[英]Uncaught TypeError: Cannot read property 'querySelector' of null
I am using Cordova app in Visual Studio 2015. I have added a simple button which changes the color of background of app to red. 我在Visual Studio 2015中使用Cordova应用程序。我添加了一个简单的按钮,可将应用程序背景的颜色更改为红色。 but it is giving above mentioned error. 但是它给出了上述错误。
index.html 的index.html
<!DOCTYPE html>
<html>
<head>
<!--
Customize the content security policy in the meta tag below as needed. Add 'unsafe-inline' to default-src to enable inline JavaScript.
For details, see http://go.microsoft.com/fwlink/?LinkID=617521
-->
<meta http-equiv="Content-Security-Policy" content="default-src 'self' data: gap: https://ssl.gstatic.com 'unsafe-eval'; style-src 'self' 'unsafe-inline'; media-src *">
<meta name="format-detection" content="telephone=no">
<meta name="msapplication-tap-highlight" content="no">
<meta name="viewport" content="user-scalable=no, initial-scale=1, maximum-scale=1, minimum-scale=1, width=device-width">
<link rel="stylesheet" type="text/css" href="css/index.css">
<title>WeatherApp</title>
</head>
<body>
<p>Hello World</p>
<input type="button" name="color" value="Change Color" id="color" onclick="changeColor()">
<script type="text/javascript" src="cordova.js"></script>
<script type="text/javascript" src="scripts/platformOverrides.js"></script>
<script type="text/javascript" src="scripts/index.js"></script>
</body>
</html>
index.js index.js
(function () {
"use strict";
document.addEventListener( 'deviceready', onDeviceReady.bind( this ), false );
function onDeviceReady() {
// Handle the Cordova pause and resume events
document.addEventListener( 'pause', onPause.bind( this ), false );
document.addEventListener('resume', onResume.bind(this), false);
// TODO: Cordova has been loaded. Perform any initialization that requires Cordova here.
var parentElement = document.getElementById('deviceready');
var listeningElement = parentElement.querySelector('.listening');
var receivedElement = parentElement.querySelector('.received');
listeningElement.setAttribute('style', 'display:none;');
receivedElement.setAttribute('style', 'display:block;');
};
function onPause() {
// TODO: This application has been suspended. Save application state here.
};
function onResume() {
// TODO: This application has been reactivated. Restore application state here.
};
function changeColor() {
var change = document.querySelector('#color');
change.addEventListener('click', change, false);
}
function change() {
var clr = document.querySelector('body');
clr.style.backgroundColor = 'red';
}
} )(); })();
var parentElement = document.getElementById('deviceready');
var listeningElement = parentElement.querySelector('.listening');
You don't have a div with ID deviceready
, so your parentElement
will be null. 您没有ID为deviceready
的div,因此您的parentElement
将为null。
EDIT : I think you can remove this whole block since it's belong to the default cordova page layout when you create a new project : 编辑:我认为您可以删除整个块,因为当您创建新项目时,它属于默认的cordova页面布局:
// TODO: Cordova has been loaded. Perform any initialization that requires Cordova here.
var parentElement = document.getElementById('deviceready');
var listeningElement = parentElement.querySelector('.listening');
var receivedElement = parentElement.querySelector('.received');
listeningElement.setAttribute('style', 'display:none;');
receivedElement.setAttribute('style', 'display:block;');
I think the dom has not yet been loaded, and you try to make a selection so it returns you a null. 我认为dom尚未加载,因此您尝试进行选择,以便它返回null。 try to move thoses lines outside the onDeviceReady() 尝试将这些行移到onDeviceReady()之外
var listeningElement = parentElement.querySelector('.listening');
var receivedElement = parentElement.querySelector('.received');
listeningElement.setAttribute('style', 'display:none;');
receivedElement.setAttribute('style', 'display:block;');
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