add onLongPress to channel preview

lib/src/channel_list_view.dart

@@ -55,6 +55,7 @@ class ChannelListView extends StatefulWidget {
     this.sort,
     this.pagination,
     this.onChannelTap,
+    this.onChannelLongPress,
     this.channelWidget,
     this.channelPreviewBuilder,
     this.errorBuilder,
@@ -92,6 +93,9 @@ class ChannelListView extends StatefulWidget {
   /// with the widget [channelWidget] as child.
   final ChannelTapCallback onChannelTap;
 
+  /// Function called when long pressing on a channel
+  final Function(Channel) onChannelLongPress;
+
   /// Widget used when opening a channel
   final Widget channelWidget;
 
@@ -271,6 +275,7 @@ class _ChannelListViewState extends State<ChannelListView>
               );
             } else {
               child = ChannelPreview(
+                onLongPress: widget.onChannelLongPress,
                 channel: channel,
                 onImageTap: widget.onImageTap != null
                     ? () {

lib/src/channel_preview.dart

@@ -23,6 +23,9 @@ class ChannelPreview extends StatelessWidget {
   /// Function called when tapping this widget
   final void Function(Channel) onTap;
 
+  /// Function called when long pressing this widget
+  final void Function(Channel) onLongPress;
+
   /// Channel displayed
   final Channel channel;
 
@@ -33,6 +36,7 @@ class ChannelPreview extends StatelessWidget {
     @required this.channel,
     Key key,
     this.onTap,
+    this.onLongPress,
     this.onImageTap,
   }) : super(key: key);
 
@@ -40,7 +44,14 @@ class ChannelPreview extends StatelessWidget {
   Widget build(BuildContext context) {
     return ListTile(
       onTap: () {
-        onTap(channel);
+        if (onTap != null) {
+          onTap(channel);
+        }
+      },
+      onLongPress: () {
+        if (onLongPress != null) {
+          onLongPress(channel);
+        }
       },
       leading: ChannelImage(
         onTap: onImageTap,