Highlighting

This section focuses on the topic of highlighting entries in the chart, both via tap-gesture and programmatically.

###Enabling / Disabling highlighting

• setHighlightPerDragEnabled(boolean enabled): Set this to true on your Chart to allow highlighting per dragging over the chart surface when it is fully zoomed out. Default: true
• setHighlightPerTapEnabled(boolean enabled): Set this to false on your Chart to prevent values from being highlighted by tap gesture. Values can still be highlighted via drag or programmatically. Default: true
• setMaxHighlightDistance(float distanceDp): Sets the maximum highlight distance in dp. Taps on the chart further away from an entry than that distance will not trigger a highlight. Default: 500dp

In addition to that, highlighting can be configured for individual DataSet objects:

  dataSet.setHighlightEnabled(true); // allow highlighting for DataSet
  dataSet.setHighlightColor(Color.BLACK); // color for highlight indicator
  // and more...

###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. Enabling and disabling highlighting can be done via ChartData or DataSet object.

###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 h The corresponding highlight object that contains information
    * about the highlighted position
    */
    public void onValueSelected(Entry e, 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);

###The Highlight class

The Highlight class represents all data associated with a highlighted Entry, such as the highlighted Entry object itself, it's position on the drawing surface, ...