Merge branch 'usb-otg-support' into 'master'

USB OTG support

See merge request fdroid/fdroidclient!830

app/src/basic/java/org/fdroid/fdroid/nearby/TreeUriScannerIntentService.java

@@ -0,0 +1,32 @@
+/*
+ * Copyright (C) 2018 Senecto Limited
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 3
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
+ * MA 02110-1301, USA.
+ */
+
+package org.fdroid.fdroid.nearby;
+
+import android.app.Activity;
+import android.content.Intent;
+
+/**
+ * Dummy version for basic app flavor.
+ */
+public class TreeUriScannerIntentService {
+    public static void onActivityResult(Activity activity, Intent intent) {
+        throw new IllegalStateException("unimplemented");
+    }
+}

app/src/basic/java/org/fdroid/fdroid/views/main/NearbyViewBinder.java

@@ -1,10 +1,9 @@
 package org.fdroid.fdroid.views.main;
 
 import android.app.Activity;
-import android.content.Intent;
 
 class NearbyViewBinder {
-    static void onActivityResult(Activity activity, Intent data) {
+    public static void updateUsbOtg(final Activity activity) {
         throw new IllegalStateException("unimplemented");
     }
 }

app/src/full/AndroidManifest.xml

@@ -28,6 +28,7 @@
 
     <uses-feature android:name="android.hardware.nfc" android:required="false"/>
     <uses-feature android:name="android.hardware.bluetooth" android:required="false"/>
+    <uses-feature android:name="android.hardware.usb.host" android:required="false"/>
 
     <uses-permission android:name="android.permission.INTERNET"/>
     <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE"/>
@@ -42,6 +43,8 @@
     <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>
     <uses-permission android:name="android.permission.WRITE_SETTINGS"/>
     <uses-permission android:name="android.permission.NFC"/>
+    <uses-permission android:name="android.permission.USB_PERMISSION"
+                     android:maxSdkVersion="22"/> <!-- maybe unnecessary -->
     <uses-permission android:name="android.permission.WAKE_LOCK"/>
 
     <uses-permission-sdk-23 android:name="android.permission.ACCESS_COARSE_LOCATION"/>
@@ -78,7 +81,6 @@
                 android:exported="false"/>
         <service android:name=".nearby.SwapService"/>
 
-        <service android:name=".nearby.LocalHTTPDManager"/>
         <service
                 android:name=".nearby.LocalRepoService"
                 android:exported="false"/>
@@ -89,6 +91,17 @@
                 android:name=".nearby.SDCardScannerService"
                 android:exported="false"/>
 
+        <activity
+                android:name=".nearby.UsbDeviceAttachedActivity"
+                android:noHistory="true">
+            <intent-filter>
+                <action android:name="android.hardware.usb.action.USB_DEVICE_ATTACHED"/>
+            </intent-filter>
+            <meta-data
+                    android:name="android.hardware.usb.action.USB_DEVICE_ATTACHED"
+                    android:resource="@xml/device_filter"/>
+        </activity>
+
         <activity
                 android:name=".panic.PanicPreferencesActivity"
                 android:label="@string/panic_settings"

app/src/full/java/org/fdroid/fdroid/nearby/TreeUriScannerIntentService.java

@@ -20,19 +20,24 @@
 package org.fdroid.fdroid.nearby;
 
 import android.annotation.TargetApi;
+import android.app.Activity;
 import android.app.IntentService;
+import android.content.ContentResolver;
 import android.content.Context;
 import android.content.Intent;
 import android.net.Uri;
+import android.os.Build;
 import android.os.Process;
 import android.support.v4.provider.DocumentFile;
 import android.util.Log;
+import android.widget.Toast;
 import org.apache.commons.io.FileUtils;
 import org.apache.commons.io.IOUtils;
 import org.fdroid.fdroid.AddRepoIntentService;
 import org.fdroid.fdroid.IndexUpdater;
 import org.fdroid.fdroid.IndexV1Updater;
 import org.fdroid.fdroid.Preferences;
+import org.fdroid.fdroid.R;
 import org.fdroid.fdroid.Utils;
 import org.fdroid.fdroid.data.Repo;
 import org.fdroid.fdroid.data.RepoProvider;
@@ -41,6 +46,7 @@ import java.io.File;
 import java.io.IOException;
 import java.io.InputStream;
 import java.security.cert.Certificate;
+import java.util.ArrayList;
 import java.util.jar.JarEntry;
 import java.util.jar.JarFile;
 import java.util.jar.JarInputStream;
@@ -57,8 +63,11 @@ import java.util.jar.JarInputStream;
  * {@link android.os.Build.VERSION_CODES#KITKAT android-19}, this approach is only
  * workable if {@link android.content.Intent#ACTION_OPEN_DOCUMENT_TREE} is available.
  * It was added in {@link android.os.Build.VERSION_CODES#LOLLIPOP android-21}.
+ * {@link android.os.storage.StorageVolume#createAccessIntent(String)} is also
+ * necessary to do this with any kind of rational UX.
  *
- * @see <a href="https://commonsware.com/blog/2017/11/15/storage-situation-removable-storage.html"> The Storage Situation: Removable Storage </a>
+ * @see <a href="https://commonsware.com/blog/2017/11/15/storage-situation-removable-storage.html">The Storage Situation: Removable Storage </a>
+ * @see <a href="https://commonsware.com/blog/2016/11/18/be-careful-scoped-directory-access.html">Be Careful with Scoped Directory Access</a>
  * @see <a href="https://developer.android.com/training/articles/scoped-directory-access.html">Using Scoped Directory Access</a>
  * @see <a href="https://developer.android.com/guide/topics/providers/document-provider.html">Open Files using Storage Access Framework</a>
  */
@@ -81,6 +90,25 @@ public class TreeUriScannerIntentService extends IntentService {
         }
     }
 
+    /**
+     * Now determine if it is External Storage that must be handled by the
+     * {@link TreeUriScannerIntentService} or whether it is External Storage
+     * like an SD Card that can be directly accessed via the file system.
+     */
+    public static void onActivityResult(Activity activity, Intent intent) {
+        Uri uri = intent.getData();
+        if (uri != null) {
+            if (Build.VERSION.SDK_INT >= 19) {
+                ContentResolver contentResolver = activity.getContentResolver();
+                int perms = Intent.FLAG_GRANT_READ_URI_PERMISSION | Intent.FLAG_GRANT_WRITE_URI_PERMISSION;
+                contentResolver.takePersistableUriPermission(uri, perms);
+            }
+            String msg = String.format(activity.getString(R.string.swap_toast_using_path), uri.toString());
+            Toast.makeText(activity, msg, Toast.LENGTH_SHORT).show();
+            scan(activity, uri);
+        }
+    }
+
     @Override
     protected void onHandleIntent(Intent intent) {
         if (intent == null || !ACTION_SCAN_TREE_URI.equals(intent.getAction())) {
@@ -95,20 +123,34 @@ public class TreeUriScannerIntentService extends IntentService {
         searchDirectory(treeFile);
     }
 
+    /**
+     * Recursively search for {@link IndexV1Updater#SIGNED_FILE_NAME} starting
+     * from the given directory, looking at files first before recursing into
+     * directories.  This is "depth last" since the index file is much more
+     * likely to be shallow than deep, and there can be a lot of files to
+     * search through starting at 4 or more levels deep, like the fdroid
+     * icons dirs and the per-app "external storage" dirs.
+     */
     private void searchDirectory(DocumentFile documentFileDir) {
         DocumentFile[] documentFiles = documentFileDir.listFiles();
         if (documentFiles == null) {
             return;
         }
+        boolean foundIndex = false;
+        ArrayList<DocumentFile> dirs = new ArrayList<>();
         for (DocumentFile documentFile : documentFiles) {
             if (documentFile.isDirectory()) {
-                searchDirectory(documentFile);
+                dirs.add(documentFile);
-            } else {
+            } else if (!foundIndex) {
                 if (IndexV1Updater.SIGNED_FILE_NAME.equals(documentFile.getName())) {
                     registerRepo(documentFile);
+                    foundIndex = true;
                 }
             }
         }
+        for (DocumentFile dir : dirs) {
+            searchDirectory(dir);
+        }
     }
 
     /**
@@ -123,9 +165,7 @@ public class TreeUriScannerIntentService extends IntentService {
     private void registerRepo(DocumentFile index) {
         InputStream inputStream = null;
         try {
-            Log.i(TAG, "FOUND: " + index.getUri());
             inputStream = getContentResolver().openInputStream(index.getUri());
-            Log.i(TAG, "repo URL: " + index.getParentFile().getUri());
             registerRepo(this, inputStream, index.getParentFile().getUri());
         } catch (IOException | IndexUpdater.SigningException e) {
             e.printStackTrace();
@@ -145,7 +185,6 @@ public class TreeUriScannerIntentService extends IntentService {
         JarEntry indexEntry = (JarEntry) jarFile.getEntry(IndexV1Updater.DATA_FILE_NAME);
         IOUtils.readLines(jarFile.getInputStream(indexEntry));
         Certificate certificate = IndexUpdater.getSigningCertFromJar(indexEntry);
-        Log.i(TAG, "Got certificate: " + certificate);
         String fingerprint = Utils.calcFingerprint(certificate);
         Log.i(TAG, "Got fingerprint: " + fingerprint);
         destFile.delete();

app/src/full/java/org/fdroid/fdroid/nearby/TreeUriUtils.java

@@ -0,0 +1,96 @@
+package org.fdroid.fdroid.nearby;
+
+import android.annotation.SuppressLint;
+import android.annotation.TargetApi;
+import android.content.Context;
+import android.net.Uri;
+import android.os.Build;
+import android.os.storage.StorageManager;
+import android.provider.DocumentsContract;
+import android.support.annotation.Nullable;
+
+import java.io.File;
+import java.lang.reflect.Array;
+import java.lang.reflect.Method;
+
+
+/**
+ * @see <a href="https://stackoverflow.com/a/36162691">Android 5.0 DocumentFile from tree URI</a>
+ */
+public final class TreeUriUtils {
+    public static final String TAG = "TreeUriUtils";
+
+    private static final String PRIMARY_VOLUME_NAME = "primary";
+
+    @Nullable
+    public static String getFullPathFromTreeUri(Context context, @Nullable final Uri treeUri) {
+        if (treeUri == null) return null;
+        String volumePath = getVolumePath(getVolumeIdFromTreeUri(treeUri), context);
+        if (volumePath == null) return File.separator;
+        if (volumePath.endsWith(File.separator))
+            volumePath = volumePath.substring(0, volumePath.length() - 1);
+
+        String documentPath = getDocumentPathFromTreeUri(treeUri);
+        if (documentPath.endsWith(File.separator))
+            documentPath = documentPath.substring(0, documentPath.length() - 1);
+
+        if (documentPath.length() > 0) {
+            if (documentPath.startsWith(File.separator))
+                return volumePath + documentPath;
+            else
+                return volumePath + File.separator + documentPath;
+        } else return volumePath;
+    }
+
+
+    @SuppressLint("ObsoleteSdkInt")
+    private static String getVolumePath(final String volumeId, Context context) {
+        if (Build.VERSION.SDK_INT < Build.VERSION_CODES.LOLLIPOP) return null;
+        try {
+            StorageManager mStorageManager =
+                    (StorageManager) context.getSystemService(Context.STORAGE_SERVICE);
+            Class<?> storageVolumeClazz = Class.forName("android.os.storage.StorageVolume");
+            Method getVolumeList = mStorageManager.getClass().getMethod("getVolumeList");
+            Method getUuid = storageVolumeClazz.getMethod("getUuid");
+            Method getPath = storageVolumeClazz.getMethod("getPath");
+            Method isPrimary = storageVolumeClazz.getMethod("isPrimary");
+            Object result = getVolumeList.invoke(mStorageManager);
+
+            final int length = Array.getLength(result);
+            for (int i = 0; i < length; i++) {
+                Object storageVolumeElement = Array.get(result, i);
+                String uuid = (String) getUuid.invoke(storageVolumeElement);
+                Boolean primary = (Boolean) isPrimary.invoke(storageVolumeElement);
+
+                // primary volume?
+                if (primary && PRIMARY_VOLUME_NAME.equals(volumeId))
+                    return (String) getPath.invoke(storageVolumeElement);
+
+                // other volumes?
+                if (uuid != null && uuid.equals(volumeId))
+                    return (String) getPath.invoke(storageVolumeElement);
+            }
+            // not found.
+            return null;
+        } catch (Exception ex) {
+            return null;
+        }
+    }
+
+    @TargetApi(Build.VERSION_CODES.LOLLIPOP)
+    private static String getVolumeIdFromTreeUri(final Uri treeUri) {
+        final String docId = DocumentsContract.getTreeDocumentId(treeUri);
+        final String[] split = docId.split(":");
+        if (split.length > 0) return split[0];
+        else return null;
+    }
+
+
+    @TargetApi(Build.VERSION_CODES.LOLLIPOP)
+    private static String getDocumentPathFromTreeUri(final Uri treeUri) {
+        final String docId = DocumentsContract.getTreeDocumentId(treeUri);
+        final String[] split = docId.split(":");
+        if ((split.length >= 2) && (split[1] != null)) return split[1];
+        else return File.separator;
+    }
+}

