add a couple more helper functions about files

app/src/main/kotlin/com/simplemobiletools/filemanager/dialogs/PropertiesDialog.kt

@@ -44,6 +44,10 @@ class PropertiesDialog : DialogFragment() {
                 properties_resolution_label.visibility = View.VISIBLE
                 properties_resolution.visibility = View.VISIBLE
                 properties_resolution.text = mItem.resolution
+            } else if (mItem.isAudio(context)) {
+
+            } else if (mItem.isVideo(context)) {
+
             }
 
             val file = File(mItem.path)

library/src/main/kotlin/com/simplemobiletools/filepicker/models/FileDirItem.kt

@@ -1,7 +1,12 @@
 package com.simplemobiletools.filepicker.models
 
+import android.content.Context
 import android.graphics.Bitmap
 import android.graphics.BitmapFactory
+import android.media.MediaMetadataRetriever
+import android.net.Uri
+import java.io.File
+import java.util.*
 
 class FileDirItem(val path: String, val name: String, val isDirectory: Boolean, val children: Int, val size: Long) :
         Comparable<FileDirItem> {
@@ -27,6 +32,33 @@ class FileDirItem(val path: String, val name: String, val isDirectory: Boolean,
         return options.outWidth != -1 && options.outHeight != -1
     }
 
+    fun isVideo(context: Context): Boolean {
+        return getMimeType(context).startsWith("video")
+    }
+
+    fun isAudio(context: Context): Boolean {
+        return getMimeType(context).startsWith("audio")
+    }
+
+    fun getMimeType(context: Context): String {
+        try {
+            val retriever = MediaMetadataRetriever()
+            retriever.setDataSource(context, Uri.fromFile(File(path)))
+            return retriever.extractMetadata(MediaMetadataRetriever.METADATA_KEY_MIMETYPE)
+        } catch (ignored: Exception) {
+
+        }
+        return ""
+    }
+
+    fun getDuration(context: Context): String {
+        val retriever = MediaMetadataRetriever()
+        retriever.setDataSource(context, Uri.fromFile(File(path)))
+        val time = retriever.extractMetadata(MediaMetadataRetriever.METADATA_KEY_DURATION)
+        val timeInMillisec = java.lang.Long.parseLong(time)
+        return getFormattedDuration((timeInMillisec / 1000).toInt())
+    }
+
     val resolution: String
         get () {
             val bitmap: Bitmap? = BitmapFactory.decodeFile(path)
@@ -35,4 +67,19 @@ class FileDirItem(val path: String, val name: String, val isDirectory: Boolean,
 
             return "${bitmap.width} x ${bitmap.height}"
         }
+
+    private fun getFormattedDuration(duration: Int): String {
+        val sb = StringBuilder(8)
+        val hours = duration / (60 * 60)
+        val minutes = duration % (60 * 60) / 60
+        val seconds = duration % (60 * 60) % 60
+
+        if (duration > 3600) {
+            sb.append(String.format(Locale.getDefault(), "%02d", hours)).append(":")
+        }
+
+        sb.append(String.format(Locale.getDefault(), "%02d", minutes))
+        sb.append(":").append(String.format(Locale.getDefault(), "%02d", seconds))
+        return sb.toString()
+    }
 }