Microsoft.Phone.Shell命名空间中定义了ApplicationBar及其相关类（ApplicationBarIconButton和ApplicationBarMenuItem），这些类派生自Object,并完全独立于常规Silverlight编程中的DependencyObject,UIElement和FrameworkElement类层次结构。ApplicationBar最多能包含4个按钮，包含的图片通常是PNG文件，位图本身的宽高都是48像素，通常是透明的，实际图片应该是白色，在位图中间显示，是一个宽高均为26像素的正方形。
<shell:ApplicationBar IsVisible="True" IsMenuEnabled="True">
<shell:ApplicationBarIconButton IconUri="/Images/appbar.transport.rew.rest.png" Text="上一首"/>
<shell:ApplicationBarIconButton IconUri="/Images/appbar.transport.play.rest.png" Text="播放"/>
<shell:ApplicationBarIconButton IconUri="/Images/appbar.transport.pause.rest.png" Text="暂停"/>
<shell:ApplicationBarIconButton IconUri="/Images/appbar.transport.ff.rest.png" Text="下一首"/>
</phone:PhoneApplicationPage.ApplicationBar>
当你点击省略号的时候，出现如下效果：
在这里，我们可以通过将ApplicationBarIconButton的IsEnabled属性设为false，从而禁用该按钮。
上面的2张图的第一个ApplicationBarIconButton的图片放错了。
一般情况下，我们要访问这些按钮可以如下做：
(this.ApplicationBar.Button[2] as ApplicationBarIconButton).IsEnabled=true or false
我们改造前面的demo来实现一个播放网络视频的案例来进一步的学习ApplicationBar的使用。
XAML文件：
<phone:PhoneApplicationPage
x:Class="PhoneApp3.MainPage"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:phone="clr-namespace:Microsoft.Phone.Controls;assembly=Microsoft.Phone"
xmlns:shell="clr-namespace:Microsoft.Phone.Shell;assembly=Microsoft.Phone"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
mc:Ignorable="d" d:DesignWidth="480" d:DesignHeight="696"
FontFamily="{StaticResource PhoneFontFamilyNormal}"
FontSize="{StaticResource PhoneFontSizeNormal}"
Foreground="{StaticResource PhoneForegroundBrush}"
SupportedOrientations="PortraitOrLandscape" Orientation="Portrait"
shell:SystemTray.IsVisible="True">
<!--LayoutRoot 是包含所有页面内容的根网格-->
<Grid x:Name="LayoutRoot" Background="Transparent">
<Grid.RowDefinitions>
<RowDefinition Height="Auto"/>
<RowDefinition Height="*"/>
</Grid.RowDefinitions>
<!--TitlePanel 包含应用程序的名称和页标题-->
<StackPanel x:Name="TitlePanel" Grid.Row="0" Margin="12,17,0,28">
<TextBlock x:Name="ApplicationTitle" Text="电影播放" Style="{StaticResource PhoneTextNormalStyle}"/>
<TextBlock x:Name="PageTitle" Text="恐怖片" Margin="9,-7,0,0" Style="{StaticResource PhoneTextTitle1Style}"/>
</StackPanel>
<!--ContentPanel - 在此处放置其他内容-->
<Grid x:Name="ContentPanel" Grid.Row="1" Margin="12,0,12,0">
<MediaElement Name="mediaElement" Source="http://www.charlespetzold.com/Media/Walrus.wmv" AutoPlay="False" MediaOpened="onMediaElementOpened" MediaFailed="onMediaElementFailed" CurrentStateChanged="onMediaElementCurrentStateChanged"/>
<TextBlock Name="statusText" HorizontalAlignment="Left" VerticalAlignment="Bottom"/>
<TextBlock Name="errorText" HorizontalAlignment="Right" VerticalAlignment="Bottom" TextWrapping="Wrap"/>
</Grid>
</Grid>
<phone:PhoneApplicationPage.ApplicationBar>
<shell:ApplicationBar IsVisible="True" IsMenuEnabled="True">
<shell:ApplicationBarIconButton IconUri="/Images/appbar.transport.rew.rest.png" Text="重置" Click="onAppbarRewindClick" x:Name="appbarRewind" IsEnabled="False"/>
<shell:ApplicationBarIconButton IconUri="/Images/appbar.transport.play.rest.png" Text="播放" Click="onAppbarPlayClick" x:Name="appBarPlay" />
<shell:ApplicationBarIconButton IconUri="/Images/appbar.transport.pause.rest.png" Text="暂停" Click="onAppbarPauseClick" x:Name="appBarPause" IsEnabled="False"/>
<shell:ApplicationBarIconButton IconUri="/Images/appbar.transport.ff.rest.png" Text="结束" Click="onAppbarEndClick" x:Name="appbarEnd" IsEnabled="False"/>
</shell:ApplicationBar>
</phone:PhoneApplicationPage.ApplicationBar>
</phone:PhoneApplicationPage>
代码：
using System;
using System.Collections.Generic;
using System.Linq;
using System.Net;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Animation;
using System.Windows.Shapes;
using Microsoft.Phone.Controls;
using Microsoft.Phone.Shell;
namespace PhoneApp3
{
public partial class MainPage : PhoneApplicationPage
{
// 构造函数
public MainPage()
{
InitializeComponent();
appbarRewind = this.ApplicationBar.Buttons[0] as ApplicationBarIconButton;
appBarPlay = this.ApplicationBar.Buttons[1] as ApplicationBarIconButton;
appBarPause = this.ApplicationBar.Buttons[2] as ApplicationBarIconButton;
appbarEnd = this.ApplicationBar.Buttons[3] as ApplicationBarIconButton;
}
void onAppbarRewindClick(object sender, EventArgs args)
{
mediaElement.Position = TimeSpan.Zero;
}
void onAppbarPlayClick(object sender,EventArgs args) {
mediaElement.Play();
}
void onAppbarPauseClick(object sender, EventArgs args)
{
mediaElement.Pause();
}
void onAppbarEndClick(object sender,EventArgs args) {
mediaElement.Position = mediaElement.NaturalDuration.TimeSpan;
}
void onMediaElementFailed(object sender,ExceptionRoutedEventArgs args)
{
errorText.Text = args.ErrorException.Message;
}
void onMediaElementOpened(object sender, RoutedEventArgs args)
{
appbarEnd.IsEnabled = true;
appbarRewind.IsEnabled = true;
}
void onMediaElementCurrentStateChanged(object sender, RoutedEventArgs ars)
{
statusText.Text = mediaElement.CurrentState.ToString();
if (mediaElement.CurrentState == MediaElementState.Stopped || mediaElement.CurrentState == MediaElementState.Paused)
{
appBarPlay.IsEnabled = true;
appBarPause.IsEnabled = false;
}
else if(mediaElement.CurrentState==MediaElementState.Playing)
{
appBarPause.IsEnabled = true;
appBarPlay.IsEnabled = false;
}
}
}
}
Enjoy yourself.
重定义问题的解决)