app/src/full/java/org/fdroid/fdroid/nearby/UsbDeviceAttachedActivity.java

@@ -0,0 +1,112 @@
+/*
+ * Copyright (C) 2018-2019 Hans-Christoph Steiner <hans@eds.org>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 3
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
+ * MA 02110-1301, USA.
+ */
+
+package org.fdroid.fdroid.nearby;
+
+import android.app.Activity;
+import android.content.BroadcastReceiver;
+import android.content.ComponentName;
+import android.content.ContentResolver;
+import android.content.Context;
+import android.content.Intent;
+import android.content.IntentFilter;
+import android.content.UriPermission;
+import android.database.ContentObserver;
+import android.hardware.usb.UsbManager;
+import android.net.Uri;
+import android.os.Build;
+import android.os.Bundle;
+import android.os.Handler;
+import android.support.annotation.Nullable;
+import android.support.annotation.RequiresApi;
+import android.text.TextUtils;
+import android.util.Log;
+import org.fdroid.fdroid.views.main.MainActivity;
+import org.fdroid.fdroid.views.main.NearbyViewBinder;
+
+import java.util.HashMap;
+
+/**
+ * This is just a shim to receive {@link UsbManager#ACTION_USB_ACCESSORY_ATTACHED}
+ * events then open up the right screen in {@link MainActivity}.
+ */
+public class UsbDeviceAttachedActivity extends Activity {
+    public static final String TAG = "UsbDeviceAttachedActivi";
+
+    private static final HashMap<Uri, ContentObserver> contentObservers = new HashMap<>();
+
+    @RequiresApi(api = 19)
+    @Override
+    protected void onCreate(@Nullable Bundle savedInstanceState) {
+        super.onCreate(savedInstanceState);
+
+        if (Build.VERSION.SDK_INT < 19) {
+            finish();
+            return;
+        }
+
+        Intent intent = getIntent();
+        if (intent == null || TextUtils.isEmpty(intent.getAction())
+                || !UsbManager.ACTION_USB_DEVICE_ATTACHED.equals(intent.getAction())) {
+            Log.i(TAG, "ignoring irrelevant intent: " + intent);
+            finish();
+            return;
+        }
+        Log.i(TAG, "handling intent: " + intent);
+
+        final ContentResolver contentResolver = getContentResolver();
+        BroadcastReceiver receiver = new BroadcastReceiver() {
+            @Override
+            public void onReceive(Context context, Intent intent) {
+                if (!UsbManager.ACTION_USB_DEVICE_DETACHED.equals(intent.getAction())) {
+                    return;
+                }
+                NearbyViewBinder.updateUsbOtg(UsbDeviceAttachedActivity.this);
+                unregisterReceiver(this);
+                for (ContentObserver contentObserver : contentObservers.values()) {
+                    contentResolver.unregisterContentObserver(contentObserver);
+                }
+            }
+        };
+        registerReceiver(receiver, new IntentFilter(UsbManager.ACTION_USB_DEVICE_DETACHED));
+
+        for (final UriPermission uriPermission : contentResolver.getPersistedUriPermissions()) {
+            Uri uri = uriPermission.getUri();
+            final ContentObserver contentObserver = new ContentObserver(new Handler()) {
+
+                @Override
+                public void onChange(boolean selfChange, Uri uri) {
+                    NearbyViewBinder.updateUsbOtg(UsbDeviceAttachedActivity.this);
+                }
+            };
+            contentResolver.registerContentObserver(uri, true, contentObserver);
+        }
+        intent.setComponent(new ComponentName(this, MainActivity.class));
+        intent.putExtra(MainActivity.EXTRA_VIEW_NEARBY, true);
+        intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK | Intent.FLAG_ACTIVITY_CLEAR_TASK);
+        startActivity(intent);
+        finish();
+    }
+
+    @Override
+    public void finish() {
+        setResult(RESULT_OK);
+        super.finish();
+    }
+}

