Receive shares and serve file requests, so other apps can reach this one

The manifest had nothing but a LAUNCHER filter, so no other app could hand Plain Files anything. It now registers for ACTION_SEND and SEND_MULTIPLE (a bar over the browser: navigate to the folder, then Save here) and for GET_CONTENT and OPEN_DOCUMENT, where tapping a file hands it back through the existing FileProvider.

Both reuse the browser instead of a second screen, because both are navigate-to-a-folder with a different verb at the end. data/ gains one port, IncomingSource, to keep a ContentResolver out of the ViewModel the way DeleteRequestFactory keeps one out of the delete path. Shared files are named from the sender OpenableColumns, allocated by the same NameAllocator a paste uses, and deleted again if they cannot be read rather than left as zero-byte stubs. While providing, a tap on a file chooses it but a tap on a folder still navigates, or the user could never reach the file.

ACTION_VIEW is deliberately not registered: the app already hands files out through the system chooser, and registering as a viewer would offer Plain Files back to itself. No new permissions - the merged release manifest still declares no INTERNET.

CHANGELOG.md

@@ -38,6 +38,27 @@ upload needs a **higher `versionCode`** than every previous upload.
 
 ### Added
 
+- **The app can receive a share, and act as a file picker.** The manifest had nothing but a
+  `LAUNCHER` filter, so no other app could hand Plain Files anything at all. It now registers
+  for `ACTION_SEND`/`SEND_MULTIPLE` — a bar appears over the browser, you navigate to the
+  folder you want, then "Save here" — and for `ACTION_GET_CONTENT`/`OPEN_DOCUMENT`, where
+  tapping a file hands it back through the existing `FileProvider`.
+
+  Both reuse the browser rather than adding a second screen, because both are the same task
+  underneath — navigate to a folder — with a different verb at the end. `data/` gains one
+  port, `IncomingSource`, so a `ContentResolver` stays out of the ViewModel exactly as
+  `DeleteRequestFactory` keeps one out of the delete path. A shared file is named from the
+  sender's `OpenableColumns` where it offers one, goes through the same `NameAllocator` a
+  paste does (so sharing the same file twice cannot overwrite the first copy), and is removed
+  again if it cannot be read rather than left as a zero-byte stub. While another app is
+  waiting for a file, tapping a *file* chooses it and tapping a *folder* still navigates —
+  without that the user could never reach the file they were trying to choose.
+
+  `ACTION_VIEW` is deliberately **not** registered: the app already hands files out through
+  the system chooser, and registering as a viewer as well would offer Plain Files back to
+  itself in that chooser. No new permissions — the merged release manifest still declares no
+  `INTERNET`.
+
 - **Recursive search.** The query box used to filter the folder you were standing in, which
   can only ever answer "is it here?" — and the usual question is "where did I put it?". It
   now walks *down* from the current folder (`domain/FileSearch`) and streams matches as they

README.md

@@ -37,8 +37,8 @@ Android 16 (API 36) from 31 August 2026.
 app/src/main/java/de/softwareapp_hb/filemanager/
 ├── core/      Pure-Kotlin engine (no Android imports!) — paths, sorting, formatting,
 │              search matching, copy/move planning, conflict policy
-├── data/      Storage backends (all-files access + SAF), volumes, bookmarks,
+├── data/      Storage backends (all-files access + SAF), volumes, shares coming in
-│              file operations, archives, deletion
+│              from other apps, file operations, archives, deletion
 ├── domain/    Browser + operation controllers, models, permission state
 ├── service/   Foreground service for long-running file operations
 ├── ui/        Compose theme, browser screen, components, ViewModels
@@ -139,8 +139,11 @@ UI.** Translated UI text has to be supplied in `values-<locale>/`.
 
 ## Known limitations
 
-- **"Open with" and Share only work in the all-files mode.** A SAF path is relative to the
+- **Sharing a file *out* only works in the all-files mode.** A SAF path is relative to the
   granted tree rather than a filesystem path, so it cannot be handed to `FileProvider`.
+  Receiving a share and being picked from another app's chooser work either way: the first
+  needs no filesystem path, and the second falls back to `RESULT_CANCELED` rather than
+  returning a URI the caller could not read.
 - **RAR, CAB, ISO and WIM are refused**, not supported — they need native code, which this
   project deliberately does not ship. (The Commons Compress jar contains no RAR classes at
   all.) **7z is different**: Commons Compress reads it in pure Java, so it *is* supported —

