我试图听一下工具栏上的按钮单击，单击该按钮时会切换抽屉式主面板的主抽屉，但效果不佳。
代码如下所示-方法void menu_icon_handler()中的代码不正确。
<!DOCTYPE html>
<link rel="import" href="../../../packages/polymer/polymer.html">
<link rel="import" href="../../../packages/core_elements/core_drawer_panel.html">
<link rel="import" href="../../../packages/core_elements/core_icon_button.html">
<link rel="import" href="../../../packages/core_elements/core_toolbar.html">
<link rel="import" href="../../../packages/paper_elements/roboto.html">
<link rel="import" href="../../../packages/core_elements/core_toolbar.html">
<link rel="import" href="../../../packages/paper_elements/paper_icon_button.html">
<link rel="import" href="./reg/registrant-view.html">
<link rel="import" href="./reg/patient-view.html">
<link rel="import" href="drawer-form.html">
<polymer-element name="main-form">
<template>
<core-drawer-panel id="core_drawer_panel">
<section id="drawer" drawer>
<drawer-form on-new-patient-event='{{newPatientHandler}}'></drawer-form>
</section>
<section id="main" main>
<core-toolbar id="core_toolbar">
<paper-icon-button
icon="menu"
id='menu_icon'
on-click='{{menu_icon_handler}}'></paper-icon-button>
<div id="div" flex>Toolbar</div>
</core-toolbar>
<section id='new-patient'>
</section>
</section>
</core-drawer-panel>
</template>
<script type="application/dart">
import 'package:polymer/polymer.dart';
import 'dart:html';
import 'package:core_elements/core_drawer_panel.dart';
@CustomTag( 'main-form' )
class MainForm extends PolymerElement
{
CoreDrawerPanel drawerPanel;
MainForm.created() : super.created();
void toggleDrawer()
{
bool state = drawerPanel.narrow;
}
void menu_icon_handler()
{
bool state = drawerPanel.narrow;
print ( state );
}
@override
void attached()
{
super.attached();
drawerPanel = $['drawerPanel'] as CoreDrawerPanel;
}
}
</script>
</polymer-element>
单击工具栏按钮时，我得到以下堆栈跟踪
异常(exception):空对象没有getter'narrow'。
NoSuchMethodError: method not found: 'narrow'
Receiver: null
我看到null，看着docs'narrow'是CoreDrawerPanel的属性
最佳答案
您通过以下方式查找元素
drawerPanel = $['drawerPanel'] as CoreDrawerPanel;
但您的HTML不包含ID为
drawerPanel的元素，但是您有ID为core_drawer_panel的元素更改此行中的id应该可以解决问题
drawerPanel = $['core_drawer_panel'] as CoreDrawerPanel;
关于dart - 如何使用工具栏按钮切换抽屉面板的主抽屉，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/25048378/