app/src/full/java/org/fdroid/fdroid/views/main/NearbyViewBinder.java

@@ -2,13 +2,21 @@ package org.fdroid.fdroid.views.main;
 
 import android.Manifest;
 import android.app.Activity;
+import android.content.Context;
 import android.content.Intent;
+import android.content.UriPermission;
 import android.content.pm.PackageManager;
+import android.hardware.usb.UsbDevice;
+import android.hardware.usb.UsbManager;
+import android.net.Uri;
 import android.os.Build;
 import android.os.Environment;
+import android.os.storage.StorageManager;
+import android.os.storage.StorageVolume;
 import android.support.annotation.RequiresApi;
 import android.support.v4.app.ActivityCompat;
 import android.support.v4.content.ContextCompat;
+import android.text.TextUtils;
 import android.util.Log;
 import android.view.View;
 import android.widget.Button;
@@ -17,11 +25,13 @@ import android.widget.ImageView;
 import android.widget.TextView;
 import android.widget.Toast;
 import org.fdroid.fdroid.R;
+import org.fdroid.fdroid.Utils;
 import org.fdroid.fdroid.nearby.SDCardScannerService;
 import org.fdroid.fdroid.nearby.SwapService;
 import org.fdroid.fdroid.nearby.TreeUriScannerIntentService;
 
 import java.io.File;
+import java.util.List;
 
 /**
  * A splash screen encouraging people to start the swap process. The swap
@@ -50,13 +60,14 @@ import java.io.File;
  * @see TreeUriScannerIntentService
  * @see org.fdroid.fdroid.nearby.SDCardScannerService
  */
-class NearbyViewBinder {
+public class NearbyViewBinder {
     public static final String TAG = "NearbyViewBinder";
 
-    static File externalStorage = null;
+    private static File externalStorage = null;
+    private static View swapView;
 
     NearbyViewBinder(final Activity activity, FrameLayout parent) {
-        View swapView = activity.getLayoutInflater().inflate(R.layout.main_tab_swap, parent, true);
+        swapView = activity.getLayoutInflater().inflate(R.layout.main_tab_swap, parent, true);
 
