Question

我在MainActivity中有这个

    db = new Database(this);

还有Database.java：

public class Database extends SQLiteOpenHelper {
    public static final String DATABASE_NAME = "days.db";
    public static final String TABLE_NAME = "days";
    public static final String COLUMN_1 = "date";
    public static final String COLUMN_2 = "blob";
    private Context context;


    public Database(Context context) {
        super(context, DATABASE_NAME, null, 1);
    }

    @Override
    public void onCreate(SQLiteDatabase db) {
        db.execSQL("create table IF NOT EXISTS " + TABLE_NAME + " (" + COLUMN_1 + " TEXT, " + COLUMN_2 + " BLOB)");
    }

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

}

但是，如果我在SQLite DB浏览器中打开数据库，则该数据库为空。未创建表。谁能复制粘贴我的代码并加以修复？

Answer 1

尝试

SQLiteDatabase db = new Database(this).getWritableDatabase();

getWritableDatabase ()

调用此方法时，将调用所需的方法，例如onCreate（SQLiteDatabase），onUpgrade（SQLiteDatabase，int，int）和onOpen（SQLiteDatabase），并创建表。

Answer 2

尝试一下：我在这里放了一个简单的数据库，因为它对我有用

 public class Database extends SQLiteOpenHelper {
private Context context1;

public Database(Context context) {

    super(context, "CREATECONTACT", null, 1);
    this.context1 = context;
}

@Override
public void onCreate(SQLiteDatabase db) {
    String query = "CREATE TABLE createContact ( \n" +
            "    ID          INTEGER        PRIMARY KEY AUTOINCREMENT\n" +
            "                               NOT NULL\n" +
            "                               UNIQUE,\n" +
            "    Name        VARCHAR( 50 )  NOT NULL,\n" +
            "    Phone       VARCHAR        NOT NULL,\n" +
            "    typeofPhone VARCHAR        NOT NULL,\n" +
            "    Email       VARCHAR        NOT NULL,\n" +
            "    typeofEmail VARCHAR        NOT NULL,\n" +
            "    FAVE        VARCHAR        NOT NULL,\n" +
            "    RED         INTEGER,\n" +
            "    GREEN       INTEGER,\n" +
            "    BLUE        INTEGER \n" +
            ");\n";
    db.execSQL(query);
}

@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
    db.execSQL("DROP TABLE IF EXISTS createContact");
    onCreate(db);
}

为什么数据库为空？

2 个答案: