Interaction with the Chart

This library allows you to fully customize the possible touch (and gesture) interaction with the chart-view and react to the interaction via callback-methods.

Enabling / disabling interaction

• setTouchEnabled(boolean enabled): Allows to enable/disable all possible touch-interactions with the chart.
• setDragEnabled(boolean enabled): Enables/disables dragging (panning) for the chart.
• setScaleEnabled(boolean enabled): Enables/disables scaling for the chart on both axes.
• setScaleXEnabled(boolean enabled): Enables/disables scaling on the x-axis.
• setScaleYEnabled(boolean enabled): Enables/disables scaling on the y-axis.
• setPinchZoom(boolean enabled): If set to true, pinch-zooming is enabled. If disabled, x- and y-axis can be zoomed separately.
• setDoubleTapToZoomEnabled(boolean enabled): Set this to false to disallow zooming the chart via double-tap on it.
• setHighlightPerDragEnabled(boolean enabled): Set this to true to allow highlighting per dragging over the chart surface when it is fully zoomed out. Default: true
• setHighlightPerTapEnabled(boolean enabled): Set this to false to prevent values from being highlighted by tap gesture. Values can still be highlighted via drag or programmatically. Default: true

Chart fling / deceleration

• setDragDecelerationEnabled(boolean enabled): If set to true, chart continues to scroll after touch up. Default: true.
• setDragDecelerationFrictionCoef(float coef): Deceleration 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. 1 is an invalid value, and will be converted to 0.9999 automatically.

Highlighting programmatically

• highlightValues(Highlight[] highs): Highlights the values at the given indices in the given DataSets. Provide null or an empty array to undo all highlighting.
• highlightValue(int xIndex, int dataSetIndex): Highlights the value at the given x-index in the given DataSet. Provide -1 as the x-index or dataSetIndex to undo all highlighting.
• getHighlighted(): Returns an Highlight[] array that contains information about all highlighted entries, their x-index and dataset-index.

Highlighting values programmatically will not generate a callback to the OnChartValueSelectedListener.

Custom highlighter

All user input in the form of highlight gestures is internally processed by the default ChartHighlighter class. It is possible to replace the default highligher with a custom implementation using the below method:

• setHighlighter(ChartHighlighter highlighter): Sets a custom highligher object for the chart that handles / processes all highlight touch events performed on the chart-view. Your custom highlighter object needs to extend the ChartHighlighter class.

Selection callbacks

This library provides a number of listeners for callbacks upon interaction. One of them is the OnChartValueSelectedListener, for callbacks when highlighting values via touch:

public interface OnChartValueSelectedListener {
    /**
    * Called when a value has been selected inside the chart.
    *
    * @param e The selected Entry.
    * @param dataSetIndex The index in the datasets array of the data object
    * the Entrys DataSet is in.
    * @param h the corresponding highlight object that contains information
    * about the highlighted position
    */
    public void onValueSelected(Entry e, int dataSetIndex, Highlight h);
    /**
    * Called when nothing has been selected or an "un-select" has been made.
    */
    public void onNothingSelected();
}

Simply let your class that should receive the callbacks implement this interface and set it as a listener to the chart:

chart.setOnChartValueSelectedListener(this);

Gesture callbacks

The OnChartGestureListener will allow you to react to gestures made on the chart:

public interface OnChartGestureListener {

    /**
     * Callbacks when a touch-gesture has started on the chart (ACTION_DOWN)
     *
     * @param me
     * @param lastPerformedGesture
     */
    void onChartGestureStart(MotionEvent me, ChartTouchListener.ChartGesture lastPerformedGesture);

    /**
     * Callbacks when a touch-gesture has ended on the chart (ACTION_UP, ACTION_CANCEL)
     *
     * @param me
     * @param lastPerformedGesture
     */
    void onChartGestureEnd(MotionEvent me, ChartTouchListener.ChartGesture lastPerformedGesture);

    /**
     * Callbacks when the chart is longpressed.
     * 
     * @param me
     */
    public void onChartLongPressed(MotionEvent me);

    /**
     * Callbacks when the chart is double-tapped.
     * 
     * @param me
     */
    public void onChartDoubleTapped(MotionEvent me);

    /**
     * Callbacks when the chart is single-tapped.
     * 
     * @param me
     */
    public void onChartSingleTapped(MotionEvent me);

    /**
     * Callbacks then a fling gesture is made on the chart.
     * 
     * @param me1
     * @param me2
     * @param velocityX
     * @param velocityY
     */
    public void onChartFling(MotionEvent me1, MotionEvent me2, float velocityX, float velocityY);

   /**
     * Callbacks when the chart is scaled / zoomed via pinch zoom gesture.
     * 
     * @param me
     * @param scaleX scalefactor on the x-axis
     * @param scaleY scalefactor on the y-axis
     */
    public void onChartScale(MotionEvent me, float scaleX, float scaleY);

   /**
    * Callbacks when the chart is moved / translated via drag gesture.
    *
    * @param me
    * @param dX translation distance on the x-axis
    * @param dY translation distance on the y-axis
    */
    public void onChartTranslate(MotionEvent me, float dX, float dY);
}

Simply let your class that should receive the callbacks implement this interface and set it as a listener to the chart:

chart.setOnChartGestureListener(this);