DatabaseUtils(this);
db.getWritableDatabase();

然后将调用DatabaseUtils'onCreate()并创建表格。

Answer 2

private void db_ini_create_table（android.database.sqlite.SQLiteDatabase db）{

    String str_sql = "create table [possible_know_persions]         ("+
                                                                        "[id]                       INTEGER         PRIMARY KEY AUTOINCREMENT               NOT NULL,"+
                                                                        "[adate]                    DATETIME        DEFAULT (datetime('now','localtime'))   NOT NULL,"+
                                                                        "[current_userid]           INTEGER         DEFAULT 0 NOT NULL                              ,"+
                                                                        "[stranger_user_id]         INTEGER         DEFAULT 0 NOT NULL                              ,"+
                                                                        "[common_friend_count]      INTEGER         DEFAULT 0 NOT NULL                              ,"+
                                                                        "[common_game_count]        INTEGER         DEFAULT 0 NOT NULL                              ,"+
                                                                        "[user_account_type]        INTEGER         DEFAULT 0 NOT NULL                              ,"+
                                                                        "[verify_type]              INTEGER         NULL                                             "+
                                                                    ");";db.execSQL(str_sql); 
    str_sql = "CREATE INDEX [possible_stranger_user_id]     on [possible_know_persions] ("+"[stranger_user_id] asc "+");";db.execSQL(str_sql);      
}

这是您的参考示例

Android - 如何使用表创建Sqlite数据库

2 个答案: