使用 JSON 填充图表时 Google 图表中的工具提示

我目前正在使用 JSON 填充我的 Google 图表，但我还需要自定义工具提示。目前我的 JSON 如下所示：

{
    "cols": [
        {"id": "", "label": "date", "type": "string"},
        {"id": "", "label": "price", "type": "number"}
    ],
    "rows": [
        {"c":[{"v": "Apr 24th","f":null}, {"v": 56000,"f":"56000"}]},
        {"c":[{"v": "May 3rd","f":null}, {"v": 68000,"f":"68000"}]},
        {"c":[{"v": "May 13th","f":null}, {"v": 50400,"f":"50400"}]}
    ]
}

但如果我也像这样在 JSON 中指定我的工具提示：

{
    "cols": [
        {"id": "", "label": "Date", "type": "string"},
        {"id": "", "label": "price", "type": "number"},
        {"id": "", "role": "tooltip", "type": "string"}
    ],
    "rows": [
        {"c":[{"v": "Apr 24th","f":"null"}, {"v": 56000,"f":"56000"}, {"v": "24 April, Price - 56000, Seller-abcd"}]},
        {"c":[{"v": "May 3rd","f":"null"}, {"v": 68000,"f":"68000"}, {"v": "3 May, Price - 68000, Seller-abcd"}]},
        {"c":[{"v": "May 13th","f":"null"}, {"v": 50400,"f":"50400"}, {"v": "23 May, Price - 50000, Seller-abcd"}]}
    ]
}

我收到一条错误消息，表明系列中的所有值都应具有相同的数据类型。

我的客户端代码如下所示：

var jsonData = $.ajax({
    url: '../phps/testPhp.php',
    dataType:"json",
    async: false
}).responseText;

var dataTable = new google.visualization.DataTable(jsonData);

var minVal = 50000;
var maxVal = 70000;    

var chart = new google.visualization.LineChart(document.getElementById('chart_div'));

var options = {
    width: 375, height: 240,
    legend: 'none',
    pointSize: 5,
    backgroundColor: 'transparent',
    vAxis: { minValue: 45000, maxValue: 70000 }
};

chart.draw(dataTable, options);

如果有人知道解决方案，请告诉我。

工具提示列定义错误；应该是这样的：

{"id": "", "role": "tooltip", "type": "string", "p" : { "role" : "tooltip" } }