sort media before displaying

app/src/main/java/com/simplemobiletools/gallery/activities/MediaActivity.java

@@ -30,6 +30,7 @@ import com.simplemobiletools.gallery.models.Medium;
 
 import java.io.File;
 import java.util.ArrayList;
+import java.util.Collections;
 import java.util.List;
 import java.util.regex.Pattern;
 
@@ -148,6 +149,8 @@ public class MediaActivity extends AppCompatActivity
             }
         }
 
+        Collections.sort(myMedia);
+
         final String[] invalids = invalidFiles.toArray(new String[invalidFiles.size()]);
         MediaScannerConnection.scanFile(getApplicationContext(), invalids, null, null);
 

app/src/main/java/com/simplemobiletools/gallery/models/Medium.java

@@ -2,7 +2,7 @@ package com.simplemobiletools.gallery.models;
 
 import java.io.Serializable;
 
-public class Medium implements Serializable {
+public class Medium implements Serializable, Comparable {
     private static final long serialVersionUID = -6543139465975455L;
     private final String path;
     private final boolean isVideo;
@@ -26,6 +26,17 @@ public class Medium implements Serializable {
         return timestamp;
     }
 
+    @Override
+    public int compareTo(Object object) {
+        Medium medium = (Medium) object;
+        if (this.timestamp < medium.getTimestamp()) {
+            return 1;
+        } else if (this.timestamp > medium.getTimestamp()) {
+            return -1;
+        }
+        return 0;
+    }
+
     @Override
     public String toString() {
         return "Medium {" +