Forget the Storage Permission: Alternatives for sharing and collaborating

Talk from Big Android BBQ 2015 on avoiding the sledgehammer of the Storage permissions when there's a better way. Learn how FileProvider, GET_CONTENT, and the Storage Access Framework can help you share and collaborate on content across apps without unnecessary permissions.

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1. Forget the Storage permission Alternatives for sharing and collaborating Ian Lake Developer Advocate, Google
2. About me ~5 years of Android Development experience Previously at Phunware, Facebook Developer Advocate at Google • Advanced Android Udacity Course • Android Development Patterns
3. To forget, we must first learn Where can we store data?
4. App Specific Storage Also App specific public obb directory, shared across users App specific private ‘internal’ directories Context.getFileDir(), getCacheDir() App specific public ‘external’ directories Context.getExternalFilesDir(), getExternalFilesDirs() Context.getExternalCacheDir(), getExternalCacheDirs() Context.getExternalMediaDirs()
5. Public storage User public ‘external’ storage directory Environment.getExternalStorageDirectory() Environment.getExternalStoragePublicDirectory(String) Other users’ external storage - never accessible
6. Do I need the storage permission? * Only for your own app <API 19 API 19-22 API 23+ App Internal No No No App External Yes No* No* User External Yes Yes Yes
7. maxSdkVersion <uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" android:maxSdkVersion="18" /> <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" android:maxSdkVersion="18" />
8. Storage permission is all or nothing There must be a better way
9. URI Based Permissions Granting limited access to specific Uris
10. Flags added to a startActivity/startService Intent Intent.FLAG_GRANT_READ_URI_PERMISSION Intent.FLAG_GRANT_WRITE_URI_PERMISSION Can be programmatically granted/revoked Context.grantUriPermission() Context.revokeUriPermission() URI Based Permissions
11. Sharing files between apps Using external storage: Requires sending app have write storage Requires receiving app have read storage Won’t work across users (Android for Work)
12. FileProvider Gives other apps access to files in getFilesDir(), getCacheDir(), or getExternal*Dir() No storage permissions required for sender or receiver Sending a URI, not a file path -> URI based permissions
13. Sender app with FileProvider // build.gradle defaultConfig { def filesAuthorityValue = applicationId + ".files" // Now we can use ${filesAuthority} in our Manifest manifestPlaceholders = [filesAuthority: filesAuthorityValue] // Now we can use BuildConfig.FILES_AUTHORITY in our code buildConfigField "String", "FILES_AUTHORITY", "\"${filesAuthorityValue}\"" }
14. Sender app with FileProvider <!-- AndroidManifest.xml --> <provider android:name="android.support.v4.content.FileProvider" android:authorities="${filesAuthority}" android:exported="false" android:grantUriPermissions="true"> <meta-data android:name="android.support.FILE_PROVIDER_PATHS" android:resource="@xml/file_paths" /> </provider>
15. <!-- res/xml/file_paths.xml --> <paths> <!-- new File(getFileDir(), “internal”) --> <files-path name="private" path="internal/" /> <!-- new File(getCacheDir(), “images”) --> <cache-path name="image_cache" path="images/" /> <!-- getExternalFilesDir() --> <external-path name="external_files" path="files/" /> </paths> Sender app with FileProvider
16. // Directory must be in file_paths.xml File imagePath = new File(context.getFilesDir(), "internal"); File newFile = new File(imagePath, "not_usually_accessible.jpg"); Uri contentUri = FileProvider.getUriForFile(context, BuildConfig.FILES_AUTHORITY, newFile); // content://${files_authority}/private/not_usually_accessible.jpg Intent shareIntent = ShareCompat.IntentBuilder.from(activity) .setType("image/jpeg").setStream(contentUri).getIntent(); // Provide read access shareIntent.setData(contentUri); shareIntent.addFlags(Intent.FLAG_GRANT_READ_URI_PERMISSION); Sender app with FileProvider
17. Uri uri = ShareCompat.IntentReader.from(activity).getStream(); Bitmap bitmap = null; try { // Works with content://, file://, or android.resource:// URIs InputStream inputStream = getContentResolver().openInputStream(uri); bitmap = BitmapFactory.decodeStream(inputStream); } catch (FileNotFoundException e) { // Inform the user that things have gone horribly wrong } Receiving app
18. Cooperation
19. ACTION_GET_CONTENT // Requestor startActivityForResult( new Intent(Intent.ACTION_GET_CONTENT) .addCategory(Intent.CATEGORY_OPENABLE) .setType("image/*"), REQUEST_IMAGE_GET)); // Provider Uri contentUri = FileProvider.getUriForFile(...); setResult(Activity.RESULT_OK, new Intent().setData(contentUri) .addFlags(Intent.FLAG_GRANT_READ_URI_PERMISSION)); // Requestor onActivityResult() if (requestCode == REQUEST_IMAGE_GET && resultCode == RESULT_OK) { Uri uri = data.getData(); // Use getContentResolver().openInputStream() } Request files by mime type Read or import data immediately
20. ACTION_GET_CONTENT with multiple files // Requestor intent.putExtra(Intent.EXTRA_ALLOW_MULTIPLE, true); // Provider ClipData clipData = ClipData.newRawUri(null, contentUri); clipData.addItem(new ClipData.Item(secondContentUri)); intent.setClipData(clipData); // FLAG_GRANT_READ_URI_PERMISSION now applies to all Uris in ClipData Added in API 18
21. ACTION_OPEN_DOCUMENT Part of the Storage Access Framework Basic API same as ACTION_GET_CONTENT Additional APIs via DocumentContract Allows persistent access
22. GET_CONTENT or OPEN_DOCUMENT? They both have a purpose
23. OPEN_DOCUMENT >= GET_CONTENT Request OPEN_DOCUMENT - Apps supporting OPEN_DOCUMENT Request GET_CONTENT - Apps supporting GET_CONTENT - Apps supporting OPEN_DOCUMENT Disable your GET_CONTENT intent filter if you implement ACTION_OPEN_DOCUMENT
24. Storage Access Framework
25. Intent Actions for Storage Access Framework ACTION_OPEN_DOCUMENT ACTION_CREATE_DOCUMENT ACTION_OPEN_DOCUMENT_TREE
26. Implementing a DocumentProvider queryRoots() queryChildDocuments() queryDocument() openDocument()
27. DocumentProvider Resources Documentation: developer.android.com/guide/topics/providers/document-provider.html LocalStorage example: github.com/ianhanniballake/LocalStorage Jeff Sharkey’s Vault example: android.googlesource.com/platform/development/+/master/samples/Vault
28. Recap Storage Permission Accessing internal app specific storage no Accessing external app specific storage maxSdkVersion="18" Sending files with ACTION_SEND no Receiving files no or maxSdkVersion="22" Requesting files with GET_CONTENT no or maxSdkVersion="22" Providing files via GET_CONTENT no Storage Access Framework no
29. Make the Storage permission the exception Google Maps Permissions Documentation https://developers.google.com/maps/documentation/android-api/config
30. Google+ +IanLake Twitter @ianhlake Contact