app/src/main/AndroidManifest.xml

@@ -69,6 +69,46 @@
                 <action android:name="android.intent.action.MAIN" />
                 <category android:name="android.intent.category.LAUNCHER" />
             </intent-filter>
+
+            <!--
+              Receiving a share. Without these the app is not a share target at all — the
+              manifest had nothing but LAUNCHER, so no other app could hand it a file.
+
+              `*/*` rather than a list of types on purpose: a file manager should accept
+              anything the user wants to put somewhere, including types it cannot preview.
+            -->
+            <intent-filter>
+                <action android:name="android.intent.action.SEND" />
+                <category android:name="android.intent.category.DEFAULT" />
+                <data android:mimeType="*/*" />
+            </intent-filter>
+            <intent-filter>
+                <action android:name="android.intent.action.SEND_MULTIPLE" />
+                <category android:name="android.intent.category.DEFAULT" />
+                <data android:mimeType="*/*" />
+            </intent-filter>
+
+            <!--
+              Supplying a file. `GET_CONTENT` and `OPEN_DOCUMENT` are how other apps ask
+              for one, and `OPENABLE` is what makes the chooser list this app for a
+              "choose a file" prompt rather than a "choose a document" one.
+
+              `ACTION_VIEW` is deliberately absent: the app already hands files *out*
+              through the system chooser, and registering as a viewer as well would risk
+              offering Plain Files back to itself in that chooser.
+            -->
+            <intent-filter>
+                <action android:name="android.intent.action.GET_CONTENT" />
+                <category android:name="android.intent.category.DEFAULT" />
+                <category android:name="android.intent.category.OPENABLE" />
+                <data android:mimeType="*/*" />
+            </intent-filter>
+            <intent-filter>
+                <action android:name="android.intent.action.OPEN_DOCUMENT" />
+                <category android:name="android.intent.category.DEFAULT" />
+                <category android:name="android.intent.category.OPENABLE" />
+                <data android:mimeType="*/*" />
+            </intent-filter>
         </activity>
 
         <!--

app/src/main/java/de/softwareapp_hb/filemanager/FileManagerApplication.kt

@@ -1,7 +1,9 @@
 package de.softwareapp_hb.filemanager
 
 import android.app.Application
+import de.softwareapp_hb.filemanager.data.ContentResolverIncomingSource
 import de.softwareapp_hb.filemanager.data.DeleteRequestFactory
+import de.softwareapp_hb.filemanager.data.IncomingSource
 import de.softwareapp_hb.filemanager.data.MediaStoreDeleter
 import de.softwareapp_hb.filemanager.data.StorageProvider
 import de.softwareapp_hb.filemanager.domain.OperationNotifier
@@ -10,9 +12,9 @@ import de.softwareapp_hb.filemanager.service.ServiceOperationNotifier
 /**
  * Application entry point and the app's tiny object graph.
  *
- * There is no dependency-injection framework here on purpose: three long-lived
+ * There is no dependency-injection framework here on purpose: four long-lived collaborators
- * collaborators are built once and handed to the one ViewModel that needs them. Nothing
+ * are built once and handed to the one ViewModel that needs them. Nothing holds a reference
- * holds a reference to an Activity, so none of this leaks.
+ * to an Activity, so none of this leaks.
  */
 class FileManagerApplication : Application() {
 
@@ -28,10 +30,15 @@ class FileManagerApplication : Application() {
     lateinit var deleteRequests: DeleteRequestFactory
         private set
 
+    /** Reads whatever another app shares in. */
+    lateinit var incoming: IncomingSource
+        private set
+
     override fun onCreate() {
         super.onCreate()
         storage = StorageProvider(this)
         notifier = ServiceOperationNotifier(this)
         deleteRequests = MediaStoreDeleter(this).factory()
+        incoming = ContentResolverIncomingSource(contentResolver)
     }
 }

app/src/main/java/de/softwareapp_hb/filemanager/MainActivity.kt

@@ -1,5 +1,6 @@
 package de.softwareapp_hb.filemanager
 
+import android.content.Intent
 import android.os.Bundle
 import androidx.activity.ComponentActivity
 import androidx.activity.compose.setContent
@@ -8,22 +9,57 @@ import androidx.compose.foundation.layout.fillMaxSize
 import androidx.compose.material3.MaterialTheme
 import androidx.compose.material3.Surface
 import androidx.compose.ui.Modifier
+import de.softwareapp_hb.filemanager.core.FileEntry
 import de.softwareapp_hb.filemanager.ui.browser.BrowserScreen
+import de.softwareapp_hb.filemanager.ui.browser.IncomingRequest
+import de.softwareapp_hb.filemanager.ui.browser.contentUriFor
 import de.softwareapp_hb.filemanager.ui.theme.FileManagerTheme
 
