为Google Charting API构建数组和格式化JSON

Question

我正在开发一个项目,我正在使用Google Charting API,我想使用json填充图表来构建数据表.

作为一个测试,我试图在尝试使用数据库中的动态数据之前构建一个简单的数组,但是我遇到了以正确格式获取json的问题.

在谷歌文档中,它说json内容应该在以下内容:

{
  "cols": [
        {"id":"","label":"Topping","pattern":"","type":"string"},
        {"id":"","label":"Slices","pattern":"","type":"number"}
      ],
  "rows": [
        {"c":[{"v":"Mushrooms","f":null},{"v":3,"f":null}]},
        {"c":[{"v":"Onions","f":null},{"v":1,"f":null}]},
        {"c":[{"v":"Olives","f":null},{"v":1,"f":null}]},
        {"c":[{"v":"Zucchini","f":null},{"v":1,"f":null}]},
        {"c":[{"v":"Pepperoni","f":null},{"v":2,"f":null}]}
      ]
}

我正在调用一个返回json代码的函数.

下面是调用函数的方法

print json_encode(test());

而测试功能是

function test()
{
    $array = array();
    $array['cols'][] = "20-01-13";
    $array['cols'][] = "21-01-13";
    $array['cols'][] = "22-01-13";
    $array['rows'][] = 22;
    $array['rows'][] = 26;
    $array['rows'][] = 12;

    return $array;
}

生成图表的javascript如下

<script>
            google.load('visualization', '1', {'packages':['corechart']});

            // Set a callback to run when the Google Visualization API is loaded.
            google.setOnLoadCallback(drawChart);

            function drawChart() {
                 var jsonData = $.ajax({
                 url: "loadGraph.php",
                 dataType:"json",
                 async: false
                }).responseText;

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

      // Instantiate and draw our chart, passing in some options.
      var chart = new google.visualization.PieChart(document.getElementById('lineGraph'));
      chart.draw(data, {width: 400, height: 240});
            }
        </script>

当我回显json时,它将以下列格式返回

{"cols":["20-01-13","21-01-13","22-01-13"],"rows":[22,26,12]}

如果我尝试将此用于谷歌图表的数据集,我会收到以下消息

Cannot read property of '1' of undefined

我只是构建一个简单的折线图,它只包含沿x轴的日期和沿y轴在该日期发生的事件的次数.

我如何构建数组以使其以正确的格式为谷歌api图表.

感谢您的任何帮助,您可以提供.

Answer 1

您需要为cols 指定参数类型.请参阅Google Charts JSON格式

您的PHP代码应类似于:

function test()
{
    $array['cols'][] = array('type' => 'string');
    $array['cols'][] = array('type' => 'string');
    $array['cols'][] = array('type' => 'string');

    $array['rows'][] = array('c' => array( array('v'=>'20-01-13'), array('v'=>22)) );
    $array['rows'][] = array('c' => array( array('v'=>'21-01-13'), array('v'=>26)));
    $array['rows'][] = array('c' => array( array('v'=>'22-01-13'), array('v'=>12)));

    return $array;
}

print json_encode(test());

你的json代码看起来更像是:

{
  "cols": [
    {"type": "string"},
    {"type": "string"},
    {"type": "string"}
    ],
  "rows": [
    {"c":[{"v":"20-01-13"}, {"v":22} ]},
    {"c":[{"v":"21-01-13"}, {"v":26} ]},
    {"c":[{"v":"22-01-13"}, {"v":12} ]}
  ]
}