Kivy开发APK连接PC本地MySQL崩溃及黑屏问题求助

我用Kivy+Python3开发了一款应用，完成界面设计后对接了MySQL数据库实现数据收发。打包成APK在Android设备测试时，界面能正常运行，但只要触发数据库交互就崩溃，加了Try-Except语句也没用。我怀疑Android与PC本地数据库的连接环节存在问题，以下是相关信息：

连接代码 #

class FifthScreen(Screen):

    users = os.environ.get('USER_NAME')
    pass_word = os.environ.get('WORDPASS')
    try:

        database = mysql.connector.connect(host="localhost", user=users, password=pass_word, database="logintest", port= "3306")
        cursor = database.cursor()

    except Error as e:
        print(e)

    admin_email = "rasheed@hotmail.com"
    admin_password = "King"
    loggedin = False

    def receive_data(self, email, password):
        try:
            self.cursor.execute("select email,password from logs")
            email_list = []
            for i in self.cursor.fetchall():
                email_list.append(i[0])
            if email.text in email_list and email.text != "":
                self.cursor.execute(f"select password,user_name from logs where email='{email.text}'")
                for j in self.cursor:
                    if email.text == self.admin_email and password.text == self.admin_password:
                        print("Hello Admin")
                        self.manager.current = 'Data_Table'
                    elif password.text == j[0]:
                        print("you successfully logged in")
                        self.manager.current = 'Doctors_Patients_Details'
                        self.loggedin = True
                        self.manager.get_screen('photo_page').ids.user_name.text = j[1]
                    else:
                        print("incorrect password ")
            else:
                print("incorrect email")
        except Error as e:
            print(e)
        finally:
            if self.database.is_connected():
                self.database.close()
                self.cursor.close()
                print("closed4")

Buildozer依赖配置 #

requirements =  python3,kivy==2.1.0,kivymd==0.104.2,pillow, requests,android,docutils,mysql_connector,mysql-connector-python,fpdf

android.permissions = INTERNET,READ_EXTERNAL_STORAGE,WRITE_EXTERNAL_STORAGE

修改后的问题（将host改为PC IP192.168.43.64，开放3306端口并关闭防火墙后） #

1. 数据库交互仍崩溃，报错信息：

Traceback (most recent call last):
    10-25 21:19:50.841  3641  4045 I python  :    File "/content/.buildozer/android/app/main.py", line 328, in receive_data
    10-25 21:19:50.843  3641  4045 I python  :  AttributeError: 'FifthScreen' object has no attribute 'cursor' 

AttributeError: 'FifthScreen' object has no attribute 'database'
10-25 21:19:50.848  3641  4045 I python  : Python for android ended.

2. 闪屏后黑屏持续3-4分钟，日志信息：

win=Window{3e4abc u0 Splash Screen org.test.test3 EXITING} destroySurfaces: appStopped=false win.mWindowRemovalAllowed=true win.mRemoveOnExit=true 

1. 修复类属性初始化问题 #

报错'FifthScreen' object has no attribute 'cursor'的核心原因：你在类定义外层直接写了数据库连接的try-except块，这里创建的database和cursor是类变量，如果连接失败（比如Android初始化时网络未就绪），这两个变量不会被赋值，后续实例调用self.cursor时就会找不到属性。另外，类初始化阶段就尝试数据库连接不合理，应该在需要的时候（比如receive_data方法内）才建立连接。

修改后的代码：

class FifthScreen(Screen):
    admin_email = "rasheed@hotmail.com"
    admin_password = "King"
    loggedin = False

    def receive_data(self, email, password):
        database = None
        cursor = None
        try:
            # 按需获取凭据
            users = os.environ.get('USER_NAME')
            pass_word = os.environ.get('WORDPASS')
            # 方法内建立连接，避免初始化阻塞
            database = mysql.connector.connect(
                host="192.168.43.64", 
                user=users, 
                password=pass_word, 
                database="logintest", 
                port="3306"
            )
            cursor = database.cursor()

            cursor.execute("select email,password from logs")
            # 简化列表生成
            email_list = [i[0] for i in cursor.fetchall()]
            
            input_email = email.text.strip()
            if input_email in email_list:
                # 使用参数化查询，避免SQL注入
                cursor.execute(
                    "select password,user_name from logs where email=%s",
                    (input_email,)
                )
                result = cursor.fetchone()
                if result:
                    db_password, user_name = result
                    input_pwd = password.text.strip()
                    if input_email == self.admin_email and input_pwd == self.admin_password:
                        print("Hello Admin")
                        self.manager.current = 'Data_Table'
                    elif input_pwd == db_password:
                        print("you successfully logged in")
                        self.manager.current = 'Doctors_Patients_Details'
                        self.loggedin = True
                        self.manager.get_screen('photo_page').ids.user_name.text = user_name
                    else:
                        print("incorrect password ")
                else:
                    print("incorrect email")
            else:
                print("incorrect email")
        except Error as e:
            print(f"数据库错误: {e}")
        finally:
            # 确保资源正常关闭，避免空指针
            if cursor:
                cursor.close()
            if database and database.is_connected():
                database.close()
                print("closed4")

2. 解决Android与PC本地MySQL的连接问题 #

• 确认网络互通：Android设备必须和PC在同一局域网，可通过ADB shell执行ping 192.168.43.64测试连通性。
• MySQL权限配置：默认MySQL用户仅允许本地访问，需创建支持局域网访问的用户：

  CREATE USER '你的用户名'@'%' IDENTIFIED BY '你的密码';
  GRANT ALL PRIVILEGES ON logintest.* TO '你的用户名'@'%';
  FLUSH PRIVILEGES;
  

  注：%允许所有IP访问，测试完成后可改为Android设备的固定IP提升安全性。
• 修改MySQL配置：打开my.cnf或my.ini，将bind-address改为0.0.0.0（允许所有IP访问），然后重启MySQL服务。

3. 解决闪屏后黑屏问题 #

黑屏是因为类初始化阶段就尝试数据库连接，阻塞了UI线程。将连接逻辑移到receive_data方法内后，启动时不会再阻塞UI。此外还可以：

• 在Buildozer配置中指定合适的API级别：android.api = 30
• 优化闪屏配置：

  android.splash_drawable = res/drawable/splash.png
  android.splash_screen_duration = 2000
  

4. 额外安全建议 #

• 禁止用字符串拼接SQL语句，改用参数化查询（如上述代码所示），避免SQL注入风险。
• 不要硬编码数据库凭据，通过环境变量或安全配置方式传递。
• 建议搭建HTTPS接口作为中间层，Android调用API间接操作数据库，直接连接MySQL存在安全隐患。

内容的提问来源于stack exchange，提问作者Abdallah Rasheed