         TextView subtext = swapView.findViewById(R.id.both_parties_need_fdroid_text);
         subtext.setText(activity.getString(R.string.nearby_splash__both_parties_need_fdroid,
@@ -131,5 +142,62 @@ class NearbyViewBinder {
                 }
             });
         }
+
+        updateUsbOtg(activity);
+    }
+
+    public static void updateUsbOtg(final Activity activity) {
+        if (Build.VERSION.SDK_INT < 24) {
+            return;
+        }
+        if (swapView == null) {
+            Utils.debugLog(TAG, "swapView == null");
+            return;
+        }
+        TextView storageVolumeText = swapView.findViewById(R.id.storage_volume_text);
+        Button requestStorageVolume = swapView.findViewById(R.id.request_storage_volume_button);
+        storageVolumeText.setVisibility(View.GONE);
+        requestStorageVolume.setVisibility(View.GONE);
+
+        final StorageManager storageManager = (StorageManager) activity.getSystemService(Context.STORAGE_SERVICE);
+        for (final StorageVolume storageVolume : storageManager.getStorageVolumes()) {
+            if (storageVolume.isRemovable() && !storageVolume.isPrimary()) {
+                Log.i(TAG, "StorageVolume: " + storageVolume);
+                final Intent intent = storageVolume.createAccessIntent(null);
+                if (intent == null) {
+                    Utils.debugLog(TAG, "Got null Storage Volume access Intent");
+                    return;
+                }
+                storageVolumeText.setVisibility(View.VISIBLE);
+
+                String text = storageVolume.getDescription(activity);
+                if (!TextUtils.isEmpty(text)) {
+                    requestStorageVolume.setText(text);
+                    UsbDevice usb = intent.getParcelableExtra(UsbManager.EXTRA_DEVICE);
+                    if (usb != null) {
+                        text = String.format("%s (%s %s)", text, usb.getManufacturerName(), usb.getProductName());
+                        Toast.makeText(activity, text, Toast.LENGTH_LONG).show();
+                    }
+                }
+
+                requestStorageVolume.setVisibility(View.VISIBLE);
+                requestStorageVolume.setOnClickListener(new View.OnClickListener() {
+                    @Override
+                    @RequiresApi(api = 24)
+                    public void onClick(View v) {
+                        List<UriPermission> list = activity.getContentResolver().getPersistedUriPermissions();
+                        if (list != null) for (UriPermission uriPermission : list) {
+                            Uri uri = uriPermission.getUri();
+                            if (uri.getPath().equals(String.format("/tree/%s:", storageVolume.getUuid()))) {
+                                intent.setData(uri);
+                                TreeUriScannerIntentService.onActivityResult(activity, intent);
+                                return;
+                            }
+                        }
+                        activity.startActivityForResult(intent, MainActivity.REQUEST_STORAGE_ACCESS);
+                    }
+                });
+            }
+        }
     }
 }

app/src/full/res/layout/main_tab_swap.xml

@@ -72,11 +72,12 @@
             android:layout_height="wrap_content"
             android:layout_weight="1"
             android:text="@string/nearby_splash__read_external_storage"
-            android:textSize="20sp"
+            android:textSize="17sp"
             android:textColor="?attr/lightGrayTextColor"
             android:textAlignment="center"
             android:gravity="center"
-            android:layout_marginEnd="24dp" app:layout_constraintEnd_toEndOf="parent" android:layout_marginRight="24dp"
+            android:layout_marginEnd="24dp" app:layout_constraintEnd_toEndOf="parent"
+            android:layout_marginRight="24dp"
             android:layout_marginStart="24dp" app:layout_constraintStart_toStartOf="parent"
             android:layout_marginLeft="24dp" android:layout_marginTop="48dp"
             app:layout_constraintTop_toBottomOf="@+id/both_parties_need_fdroid_text"
@@ -96,4 +97,35 @@
             app:layout_constraintTop_toBottomOf="@+id/read_external_storage_text"
             android:visibility="gone"
             tools:visibility="visible"/>
+
+    <TextView
+            android:id="@+id/storage_volume_text"
+            android:layout_width="0dp"
+            android:layout_height="wrap_content"
+            android:layout_weight="1"
+            android:text="@string/nearby_splash__document_tree"
+            android:textSize="17sp"
+            android:textColor="?attr/lightGrayTextColor"
+            android:textAlignment="center"
+            android:gravity="center"
+            android:layout_marginEnd="24dp" app:layout_constraintEnd_toEndOf="parent"
+            android:layout_marginRight="24dp"
+            android:layout_marginStart="24dp" app:layout_constraintStart_toStartOf="parent"
+            android:layout_marginLeft="24dp" android:layout_marginTop="48dp"
+            app:layout_constraintTop_toBottomOf="@+id/request_read_external_storage_button"
+            android:visibility="gone"/>
+    <Button
+            android:id="@+id/request_storage_volume_button"
+            android:layout_width="wrap_content"
+            android:layout_height="wrap_content"
+            android:maxEms="16"
+            android:text="@string/nearby_splash__request_permission"
+            style="@style/DetailsSecondaryButtonStyle"
+            app:layout_constraintEnd_toEndOf="parent"
+            android:layout_marginEnd="8dp" android:layout_marginRight="8dp"
+            app:layout_constraintStart_toStartOf="parent" android:layout_marginLeft="8dp"
+            android:layout_marginStart="8dp" android:layout_marginTop="24dp"
+            app:layout_constraintTop_toBottomOf="@+id/storage_volume_text"
+            android:visibility="gone"/>
+
 </android.support.constraint.ConstraintLayout>

