Question

MainActivity.class

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    DatabaseHandler db = new DatabaseHandler(this);

    // Inserting Users
    Log.d("Insert: ", "Inserting ..");
    db.addContact(new Contact("Ravi", "kumar", 1, getDateTime()));
}

 public String getDateTime() {
    SimpleDateFormat simpleDateFormat = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss", Locale.getDefault());
    Date date = new Date();
    return simpleDateFormat.format(date);
}

DatabaseHandler.class

public class DatabaseHandler extends SQLiteOpenHelper {


    Context context;
    private static final int DATABASE_VERSION = 1;
    private static final String DATABASE_NAME = "dbname";
    private static final String TABLE_USERS = "users";

    private static final String USERS_ID = "id";
    private static final String USER_NAME = "name";
    private static final String USER_LAST_NAME = "lastname";
    private static final String USER_USER_LEVEL = "userlevel";
    private static final String USER_LOGIN_TIME = "lastlogin";


    String CREATE_USERS_TABLE = "CREATE TABLE " + TABLE_USERS + "("
            + USERS_ID + " INTEGER PRIMARY KEY AUTOINCREMENT," + USER_NAME + " TEXT,"
            + USER_LAST_NAME + " TEXT NULL," + USER_USER_LEVEL + " INTEGER," + USER_LOGIN_TIME + " TEXT" + ")";




    public DatabaseHandler(Context context) {
        super(context, DATABASE_NAME, null, DATABASE_VERSION);
        this.context = context;

        Toast.makeText(context,"Constructor is called", Toast.LENGTH_LONG).show();
        System.out.println("Sql query : " +CREATE_USERS_TABLE);

    }

    @Override
    public void onCreate(SQLiteDatabase db) {


        db.execSQL(CREATE_USERS_TABLE);

        Toast.makeText(context,"on Create is called", Toast.LENGTH_LONG).show();


    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int i, int i2) {

        //db.execSQL("DROP TABLE IF EXISTS " +CREATE_USERS_TABLE);
        db.execSQL("DROP TABLE IF EXISTS " +CREATE_USERS_TABLE );
        onCreate(db);

        Toast.makeText(context,"on Upgrade is called", Toast.LENGTH_LONG).show();



    }


    public void addContact(Contact contact) {
        SQLiteDatabase db = this.getWritableDatabase();

        ContentValues values = new ContentValues();
        values.put(USER_NAME, contact.get_name()); // Contact Name
        values.put(USER_LAST_NAME, contact.get_lname());
        values.put(USER_USER_LEVEL, contact.get_level()); // Contact Phone Number
        values.put(USER_LOGIN_TIME,contact.get_lastlogin());
        //Inserting Row
        db.insert(TABLE_USERS, null, values);

        db.close(); // Closing database connection
    }

  .....
  ..

上面的代码创建了一个数据库，表并插入了数据。但是，如果我更改架构，例如将lastlogin更改为lastlogiin，

private static final String USER_LOGIN_TIME = "lastlogiin";

它没有生效。然后，我将数据库版本更改为

private static final int DATABASE_VERSION = 2;

但是，它会引发错误。

Logcat：

 at dalvik.system.NativeStart.main(Native Method)      Caused by:
android.database.sqlite.SQLiteException: near "CREATE": syntax error:
, while compiling: DROP TABLE IF EXISTS CREATE TABLE users(id INTEGER
PRIMARY KEY AUTOINCREMENT,name TEXT,lastname TEXT NULL,userlevel
INTEGER,lastlogiin TEXT)

Answer 1

@ user3289108替换 onUpgrade（）方法中的以下行

 db.execSQL("DROP TABLE IF EXISTS " +CREATE_USERS_TABLE );

要

db.execSQL("DROP TABLE IF EXISTS " + TABLE_USERS );

CREATE：语法错误：，编译时：DROP TABLE IF EXISTS

1 个答案: