Android 设备的图像无法显示，但 buildozer 目录中的图像可以显示在移动应用程序上

Question

I am doing the mobile application which shows an image from the storage of an android device on the mobile application.

The issue I faced:

• When opening an image file from the android device's storage on the mobile apps, the Image Widget shows a black screen. (refer to Figure 1) However, the image file is in the directory of the bulldozer, and it is able to display on the Image Widget. (refer to Figure 2)

The things I tried:

1. The apps will directly open Image from the android device's storage on the Image Widget after the user had selected the image.

2. The code below shows, that the apps will open the Image from the android device's storage through the PIL.Image.open. After that, the apps will use the PIL.Image to save the image inside the directory of the program.

Both ways brought out the same outcome (black screen).

Figure 1: Black Screen

Figure 2: Image from the directory of buildozer

Both images are the same below

Image used: Raindowntothestreet.png

Figure 3: Raindowntothestreet.png

The code is below. showing 2）from the things I tried

import os

os.environ['KIVY_IMAGE'] = 'pil,sdl2'

class MainPage(FloatLayout):
    # Getting the folder address of the program located
    running_program_path = os.path.abspath(os.path.dirname(__file__))
    path_file_notation = ""

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

        # def image and label as ""
        self.image_selected.source = ""
        self.label_selected.text = ""
        
        # To show the Image from the directory of the buildozer
        self.image_selected.source = "Raindowntothestreet.png"



    def selected(self, selection):
        if selection:
            # opening selected file
            img = PIL_Image.open(selection[0])

            # create directory folder for the files
            # path_notation = self.running_program_path
            # if not os.path.isdir(path_notation):
            #     os.makedirs(path_notation)

            # creating temporary file name with datetime, string, random
            currentDateTime = datetime.now()
            currentDate = currentDateTime.strftime("%Y%m%d")
            currentTime = currentDateTime.strftime("%H%M%S")
            alphabet1 = random.choice(string.ascii_letters)
            alphabet2 = random.choice(string.ascii_letters)

            # create a temporary file for the selected file
            self.path_file_notation = f"temp" + currentDate + currentTime + alphabet1 + 
                                      alphabet2 + f".png"

            # save the selected at the program directory
            img.save(self.path_file_notation)

            # showing the file on the Image Widget
            self.image_selected.source = self.path_file_notation

            # showing the path of file located
            self.label_selected.text = "Source: " + selection[0]
            print(self.image_selected.source)

In the buildozer.spec,

• the android's permission like READ_EXTERNAL_STORAGE and WRITE_EXTERNAL_STORAGE are already mentioned in the android.permissions. at below

• android.permissions = INTERNET,READ_EXTERNAL_STORAGE,WRITE_EXTERNAL_STORAGE

• requirements = kivy,python3,pillow,plyer,jnius,android,datetime

• source.include_exts = py,png,jpg,kv,atlas

Answer 1

Specially for your question, I created an example for working with images on Linux/Windows/macOS and Android . Most importantly, all changes to widgets should occur in the main thread. In my example, you can use both an image in a temporary folder and an existing image (I don't recommend doing this, it's better to work with a copy). I created this example, because plyer does not work correctly with the selection of images at the moment. Cross-platform image picker