Python+kivy+SQLite：如何一起使用

Question

我是 python、kivy 和 sqlite 的新手。但我必须完成这项艰巨的任务。 :-( 任何形式的帮助将不胜感激。在此先感谢！

任务是：在android的kivy屏幕上显示来自.db文件的数据。

我从http://zetcode.com/db/sqlitepythontutorial/创建了数据库文件

在这里我再次发布代码。

#!/usr/bin/python
# -*- coding: utf-8 -*-

import sqlite3 as lite
import sys

con = lite.connect('test.db')

with con:

    cur = con.cursor()    
    cur.execute("CREATE TABLE Cars(Id INT, Name TEXT, Price INT)")
    cur.execute("INSERT INTO Cars VALUES(1,'Audi',52642)")
    cur.execute("INSERT INTO Cars VALUES(2,'Mercedes',57127)")
    cur.execute("INSERT INTO Cars VALUES(3,'Skoda',9000)")
    cur.execute("INSERT INTO Cars VALUES(4,'Volvo',29000)")
    cur.execute("INSERT INTO Cars VALUES(5,'Bentley',350000)")
    cur.execute("INSERT INTO Cars VALUES(6,'Citroen',21000)")
    cur.execute("INSERT INTO Cars VALUES(7,'Hummer',41400)")
    cur.execute("INSERT INTO Cars VALUES(8,'Volkswagen',21600)")

然后将数据库保存到C:\\test.db。

然后我用label 和button 制作了一个kivy 屏幕。

# -*- coding: utf-8 -*-

from kivy.app import App
from kivy.uix.boxlayout import BoxLayout
from kivy.uix.label import Label
from kivy.lang import Builder

import random

root_widget = Builder.load_string('''
BoxLayout:
    orientation: 'vertical'
    Label:
        text: 'Hello'  #How to define it?
        font_size: 30
    Button:
        size: root.width/2, 15
        text: 'next random'
        font_size: 30
#        on_release:  #How to define it?
''')

class TestApp(App):
    def build(self):
        return root_widget

if __name__ == '__main__':
    TestApp().run()

我想要label 上显示的db file 中的random 汽车名称，每次都点击button。

最初的label 文本，现在是“Hello”这个词，应该被一个随机的车名替换。因此，每次运行程序时，label 上都会显示汽车名称。

但我真的不知道如何编写代码。

感谢您的帮助。

#更新

我编写了代码，但它不起作用。

# -*- coding: utf-8 -*-

from kivy.app import App
from kivy.uix.boxlayout import BoxLayout
from kivy.uix.label import Label
from kivy.lang import Builder
from kivy.clock import mainthread
import sqlite3

import random


class MyBoxLayout(BoxLayout):

    def init(self, **kwargs):
        super().__init__(**kwargs)

        @mainthread  # execute within next frame
        def delayed():
            self.load_random_car()
        delayed()

    def load_random_car(self):
        conn = sqlite3.connect("C:\\test.db")
        cur = conn.cursor()

        ####Length of db file
        with conn:
            cur = conn.cursor()
            cur.execute("SELECT * FROM Cars")
            rows = cur.fetchall()
        LengthSQLFile = len(rows)
        print LengthSQLFile


        CurrentNo = random.randint(0, LengthSQLFile)
        CurrentNo_ForSearch = (CurrentNo ,)
        cur.execute("select * from Cars where rowid = ?" , CurrentNo_ForSearch)

        CurrentAll = cur.fetchone()
        CurrentAll = list(CurrentAll)   # Change it from tuple to list
        print CurrentAll

        Current    = CurrentAll[1]
        self.ids.label.text = Current #"fetch random car data from db and put here"


root_widget = Builder.load_string('''
BoxLayout:
    orientation: 'vertical'
    Label:
        id: label
        font_size: 30
    Button:
        size: root.width/2, 15
        text: 'next random'
        font_size: 30
        on_release:  root.load_random_car()

''')


class TestApp(App):
    def build(self):
#        MyBoxLayout(BoxLayout)
        return root_widget

if __name__ == '__main__':
    TestApp().run()

#2 更新：

现在的代码是...它显示错误消息：AttributeError: 'BoxLayout' object has no attribute 'load_random_car'

# -*- coding: utf-8 -*-

from kivy.app import App
from kivy.uix.boxlayout import BoxLayout
from kivy.uix.label import Label
from kivy.lang import Builder
from kivy.clock import mainthread
import sqlite3

import random

class MyBoxLayout(BoxLayout):

    def init(self, **kwargs):
        super().__init__(**kwargs)

        @mainthread  # execute within next frame
        def delayed():
            self.load_random_car()
        delayed()

    def load_random_car(self):
        conn = sqlite3.connect("C:\\test.db")
        cur = conn.cursor()

        cur.execute("SELECT * FROM Cars ORDER BY RANDOM() LIMIT 1;")

        currentAll = cur.fetchone()
        currentAll = list(currentAll)   # Change it from tuple to list
        print currentAll

        current    = currentAll[1]
        self.ids.label.text = current #"fetch random car data from db and put here"


root_widget = Builder.load_string('''
BoxLayout:
    orientation: 'vertical'
    Label:
        id: label
        font_size: 30
    Button:
        size: root.width/2, 15
        text: 'next random'
        font_size: 30
        on_release:  root.load_random_car()

''')


class TestApp(App):
    def build(self):
#        MyBoxLayout(BoxLayout)
        return root_widget

if __name__ == '__main__':
    TestApp().run()

Answer 1

最简单的方法是为盒子布局编写自定义 init 方法：

from kivy.uix.boxlayout import BoxLayout
from kivy.clock import mainthread

class MyBoxLayout(BoxLayout):

    def init(self, **kwargs):
        super().__init__(**kwargs)

        @mainthread  # execute within next frame
        def delayed():
            self.load_random_car()
        delayed()

    def load_random_car(self):
        self.ids.label.text = "fetch random car data from db and put here"

这是更新后的小部件结构的样子：

MyBoxLayout:
    Label:
        id: label
    Button:
        on_release:  root.load_random_car()