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Allow deceleration when dragging and release the chart
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@danielgindi
danielgindi committed Apr 30, 2015
1 parent 6ca1e0a commit 3cb2bdf
Showing 1 changed file with 119 additions and 20 deletions.
139 changes: 119 additions & 20 deletions Charts/Classes/Charts/BarLineChartViewBase.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -40,6 +40,12 @@ public class BarLineChartViewBase: ChartViewBase, UIGestureRecognizerDelegate
/// Sets drawing the borders rectangle to true. If this is enabled, there is no point drawing the axis-lines of x- and y-axis.
public var drawBordersEnabled = false

/// If set to true, chart continues to scroll after touch up
public var dragDeccelarationEnabled = true

/// Deccelaration friction coefficient in [0 ; 1] interval, higher values indicate that speed will decrease slowly, for example if it set to 0, it will stop immediately, if set to 1, it will scroll with constant speed, until the last point
private var _dragDeccelarationFrictionCoef: CGFloat = 0.9

/// the object representing the labels on the y-axis, this object is prepared
/// in the pepareYLabels() method
internal var _leftAxis: ChartYAxis!
Expand Down Expand Up @@ -483,6 +489,12 @@ public class BarLineChartViewBase: ChartViewBase, UIGestureRecognizerDelegate
/// the last highlighted object
private var _lastHighlighted: ChartHighlight!;

private var _lastPanPoint = CGPoint() /// This is to prevent using setTranslation which resets velocity

private var _deccelarationLastTime: NSTimeInterval = 0.0
private var _deccelarationDisplayLink: CADisplayLink!
private var _deccelarationVelocity = CGPoint()

@objc private func tapGestureRecognized(recognizer: UITapGestureRecognizer)
{
if (_dataNotSet)
Expand Down Expand Up @@ -539,6 +551,8 @@ public class BarLineChartViewBase: ChartViewBase, UIGestureRecognizerDelegate
{
if (recognizer.state == UIGestureRecognizerState.Began)
{
stopDecceleration();

if (!_dataNotSet && (_pinchZoomEnabled || _scaleXEnabled || _scaleYEnabled))
{
_isScaling = true;
Expand Down Expand Up @@ -607,45 +621,45 @@ public class BarLineChartViewBase: ChartViewBase, UIGestureRecognizerDelegate
{
if (recognizer.state == UIGestureRecognizerState.Began)
{
stopDecceleration();

if (!_dataNotSet && _dragEnabled && !self.hasNoDragOffset || !self.isFullyZoomedOut)
{
_isDragging = true;

_closestDataSetToTouch = getDataSetByTouchPoint(recognizer.locationOfTouch(0, inView: self));

_lastPanPoint = recognizer.translationInView(self);
}
}
else if (recognizer.state == UIGestureRecognizerState.Ended || recognizer.state == UIGestureRecognizerState.Cancelled)
{
if (_isDragging)
{
if (recognizer.state == UIGestureRecognizerState.Ended && isDragDeccelarationEnabled)
{
stopDecceleration();

_deccelarationLastTime = CACurrentMediaTime();
_deccelarationVelocity = recognizer.velocityInView(self);

_deccelarationDisplayLink = CADisplayLink(target: self, selector: Selector("deccelerationLoop"));
_deccelarationDisplayLink.addToRunLoop(NSRunLoop.mainRunLoop(), forMode: NSRunLoopCommonModes);
}

_isDragging = false;
}
}
else if (recognizer.state == UIGestureRecognizerState.Changed)
{
if (_isDragging)
{
var translation = recognizer.translationInView(self);
var originalTranslation = recognizer.translationInView(self);
var translation = CGPoint(x: originalTranslation.x - _lastPanPoint.x, y: originalTranslation.y - _lastPanPoint.y);

if (isAnyAxisInverted && _closestDataSetToTouch !== nil
&& getAxis(_closestDataSetToTouch.axisDependency).isInverted)
{
if (self is HorizontalBarChartView)
{
translation.x = -translation.x;
}
else
{
translation.y = -translation.y;
}
}
performPanChange(translation: translation);

var matrix = CGAffineTransformMakeTranslation(translation.x, translation.y);
matrix = CGAffineTransformConcat(_viewPortHandler.touchMatrix, matrix);

