Android intent filter: associate app with file extension

The answeres given by Phyrum Tea and yuku are very informative already.

I want to add that starting with Android 7.0 Nougat there is a change to the way file sharing between apps is handled:

From official Android 7.0 Changes:

For apps targeting Android 7.0, the Android framework enforces the StrictMode API policy that prohibits exposing file:// URIs outside your app. If an intent containing a file URI leaves your app, the app fails with a FileUriExposedException exception.

To share files between applications, you should send a content:// URI and grant a temporary access permission on the URI. The easiest way to grant this permission is by using the FileProvider class. For more information on permissions and sharing files, see Sharing Files.

If you have your own custom file ending without a specific mime-type (or i guess even with one) you may have to add a second scheme value to your intent-filter to make it work with FileProviders too.

Example:

<intent-filter>
    <action android:name="android.intent.action.VIEW" />

    <category android:name="android.intent.category.DEFAULT" />
    <category android:name="android.intent.category.BROWSABLE" />

    <data android:scheme="file" />
    <data android:scheme="content" />
    <data android:mimeType="*/*" />
    <!--
        Work around Android's ugly primitive PatternMatcher
        implementation that can't cope with finding a . early in
        the path unless it's explicitly matched.
    -->
    <data android:host="*" />
    <data android:pathPattern=".*\\.sfx" />
    <data android:pathPattern=".*\\..*\\.sfx" />
    <data android:pathPattern=".*\\..*\\..*\\.sfx" />
    <data android:pathPattern=".*\\..*\\..*\\..*\\.sfx" />
    <!-- keep going if you need more -->

</intent-filter>

The important thing here is the addition of

<data android:scheme="content" />

to the filter.

I had a hard time finding out about this little change which kept my activity from opening on Android 7.0 devices while everything was fine on older versions. I hope it helps someone.

My findings:

You need several filters to deal with the different ways of retrieving a file. ie, by gmail attachment, by file explorer, by HTTP, by FTP... They all send very different intents.

And you need to filter out the intent that trigger your activity in your activity code.

For the example below, I created a fake file type new.mrz. And I retrieved it from gmail attachment and file explorer.

Activity code added in the onCreate():

        Intent intent = getIntent();
        String action = intent.getAction();

        if (action.compareTo(Intent.ACTION_VIEW) == 0) {
            String scheme = intent.getScheme();
            ContentResolver resolver = getContentResolver();

            if (scheme.compareTo(ContentResolver.SCHEME_CONTENT) == 0) {
                Uri uri = intent.getData();
                String name = getContentName(resolver, uri);

                Log.v("tag" , "Content intent detected: " + action + " : " + intent.getDataString() + " : " + intent.getType() + " : " + name);
                InputStream input = resolver.openInputStream(uri);
                String importfilepath = "/sdcard/My Documents/" + name; 
                InputStreamToFile(input, importfilepath);
            }
            else if (scheme.compareTo(ContentResolver.SCHEME_FILE) == 0) {
                Uri uri = intent.getData();
                String name = uri.getLastPathSegment();

                Log.v("tag" , "File intent detected: " + action + " : " + intent.getDataString() + " : " + intent.getType() + " : " + name);
                InputStream input = resolver.openInputStream(uri);
                String importfilepath = "/sdcard/My Documents/" + name; 
                InputStreamToFile(input, importfilepath);
            }
            else if (scheme.compareTo("http") == 0) {
                // TODO Import from HTTP!
            }
            else if (scheme.compareTo("ftp") == 0) {
                // TODO Import from FTP!
            }
        }

Gmail attachement filter:

        <intent-filter android:label="@string/app_name">
            <action android:name="android.intent.action.VIEW" />
            <category android:name="android.intent.category.DEFAULT" />
            <data android:scheme="content" />
            <data android:mimeType="application/octet-stream" />
        </intent-filter>

• LOG: Content intent detected: android.intent.action.VIEW : content://gmail-ls/[email protected]/messages/2950/attachments/0.1/BEST/false : application/octet-stream : new.mrz

File explorer filter:

        <intent-filter android:label="@string/app_name">
            <action android:name="android.intent.action.VIEW" />
            <category android:name="android.intent.category.DEFAULT" />
            <data android:scheme="file" />
            <data android:pathPattern=".*\\.mrz" />
        </intent-filter>

• LOG: File intent detected: android.intent.action.VIEW : file:///storage/sdcard0/My%20Documents/new.mrz : null : new.mrz

HTTP filter:

        <intent-filter android:label="@string/rbook_viewer">
            <action android:name="android.intent.action.VIEW" />
            <category android:name="android.intent.category.DEFAULT" />
            <data android:scheme="http" />
            <data android:pathPattern=".*\\.mrz" />
        </intent-filter>

Private functions used above:

private String getContentName(ContentResolver resolver, Uri uri){
    Cursor cursor = resolver.query(uri, null, null, null, null);
    cursor.moveToFirst();
    int nameIndex = cursor.getColumnIndex(MediaStore.MediaColumns.DISPLAY_NAME);
    if (nameIndex >= 0) {
        return cursor.getString(nameIndex);
    } else {
        return null;
    }
}

private void InputStreamToFile(InputStream in, String file) {
    try {
        OutputStream out = new FileOutputStream(new File(file));

        int size = 0;
        byte[] buffer = new byte[1024];

        while ((size = in.read(buffer)) != -1) {
            out.write(buffer, 0, size);
        }

        out.close();
    }
    catch (Exception e) {
        Log.e("MainActivity", "InputStreamToFile exception: " + e.getMessage());
    }
}

You need multiple intent filters to address different situation you want to handle.

Example 1, handle http requests without mimetypes:

  <intent-filter>
    <action android:name="android.intent.action.VIEW" />
    <category android:name="android.intent.category.BROWSABLE" />
    <category android:name="android.intent.category.DEFAULT" />
    <data android:scheme="http" />
    <data android:host="*" />
    <data android:pathPattern=".*\\.pdf" />
  </intent-filter>

Handle with mimetypes, where the suffix is irrelevant:

  <intent-filter>
    <action android:name="android.intent.action.VIEW" />
    <category android:name="android.intent.category.BROWSABLE" />
    <category android:name="android.intent.category.DEFAULT" />
    <data android:scheme="http" />
    <data android:host="*" />
    <data android:mimeType="application/pdf" />
  </intent-filter>

Handle intent from a file browser app:

  <intent-filter>
    <action android:name="android.intent.action.VIEW" />
    <category android:name="android.intent.category.DEFAULT" />
    <data android:scheme="file" />
    <data android:host="*" />
    <data android:pathPattern=".*\\.pdf" />
  </intent-filter>

The other solutions did not work reliably for me until I added:

android:mimeType="*/*" 

Before that it worked in some applications, in some not...

complete solution for me:

<intent-filter>
  <action android:name="android.intent.action.VIEW" />
  <category android:name="android.intent.category.DEFAULT" />
  <data android:scheme="file"  android:host="*" android:pathPattern=".*\\.EXT" android:mimeType="*/*"  />
</intent-filter>