Open an Alert dialog box while clicking on the camera icon button if the the camera is not open yet in kivymd

Open an Alert dialog box while clicking on the camera icon button if the the camera is not open yet in kivymd

Problem Description:

I’m beginner in Kivy, I make a screen which has an image in which a camera live feed is fitted and 2 buttons the 1st start camera which open the webcam and the 2nd is the icon button to take a picture and store it locally but the problem is that if i clicked the icon button before clicking the start camera it give me this error.

cv2.imwrite(image_name, self.image_frame)
 AttributeError: 'WebCamScreen' object has no attribute 'image_frame'

So , how should i put a dialogbox or some other condition to tell the user to start camera first.

Here is my WebCamScreen code

class WebCamScreen(Screen):
    def do_start(self):
        self.capture = cv2.VideoCapture(0)
        Clock.schedule_interval(self.load_video, 1.0 / 24.0)

    def load_video(self, *args):
        ret, frame = self.capture.read()
        self.image_frame = frame
        # frame = frame[220:220+250, 400:400+250, :]
        buffer = cv2.flip(frame, 0).tostring()
        image_texture = Texture.create(size=(frame.shape[1], frame.shape[0]), colorfmt="bgr")
        image_texture.blit_buffer(buffer, colorfmt="bgr", bufferfmt="ubyte")
        self.ids.img.texture = image_texture

    def capture_image(self):
        image_name = "first_pic.jpg"
        cv2.imwrite(image_name, self.image_frame)

and kv code is below

<WebCamScreen>
    MDFloatLayout:
        MDRaisedButton:
            text: "Start Camera"
            size_hint_x: None
            size_hint_y: None
            md_bg_color: "orange"
            pos_hint: {"center_x": 0.5, "center_y": 0.95}
            on_release:
                root.do_start()
            
        Image:
            id: img
            size_hint_x: 0.85
            size_hint_y: 0.5
            pos_hint: {"center_x": 0.5, "center_y": 0.6}
            
        MDIconButton:
            icon: "camera"
            md_bg_color: "orange"
            pos_hint: {"center_x": .5, "center_y": .2}
            on_release:
                root.capture_image() 

Solution – 1

You can put that line that causes the exception in a try block. And in the except block display a Popup.

Or you can disable the capture_image Button, and enable it from within the load_video() method.