Add instructions to SD card permission dialog

vlc-android/res/layout/dialog_sd_write.xml

+<?xml version="1.0" encoding="utf-8"?>
+<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
+    android:layout_width="wrap_content"
+    android:layout_height="wrap_content"
+    android:gravity="center">
+    <ImageView
+        android:layout_width="@dimen/dialog_sd_wisard_width"
+        android:layout_height="@dimen/dialog_sd_wisard_height"
+        android:scaleType="centerInside"
+        android:src="@drawable/img_tips_sdcard" />
+</LinearLayout>
\ No newline at end of file

vlc-android/res/values-sw600dp/dimens.xml

@@ -15,4 +15,7 @@
     <!-- pop-Up player -->
     <dimen name="video_pip_width">512dp</dimen>
     <dimen name="video_pip_heigth">288dp</dimen>
+
+    <dimen name="dialog_sd_wisard_width">448dp</dimen>
+    <dimen name="dialog_sd_wisard_height">576dp</dimen>
 </resources>
\ No newline at end of file

vlc-android/res/values/dimens.xml

@@ -72,4 +72,6 @@
     <dimen name="audio_player_cover_margin">8dp</dimen>
     <dimen name="audio_player_elevation">16dp</dimen>
     <dimen name="progress_layout_height">24dp</dimen>
+    <dimen name="dialog_sd_wisard_width">320dp</dimen>
+    <dimen name="dialog_sd_wisard_height">420dp</dimen>
 </resources>
\ No newline at end of file

vlc-android/res/values/strings.xml

@@ -589,4 +589,7 @@
     <string name="msg_delete_failed">Failed to delete media %1$s</string>
     <string name="renderer_list_title">Displays</string>
     <string name="feedback_player_crashed">Sorry, VLC just crashed. Please try again.</string>
+    <string name="sdcard_permission_dialog_title">You have to grant VLC write access to your SD Card</string>
+    <string name="sdcard_permission_dialog_message">VLC cannot delete this file without write access permission.\nPlease go to your SD Card and click on \"Select\".\nYou may have to click on \"Show SD card\" first in the top-right menu</string>
+    <string name="dialog_sd_wizard">Show me</string>
 </resources>

vlc-android/src/org/videolan/vlc/gui/helpers/hf/WriteExternalDelegate.kt

@@ -9,9 +9,11 @@ import android.os.Bundle
 import android.provider.DocumentsContract
 import android.support.v4.app.FragmentActivity
 import android.support.v4.provider.DocumentFile
+import android.support.v7.app.AlertDialog
 import android.support.v7.preference.PreferenceManager
 import android.text.TextUtils
 import org.videolan.libvlc.util.AndroidUtil
+import org.videolan.vlc.R
 import org.videolan.vlc.VLCApplication
 import org.videolan.vlc.util.AndroidDevices
 import org.videolan.vlc.util.FileUtils
@@ -22,9 +24,30 @@ class WriteExternalDelegate : BaseHeadlessFragment() {
     @TargetApi(Build.VERSION_CODES.O)
     override fun onCreate(savedInstanceState: Bundle?) {
         super.onCreate(savedInstanceState)
-        val intent = Intent(Intent.ACTION_OPEN_DOCUMENT_TREE)
-        arguments?.getString(KEY_STORAGE_PATH)?.let { intent.putExtra(DocumentsContract.EXTRA_INITIAL_URI, Uri.parse(it)) }
-        startActivityForResult(intent, REQUEST_CODE_STORAGE_ACCES)
+        showDialog()
+    }
+
+    private fun showDialog() {
+        if (!isAdded) return
+        val builder = AlertDialog.Builder(activity)
+        builder.setMessage(R.string.sdcard_permission_dialog_message)
+                .setTitle(R.string.sdcard_permission_dialog_title)
+                .setPositiveButton(R.string.ok, { _, _ ->
+                    val intent = Intent(Intent.ACTION_OPEN_DOCUMENT_TREE)
+                    arguments?.getString(KEY_STORAGE_PATH)?.let { intent.putExtra(DocumentsContract.EXTRA_INITIAL_URI, Uri.parse(it)) }
+                    startActivityForResult(intent, REQUEST_CODE_STORAGE_ACCES)
+                })
+                .setNeutralButton(getString(R.string.dialog_sd_wizard), { _, _ ->
+                    showHelpDialog()
+                }).create().show()
+    }
+
+    private fun showHelpDialog() {
+        if (!isAdded) return
+        val inflater = activity.layoutInflater
+        AlertDialog.Builder(activity).setView(inflater.inflate(R.layout.dialog_sd_write, null))
+                .setOnDismissListener { showDialog() }
+                .create().show()
     }
 
     override fun onActivityResult(requestCode: Int, resultCode: Int, data: Intent?) {