Android 11 ACTION_OPEN_DOCUMENT_TREE：将初始 URI 设置为文档文件夹

Question

在 Android 11 中使用范围存储模型，我想让用户能够选择文件夹，从文档文件夹开始：

val intent = Intent(Intent.ACTION_OPEN_DOCUMENT_TREE)
intent.putExtra(DocumentsContract.EXTRA_INITIAL_URI,    ???     )
startActivityForResult(intent, OPEN_DIRECTORY_REQUEST_CODE,null)

问题是，如何生成手机文档文件夹的正确 URI？（它位于 root / 中）在官方文档中，没有给出示例。我真的希望所有标准位置都有一些简洁的常量？

Answer 1

我们将操纵INITIAL_URI从 获得的StorageManager..getPrimaryStorageVolume().createOpenDocumentTreeIntent()。

if (android.os.Build.VERSION.SDK_INT >= android.os.Build.VERSION_CODES.Q) {
    StorageManager sm = (StorageManager) context.getSystemService(Context.STORAGE_SERVICE);

    Intent intent = sm.getPrimaryStorageVolume().createOpenDocumentTreeIntent();
    //String startDir = "Android";
    //String startDir = "Download"; // Not choosable on an Android 11 device
    //String startDir = "DCIM";
    //String startDir = "DCIM/Camera";  // replace "/", "%2F"
    //String startDir = "DCIM%2FCamera";
    String startDir = "Documents";

    Uri uri = intent.getParcelableExtra("android.provider.extra.INITIAL_URI");

    String scheme = uri.toString();

    Log.d(TAG, "INITIAL_URI scheme: " + scheme);

    scheme = scheme.replace("/root/", "/document/");

    scheme += "%3A" + startDir;

    uri = Uri.parse(scheme);

    intent.putExtra("android.provider.extra.INITIAL_URI", uri);

    Log.d(TAG, "uri: " + uri.toString());

    ((Activity) context).startActivityForResult(intent, REQUEST_ACTION_OPEN_DOCUMENT_TREE);

    return;
}

Answer 2

如何生成手机文档文件夹的正确 URI？

测试于：

1. 小米M2102J20SI
2. 模拟器 Pixel 4 XL API 30

函数askPermission()打开目标目录。

@RequiresApi(Build.VERSION_CODES.Q)
private fun askPermission() {
    val storageManager = application.getSystemService(Context.STORAGE_SERVICE) as StorageManager
    val intent =  storageManager.primaryStorageVolume.createOpenDocumentTreeIntent()

    val targetDirectory = "WhatsApp%2FMedia%2F.Statuses" // add your directory to be selected by the user
    var uri = intent.getParcelableExtra<Uri>("android.provider.extra.INITIAL_URI") as Uri
    var scheme = uri.toString()
    scheme = scheme.replace("/root/", "/document/")
    scheme += "%3A$targetDirectory"
    uri = Uri.parse(scheme)
    intent.putExtra("android.provider.extra.INITIAL_URI", uri)
    startActivityForResult(intent, REQUEST_CODE)
}

文件的 URI 将返回onActivityResult()

 override fun onActivityResult(requestCode: Int, resultCode: Int, data: Intent?) {
        super.onActivityResult(requestCode, resultCode, data)
        if (resultCode == RESULT_OK && requestCode == REQUEST_CODE) {
            if (data != null) {
                data.data?.let { treeUri ->

                    // treeUri is the Uri of the file
                    
                   // if life long access is required the takePersistableUriPermission() is used

                    contentResolver.takePersistableUriPermission(
                            treeUri,
                            Intent.FLAG_GRANT_READ_URI_PERMISSION or
                                    Intent.FLAG_GRANT_WRITE_URI_PERMISSION
                    )

                  readSDK30(treeUri)
                }
            }
        }
    }

函数readSDK30()用于读取文件和文件夹Uri

  private fun readSDK30(treeUri: Uri) {
        val tree = DocumentFile.fromTreeUri(this, treeUri)!!

        thread {
            val uriList  = arrayListOf<Uri>()
            listFiles(tree).forEach { uri ->
                 
                // Collect all the Uri from here
            }
            
        }
    }

函数listFiles()返回给定的所有文件和文件夹Uri

fun listFiles(folder: DocumentFile): List<Uri> {
            return if (folder.isDirectory) {
                folder.listFiles().mapNotNull { file ->
                    if (file.name != null) file.uri else null
                }
            } else {
                emptyList()
            }
        }