使用Python/Kivy+Buildozer在Colab打包的APK无法在Android创建目录

问题情况 #

• 非专业开发者，此前正常运行半年的简易Android应用，重新打包APK后无法创建目录/storage/emulated/0/MK_Eng
• 已确认路径正确、权限已配置、所需模块导入完成，调试多日未解决

核心代码片段 #

import os

if kivy.platform == 'win':
    dirname='C:/MK_Eng/'
    filename='C:/MK_Eng/eng-rus-new.txt'
elif kivy.platform == 'android':
    from android.permissions import request_permissions, Permission
    from android.storage import primary_external_storage_path
    request_permissions([Permission.READ_EXTERNAL_STORAGE, Permission.WRITE_EXTERNAL_STORAGE])
    dir = primary_external_storage_path()
    dirname = os.path.join(dir, 'MK_Eng')
    filename='/storage/emulated/0/MK_Eng/eng-rus-new.txt'


if not os.path.isdir(dirname):
    # Create Directory
    os.mkdir(dirname)

Buildozer配置片段 #

#(list) Source files to include (let empty to include all the files)
source.include_exts = py,png,jpg,kv,atlas,txt

#(list) Application requirements
#comma separated e.g. requirements = sqlite3,kivy
requirements = python3,kivy,android.permissions

#(list) Permissions
android.permissions = INTERNET,READ_EXTERNAL_STORAGE,WRITE_EXTERNAL_STORAGE

#(str) python-for-android branch to use, defaults to master
p4a.branch = develop

解决步骤 #

1. 处理权限请求的异步问题
   request_permissions是异步操作，直接调用后立刻创建目录会导致权限未生效。需要等待权限请求结果返回后再执行操作：

   from android.permissions import request_permissions, Permission, check_permission
   
   def create_dir_after_permission(permission, results):
       if all(results):
           if not os.path.isdir(dirname):
               os.mkdir(dirname)
       # 权限被拒绝的情况可在此添加提示逻辑
   
   if kivy.platform == 'android':
       # 先检查权限状态，已授权直接创建目录
       if check_permission(Permission.WRITE_EXTERNAL_STORAGE) and check_permission(Permission.READ_EXTERNAL_STORAGE):
           if not os.path.isdir(dirname):
               os.mkdir(dirname)
       else:
           # 未授权则发起请求，指定回调函数
           request_permissions([Permission.READ_EXTERNAL_STORAGE, Permission.WRITE_EXTERNAL_STORAGE], create_dir_after_permission)
   

2. 适配Android 10+的Scoped Storage政策
   Android 10（API 29）及以上启用了Scoped Storage，直接操作外部存储根目录会受限。可以选择两种方案：

   • 降低API版本到28（避开Scoped Storage），在Buildozer配置中添加：

     android.api = 28
     android.target_sdk = 28
     

   • 适配高版本，申请MANAGE_EXTERNAL_STORAGE权限（需用户手动在设置中授权），配置如下：

     android.permissions = INTERNET,READ_EXTERNAL_STORAGE,WRITE_EXTERNAL_STORAGE,MANAGE_EXTERNAL_STORAGE
     android.target_sdk = 33
     

3. 统一路径拼接方式
   代码中filename直接写死路径，建议和dirname保持一致，用os.path.join拼接，避免路径错误：

   filename = os.path.join(dirname, 'eng-rus-new.txt')
   

4. 调整Python-for-Android分支
   p4a.branch = develop可能存在兼容性问题，尝试切换到稳定的master分支：

   p4a.branch = master
   

内容的提问来源于stack exchange，提问作者Michael