 class MainActivity : ComponentActivity() {
+
     override fun onCreate(savedInstanceState: Bundle?) {
         enableEdgeToEdge()
         super.onCreate(savedInstanceState)
+
+        // A share or an "open" request arrives with the launch intent. An ordinary launch
+        // has neither, and the browser then behaves exactly as it always did — the two
+        // flows are the same screen with one extra bar on it.
+        val incoming = IncomingRequest.from(intent)
+
         setContent {
             FileManagerTheme {
                 Surface(
                     modifier = Modifier.fillMaxSize(),
                     color = MaterialTheme.colorScheme.background,
                 ) {
-                    BrowserScreen()
+                    BrowserScreen(
+                        incoming = incoming,
+                        onDeliver = ::deliver,
+                        onDone = ::finish,
+                    )
                 }
             }
         }
     }
+
+    /**
+     * Hand a file back to whoever asked for it.
+     *
+     * A path reached through the SAF fallback is relative to the granted tree rather than a
+     * filesystem path, so no `content://` URI can be built for it — the caller then gets
+     * `RESULT_CANCELED`, which is honest, rather than a URI it could not read.
+     */
+    private fun deliver(entry: FileEntry) {
+        val uri = contentUriFor(this, entry)
+        if (uri == null) {
+            setResult(RESULT_CANCELED)
+            return
+        }
+        setResult(
+            RESULT_OK,
+            Intent()
+                .setData(uri)
+                .addFlags(Intent.FLAG_GRANT_READ_URI_PERMISSION),
+        )
+    }
 }

app/src/main/java/de/softwareapp_hb/filemanager/data/IncomingSource.kt

@@ -0,0 +1,48 @@
+package de.softwareapp_hb.filemanager.data
+
+import android.content.ContentResolver
+import android.net.Uri
+import android.provider.OpenableColumns
+import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.withContext
+import java.io.OutputStream
+
+/**
+ * Something another app has handed to this one.
+ *
+ * A port rather than a `ContentResolver` on the ViewModel, for the same reason
+ * [DeleteRequestFactory] is one: it keeps a `Context` out of the ViewModel, and it lets a
+ * test hand over plain bytes instead of standing up a real document provider.
+ */
+interface IncomingSource {
+
+    /** The name to save [uri] under, before any clash is resolved. `null` when unknown. */
+    fun suggestedName(uri: Uri): String?
+
+    /** Copy [uri]'s bytes into [destination], which the caller has already created. */
+    suspend fun writeTo(uri: Uri, destination: OutputStream)
+}
+
+/**
+ * The real one, over the platform's content resolver.
+ *
+ * A shared file arrives as a `content://` URI owned by whichever app sent it, so the only
+ * way to its bytes is through the resolver — and the only honest name for it is the one the
+ * sender advertises through [OpenableColumns].
+ */
+class ContentResolverIncomingSource(private val resolver: ContentResolver) : IncomingSource {
+
+    override fun suggestedName(uri: Uri): String? = runCatching {
+        resolver.query(uri, arrayOf(OpenableColumns.DISPLAY_NAME), null, null, null)
+            ?.use { cursor -> if (cursor.moveToFirst()) cursor.getString(0) else null }
+            ?: uri.lastPathSegment?.trimEnd('/')?.substringAfterLast('/')
+    }.getOrNull()?.takeIf { it.isNotBlank() }
+
+    override suspend fun writeTo(uri: Uri, destination: OutputStream) {
+        withContext(Dispatchers.IO) {
+            val input = resolver.openInputStream(uri)
+                ?: throw StorageException("The sending app would not open $uri")
+            input.use { it.copyTo(destination) }
+        }
+    }
+}

app/src/main/java/de/softwareapp_hb/filemanager/ui/browser/BrowserScreen.kt

@@ -4,6 +4,7 @@ import android.content.Intent
 import androidx.activity.compose.rememberLauncherForActivityResult
 import androidx.activity.result.contract.ActivityResultContracts
 import androidx.compose.foundation.layout.Box
+import androidx.compose.foundation.layout.Column
 import androidx.compose.foundation.layout.PaddingValues
 import androidx.compose.foundation.layout.fillMaxSize
 import androidx.compose.foundation.layout.padding
@@ -70,7 +71,12 @@ import de.softwareapp_hb.filemanager.ui.viewer.TextEditorScreen
 
 @OptIn(ExperimentalMaterial3Api::class)
 @Composable
-fun BrowserScreen(viewModel: BrowserViewModel = viewModel(factory = BrowserViewModel.Factory)) {
+fun BrowserScreen(
+    incoming: IncomingRequest? = null,
+    onDeliver: (FileEntry) -> Unit = {},
+    onDone: () -> Unit = {},
+    viewModel: BrowserViewModel = viewModel(factory = BrowserViewModel.Factory),
+) {
     val state by viewModel.state.collectAsStateWithLifecycle()
     val context = LocalContext.current
     val provider = remember(context) { (context.applicationContext as FileManagerApplication).storage }
@@ -84,6 +90,17 @@ fun BrowserScreen(viewModel: BrowserViewModel = viewModel(factory = BrowserViewM
     var searchOpen by remember { mutableStateOf(false) }
     var menuOpen by remember { mutableStateOf(false) }
 
