IssueTracker

As the title says: Intent.createChooser() does not copy EXTRA_STREAM to ClipData on the chooser intent. This means it doesn't grant the system's share sheet UI access to content uris.

Note: This issue is related to #173137936 - ShareCompat.IntentBuilder + startChooser() doesn't grant system's share sheet UI access to content - it turns out Android core has the same problem.

Reproduce:

Intent intent = new Intent(INTENT.ACTION_SEND);
intent.putExtra(Intent.EXTRA_STREAM, uri);
intent.addFlags(Intent.FLAG_GRANT_READ_URI_PERMISISON);
Intent chooserIntent = Intent.createChooser(intent, null);
startActivity(chooserIntent);

Result:

chooserIntent does not include ClipData nor any necessary flags for the uri. Whatever app handles ACTION_CHOOSER does not have access to that uri.

Solution

I propose a change to Intent.createChooser() and add something like the following (pseudo) code:

if (permFlags != 0) {
  /* ... */
  if (targetClipData == null && target.hasExtra(EXTRA_STREAM)) {
    intent.setClipData( ClipData.newRawUri(null, target.getExtra(EXTRA_STREAM)) );
  }

Note: the above code example does not account for an array of uris, so it should probably check for Intent.ACTION_SEND_MULTIPLE and act accordingly.

Context / background:

With Android Jelly Bean (API 16) Intent.setClipData(android.content.ClipData) was introduced. However, many apps - including many Google apps like Chrome (issue) and Photos and from what I can tell even Android's stock Files app - don't use it. Instead, they only provide an (array of) EXTRA_STREAM and add the FLAG_GRANT_READ_URI_PERMISISON, then call it a day (see code snippet above)

Intent intent = new Intent(INTENT.ACTION_SEND);
intent.putExtra(Intent.EXTRA_STREAM, uri);
intent.addFlags(Intent.FLAG_GRANT_READ_URI_PERMISISON);
Intent chooserIntent = Intent.createChooser(intent, null);
startActivity(chooserIntent);

instead of

Intent intent = new Intent(INTENT.ACTION_SEND);
intent.setClipData(ClipData.newRawUri(null, uri);
intent.putExtra(Intent.EXTRA_STREAM, uri);
Intent chooserIntent = Intent.createChooser(intent, null);
startActivity(chooserIntent);

In this very common scenario, Intent.createChooser() will not call setClipData() with the provided EXTRA_STREAM uri(s) and addFlags(FLAG_GRANT_READ_URI_PERMISISON) on the chooser intent it creates (see Intent.createChooser() source code).

This results in a chooser intent that does not grant the (system's, or any other) share sheet UI access to the uri(s). However, it needs this access so it can grant it to the 'destination' app the user then chooses.

From what I've learned from the Android system share menu's source code, it leverages its system app privileges to start the destination app on the sending app's behalf. That way the system share menu can grant read permission for content:// uris that it doesn't actually has access to. As you can probably imagine, 3rd party share menu replacement apps are not allowed to pull these kinds of shenanigans.

For sake of consistency and to encourage developers to follow the documentation (see below), I think it may also be time to deprecate (and eventually remove) the system share menu's ability to launch an activity on behalf of the sender, at least not when targeting SDK 16 or later. The fact this problem has gone unnoticed for so long (since SDK 16) and apps - including Google and Android stock apps - are still not using these APIs correctly, proves this 'fallback' is, in the end, encouraging bad practice. The system's share menu should probably not have to use workarounds like this unless it's absolutely necessary.

Relevant Android documentation:

Intent#ACTION_SEND

Context#startActivity(Intent) will copy EXTRA_STREAM to ClipData - but it doesn't copy ClipData (and necessary flags) if the intent is encapsulated in a chooser intent:

As of Build.VERSION_CODES.JELLY_BEAN, the data being sent can be supplied through setClipData(android.content.ClipData). This allows you to use FLAG_GRANT_READ_URI_PERMISSION when sharing content: URIs and other advanced features of ClipData. If using this approach, you still must supply the same data through the EXTRA_TEXT or EXTRA_STREAM fields described below for compatibility with old applications. If you don't set a ClipData, it will be copied there for you when calling Context#startActivity(Intent).

Source: https://developer.android.com/reference/android/content/Intent#ACTION_SEND

Intent#ACTION_CHOOSER

Intent.createChooser() seems to handle copying uri(s) and necessary flags to the chooser intent - but it doesn't when only the EXTRA_STREAM (and no ClipData is set):

If you need to grant URI permissions through a chooser, you must specify the permissions to be granted on the ACTION_CHOOSER Intent in addition to the EXTRA_INTENT inside. This means using setClipData(ClipData) to specify the URIs to be granted as well as FLAG_GRANT_READ_URI_PERMISSION and/or FLAG_GRANT_WRITE_URI_PERMISSION as appropriate.

Source: https://developer.android.com/reference/android/content/Intent#ACTION_CHOOSER