handle_touches.md

Touch Interactivity

LineChart	BarChart	PieChart

The Touch Flow

When user touches on the chart, touch will handle by the painter to determine which elements of the chart is touched and it makes an object that contains touch information (for example a LineTouchResponse, you can listen to the touchCallback provided in each ChartTouchData classes like LineTouchData.

If you set handleBuiltInTouches true, it will handle touch by showing a tooltip or an indicator on the touched spot (in the line and bar chart), you can also handle your own touch handling along with the built in touches.

How to use? (for example in LineChart)

In the Line and Bar Charts we show a built in tooltip on the touched spots, then you just need to config how to show it, just fill the touchTooltipData in the LineTouchData.

LineChart(
  LineChartData(
    lineTouchData: LineTouchData(
      touchTooltipData: TouchTooltipData (
        tooltipBgColor: Colors.blueGrey.withOpacity(0.8),
         .
         .
         .
      )
    )
  )
)

But if you want more customization on touch behaviors, implement the touchCallback and handle it.

LineChart(
  LineChartData(
    lineTouchData: LineTouchData(
      touchCallback: (LineTouchResponse touchResponse) {
        // handle it
      },
      .
      .
      .
    )
  )
)