+    // Taken on once. A recomposition must not re-arm the bar the user just dismissed.
+    LaunchedEffect(incoming) { viewModel.onIncomingRequest(incoming) }
+
+    // Handing a file back closes the screen: whoever asked for it is waiting on a result.
+    LaunchedEffect(state.pendingDeliver) {
+        state.pendingDeliver?.let { entry ->
+            onDeliver(entry)
+            onDone()
+        }
+    }
+
     val permissionLauncher = rememberLauncherForActivityResult(
         ActivityResultContracts.RequestMultiplePermissions(),
     ) {
@@ -229,9 +246,35 @@ fun BrowserScreen(viewModel: BrowserViewModel = viewModel(factory = BrowserViewM
         },
         snackbarHost = { SnackbarHost(snackbarHostState) },
     ) { innerPadding ->
+        Column(
+            modifier = Modifier
+                .fillMaxSize()
+                .padding(innerPadding),
+        ) {
+            // Files shared in: the user still needs to choose a folder, so this sits above
+            // the listing rather than replacing it.
+            state.receiving?.let { uris ->
+                IncomingBar(
+                    message = pluralStringResource(R.plurals.incoming_save_here, uris.size, uris.size),
+                    // No destination until the user is inside a folder.
+                    actionLabel = state.path?.let { stringResource(R.string.incoming_save_action) },
+                    onAction = { state.path?.let(viewModel::receiveInto) },
+                    onCancel = viewModel::cancelIncoming,
+                )
+            }
+
+            if (state.providing) {
+                IncomingBar(
+                    message = stringResource(R.string.incoming_pick_hint),
+                    actionLabel = null,
+                    onAction = {},
+                    onCancel = viewModel::cancelIncoming,
+                )
+            }
+
             BrowserContent(
                 state = state,
-            contentPadding = innerPadding,
+                contentPadding = PaddingValues(0.dp),
                 crumbLabel = crumbLabel,
                 onOpenEntry = viewModel::open,
                 onFocusEntry = viewModel::focus,
@@ -250,6 +293,7 @@ fun BrowserScreen(viewModel: BrowserViewModel = viewModel(factory = BrowserViewM
                 onPickFolder = { treeLauncher.launch(null) },
             )
         }
+    }
 
     if (showSort) {
         SortSheet(

app/src/main/java/de/softwareapp_hb/filemanager/ui/browser/BrowserUiState.kt

@@ -1,5 +1,6 @@
 package de.softwareapp_hb.filemanager.ui.browser
 
+import android.net.Uri
 import androidx.activity.result.IntentSenderRequest
 import androidx.annotation.AnyRes
 import androidx.annotation.StringRes
@@ -138,6 +139,12 @@ data class BrowserUiState(
     /** Set when the system should confirm a delete; the screen launches it and clears it. */
     val pendingDeleteRequest: IntentSenderRequest? = null,
     val conflict: ConflictPrompt? = null,
+    /** Files another app has shared in, waiting for the user to pick a folder for them. */
+    val receiving: List<Uri>? = null,
+    /** `true` while another app is waiting for a file this one has to supply. */
+    val providing: Boolean = false,
+    /** The file the user chose to hand back; the screen returns it and closes. */
+    val pendingDeliver: FileEntry? = null,
     /** The last destructive change the app made, waiting to be taken back. */
     val undo: Undo? = null,
     /** A viewer, editor or the storage-usage view taking over the screen. */

app/src/main/java/de/softwareapp_hb/filemanager/ui/browser/BrowserViewModel.kt

@@ -22,6 +22,7 @@ import de.softwareapp_hb.filemanager.core.SortSpec
 import de.softwareapp_hb.filemanager.core.StoragePath
 import de.softwareapp_hb.filemanager.core.TransferAction
 import de.softwareapp_hb.filemanager.data.DeleteRequestFactory
+import de.softwareapp_hb.filemanager.data.IncomingSource
 import de.softwareapp_hb.filemanager.data.StorageAccessMode
 import de.softwareapp_hb.filemanager.data.StorageLocation
 import de.softwareapp_hb.filemanager.data.StorageSource
@@ -65,6 +66,7 @@ class BrowserViewModel(
     private val notifier: OperationNotifier = OperationNotifier.None,
     private val deleteRequests: DeleteRequestFactory = DeleteRequestFactory { _, _ -> null },
     private val savedState: SavedStateHandle = SavedStateHandle(),
+    private val incoming: IncomingSource? = null,
 ) : ViewModel() {
 
     private val _state = MutableStateFlow(restoredViewState())
@@ -392,6 +394,14 @@ class BrowserViewModel(
 
     /** Open an entry: folders navigate, images and text open in the built-in viewers. */
     fun open(entry: FileEntry) {
+        // While another app is waiting for a file, "open" on a *file* means "hand this one
+        // back". Folders still navigate — without that the user could never reach the file
+        // they are trying to choose.
+        if (_state.value.providing && !entry.isDirectory) {
+            _state.update { it.copy(pendingDeliver = entry) }
+            return
+        }
+
         when {
             entry.isDirectory -> openDirectory(entry.path)
             entry.kind == FileKind.IMAGE -> _state.update { it.copy(overlay = Overlay.Image(entry)) }
@@ -616,6 +626,76 @@ class BrowserViewModel(
         if (here == null) refresh() else load(here)
     }
 
