recheck every 3 seconds if some media changed at folders view

app/src/main/kotlin/com/simplemobiletools/gallery/activities/MainActivity.kt

@@ -7,6 +7,7 @@ import android.content.pm.PackageManager
 import android.net.Uri
 import android.os.AsyncTask
 import android.os.Bundle
+import android.os.Handler
 import android.provider.MediaStore
 import android.support.v4.app.ActivityCompat
 import android.support.v7.widget.GridLayoutManager
@@ -32,6 +33,7 @@ class MainActivity : SimpleActivity(), DirectoryAdapter.DirOperationsListener {
     private val STORAGE_PERMISSION = 1
     private val PICK_MEDIA = 2
     private val PICK_WALLPAPER = 3
+    private val LAST_MEDIA_CHECK_PERIOD = 3000L
 
     lateinit var mDirs: ArrayList<Directory>
 
@@ -46,6 +48,8 @@ class MainActivity : SimpleActivity(), DirectoryAdapter.DirOperationsListener {
     private var mStoredAnimateGifs = true
     private var mStoredCropThumbnails = true
     private var mLoadedInitialPhotos = false
+    private var mLastMediaModified = 0
+    private var mLastMediaHandler = Handler()
 
     private var mCurrAsyncTask: GetDirectoriesAsynctask? = null
 
@@ -119,6 +123,7 @@ class MainActivity : SimpleActivity(), DirectoryAdapter.DirOperationsListener {
         mStoredAnimateGifs = config.animateGifs
         mStoredCropThumbnails = config.cropThumbnails
         MyScalableRecyclerView.mListener = null
+        mLastMediaHandler.removeCallbacksAndMessages(null)
     }
 
     override fun onStop() {
@@ -321,9 +326,11 @@ class MainActivity : SimpleActivity(), DirectoryAdapter.DirOperationsListener {
     }
 
     private fun gotDirectories(dirs: ArrayList<Directory>) {
+        mLastMediaModified = getLastMediaModified()
         directories_refresh_layout.isRefreshing = false
         mIsGettingDirs = false
 
+        checkLastMediaChanged()
         if (dirs.hashCode() == mDirs.hashCode())
             return
 
@@ -352,6 +359,19 @@ class MainActivity : SimpleActivity(), DirectoryAdapter.DirOperationsListener {
         directories_fastscroller.setViews(directories_grid, directories_refresh_layout)
     }
 
+    private fun checkLastMediaChanged() {
+        mLastMediaHandler.removeCallbacksAndMessages(null)
+        mLastMediaHandler.postDelayed({
+            val lastModified = getLastMediaModified()
+            if (mLastMediaModified != lastModified) {
+                getDirectories()
+                mLastMediaModified = lastModified
+            } else {
+                checkLastMediaChanged()
+            }
+        }, LAST_MEDIA_CHECK_PERIOD)
+    }
+
     override fun refreshItems() {
         getDirectories()
     }

app/src/main/kotlin/com/simplemobiletools/gallery/extensions/context.kt

@@ -194,3 +194,20 @@ fun Context.getNoMediaFolders(): ArrayList<String> {
 
     return folders
 }
+
+
+fun Context.getLastMediaModified(): Int {
+    val uri = MediaStore.Files.getContentUri("external")
+    val projection = arrayOf(MediaStore.Images.Media._ID, MediaStore.Images.Media.DATE_MODIFIED)
+    val order = "${MediaStore.Images.Media.DATE_MODIFIED} DESC"
+    var cursor: Cursor? = null
+    try {
+        cursor = contentResolver.query(uri, projection, null, null, order)
+        if (cursor?.moveToFirst() == true) {
+            return cursor.getIntValue(MediaStore.Images.Media.DATE_MODIFIED)
+        }
+    } finally {
+        cursor?.close()
+    }
+    return 0
+}