app/src/full/res/xml/device_filter.xml

@@ -0,0 +1,26 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!--
+/**
+ * (C) Copyright 2014 mjahnen <jahnen@in.tum.de>
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+-->
+<resources>
+
+    <usb-device
+        class="8"
+        protocol="80"
+        subclass="6" />
+
+</resources>

app/src/main/java/org/fdroid/fdroid/net/TreeUriDownloader.java

@@ -91,7 +91,7 @@ public class TreeUriDownloader extends Downloader {
 
     @Override
     protected long totalDownloadSize() {
-        return documentFile.length();
+        return documentFile.length(); // TODO how should this actually be implemented?
     }
 
     @Override

app/src/main/java/org/fdroid/fdroid/views/main/MainActivity.java

@@ -58,11 +58,12 @@ import org.fdroid.fdroid.Utils;
 import org.fdroid.fdroid.data.NewRepoConfig;
 import org.fdroid.fdroid.nearby.SDCardScannerService;
 import org.fdroid.fdroid.nearby.SwapService;
+import org.fdroid.fdroid.nearby.SwapWorkflowActivity;
+import org.fdroid.fdroid.nearby.TreeUriScannerIntentService;
 import org.fdroid.fdroid.nearby.WifiStateChangeService;
 import org.fdroid.fdroid.views.AppDetailsActivity;
 import org.fdroid.fdroid.views.ManageReposActivity;
 import org.fdroid.fdroid.views.apps.AppListActivity;
-import org.fdroid.fdroid.nearby.SwapWorkflowActivity;
 
 import java.lang.reflect.Field;
 
@@ -85,10 +86,12 @@ public class MainActivity extends AppCompatActivity implements BottomNavigationB
     private static final String TAG = "MainActivity";
 
     public static final String EXTRA_VIEW_UPDATES = "org.fdroid.fdroid.views.main.MainActivity.VIEW_UPDATES";
+    public static final String EXTRA_VIEW_NEARBY = "org.fdroid.fdroid.views.main.MainActivity.VIEW_NEARBY";
     public static final String EXTRA_VIEW_SETTINGS = "org.fdroid.fdroid.views.main.MainActivity.VIEW_SETTINGS";
 
     static final int REQUEST_LOCATION_PERMISSIONS = 0xEF0F;
     static final int REQUEST_STORAGE_PERMISSIONS = 0xB004;
+    public static final int REQUEST_STORAGE_ACCESS = 0x40E5;
 
     private static final String ADD_REPO_INTENT_HANDLED = "addRepoIntentHandled";
 
