Fix juddering on Android

[Tommigun1980]

Fix juddering when dragging the pane on Androids.

[AEZ314]

Hey solved it yet?

[james937nrg]

I am having this issue on Android. @Tommigun1980 I might try to fix it... do you have any pointers to help me start?

[JensMig]

The problem here is, that in the MessagesPanel_PanUpdate handler in DragView.xaml.cs the panning of the panel is handled via total movement. These numbers are provided by the PanUpdatedEventArgs. At least in the Android emulator these total values mean total values since last event raised, which is more like a delta. So delta is handled twice which leads to the mentioned problem.

If you just take the total value as delta, it works smoothly:

		    case GestureStatus.Running:
                    if (!this.AnimationIsRunning(SwipeAnimationName))
                    {
                        var total = this.IsVertical() ? e.TotalY : e.TotalX;
                        if (!this.IsPositiveGrowthAxis())
                            total = -total;
                        this.PanPanel(total);
                        this.dragPoints.Add(new DragPoint()
                        {
                            total = total,
                            ticks = Stopwatch.GetTimestamp()
                        });
                    }
                    break;

No idea what this means on iOS. Maybe you need a switch here.