持久权限 URI android Q

Question

I'm using the emulator and I send the intent in this way:

StorageManager sm = (StorageManager) context.getSystemService(Context.STORAGE_SERVICE);
Intent i;
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.Q) {
   i = sm.getPrimaryStorageVolume().createOpenDocumentTreeIntent();
} else {
   return null;
}
i.addFlags(Intent.FLAG_GRANT_READ_URI_PERMISSION);
i.addFlags(Intent.FLAG_GRANT_WRITE_URI_PERMISSION);
i.addFlags(Intent.FLAG_GRANT_PERSISTABLE_URI_PERMISSION);

and in onActivityResult() :

Uri uri = data.getData();
if (uri == null)
    return null;
context.getContentResolver()
                .takePersistableUriPermission(uri,
                        Intent.FLAG_GRANT_READ_URI_PERMISSION | Intent.FLAG_GRANT_WRITE_URI_PERMISSION);

Every time I reboot, the app doesn't have access. Can anyone confirm about this bug on beta 6 on the emulator? Am I doing anything wrong?

Answer 1

I converted your code snippets into this Kotlin activity:

package com.commonsware.jetpack.myapplication

import android.content.Context
import android.content.Intent
import android.content.SharedPreferences
import android.net.Uri
import android.os.Bundle
import android.os.storage.StorageManager
import android.widget.Toast
import androidx.appcompat.app.AppCompatActivity
import androidx.documentfile.provider.DocumentFile

private const val PREF_URI = "uri"
private const val REQUEST_SAF = 1337

class MainActivity : AppCompatActivity() {
  private val prefs: SharedPreferences by lazy {
    getSharedPreferences("test", Context.MODE_PRIVATE)
  }

  override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)
    setContentView(R.layout.activity_main)

    val uriString = prefs.getString(PREF_URI, null)
    val storageManager = getSystemService(StorageManager::class.java)!!

    if (uriString == null) {
      startActivityForResult(
        storageManager.primaryStorageVolume.createOpenDocumentTreeIntent(),
        REQUEST_SAF
      )
    } else {
      val uri = Uri.parse(uriString)
      val docFile = DocumentFile.fromTreeUri(this, uri)

      Toast.makeText(
        this,
        "canRead: ${docFile?.canRead()} canWrite: ${docFile?.canWrite()}",
        Toast.LENGTH_LONG
      ).show()
    }
  }

  override fun onActivityResult(
    requestCode: Int,
    resultCode: Int,
    data: Intent?
  ) {
    val uri = data?.data

    if (uri == null) {
      Toast.makeText(this, "Did not get a Uri??!?", Toast.LENGTH_LONG).show()
    } else {
      contentResolver.takePersistableUriPermission(
        uri,
        Intent.FLAG_GRANT_READ_URI_PERMISSION or Intent.FLAG_GRANT_WRITE_URI_PERMISSION
      )

      prefs.edit().putString(PREF_URI, uri.toString()).apply()
      Toast.makeText(this, "OK, run the activity again", Toast.LENGTH_LONG).show()
    }

    finish()
  }
}

I then ran the app containing this activity as its launcher activity and chose Downloads/ as the document tree. Subsequent launches of this activity — both before and after a reboot — show canRead() and canWrite() both return true . This was tested on a Google Pixel running Q Beta 6.

I cannot try this on a Q emulator because Google , so I cannot confirm if I can reproduce your behavior there. But, the fact that this works as expected on hardware should be a positive sign.

Answer 2

For those who appreciate the accepted answer, but do not want to use startActivityForResult , which was deprecated after the original answer was accepted.

My example shows how to save a file to storage from within your app.

First, create a class-wide variable to hold the ActivityResultLauncher information:

private lateinit var saveDataResultLauncher: ActivityResultLauncher<String>

Then, instead of using the deprecated feature, you can put this, for example, in your MainActivity 's onCreate fun:

/** Backup Website Entries */
saveDataResultLauncher = registerForActivityResult(ActivityResultContracts.CreateDocument()) {}

Make the user choose a location to save a file, after pressing a menu item bound to the functionality implemented above:

override fun onOptionsItemSelected(item: MenuItem): Boolean {
    return when (item.itemId) {
      R.id.action_save_file -> {
        saveDataResultLauncher.launch("example.txt")
        true
      }
      else -> super.onOptionsItemSelected(item)
    }
  }