我试图使用Android数据绑定在xml中使用和"&&"运算符,

android:visibility="@{(bean.currentSpaceId == bean.selectedSpaceId **&&** bean.currentSpaceId > 0)? View.VISIBLE: View.GONE}"

但我得到了编译错误:

错误:任务':app:dataBindingProcessLayoutsDevDebug'的执行失败.org.xml.sax.SAXParseException; systemId:file:/Users/path/app/build/intermediates/res/merged/dev/debug/layout/fragment_space.xml; lineNumber:106; columnNumber:89; 实体名称必须紧跟实体引用中的"&".

安卓工作室中的红色高亮显示错误"未转义和未终止字符".

那我该怎么办？

编辑: 找到答案,这些角色需要转义:

'&' --> '&'

'<' --> '&lt;'

'>' --> '&gt;'

我有一个自定义复选框控件,我使用ICommand属性和相应的可绑定属性创建(我的复选框是一个Xamarin.Forms XAML页面),代码是:

CheckBox.xaml

<Image x:Name="imgCheckBox"
       WidthRequest="20"
       HeightRequest="20"/>

<Label x:Name="lblCheckBox"
       TextColor="Black"
       VerticalOptions="CenterAndExpand"/>

<TapGestureRecognizer Tapped="OnCheckBoxTapped"/>

CheckBox.xaml.cs

public partial class CheckBox : ContentView
{
    private static ImageSource uncheckedImage;
    private static ImageSource checkedImage;

    public CheckBox()
    {
        InitializeComponent();
        uncheckedImage = ImageSource.FromResource("cbUnchecked.png");
        checkedImage = ImageSource.FromResource("cbChecked.png");
        imgCheckBox.Source = uncheckedImage;
    }

    public static readonly BindableProperty IsCheckedProperty =
        BindableProperty.Create<CheckBox, bool>(
            checkbox => 
                checkbox.IsChecked,
                false,
                propertyChanged: (bindable, oldValue, newValue) =>
                {
                    CheckBox checkbox = (CheckBox)bindable;
                    EventHandler<bool> eventHandler = checkbox.CheckedChanged;
                    if (eventHandler != null)
                    {
                        eventHandler(checkbox, newValue);
                    }
                });        

    public bool …

在JavaFX的上下文中,在更改时属性"无效"是什么意思？我不明白使用这个术语的原因.

JavaFX属性是可观察的对象并包装字段值.因此,当属性更新或变为无效时,会通知其listerners /观察者.这是什么意思？

绑定不适用于Image标记.当我调试时,我看到Extension类中的Source值始终为null？但标签的内容不是空的.

XAML

<Label Text="{Binding Image}" />
<Image Source="{classes:ImageResource Source={Binding Image}}" />

ImageResourceExtension

// You exclude the 'Extension' suffix when using in Xaml markup
[Preserve(AllMembers = true)]
[ContentProperty("Source")]
public class ImageResourceExtension : BindableObject, IMarkupExtension
{
    public static readonly BindableProperty SourceProperty = BindableProperty.Create(nameof(Source), typeof(string), typeof(string), null);
    public string Source
    {
        get { return (string)GetValue(SourceProperty); }
        set { SetValue(SourceProperty, value); }
    }

    public object ProvideValue(IServiceProvider serviceProvider)
    {
        if (Source == null)
            return null;

        // Do your translation lookup here, using whatever method you …

In Xamarin.Forms 3.5 Microsoft introduced us to bindable layouts which can be used to dynamically fill layouts (e.g. StackLayout, Grid, etc.).

To use this in a grid with a single column is pretty straightforward:

<Grid BindableLayout.ItemsSource="{Binding Items}">
    <BindableLayout.ItemTemplate>
        <DataTemplate>
            <Label Text="{Binding MyProperty}"/>
        </DataTemplate>
    </BindableLayout.ItemTemplate>
</Grid>

Now my question is how this can be used to populate a grid with more than one column due to the fact that DataTemplate only allows one view as content. Sure I could …

我使用Aurelia的1.0.0-beta.1并尝试编写一些单元测试.

我有这样的customElement:

...
@inject(BindingEngine, Class1, Class2)
export class MyElement{

@bindable data;

constructor (bindingEngine, class1, class2) {
    ...
}
...

我想创建一个可测试的MyElement实例,其中包含Class1和Class2的Mocks以及可绑定字段数据.

到目前为止,我发现的是,由于此处描述的 API更改,使用BehaviorInstance的示例不再有效.

在查看aurelia-templating的测试之后,我的方法现在看起来像这样:

import {TemplatingEngine} from 'aurelia-templating';
import {Container} from 'aurelia-dependency-injection';
import {BindingEngine} from 'aurelia-binding';

import { Class1Mock, Class2Mock } from './myMocks';

describe('The MyElement customElement', () => {
    let container;
    let bindingEngine;
    let templateEngine;

    let myElement;

    beforeEach(() => {
        container = new Container();

        //Add my mocks to DI container?
        container.registerInstance('Class1', new Class1Mock());
        container.registerInstance('Class2', new Class2Mock()); …

问题解决了,见下文

题

我在Flex Builder 3中工作,我有两个ActionScript 3类(ABC和XYZ)和一个Flex MXML项目(main.mxml).我有XYZ一个属性的实例ABC,我希望在文本控件的Flex项目中XYZ显示属性([Bindable]).

不幸的是,只有prop3和prop4更新的时候都改变了.我已进入调试器以确保prop1并prop2更改,但它们未在文本控件中更新.

这是代码:

ABC.as

[Bindable]
public class ABC extends UIComponent {
    /* Other properties */

    public var xyz:XYZ = new XYZ();

    /* Methods that update xyz */
}

XYZ.as

[Bindable]
public class XYZ extends Object {
     private var _prop1:uint = 0;
     private var _prop2:uint = 0;
     private var _prop3:uint = 0;
     private …