use getter instead of direct access of Activity

Signed-off-by: tobiasKaminsky <tobias@kaminsky.me>

build.gradle

@@ -210,9 +210,9 @@ dependencies {
     // dependencies for app building
     implementation 'androidx.multidex:multidex:2.0.1'
 //    implementation project('nextcloud-android-library')
-    genericImplementation 'com.github.nextcloud:android-library:master-SNAPSHOT'
-    gplayImplementation 'com.github.nextcloud:android-library:master-SNAPSHOT'
-    versionDevImplementation 'com.github.nextcloud:android-library:master-SNAPSHOT'
+    genericImplementation 'com.github.nextcloud:android-library:cleanupActivity-SNAPSHOT'
+    gplayImplementation 'com.github.nextcloud:android-library:cleanupActivity-SNAPSHOT'
+    versionDevImplementation 'com.github.nextcloud:android-library:cleanupActivity-SNAPSHOT'
     implementation 'androidx.constraintlayout:constraintlayout:1.1.3'
     implementation 'androidx.legacy:legacy-support-v4:1.0.0'
     implementation 'com.google.android.material:material:1.0.0'

src/main/java/com/owncloud/android/ui/adapter/ActivityAndVersionListAdapter.java

@@ -50,13 +50,13 @@ public class ActivityAndVersionListAdapter extends ActivityListAdapter {
                 long o1Date;
                 long o2Date;
                 if (o1 instanceof Activity) {
-                    o1Date = ((Activity) o1).datetime.getTime();
+                    o1Date = ((Activity) o1).getDatetime().getTime();
                 } else {
                     o1Date = ((FileVersion) o1).getModifiedTimestamp();
                 }
 
                 if (o2 instanceof Activity) {
-                    o2Date = ((Activity) o2).datetime.getTime();
+                    o2Date = ((Activity) o2).getDatetime().getTime();
                 } else {
                     o2Date = ((FileVersion) o2).getModifiedTimestamp();
                 }