@@ -133,6 +136,15 @@ public class MainActivity extends AppCompatActivity implements BottomNavigationB
             bottomNavigation
                     .addItem(new BottomNavigationItem(R.drawable.ic_categories, R.string.main_menu__categories))
                     .addItem(new BottomNavigationItem(R.drawable.ic_nearby, R.string.main_menu__swap_nearby));
+
+            bottomNavigation.setOnClickListener(new View.OnClickListener() {
+                @Override
+                public void onClick(View v) {
+                    if (bottomNavigation.getCurrentSelectedPosition() == 2) {
+                        NearbyViewBinder.updateUsbOtg(MainActivity.this);
+                    }
+                }
+            });
         }
         bottomNavigation.setTabSelectedListener(this)
                 .setBarBackgroundColor(getBottomNavigationBackgroundColorResId())
@@ -217,6 +229,11 @@ public class MainActivity extends AppCompatActivity implements BottomNavigationB
             pager.scrollToPosition(adapter.adapterPositionFromItemId(R.id.updates));
             selectedMenuId = R.id.updates;
             setSelectedMenuInNav();
+        } else if (getIntent().hasExtra(EXTRA_VIEW_NEARBY)) {
+            getIntent().removeExtra(EXTRA_VIEW_NEARBY);
+            pager.scrollToPosition(adapter.adapterPositionFromItemId(R.id.nearby));
+            selectedMenuId = R.id.nearby;
+            setSelectedMenuInNav();
         } else if (getIntent().hasExtra(EXTRA_VIEW_SETTINGS)) {
             getIntent().removeExtra(EXTRA_VIEW_SETTINGS);
             pager.scrollToPosition(adapter.adapterPositionFromItemId(R.id.settings));
@@ -246,6 +263,14 @@ public class MainActivity extends AppCompatActivity implements BottomNavigationB
         checkForAddRepoIntent(intent);
     }
 
+    @Override
+    protected void onActivityResult(int requestCode, int resultCode, Intent data) {
+        super.onActivityResult(requestCode, resultCode, data);
+        if (requestCode == REQUEST_STORAGE_ACCESS) {
+            TreeUriScannerIntentService.onActivityResult(this, data);
+        }
+    }
+
     @Override
     public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) { // NOCHECKSTYLE LineLength
         super.onRequestPermissionsResult(requestCode, permissions, grantResults);

app/src/main/java/org/fdroid/fdroid/views/main/MainViewAdapter.java

@@ -82,7 +82,7 @@ class MainViewAdapter extends RecyclerView.Adapter<MainViewController> {
     @NonNull
     @Override
     public MainViewController onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
-        MainViewController holder = createEmptyView();
+        MainViewController holder = createEmptyView(activity);
         switch (viewType) {
             case R.id.whats_new:
                 holder.bindWhatsNewView();
@@ -106,7 +106,7 @@ class MainViewAdapter extends RecyclerView.Adapter<MainViewController> {
         return holder;
     }
 
-    private MainViewController createEmptyView() {
+    static MainViewController createEmptyView(AppCompatActivity activity) {
         FrameLayout frame = new FrameLayout(activity);
         frame.setLayoutParams(new FrameLayout.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT,
                 ViewGroup.LayoutParams.MATCH_PARENT));

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

@@ -458,7 +458,8 @@ This often occurs with apps installed via Google Play or other sources, if they
     <!-- The word "nearby" should be the same as used for Google/Android Nearby. This is a button label, it should ideally be 10-20 characters. -->
     <string name="nearby_splash__find_people_button">Find people nearby</string>
     <string name="nearby_splash__both_parties_need_fdroid">Both parties need %1$s to use nearby.</string>
-    <string name="nearby_splash__read_external_storage">SD Cards can be used to swap!</string>
+    <string name="nearby_splash__read_external_storage">Search SD Card for repos and mirrors.</string>
+    <string name="nearby_splash__document_tree">Search USB OTG for repos and mirrors.</string>
     <!-- This is a button label for a small button, the text needs to be under 10 characters, the shorter the better. Also, a literal translation probably will miss the point. "Try it" is more a saying than two words. Google has been pushing these short buttons, like "Got it" and "Try now" so this button is trying to match those buttons in Android. -->
     <string name="nearby_splash__request_permission">Try it</string>