谷歌图表：修改toopl提示

Question

I have a joint chart using google chart API. Here i want to update the tool tip of the chart.

As there is a lot of overlap in these charts i might not be able to actually hover over each discrete point and see data.

Answer 1

you can use a DataView to provide a calculated column
which builds the tooltip for that row

see following snippet...

var dataView = new google.visualization.DataView(joinedData);
dataView.setColumns([0, 1, {
  calc: function (dt, row) {
    return getTooltip(dt, row);
  },
  role: 'tooltip',
  type: 'string',
  p: {
    html: true
  }
}, 2, {
  calc: function (dt, row) {
    return getTooltip(dt, row);
  },
  role: 'tooltip',
  type: 'string',
  p: {
    html: true
  }
}]);

function getTooltip(dt, row) {
  var tooltip = '<div class="tooltip">';
  tooltip += '<div>' + dt.getFormattedValue(row, 0) + '</div>';

  tooltip += '<div>' + dt.getColumnLabel(1) + '</div>';
  if (dt.getValue(row, 1) === null) {
    tooltip += '<div>' + dt.getFormattedValue(row + 1, 1) + '</div>';
  } else {
    tooltip += '<div>' + dt.getFormattedValue(row, 1) + '</div>';
  }

  tooltip += '<div>' + dt.getColumnLabel(2) + '</div>';
  if (dt.getValue(row, 2) === null) {
    if (row > 0) {
      tooltip += '<div>' + dt.getFormattedValue(row - 1, 2) + '</div>';
    }
  } else {
    tooltip += '<div>' + dt.getFormattedValue(row, 2) + '</div>';
  }

  tooltip += '</div>';
  return tooltip;
}

---

full snippet --> http://jsfiddle.net/sqdfrf8f/1/

---

note: there is some sort of bug,
in that the chart will not respect column properties on data views
so the html property doesn't get set
the work around is to use data view method --> toDataTable()

also: need to use updated library for google charts, see --> update library loader code