+    // ------------------------------------------------------------------ incoming
+
+    /**
+     * Take on what another app handed over, once, when the screen starts.
+     *
+     * The browser is reused for both cases rather than a second screen being built: a user
+     * choosing where to save a shared file and a user choosing a file to hand back are
+     * doing the same thing — navigating to a folder — and only the verb at the end differs.
+     */
+    fun onIncomingRequest(request: IncomingRequest?) {
+        when (request) {
+            is IncomingRequest.Receive -> _state.update { it.copy(receiving = request.uris) }
+            IncomingRequest.Provide -> _state.update { it.copy(providing = true) }
+            null -> Unit
+        }
+    }
+
+    /** Give up on receiving or providing, leaving an ordinary browser behind. */
+    fun cancelIncoming() {
+        _state.update { it.copy(receiving = null, providing = false, pendingDeliver = null) }
+    }
+
+    /**
+     * Save the shared files into [folder] — wherever the user navigated to.
+     *
+     * Names come from the sending app where it offers one, and clashes go through the same
+     * [NameAllocator] a paste does, so sharing the same file twice cannot overwrite the
+     * first copy.
+     */
+    fun receiveInto(folder: StoragePath) {
+        val uris = _state.value.receiving ?: return
+        val reader = incoming ?: return
+        val source = storage.activeSource() ?: return
+
+        viewModelScope.launch {
+            _state.update { it.copy(loading = true) }
+            notifier.start(OperationKind.COPY)
+
+            val taken = source.list(folder).mapTo(HashSet()) { it.name }
+            val failures = ArrayList<OperationFailure>()
+            var saved = 0
+
+            for (uri in uris) {
+                val base = reader.suggestedName(uri) ?: FALLBACK_RECEIVED_NAME
+                val name = NameAllocator.uniqueName(base) { it in taken }
+                val target = folder.child(name)
+                try {
+                    source.createFile(target)
+                    source.openWrite(target).use { output -> reader.writeTo(uri, output) }
+                    taken += name
+                    saved++
+                } catch (cancellation: CancellationException) {
+                    throw cancellation
+                } catch (failure: Exception) {
+                    // Do not leave a zero-byte stub behind for a share that never arrived.
+                    runCatching { source.delete(target) }
+                    failures += OperationFailure(target, failure.message ?: "It could not be saved")
+                }
+            }
+
+            notifier.stop()
+            _state.update { it.copy(loading = false, receiving = null) }
+
+            val result = OperationResult(OperationKind.COPY, saved, failures, false)
+            if (result.succeeded) messagePlural(R.plurals.message_received, saved) else report(result)
+
+            load(folder)
+        }
+    }
+
     // --------------------------------------------------------------------- undo
 
     /**
@@ -894,6 +974,9 @@ class BrowserViewModel(
         private const val KEY_VIEW_MODE = "browser.viewMode"
         private const val KEY_SHOW_HIDDEN = "browser.showHidden"
 
+        /** Used when the sending app offers no name at all for a shared file. */
+        private const val FALLBACK_RECEIVED_NAME = "shared-file"
+
         val Factory: ViewModelProvider.Factory = viewModelFactory {
             initializer {
                 val app = this[ViewModelProvider.AndroidViewModelFactory.APPLICATION_KEY]
@@ -903,6 +986,7 @@ class BrowserViewModel(
                     notifier = app.notifier,
                     deleteRequests = app.deleteRequests,
                     savedState = createSavedStateHandle(),
+                    incoming = app.incoming,
                 )
             }
         }

app/src/main/java/de/softwareapp_hb/filemanager/ui/browser/IncomingBar.kt

@@ -0,0 +1,60 @@
+package de.softwareapp_hb.filemanager.ui.browser
+
+import androidx.compose.foundation.layout.Row
+import androidx.compose.foundation.layout.fillMaxWidth
+import androidx.compose.foundation.layout.padding
+import androidx.compose.material.icons.Icons
+import androidx.compose.material.icons.filled.Close
+import androidx.compose.material3.Icon
+import androidx.compose.material3.IconButton
+import androidx.compose.material3.MaterialTheme
+import androidx.compose.material3.Surface
+import androidx.compose.material3.Text
+import androidx.compose.material3.TextButton
+import androidx.compose.runtime.Composable
+import androidx.compose.ui.Alignment
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.res.stringResource
+import androidx.compose.ui.unit.dp
+import de.softwareapp_hb.filemanager.R
+
+/**
+ * The bar shown while another app is waiting on this one.
+ *
+ * It sits *above* the listing rather than over it, because the whole point is that the user
+ * can still navigate: choosing where a shared file should go is exactly why the browser was
+ * reused instead of a dedicated dialog.
+ */
+@Composable
+fun IncomingBar(
+    message: String,
+    actionLabel: String?,
+    onAction: () -> Unit,
+    onCancel: () -> Unit,
+    modifier: Modifier = Modifier,
+) {
+    Surface(
+        modifier = modifier.fillMaxWidth(),
+        color = MaterialTheme.colorScheme.primaryContainer,
+    ) {
+        Row(
+            modifier = Modifier.padding(start = 16.dp, end = 4.dp, top = 4.dp, bottom = 4.dp),
+            verticalAlignment = Alignment.CenterVertically,
+        ) {
+            Text(
+                text = message,
+                style = MaterialTheme.typography.bodyMedium,
+                modifier = Modifier.weight(1f),
+            )
+            actionLabel?.let { label ->
+                TextButton(onClick = onAction) { Text(label) }
+            }
+            IconButton(onClick = onCancel) {
+                Icon(
+                    imageVector = Icons.Filled.Close,
+                    contentDescription = stringResource(R.string.incoming_cancel),
+                )
+            }
+        }
+    }
+}

