我一直在浏览器上遇到此 CORS 问题：“从源 'http://localhost:3000' 获取访问 'http://localhost:5000/register' 已被 CORS 策略阻止：对预检请求的响应没有通过访问控制检查：它没有 HTTP ok 状态。”我尝试了使用flask_cors、设置标头以在检测到OPTIONS 请求时允许CORS 等所有可能的技术。但是，我仍然遇到相同的错误。你知道我该如何解决这个问题吗？

init.py

  from flask import flask

from flask_socketio import SocketIO

from flask_socketio import join_room,leave_room,send
from flask_sqlalchemy import SQLAlchemy
from flask_bcrypt import Bcrypt
from flask_login import Loginmanager
from flask_jwt_extended import JWTManager

from flask_cors import CORS


app = flask(__name__)
app.config['SECRET_KEY'] = "\xe1\xe1\xf1%S!\xe7\xb6J%\xb5\x14\xc1#\x1a\x05\x89\x7f\xb0\x9e\x0e\x07\xb1\t"
app.config['SQLALCHEMY_DATABASE_URI'] = 'sqlite:///site.db'

app.config['UPLOAD_FOLDER'] = r"C:\Users\matth\Personal_Projects\social-media-app\public\images\useruploads"
app.config['CORS_HEADERS'] = 'Content-Type'

CORS(app,origins = ['http://localhost:3000'])
bcrypt = Bcrypt(app)
socketio = SocketIO(app,cors_allowed_origins = "*")

db = SQLAlchemy(app)
login_manager = Loginmanager()
login_manager.init_app(app)

jwt = JWTManager(app)

routes.py

from flask_socketio import join_room,send
from werkzeug import secure_filename
from database.UserModel import User
from database import app,db
from flask import request,make_response
from flask_login import login_user
import json
import bcrypt
from werkzeug.utils import secure_filename
import os
from flask_jwt_extended import create_access_token
from flask_jwt_extended import get_jwt_identity
from flask_jwt_extended import set_access_cookies
from flask_jwt_extended import unset_jwt_cookies
from flask_jwt_extended import jwt_required
from flask_cors import cross_origin

@app.route("/register",methods= ['POST','GET','OPTIONS'])
@cross_origin()
def registerForm():
    if request.method == 'POST':
        print("tested",flush=True)
        username = request.form["username"]
        email = request.form["Email"]
        password = request.form["password"]
        confirmPassword = request.form["confirmPassword"]
        duplicateEmail =  User.query.filter_by(email=email).first()
        duplicateUser = User.query.filter_by(username = username).first()
        print("sent by server",flush=True)
        file = request.files["file"]
        if file:
            filename = secure_filename(file.filename + "-" + username)
            print("File name is " + filename)
            file.save(os.path.join(app.config['UPLOAD_FOLDER'],filename))


        if password != confirmPassword:
            return json.dumps({"passwordError": "Passwords Do Not Match! "}),403

        if  duplicateEmail is not None:
            return json.dumps({"duplicateEmailError": "E-mail Already Exists! Please sign in."}),409

        if duplicateUser is not None:
            return json.dumps({"duplicateusernameEror": "username Already Exists! Please choose a different one."}),409

        pw_hash = bcrypt.generate_password_hash(password).decode('utf-8')
        user = User(username = username,email = email,password = pw_hash,image_url = filename,online = False )
     
        db.session.add(user)
        db.session.commit()

       
        
        return json.dumps({"success": "ok"}),200
    
    if request.method == 'OPTIONS':
        print("Hello",flush= True)
        res = make_response()
        res.headers.add('access-control-allow-origin',"*")
        res.headers.add('access-Control-Allow-Methods',"*")
        res.headers.add("access-Control-Allow-Headers",[" Content-Type","access-control-allow-origin"])

        return res