无法在 android 内部存储中创建文件夹

Question

I'm trying to create a folder in the internal storage of the phone but it just doesn't create it no matter what i do

Things I've tried:

• unplugging the phone from the computer

• set permissions both in manifest and programatically for API 23+

• every single variation of folder getting i could find: Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_DOWNLOADS) Environment.getDataDirectory() etc..

• searched every single article or variation of the article for similar problems

• tried both variations of mkdir() and mkdirs()

• checked phone if folder exists

This code is also tied to a button so the permission asking should already be granted the second time i press it.

File sdir = new File (Environment.getExternalStorageDirectory().getpath(), "/DBTEST/");

String[] PERMISSIONS_STORAGE = {
        Manifest.permission.WRITE_EXTERNAL_STORAGE
};
ActivityCompat.requestPermissions(MainActivity.this, PERMISSIONS_STORAGE, 1);

System.out.println("DIRECTORY CREATED: " + sdir.mkdirs());
System.out.println("EXISTS: " + sdir.exists());

System.out: DIRECTORY CREATED: false
System.out: EXISTS: false

<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    package="com.example.testM">

    <uses-permission android:name="android.permission.RECEIVE_BOOT_COMPLETED" />
    <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
    <uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />

Answer 1

Try changing this line:

File sdir = new File (Environment.getExternalStorageDirectory().getpath(), "/DBTEST/");

to

File sdir = new File (Environment.getExternalFilesDir(null) + "/DBTEST/");

According to the developer docs:

getExternalStorageDirectory() - This method was deprecated in API level 29. To improve user privacy, direct access to shared/external storage devices is deprecated. When an app targets Build.VERSION_CODES.Q, the path returned from this method is no longer directly accessible to apps. Apps can continue to access content stored on shared/external storage by migrating to alternatives such as Context#getExternalFilesDir(String), MediaStore, or Intent#ACTION_OPEN_DOCUMENT.

getExternalFilesDir(null) will return your apps storage folder at (Internal Storage)/Android/data/your.app.name/file/

If you want to access certain OS defined folders you just pass environmental constants defined here:

https://developer.android.com/reference/android/content/Context#getExternalFilesDir(java.lang.String)

and here

https://developer.android.com/reference/android/os/Environment

under the "Fields" section.

Ex. downloads would be: getExternalFilesDir(Environment.DIRECTORY_DOWNLOADS)

Answer 2

This is a privacy restriction introduced in Android-Q. Direct access to shared/external storage devices is deprecated when an app targets API 29 and the path returned from getExternalStorageDirectory method is no longer directly accessible to apps. Use the app-specific directory to write & read files.

By default, apps targeting Android 10 and higher are given scoped access into external storage , or scoped storage. Such apps can see the following types of files within an external storage device without needing to request any storage-related user permissions:

• Files in the app-specific directory, accessed using getExternalFilesDir() .
• Photos, videos, and audio clips that the app created from themedia store .