app/src/main/java/de/softwareapp_hb/filemanager/ui/browser/IncomingRequest.kt

@@ -0,0 +1,46 @@
+package de.softwareapp_hb.filemanager.ui.browser
+
+import android.content.Intent
+import android.net.Uri
+import androidx.core.content.IntentCompat
+
+/**
+ * What another app asked this one to do.
+ *
+ * Both cases reuse the same browser, because both are the same task underneath: the user
+ * has to navigate to a folder. Only the verb at the end differs — save here, or hand this
+ * one back.
+ */
+sealed interface IncomingRequest {
+
+    /** Files shared into the app ([Intent.ACTION_SEND] or its multiple counterpart). */
+    data class Receive(val uris: List<Uri>) : IncomingRequest
+
+    /** Another app is waiting for a file (`ACTION_GET_CONTENT` / `ACTION_OPEN_DOCUMENT`). */
+    data object Provide : IncomingRequest
+
+    companion object {
+
+        /** Read [intent], or `null` when this is an ordinary launch. */
+        fun from(intent: Intent?): IncomingRequest? = when (intent?.action) {
+            Intent.ACTION_SEND ->
+                receive(listOfNotNull(IntentCompat.getParcelableExtra(intent, Intent.EXTRA_STREAM, Uri::class.java)))
+
+            Intent.ACTION_SEND_MULTIPLE ->
+                receive(IntentCompat.getParcelableArrayListExtra(intent, Intent.EXTRA_STREAM, Uri::class.java).orEmpty())
+
+            Intent.ACTION_GET_CONTENT, Intent.ACTION_OPEN_DOCUMENT -> Provide
+
+            else -> null
+        }
+
+        /**
+         * A share with nothing attached is not a receive request.
+         *
+         * Some launchers fire `ACTION_SEND` with no stream; treating that as "save zero
+         * files here" would put a pointless banner over the browser.
+         */
+        private fun receive(uris: List<Uri>): IncomingRequest? =
+            uris.takeIf { it.isNotEmpty() }?.let(::Receive)
+    }
+}

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

@@ -55,6 +55,15 @@
     <string name="browser_action_select_all">Select all</string>
     <string name="browser_action_clear_selection">Clear selection</string>
     <string name="browser_action_undo">Undo</string>
+
+    <!-- ===== Browser: files another app has handed over ===== -->
+    <plurals name="incoming_save_here">
+        <item quantity="one">Save %1$d file into this folder</item>
+        <item quantity="other">Save %1$d files into this folder</item>
+    </plurals>
+    <string name="incoming_save_action">Save here</string>
+    <string name="incoming_pick_hint">Navigate to a file and tap it to hand it back</string>
+    <string name="incoming_cancel">Cancel</string>
     <string name="browser_action_more">More options</string>
     <string name="browser_action_refresh">Refresh</string>
     <string name="browser_action_cancel">Cancel</string>
@@ -140,6 +149,10 @@
         <item quantity="one">Put %1$d item back</item>
         <item quantity="other">Put %1$d items back</item>
     </plurals>
+    <plurals name="message_received">
+        <item quantity="one">Saved %1$d shared file</item>
+        <item quantity="other">Saved %1$d shared files</item>
+    </plurals>
     <plurals name="message_failed">
         <item quantity="one">%1$d item could not be processed</item>
         <item quantity="other">%1$d items could not be processed</item>

app/src/test/java/de/softwareapp_hb/filemanager/ui/browser/BrowserViewModelTest.kt

