如何在方法onUpgrade中删除数据库？

Question

How can i remove file with my database on SQLite in method onUpgrade?

I tried:

public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
    context.deleteDatabase(DATABASE_NAME);

    onCreate(db);
}

error: context cannot be resolved.

and second:

public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
    File dbFile = getDatabasePath("your_db_file_name");
    boolean deleted = dbFile.delete();

    onCreate(db);
}

error: The method getDatabasePath(String) is undefined for the type TestDatabase.

Answer 1

You cannot delete the file as it is in use at the point this method is called.

Instead, if you really want to the delete the database run

File dbFile = getDatabasePath("your_db_file_name");
if(dbFile.exists() && dbFile.delete())
{
    // Create new database if that is what you want to do.
}

Before you actually instantiate the DatabaseHelper object. Without knowing the rest of your code it is hard to give a more detailed solution.

Answer 2

you can create a method to clean the table and call it before you add the new values to it

public void delete_ALL_ROWS()
    {
        ourHelper = new DbHelper(ourContext);
        ourDatabase = ourHelper.getWritableDatabase();

        String deleteSQL = "DELETE FROM " + DATABASE_TABLE;

        ourDatabase.execSQL(deleteSQL);

        ourHelper.close();
    }

Answer 3

In your onUpgrade function you should simply run the drop table statements

@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
    // delete our old table
    db.execSQL("DROP TABLE IF EXISTS " + tableName);

    // create our new table
    onCreate(db);
}