Request write permission to save to external storage

android/AndroidManifest.xml

@@ -6,6 +6,7 @@
     <uses-sdk/>
 
     <uses-permission android:name="android.permission.INTERNET" />
+    <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
 
     <application
         android:allowBackup="true"

android/src/com/unciv/app/AndroidLauncher.kt

@@ -1,6 +1,7 @@
 package com.unciv.app
 
 import android.content.Intent
+import android.content.pm.PackageManager.PERMISSION_GRANTED
 import android.os.Build
 import android.os.Bundle
 import androidx.core.app.NotificationManagerCompat
@@ -84,6 +85,13 @@ class AndroidLauncher : AndroidApplication() {
         super.onResume()
     }
 
+    override fun onRequestPermissionsResult(requestCode: Int, permissions: Array<out String>, grantResults: IntArray) {
+        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.KITKAT && requestCode == REQ_WRITE_STORAGE && grantResults[0] == PERMISSION_GRANTED) {
+            customSaveLocationHelper?.continuePreviousRequest()
+        }
+        super.onRequestPermissionsResult(requestCode, permissions, grantResults)
+    }
+
     override fun onActivityResult(requestCode: Int, resultCode: Int, data: Intent?) {
         if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.KITKAT) {
             // This should only happen on API 19+ but it's wrapped in the if check to keep the

android/src/com/unciv/app/CustomSaveLocationHelperAndroid.kt

@@ -1,10 +1,13 @@
 package com.unciv.app
 
+import android.Manifest.permission.WRITE_EXTERNAL_STORAGE
 import android.app.Activity
 import android.content.Intent
+import android.content.pm.PackageManager.PERMISSION_GRANTED
 import android.net.Uri
 import android.os.Build
 import androidx.annotation.RequiresApi
+import androidx.core.content.ContextCompat
 import com.unciv.logic.CustomSaveLocationHelper
 import com.unciv.logic.GameInfo
 import com.unciv.logic.GameSaver
@@ -13,12 +16,16 @@ import java.util.concurrent.atomic.AtomicReference
 
 const val REQ_SAVE_GAME = 1
 const val REQ_LOAD_GAME = 2
+const val REQ_WRITE_STORAGE = 3
 
 // The Storage Access Framework is available from API 19 and up:
 // https://developer.android.com/guide/topics/providers/document-provider
 @RequiresApi(Build.VERSION_CODES.KITKAT)
 class CustomSaveLocationHelperAndroid(private val activity: Activity) : CustomSaveLocationHelper {
     private val callback = AtomicReference<Pair<Thread, (Uri?) -> Unit>?>()
+    private var cachedSaveRequest: SaveRequest? = null
+        @Synchronized get
+        @Synchronized set
 
     override fun saveGame(gameInfo: GameInfo, gameName: String, forcePrompt: Boolean, block: (() -> Unit)?) {
         callback.set(Thread.currentThread() to { uri ->
@@ -33,6 +40,17 @@ class CustomSaveLocationHelperAndroid(private val activity: Activity) : CustomSa
                 return
             }
         }
+
+        // For some reason it seems you can save to an existing file that you open without the
+        // permission, but you can't write to a file that you've requested be created so if this is
+        // a "Save as" operation then we need to get permission to write first
+        if (ContextCompat.checkSelfPermission(activity, WRITE_EXTERNAL_STORAGE) != PERMISSION_GRANTED
+                && Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
+            cachedSaveRequest = SaveRequest(gameInfo, gameName, forcePrompt, block)
+            activity.requestPermissions(arrayOf(WRITE_EXTERNAL_STORAGE), REQ_WRITE_STORAGE)
+            return
+        }
+
         Intent(Intent.ACTION_CREATE_DOCUMENT).apply {
             type = "application/json"
             putExtra(Intent.EXTRA_TITLE, gameName)
@@ -40,6 +58,12 @@ class CustomSaveLocationHelperAndroid(private val activity: Activity) : CustomSa
         }
     }
 
+    fun continuePreviousRequest() {
+        cachedSaveRequest?.let {
+            saveGame(it.gameInfo, it.gameName, it.forcePrompt, it.block)
+            cachedSaveRequest = null
+        }
+    }
 
     // This will be called on the main thread
     fun handleIntentData(uri: Uri?) {
@@ -63,11 +87,11 @@ class CustomSaveLocationHelperAndroid(private val activity: Activity) : CustomSa
         callback.set(Thread.currentThread() to { uri ->
             uri?.let {
                 val game = activity.contentResolver.openInputStream(it)
-                                ?.reader()
-                                ?.readText()
-                                ?.run {
-                                    GameSaver.gameInfoFromString(this)
-                                }?: return@let
+                        ?.reader()
+                        ?.readText()
+                        ?.run {
+                            GameSaver.gameInfoFromString(this)
+                        } ?: return@let
                 // If the user has saved the game from another platform (like Android),
                 // then the save location might not be right so we have to correct for that
                 // here
@@ -82,3 +106,10 @@ class CustomSaveLocationHelperAndroid(private val activity: Activity) : CustomSa
         }
     }
 }
+
+data class SaveRequest(
+        val gameInfo: GameInfo,
+        val gameName: String,
+        val forcePrompt: Boolean,
+        val block: (() -> Unit)?
+)