Don't require an Activity unless absolutely necessary

android/src/main/kotlin/codeux/design/filepicker/file_picker_writable/FilePickerWritableImpl.kt

@@ -4,6 +4,7 @@ import android.app.Activity
 import android.app.Activity.RESULT_OK
 import android.content.ActivityNotFoundException
 import android.content.ContentResolver
+import android.content.Context
 import android.content.Intent
 import android.database.Cursor
 import android.net.Uri
@@ -19,8 +20,11 @@ import kotlinx.coroutines.launch
 import kotlinx.coroutines.withContext
 import java.io.File
 
-interface ActivityProvider : CoroutineScope {
+interface ContextProvider : CoroutineScope {
   val activity: Activity?
+
+  val applicationContext: Context?
+
   fun logDebug(message: String, e: Throwable? = null)
   @MainThread
   fun openFile(fileInfo: Map<String, String>)
@@ -29,7 +33,7 @@ interface ActivityProvider : CoroutineScope {
 }
 
 class FilePickerWritableImpl(
-  private val plugin: ActivityProvider
+  private val plugin: ContextProvider
 ) : PluginRegistry.ActivityResultListener, PluginRegistry.NewIntentListener {
 
   companion object {
@@ -175,8 +179,8 @@ class FilePickerWritableImpl(
     fileUri: Uri,
     initialFileContent: File
   ) {
-    val activity = requireActivity()
-    val contentResolver = activity.applicationContext.contentResolver
+    val context = requireContext()
+    val contentResolver = context.applicationContext.contentResolver
     val takeFlags: Int = Intent.FLAG_GRANT_READ_URI_PERMISSION or
       Intent.FLAG_GRANT_WRITE_URI_PERMISSION
     contentResolver.takePersistableUriPermission(fileUri, takeFlags)
@@ -213,9 +217,9 @@ class FilePickerWritableImpl(
 
   @MainThread
   private suspend fun copyContentUriAndReturnFileInfo(fileUri: Uri): Map<String, String> {
-    val activity = requireActivity()
+    val context = requireContext()
 
-    val contentResolver = activity.applicationContext.contentResolver
+    val contentResolver = context.applicationContext.contentResolver
 
     return withContext(Dispatchers.IO) {
       var persistable = false
@@ -235,7 +239,7 @@ class FilePickerWritableImpl(
           // use a maximum of 20 characters.
           // It's just a temp file name so does not really matter.
           fileName.take(20),
-          null, activity.cacheDir
+          null, context.cacheDir
         )
       plugin.logDebug("Copy file $fileUri to $tempFile")
       contentResolver.openInputStream(fileUri).use { input ->
@@ -301,8 +305,8 @@ class FilePickerWritableImpl(
       throw FilePickerException("File at source not found. $file")
     }
     val fileUri = Uri.parse(identifier)
-    val activity = requireActivity()
-    val contentResolver = activity.contentResolver
+    val context = requireContext()
+    val contentResolver = context.contentResolver
     withContext(Dispatchers.IO) {
       // with Android 10 and later, use wt
       // https://issuetracker.google.com/issues/135714729?pli=1
@@ -319,16 +323,16 @@ class FilePickerWritableImpl(
   }
 
   fun disposeIdentifier(identifier: String) {
-    val activity = requireActivity()
-    val contentResolver = activity.applicationContext.contentResolver
+    val context = requireContext()
+    val contentResolver = context.applicationContext.contentResolver
     val takeFlags: Int = Intent.FLAG_GRANT_READ_URI_PERMISSION or
       Intent.FLAG_GRANT_WRITE_URI_PERMISSION
     contentResolver.releasePersistableUriPermission(Uri.parse(identifier), takeFlags)
   }
 
   fun disposeAllIdentifiers() {
-    val activity = requireActivity()
-    val contentResolver = activity.applicationContext.contentResolver
+    val context = requireContext()
+    val contentResolver = context.applicationContext.contentResolver
     val takeFlags: Int = Intent.FLAG_GRANT_READ_URI_PERMISSION or
       Intent.FLAG_GRANT_WRITE_URI_PERMISSION
     for (permission in contentResolver.persistedUriPermissions) {
@@ -340,6 +344,9 @@ class FilePickerWritableImpl(
   private fun requireActivity() = (plugin.activity
     ?: throw FilePickerException("Illegal state, expected activity to be there."))
 
+  private fun requireContext() = (plugin.activity ?: plugin.applicationContext
+    ?: throw FilePickerException("Illegal state, expected application context or activity to be there."))
+
   private val CONTENT_PROVIDER_SCHEMES = setOf(
     ContentResolver.SCHEME_CONTENT,
     ContentResolver.SCHEME_FILE,

android/src/main/kotlin/codeux/design/filepicker/file_picker_writable/FilePickerWritablePlugin.kt

@@ -1,14 +1,14 @@
 package codeux.design.filepicker.file_picker_writable
 
 import android.app.Activity
+import android.content.Context
 import android.net.Uri
 import android.util.Log
 import androidx.annotation.MainThread
 import androidx.annotation.NonNull
 import io.flutter.embedding.engine.plugins.FlutterPlugin
 import io.flutter.embedding.engine.plugins.activity.ActivityAware
 import io.flutter.embedding.engine.plugins.activity.ActivityPluginBinding
-import io.flutter.plugin.common.BinaryMessenger
 import io.flutter.plugin.common.EventChannel
 import io.flutter.plugin.common.MethodCall
 import io.flutter.plugin.common.MethodChannel
@@ -25,7 +25,7 @@ private const val TAG = "FilePickerWritable"
 /** FilePickerWritablePlugin */
 class FilePickerWritablePlugin : FlutterPlugin, MethodCallHandler,
   ActivityAware,
-  ActivityProvider, CoroutineScope by MainScope() {
+  ContextProvider, CoroutineScope by MainScope() {
   /// The MethodChannel that will the communication between Flutter and native Android
   ///
   /// This local reference serves to register the plugin with the Flutter Engine and unregister it
@@ -34,23 +34,26 @@ class FilePickerWritablePlugin : FlutterPlugin, MethodCallHandler,
   private val impl: FilePickerWritableImpl = FilePickerWritableImpl(this)
   private var currentBinding: ActivityPluginBinding? = null
 
+  override var applicationContext: Context? = null
+
   private val eventQueue = LinkedList<Map<String, String>>()
   private var eventSink: EventChannel.EventSink? = null
 
   override fun onAttachedToEngine(
     @NonNull flutterPluginBinding: FlutterPlugin.FlutterPluginBinding
   ) {
-    initializePlugin(flutterPluginBinding.binaryMessenger)
+    initializePlugin(flutterPluginBinding)
   }
 
-  private fun initializePlugin(binaryMessenger: BinaryMessenger) {
+  private fun initializePlugin(flutterPluginBinding: FlutterPlugin.FlutterPluginBinding) {
+    applicationContext = flutterPluginBinding.applicationContext
     channel = MethodChannel(
-      binaryMessenger,
+      flutterPluginBinding.binaryMessenger,
       "design.codeux.file_picker_writable"
     )
     channel.setMethodCallHandler(this)
     EventChannel(
-      binaryMessenger,
+      flutterPluginBinding.binaryMessenger,
       "design.codeux.file_picker_writable/events"
     ).setStreamHandler(object :
       EventChannel.StreamHandler {