Kivy按钮调用外部模块报错：NameError: name 'Aruco' is not defined

我在单个文件中编写了Kivy代码，尝试将其中一个按钮与外部Python模块（Aruco.py）关联，希望点击按钮时运行该模块的detect()方法。已在main.py中导入Aruco模块，但点击按钮时触发错误：NameError: name 'Aruco' is not defined。

相关代码 #

main.py #

import kivy
from kivy.app import App
from kivy.uix.widget import Widget
from kivy.properties import ObjectProperty
from kivy.uix.screenmanager import ScreenManager, Screen
from kivy.lang.builder import Builder
import sqlite3
import Aruco

class MainWindow(Screen):
    pass

class InfoWindow(Screen):
    pass

class LocaliseWindow(Screen):
    pass

class WindowManager(ScreenManager):
    pass

kv = Builder.load_string("""
WindowManager:
    MainWindow:
    LocaliseWindow:
    InfoWindow


<MainWindow>:
    name: "main"
    GridLayout:
        padding: 50
        spacing: 20
        cols:1
        size: root.width, root.height
        Camera:
            id: camera
            play: True
        GridLayout:
            cols:2
            spacing: 20
            Button:
                text: "Localise"
                on_release: 
                    app.root.current = "localise"
                    root.manager.transition.direction = "left"
                background_normal: ""
                background_color: "#05b4ff"
            Button:
                text: "Info"
                on_press:
                    app.root.current = "info"
                    root.manager.transition.direction = "left"
                background_normal: ""
                background_color: "#05b4ff"

<LocaliseWIndow>:
    name: "localise"
    BoxLayout:
        padding: 50
        spacing: 10
        orientation: "vertical"
        Label:
            id: choose_destination
            font_size: 24
            text: "Choose Destination"
        Button:
            id:Maths
            text: "Maths"
            on_press: Aruco.detect()
            background_normal: ""
            background_color: "#05b4ff"
        Button:
            id: English
            text: "English"
            on_press: app.submit()
            background_normal: ""
            background_color: "#05b4ff"
        Button:
            id: Science
            text: "Science"
            on_press: app.submit()
            background_normal: ""
            background_color: "#05b4ff"
        Button:
            id: Humanities
            text: "Humanities"
            on_press: app.submit()
            background_normal: ""
            background_color: "#05b4ff"
        Button:
            id: Office
            text: "Office"
            on_press: app.submit()
            background_normal: ""
            background_color: "#05b4ff"
        Button:
            id: Restroom
            text: "Restroom"
            on_press: app.submit()
            background_normal: ""
            background_color: "#05b4ff"
        Button:
            text: "Back"
            on_release: 
                app.root.current = "main"
                root.manager.transition.direction = "right" 
            
<InfoWindow>:
    name:"info"
    BoxLayout:
        padding: 50
        spacing: 10
        orientation: "vertical"
        Label:
            text: "1. Press Localise"
        Label:
            text: "2. Choose Destination"
        Label:
            text: "3. Scan nearest Aruco Marker when prompted"
        Label:
            text: "4. Follow the path to destination"
        Button:
            text: "Back"
            on_release:
                app.root.current = "main"
                root.manager.transition.direction = "right"

            
""")

class MyApp(App):
    def build(self):
        conn = sqlite3.connect("database.db")
        c = conn.cursor()
        c.execute("""CREATE TABLE if not exists locations(
            place text,
            xcoor int,
            ycoor int)
        """)
        conn.commit()
        conn.close()
        return kv

    def submit(self):
        conn = sqlite3.connect("database.db")
        c = conn.cursor()

        c.execute("SELECT * FROM locations")

        print(c.fetchall())

        conn.commit()
        conn.close()
        

if __name__ == "__main__":
    MyApp().run()

Aruco.py #

import numpy as np
import time
import cv2

def detect():
    ARUCO_DICT = {
        "DICT_4X4_50": cv2.aruco.DICT_4X4_50,
        "DICT_4X4_100": cv2.aruco.DICT_4X4_100,
        "DICT_4X4_250": cv2.aruco.DICT_4X4_250,
        "DICT_4X4_1000": cv2.aruco.DICT_4X4_1000,
        "DICT_5X5_50": cv2.aruco.DICT_5X5_50,
        "DICT_5X5_100": cv2.aruco.DICT_5X5_100,
        "DICT_5X5_250": cv2.aruco.DICT_5X5_250,
        "DICT_5X5_1000": cv2.aruco.DICT_5X5_1000,
        "DICT_6X6_50": cv2.aruco.DICT_6X6_50,
        "DICT_6X6_100": cv2.aruco.DICT_6X6_100,
        "DICT_6X6_250": cv2.aruco.DICT_6X6_250,
        "DICT_6X6_1000": cv2.aruco.DICT_6X6_1000,
        "DICT_7X7_50": cv2.aruco.DICT_7X7_50,
        "DICT_7X7_100": cv2.aruco.DICT_7X7_100,
        "DICT_7X7_250": cv2.aruco.DICT_7X7_250,
        "DICT_7X7_1000": cv2.aruco.DICT_7X7_1000,
        "DICT_ARUCO_ORIGINAL": cv2.aruco.DICT_ARUCO_ORIGINAL,
        "DICT_APRILTAG_16h5": cv2.aruco.DICT_APRILTAG_16h5,
        "DICT_APRILTAG_25h9": cv2.aruco.DICT_APRILTAG_25h9,
        "DICT_APRILTAG_36h10": cv2.aruco.DICT_APRILTAG_36h10,
        "DICT_APRILTAG_36h11": cv2.aruco.DICT_APRILTAG_36h11
    }


