handle_touches.md

Touch Interactivity

LineChart	BarChart	PieChart

The Interaction Flow

When an interaction happens, our renderers give us a FlTouchEvent. We pass it to correspond painter class. Then it calculates and gives us a TouchResponse (per interaction). Then we call the touchCallback function that provided through the chart's data.

If you set handleBuiltInTouches true, it will handle touch by showing a tooltip or an indicator on the touched spot (in the line, bar and scatter charts), 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 (
        getTooltipColor: (touchedSpot) => 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: (FlTouchEvent event, LineTouchResponse touchResponse) {
        if (event is FlTapUpEvent) {
          // handle tap here  
        }
      },
      .
      .
      .
    )
  )
)