_viewPortHandler.refresh(newMatrix: matrix, chart: self, invalidate: true);

recognizer.setTranslation(CGPoint(x: 0.0, y: 0.0), inView: self);
_lastPanPoint = originalTranslation;
}
else if (isHighlightPerDragEnabled)
{
Expand All @@ -662,6 +676,60 @@ public class BarLineChartViewBase: ChartViewBase, UIGestureRecognizerDelegate
}
}

private func performPanChange(var #translation: CGPoint)
{
if (isAnyAxisInverted && _closestDataSetToTouch !== nil
&& getAxis(_closestDataSetToTouch.axisDependency).isInverted)
{
if (self is HorizontalBarChartView)
{
translation.x = -translation.x;
}
else
{
translation.y = -translation.y;
}
}

var matrix = CGAffineTransformMakeTranslation(translation.x, translation.y);
matrix = CGAffineTransformConcat(_viewPortHandler.touchMatrix, matrix);

_viewPortHandler.refresh(newMatrix: matrix, chart: self, invalidate: true);
}

public func stopDecceleration()
{
if (_deccelarationDisplayLink !== nil)
{
_deccelarationDisplayLink.removeFromRunLoop(NSRunLoop.mainRunLoop(), forMode: NSRunLoopCommonModes);
_deccelarationDisplayLink = nil;
}
}

@objc private func deccelerationLoop()
{
var currentTime = CACurrentMediaTime();

_deccelarationVelocity.x *= _dragDeccelarationFrictionCoef;
_deccelarationVelocity.y *= _dragDeccelarationFrictionCoef;

var timeInterval = CGFloat(currentTime - _deccelarationLastTime);

var distance = CGPoint(
x: _deccelarationVelocity.x * timeInterval,
y: _deccelarationVelocity.y * timeInterval
);

performPanChange(translation: distance);

_deccelarationLastTime = currentTime;

if(abs(_deccelarationVelocity.x) < 0.001 && abs(_deccelarationVelocity.y) < 0.001)
{
stopDecceleration();
}
}

public func gestureRecognizer(gestureRecognizer: UIGestureRecognizer, shouldRecognizeSimultaneouslyWithGestureRecognizer otherGestureRecognizer: UIGestureRecognizer) -> Bool
{
if ((gestureRecognizer.isKindOfClass(UIPinchGestureRecognizer) && otherGestureRecognizer.isKindOfClass(UIPanGestureRecognizer)) || (gestureRecognizer.isKindOfClass(UIPanGestureRecognizer) && otherGestureRecognizer.isKindOfClass(UIPinchGestureRecognizer)))
Expand Down Expand Up @@ -1026,7 +1094,38 @@ public class BarLineChartViewBase: ChartViewBase, UIGestureRecognizerDelegate
{
return drawBordersEnabled;
}


/// :returns: true if chart continues to scroll after touch up, false if not.
/// :default: true
public var isDragDeccelarationEnabled: Bool
{
return dragDeccelarationEnabled;
}

/// Deccelaration friction coefficient in [0 ; 1] interval, higher values indicate that speed will decrease slowly, for example if it set to 0, it will stop immediately, if set to 1, it will scroll with constant speed, until the last point
/// :default: true
public var dragDeccelarationFrictionCoef: CGFloat
{
get
{
return _dragDeccelarationFrictionCoef;
}
set
{
var val = newValue;
if (val > 1.0)
{
val = 1.0;
}
if (val < 0.0)
{
val = 0.0;
}

_dragDeccelarationFrictionCoef = val;
}
}

/// Returns the Highlight object (contains x-index and DataSet index) of the selected value at the given touch point inside the Line-, Scatter-, or CandleStick-Chart.
public func getHighlightByTouchPoint(var pt: CGPoint) -> ChartHighlight!
{
Expand Down

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