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<p>我正在与一个树莓pi3灯服务器显示一个AM2302传感器的数据。我有一个php文件,它从传感器读取值并以json格式显示。你知道吗</p>
<p>我需要关于如何用google面积图显示历史数据的帮助,这些数据是从python程序读取的,每一分钟存储到mysql数据库中。你知道吗</p>
<p>下面是读取数据的文件名为:read_传感器.php(从传感器收集数据的装置)。你知道吗</p>
<pre><code><?php
// Settings
// host, user and password settings
$host = "localhost";
$user = "logger";
$password = "password";
$database = "temperatures";
// make connection to database
$connectdb = mysqli_connect($host,$user,$password)
or die ("Cannot reach database");
// select db
mysqli_select_db($connectdb,$database)
or die ("Cannot select database");
// sql command that selects all entires from current time and X hours backward
$sql= "SELECT temperature, humidity, sensor, dateandtime FROM temperaturedata where sensor = 'Exterior' order by dateandtime desc LIMIT 10";
// set query to variable
$temperatures = mysqli_query($connectdb,$sql);
// create content to web page
?>
<?php
// loop all the results that were read from database and "draw" to web page
$temps = [];
while($temperature = mysqli_fetch_assoc($temperatures)) {
$temps[] = $temperature;
}
echo json_encode($temps);;
?>
</code></pre>
<p>它显示以下结果:</p>
<pre><code>[
{"temperature":"26.8","humidity":"82.2","sensor":"Exterior","dateandtime":"2019-03-11 09:21:02"},
{"temperature":"26.8","humidity":"83.7","sensor":"Exterior","dateandtime":"2019-03-11 09:20:01"},
{"temperature":"26.8","humidity":"82.8","sensor":"Exterior","dateandtime":"2019-03-11 09:19:01"},
{"temperature":"26.8","humidity":"82.7","sensor":"Exterior","dateandtime":"2019-03-11 09:18:01"},
{"temperature":"27","humidity":"82.6","sensor":"Exterior","dateandtime":"2019-03-11 09:17:01"},
{"temperature":"27.2","humidity":"83","sensor":"Exterior","dateandtime":"2019-03-11 09:16:02"},
{"temperature":"27.2","humidity":"83.1","sensor":"Exterior","dateandtime":"2019-03-11 09:15:01"},
{"temperature":"27.1","humidity":"82.8","sensor":"Exterior","dateandtime":"2019-03-11 09:14:02"},
{"temperature":"27.1","humidity":"82.9","sensor":"Exterior","dateandtime":"2019-03-11 09:13:01"},
{"temperature":"27","humidity":"82.8","sensor":"Exterior","dateandtime":"2019-03-11 09:12:01"}
]
</code></pre>
<p>这是我的密码索引.php文件:</p>
<pre><code><html>
<head>
<title>Google Charts Tutorial</title>
<script type = "text/javascript" src =
"https://www.gstatic.com/charts/loader.js">
</script>
<script type = "text/javascript">
google.charts.load('current', {packages: ['corechart']});
</script>
</head>
<body>
<div id = "container" style = "width: 550px; height: 400px; margin: 0 auto">
</div>
<script language = "JavaScript">
function drawChart() {
// Define the chart to be drawn.
var dataArea = new google.visualization.DataTable();
dataArea.addColumn('string', 'Date');
dataArea.addColumn('number', 'Temperature');
dataArea.addColumn('number', 'Humidity');
var options = {title: 'Company Performance',
hAxis: {title: 'Year', titleTextStyle: {color: '#333'}},
vAxis: {minValue: 0}
};
$.ajax({
url: "read_sensors.php",
dataType: 'json'
}).done(function (data) {
$.each(data, function (index, row) {
dataArea.addRow([
row.dateandtime,
parseFloat(row.temperature),
parseFloat(row.humidity)
]);
});
});
var chartArea = new
google.visualization.AreaChart(document.getElementById("chart_area"));
chartArea.draw(dataArea);
}
google.charts.setOnLoadCallback(drawChart);
</script>
</body>
</html>
</code></pre>
<p>当我进入索引.php页面显示为空白(无)</p>
<p>这是型号代码:</p>
<pre><code><html>
<head>
<title>Google Charts Tutorial</title>
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<script src="https://www.gstatic.com/charts/loader.js"></script>
</script>
<script type = "text/javascript">
</script>
</head>
<body>
<div id = "chart_area" style = "width: 550px; height: 400px; margin: 0 auto">
</div>
<script language = "JavaScript">
function drawChart() {
// Define the chart to be drawn.
var dataArea = new google.visualization.DataTable();
dataArea.addColumn('string', 'Date');
dataArea.addColumn('number', 'Temperature');
dataArea.addColumn('number', 'Humidity');
var options = {title: 'Company Performance',
hAxis: {title: 'Year', titleTextStyle: {color: '#333'}},
vAxis: {minValue: 0}
};
$.ajax({
url: "read_sensors.php",
dataType: 'json',
}).done(function (data) {
complete: function(data) {
$.each(data, function(index, row) {
dataArea.addRow([
row.dateandtime,
parseFloat(row.temperature),
parseFloat(row.humidity)
]);
});
var chartArea = new google.visualization.AreaChart(document.getElementById("chart_area"));
chartArea.draw(dataArea);
}
});
}
google.charts.load('current', {packages: ['corechart']});
google.charts.setOnLoadCallback(drawChart);
</script>
</body>
</html>
</code></pre>