在Google可視化餅圖[corechart]中獲取點擊標籤

Question

如何在Google可視化餅圖[corechart]中獲得點擊標籤名稱？即如何使用getSelection()？

 google.load("visualization", "1", {packages:["corechart"]}); 
    google.setOnLoadCallback(drawChart); 
    function drawChart() { 
    var data = new google.visualization.DataTable(); 
    data.addColumn('string', 'Task'); 
    data.addColumn('number', ''); 
    data.addRows(6); 
    data.setValue(0, 0, 'Demographics'); 
    data.setValue(0, 1, 1); 
    data.setValue(1, 0, 'Behavior'); 
    data.setValue(1, 1, 1); 
    data.setValue(2, 0, 'Campaign'); 
    data.setValue(2, 1, 1); 
    data.setValue(3, 0, 'Purchases'); 
    data.setValue(3, 1, 1); 
    data.setValue(4, 0, 'Social'); 
    data.setValue(4, 1, 1); 
    data.setValue(5, 0, 'Support'); 
    data.setValue(5, 1, 1); 

    var chart = new google.visualization.PieChart(document.getElementById('chart_div')); 
    chart.draw(data, {width: 500, height: 500, pieSliceText: 'label', legend: 'none', is3D: true, 
     colors: ['#000033', '#00004D', '#000066', '#000080', '#333399' , '#00001A'], 
     }); 
    google.visualization.events.addListener(chart, 'select', selectHandler); 
    function selectHandler(e) { 
     alert("Need to get clicked pie slice"); 
    } 
} 

Answer 1

google.visualization.events.addListener(chart, 'select', function(e) { 
     var selection = chart.getSelection(); 
     alert(pieSlice[selection[0].row]); 

    });