improve buttonNextEp hiding behaviour

* the button will be diabled on PlayerActivity.playNextEpisode()
* the button will only be enabled if PlayerViewModel.playNextEpisode() returns
* remainingTime will be set to 0, if duration < 0, this fixes the button reapring after a few 100 ms when beeing pressed

fixes #53

app/src/main/java/org/mosad/teapod/ui/activity/player/PlayerActivity.kt

@@ -302,6 +302,8 @@ class PlayerActivity : AppCompatActivity() {
                 if (model.player.duration > 0) {
                     remainingTime = model.player.duration - currentPosition
                     remainingTime = if (remainingTime < 0) 0 else remainingTime
+                } else {
+                    remainingTime = 0
                 }
 
                 // TODO add metaDB ending_start support
@@ -428,8 +430,16 @@ class PlayerActivity : AppCompatActivity() {
     }
 
     private fun playNextEpisode() {
-        model.playNextEpisode()
+        // disable the next episode buttons, so a user can't double click it
+        playerBinding.buttonNextEp.isClickable = false
+        controlsBinding.buttonNextEpC.isClickable = false
+
         hideButtonNextEp()
+        model.playNextEpisode()
+
+        // enable the next episode buttons when playNextEpisode() has returned
+        playerBinding.buttonNextEp.isClickable = true
+        controlsBinding.buttonNextEpC.isClickable = true
     }
 
     private fun skipOpening() {