Check for Adobe Acrobat reader

FAQ.md

@@ -49,7 +49,7 @@ Since FairEmail is meant to be privacy friendly, the following will not be added
 
 * Open links without confirmation
 * Show original message without confirmation
-* Direct file/folder access: for security/privacy reasons (other) apps should use the [Storage Access Framework](https://developer.android.com/guide/topics/providers/document-provider), see also [this FAQ](#user-content-faq49)
+* Direct file/folder access: for security/privacy reasons (other) apps should use the [Storage Access Framework](https://developer.android.com/guide/topics/providers/document-provider), see also [this FAQ](#user-content-faq49) and [this FAQ](#user-content-faq68)
 
 Confirmation is just one tap, which is just a small price for better privacy.
 Note that your contacts could unknowingly send malicious messages if they got infected with malware.
@@ -125,6 +125,7 @@ Stripped and reformatted messages are often better readable than original messag
 * [(65) Why are some attachments shown dimmed?](#user-content-faq65)
 * [(66) Is FairEmail available in the Google Play Family Library?](#user-content-faq66)
 * [(67) How can I snooze conversations?](#user-content-faq67)
+* [(68) Why can Adobe Acrobat reader not open PDF attachments?](#user-content-faq68)
 
 [I have another question.](#support)
 
@@ -1043,6 +1044,19 @@ By selecting a zero snooze duration you can cancel snoozing.
 
 <br />
 
+<a name="faq68"></a>
+**(68) Why can Adobe Acrobat reader not open PDF attachments?**
+
+Adobe Acrobat reader still expects full access to all stored files,
+while apps should use the [Storage Access Framework](https://developer.android.com/guide/topics/providers/document-provider) since Android KitKat (2013)
+to have access to actively shared files only. This is for privacy and security reasons.
+
+You can workaround this by saving the attachment and opening it from the Adobe Acrobat reader,
+but you are advised to install an up-to-date and preferably open source PDF reader,
+for example one listed [here](https://github.com/offa/android-foss#-document--pdf-viewer).
+
+<br />
+
 ## Support
 
 If you have another question, want to request a feature or report a bug, you can use [this forum](https://forum.xda-developers.com/android/apps-games/source-email-t3824168).

app/src/main/java/eu/faircode/email/AdapterAttachment.java

@@ -193,6 +193,8 @@ public class AdapterAttachment extends RecyclerView.Adapter<AdapterAttachment.Vi
                     List<NameResolveInfo> targets = new ArrayList<>();
                     List<ResolveInfo> ris = pm.queryIntentActivities(intent, PackageManager.MATCH_DEFAULT_ONLY);
                     for (ResolveInfo ri : ris) {
+                        if ("com.adobe.reader".equals(ri.activityInfo.packageName))
+                            Toast.makeText(context, R.string.title_no_adobe, Toast.LENGTH_LONG).show();
                         Log.i("Target=" + ri);
                         context.grantUriPermission(ri.activityInfo.packageName, uri, Intent.FLAG_GRANT_READ_URI_PERMISSION);
                         targets.add(new NameResolveInfo(

app/src/main/res/values/strings.xml

@@ -431,6 +431,7 @@
     <string name="title_days">Days</string>
     <string name="title_report">Report</string>
     <string name="title_no_ask_again">Do not ask this again</string>
+    <string name="title_no_adobe">Adobe Acrobat reader cannot open safely shared files, see the FAQ for more information</string>
 
     <string name="title_try">Try FairEmail, an open source, privacy friendly email app for Android</string>