@@ -2,6 +2,7 @@ package de.softwareapp_hb.filemanager.ui.browser
 
 import android.app.PendingIntent
 import android.content.Intent
+import android.net.Uri
 import androidx.activity.result.IntentSenderRequest
 import androidx.lifecycle.SavedStateHandle
 import de.softwareapp_hb.filemanager.core.ConflictPolicy
@@ -10,6 +11,7 @@ import de.softwareapp_hb.filemanager.core.SortDirection
 import de.softwareapp_hb.filemanager.core.SortKey
 import de.softwareapp_hb.filemanager.core.StoragePath
 import de.softwareapp_hb.filemanager.data.DeleteRequestFactory
+import de.softwareapp_hb.filemanager.data.IncomingSource
 import de.softwareapp_hb.filemanager.data.StorageAccessMode
 import de.softwareapp_hb.filemanager.data.VolumeInfo
 import de.softwareapp_hb.filemanager.domain.OperationKind
@@ -19,6 +21,7 @@ import de.softwareapp_hb.filemanager.domain.testutil.InMemoryStorageSource
 import de.softwareapp_hb.filemanager.ui.browser.testutil.FakeStorageLocation
 import kotlinx.coroutines.Dispatchers
 import kotlinx.coroutines.ExperimentalCoroutinesApi
+import kotlinx.coroutines.runBlocking
 import kotlinx.coroutines.test.UnconfinedTestDispatcher
 import kotlinx.coroutines.test.resetMain
 import kotlinx.coroutines.test.setMain
@@ -34,6 +37,7 @@ import org.junit.runner.RunWith
 import org.robolectric.RobolectricTestRunner
 import org.robolectric.RuntimeEnvironment
 import org.robolectric.annotation.Config
+import java.io.OutputStream
 
 @OptIn(ExperimentalCoroutinesApi::class)
 @RunWith(RobolectricTestRunner::class)
@@ -59,10 +63,26 @@ class BrowserViewModelTest {
         override fun stop() = Unit
     }
 
+    /** Bytes per shared URI, and the name the sending app advertises for it. */
+    private val sharedBytes = mutableMapOf<Uri, String>()
+    private val sharedNames = mutableMapOf<Uri, String>()
+
+    private val fakeIncoming = object : IncomingSource {
+        override fun suggestedName(uri: Uri): String? = sharedNames[uri]
+
+        override suspend fun writeTo(uri: Uri, destination: OutputStream) {
+            // `getValue` throws for a URI with no bytes, which is how a refusing sender is
+            // simulated.
+            destination.write(sharedBytes.getValue(uri).toByteArray())
+        }
+    }
+
     @Before
     fun setUp() {
         Dispatchers.setMain(UnconfinedTestDispatcher())
         recordedNotifications.clear()
+        sharedBytes.clear()
+        sharedNames.clear()
 
         storage = InMemoryStorageSource(
             roots = listOf(FileEntry(root, isDirectory = true, sizeBytes = 0L, lastModifiedMillis = 0L)),
@@ -89,7 +109,8 @@ class BrowserViewModelTest {
     private fun viewModel(
         deleteRequests: DeleteRequestFactory = DeleteRequestFactory { _, _ -> null },
         savedState: SavedStateHandle = SavedStateHandle(),
-    ) = BrowserViewModel(location, recordingNotifier, deleteRequests, savedState)
+        incoming: IncomingSource? = fakeIncoming,
+    ) = BrowserViewModel(location, recordingNotifier, deleteRequests, savedState, incoming)
 