    def aruco_display(corners, ids, rejected, image):
        if len(corners) > 0:

            ids = ids.flatten()

            for (markerCorner, markerID) in zip(corners, ids):
            
                corners = markerCorner.reshape((4, 2))
                (topLeft, topRight, bottomRight, bottomLeft) = corners
            
                topRight = (int(topRight[0]), int(topRight[1]))
                bottomRight = (int(bottomRight[0]), int(bottomRight[1]))
                bottomLeft = (int(bottomLeft[0]), int(bottomLeft[1]))
                topLeft = (int(topLeft[0]), int(topLeft[1]))

                cv2.line(image, topLeft, topRight, (0, 255, 0), 2)
                cv2.line(image, topRight, bottomRight, (0, 255, 0), 2)
                cv2.line(image, bottomRight, bottomLeft, (0, 255, 0), 2)
                cv2.line(image, bottomLeft, topLeft, (0, 255, 0), 2)
            
                cX = int((topLeft[0] + bottomRight[0]) / 2.0)
                cY = int((topLeft[1] + bottomRight[1]) / 2.0)
                cv2.circle(image, (cX, cY), 4, (0, 0, 255), -1)
            
                cv2.putText(image, str(markerID),(topLeft[0], topLeft[1] - 10), cv2.FONT_HERSHEY_SIMPLEX,
                    0.5, (0, 255, 0), 2)
                print("ArUco marker ID: {}".format(markerID))
                return markerID
        return image



    aruco_type = "DICT_5X5_100"

    arucoDict = cv2.aruco.Dictionary_get(ARUCO_DICT[aruco_type])

    arucoParams = cv2.aruco.DetectorParameters_create()


    capture = cv2.VideoCapture(0)

    capture.set(cv2.CAP_PROP_FRAME_WIDTH, 1280)
    capture.set(cv2.CAP_PROP_FRAME_HEIGHT, 720)


    while capture.isOpened():
    
        ret, img = capture.read()

        h, w, _ = img.shape

        width = 1000
        height = int(width*(h/w))
        img = cv2.resize(img, (width, height), interpolation=cv2.INTER_CUBIC)
 
        corners, ids, rejected = cv2.aruco.detectMarkers(img, arucoDict, parameters=arucoParams)

        detected_markers = aruco_display(corners, ids, rejected, img)

        cv2.imshow("Image", detected_markers)

        key = cv2.waitKey(1) & 0xFF
        if key == ord(" "):
            break

    cv2.destroyAllWindows()
    capture.release()
    return markerID

解决方案 #

1. 修复KV语言的作用域问题 #

KV语言无法直接访问全局导入的模块，不能直接在按钮on_press事件中写Aruco.detect()，需要通过App实例或屏幕类间接调用：

方法一：通过App类封装调用

修改MyApp类，添加调用Aruco模块的方法：

class MyApp(App):
    # ... 原有代码 ...
    
    def run_aruco_detect(self):
        Aruco.detect()

修改KV中Maths按钮的事件：

Button:
    id:Maths
    text: "Maths"
    on_press: app.run_aruco_detect()
    background_normal: ""
    background_color: "#05b4ff"

方法二：通过LocaliseWindow类封装调用

修改LocaliseWindow类，添加调用方法：

class LocaliseWindow(Screen):
    def detect_aruco(self):
        Aruco.detect()

修改KV中按钮事件：

Button:
    id:Maths
    text: "Maths"
    on_press: root.detect_aruco()
    background_normal: ""
    background_color: "#05b4ff"

2. 修复KV中的拼写错误 #

KV中定义的屏幕为<LocaliseWIndow>，但Python类名是LocaliseWindow（字母i和l顺序错误），会导致屏幕无法加载，修正为：

<LocaliseWindow>:
    name: "localise"
    # ... 原有内容 ...

3. 修复Aruco.py的变量作用域问题 #

detect()函数末尾return markerID会报错，因为markerID是aruco_display内部的局部变量，仅在检测到标记时定义。修改如下：

调整aruco_display函数返回值

def aruco_display(corners, ids, rejected, image):
    markerID = None
    if len(corners) > 0:
        ids = ids.flatten()
        for (markerCorner, markerID) in zip(corners, ids):
            # ... 原有绘制标记的代码 ...
            cv2.putText(image, str(markerID),(topLeft[0], topLeft[1] - 10), cv2.FONT_HERSHEY_SIMPLEX,
                0.5, (0, 255, 0), 2)
            print("ArUco marker ID: {}".format(markerID))
    return image, markerID

修改detect函数接收返回值

def detect():
    # ... 原有代码 ...
    markerID = None
    while capture.isOpened():
        # ... 原有代码 ...
        detected_markers, markerID = aruco_display(corners, ids, rejected, img)
        cv2.imshow("Image", detected_markers)
        # ... 原有代码 ...
    
    cv2.destroyAllWindows()
    capture.release()
    return markerID

这样可以避免cv2.imshow接收非图像类型参数导致的报错。

内容的提问来源于stack exchange，提问作者Nigel Mathews