     @Test
     fun `starts on the root list`() {
@@ -578,4 +599,121 @@ class BrowserViewModelTest {
         assertTrue(storage.contains(downloads.child("a.txt")))
         assertFalse(storage.contains(downloads.child("renamed.txt")))
     }
+
+    // ---------------------------------------------------------------- incoming
+
+    @Test
+    fun `a shared file is saved into the folder the user chose`() {
+        val uri = Uri.parse("content://sender/holiday")
+        sharedNames[uri] = "holiday.jpg"
+        sharedBytes[uri] = "jpeg bytes"
+
+        val model = viewModel()
+        model.openDirectory(downloads)
+        model.onIncomingRequest(IncomingRequest.Receive(listOf(uri)))
+
+        model.receiveInto(downloads)
+
+        assertEquals("jpeg bytes", storage.contentOf(downloads.child("holiday.jpg")))
+        assertNull(model.state.value.receiving)
+    }
+
+    @Test
+    fun `a shared file never overwrites one already in the folder`() = runBlocking {
+        val uri = Uri.parse("content://sender/clash")
+        sharedNames[uri] = "a.txt"
+        sharedBytes[uri] = "shared bytes"
+
+        val model = viewModel()
+        model.openDirectory(downloads)
+        model.onIncomingRequest(IncomingRequest.Receive(listOf(uri)))
+
+        model.receiveInto(downloads)
+
+        assertEquals("first", storage.contentOf(downloads.child("a.txt")))
+        val landed = storage.list(downloads).map { it.name }.filter { it != "a.txt" }
+        assertTrue(landed.any { storage.contentOf(downloads.child(it)) == "shared bytes" })
+    }
+
+    @Test
+    fun `a file the sender cannot name still lands under a usable one`() {
+        val uri = Uri.parse("content://sender/nameless")
+        sharedBytes[uri] = "bytes"
+
+        val model = viewModel()
+        model.openDirectory(downloads)
+        model.onIncomingRequest(IncomingRequest.Receive(listOf(uri)))
+
+        model.receiveInto(downloads)
+
+        assertEquals("bytes", storage.contentOf(downloads.child("shared-file")))
+    }
+
+    @Test
+    fun `a share that cannot be read leaves nothing behind`() {
+        val broken = Uri.parse("content://sender/broken")
+        val fine = Uri.parse("content://sender/fine")
+        sharedNames[broken] = "broken.txt"
+        sharedNames[fine] = "fine.txt"
+        sharedBytes[fine] = "fine"
+        // `broken` is advertised but has no bytes, so the sending app refuses to open it.
+
+        val model = viewModel()
+        model.openDirectory(downloads)
+        model.onIncomingRequest(IncomingRequest.Receive(listOf(broken, fine)))
+
+        model.receiveInto(downloads)
+
+        assertFalse("no zero-byte stub survives", storage.contains(downloads.child("broken.txt")))
+        assertEquals("fine", storage.contentOf(downloads.child("fine.txt")))
+    }
+
+    @Test
+    fun `cancelling a share leaves an ordinary browser`() {
+        val uri = Uri.parse("content://sender/holiday")
+        sharedBytes[uri] = "bytes"
+        val model = viewModel()
+        model.onIncomingRequest(IncomingRequest.Receive(listOf(uri)))
+
+        model.cancelIncoming()
+
+        assertNull(model.state.value.receiving)
+    }
+
+    @Test
+    fun `with no reader wired up, a share is not silently pretended`() = runBlocking {
+        val uri = Uri.parse("content://sender/holiday")
+        sharedBytes[uri] = "bytes"
+        val model = viewModel(incoming = null)
+        model.openDirectory(downloads)
+        model.onIncomingRequest(IncomingRequest.Receive(listOf(uri)))
+
+        model.receiveInto(downloads)
+
+        assertTrue(storage.list(downloads).none { it.name == "shared-file" })
+    }
+
+    @Test
+    fun `while providing, tapping a file chooses it instead of opening it`() {
+        val model = viewModel()
+        model.onIncomingRequest(IncomingRequest.Provide)
+        model.openDirectory(downloads)
+
+        model.open(model.state.value.entries.single { it.name == "a.txt" })
+
+        assertEquals(downloads.child("a.txt"), model.state.value.pendingDeliver?.path)
+        assertEquals("no viewer took over", Overlay.None, model.state.value.overlay)
+    }
+
+    @Test
+    fun `while providing, a folder still navigates so the file can actually be reached`() {
+        val model = viewModel()
+        model.onIncomingRequest(IncomingRequest.Provide)
+        model.openDirectory(root)
+
+        model.open(model.state.value.entries.single { it.path == downloads })
+
+        assertEquals(downloads, model.state.value.path)
+        assertNull(model.state.value.pendingDeliver)
+    }
 }

docs/ROADMAP.md

@@ -28,6 +28,7 @@ Legend: ✅ done · 🚧 in progress · ⏳ not started · 💡 candidate (propo
 | Language / UI | Kotlin + Jetpack Compose | Mirrors the sibling app's proven, installed toolchain; no NDK |
 | Storage access | `MANAGE_EXTERNAL_STORAGE` first, SAF fallback | Google Play explicitly permits "All files access" for file managers; SAF keeps the app usable if the user declines |
 | Connectivity | Local-first (no `INTERNET` in v1) | Preserves the "nothing leaves the device" claim and keeps the Data Safety form trivial |
+| File sharing | Receives `SEND`/`SEND_MULTIPLE`, serves `GET_CONTENT`/`OPEN_DOCUMENT`, and deliberately does **not** register `ACTION_VIEW` | A file manager should be able to receive a file and to supply one, and neither costs a permission. Registering as a viewer as well would put Plain Files in the "open with" chooser the app itself uses, offering it back to itself |
 | Monetisation | One-time paid (€4.49; €2.29 launch price), set in the Console | No Billing client, no `BILLING` permission, no purchase code — which is what keeps "nothing leaves the device" true in the shipped APK. Free → paid is impossible after the first upload, so the price must be set beforehand. See [MONETISATION](MONETISATION.md) |
 
 ## Deliberately deferred (post-1.0)

docs/STORE_LISTING.md

@@ -97,6 +97,12 @@ ANY SIZE OF SCREEN
 • Pictures preview at full size beside the list, with their details
 • The same layout on a phone, a 7-inch tablet and a 10-inch tablet
 
+WORKS WITH YOUR OTHER APPS
+• Share a file to Plain Files from anywhere, then pick the folder to drop it in
+• Choose Plain Files when another app asks you for a file
+• Search a whole folder tree, not just the folder you are looking at
+• Delete, rename or move by mistake? Undo it
+
 MANAGE YOUR FILES
 • Copy, move, rename and delete, one item or many at once
 • Create folders and edit text files in the built-in editor