[英]Performance lag in scrollTo function for LongListSelector in WP8?
为了演示问题,这里是我的代码背后的代码
public partial class MainPage : PhoneApplicationPage
{
ObservableCollection<ABC> listTest = new ObservableCollection<ABC>();
// Constructor
public MainPage()
{
InitializeComponent();
for (int i = 0; i < 50; i++)
{
ABC conv = new ABC(string.Format("Test:{0}", i));
listTest.Add(conv);
}
testLls.ItemsSource = listTest;
}
private void Button_Tap_1(object sender, System.Windows.Input.GestureEventArgs e)
{
testLls.ScrollTo(listTest[listTest.Count - 1]);
}
private void TitlePanel_Tap_1(object sender, System.Windows.Input.GestureEventArgs e)
{
Stopwatch st = Stopwatch.StartNew();
testLls.ScrollTo(listTest[listTest.Count - 1]);
st.Stop();
Debug.WriteLine("tttt:", st.ElapsedMilliseconds);
}
class ABC
{
private string _name;
public ABC(string aa)
{
this._name = aa;
}
public string Name
{
get
{
return _name;
}
}
public Visibility GroupMemberVisibility
{
get
{
return Visibility.Collapsed;
}
}
}
}
Xaml代码
<StackPanel x:Name="TitlePanel" Grid.Row="0" Margin="12,17,0,28" Tap="TitlePanel_Tap_1">
<TextBlock Text="MY APPLICATION" Style="{StaticResource PhoneTextNormalStyle}" Margin="12,0"/>
<TextBlock Text="page name" Margin="9,-7,0,0" Style="{StaticResource PhoneTextTitle1Style}"/>
</StackPanel>
<!--ContentPanel - place additional content here-->
<Grid x:Name="ContentPanel" Grid.Row="1" Margin="12,0,12,0">
<phone:LongListSelector Name="testLls" VirtualizingStackPanel.VirtualizationMode="Standard" >
<phone:LongListSelector.ItemTemplate>
<DataTemplate x:Name="dtRecievedBubbleText" >
<Grid x:Name="LayoutRoot" Background="Transparent" Margin="24 0 0 14" HorizontalAlignment="Left">
<Grid.RowDefinitions>
<RowDefinition Height="14" />
<RowDefinition Height="Auto" />
</Grid.RowDefinitions>
<Grid Grid.Row="1">
<Grid.RowDefinitions>
<RowDefinition Height="Auto" />
<RowDefinition Height="Auto" />
<RowDefinition Height="Auto" />
</Grid.RowDefinitions>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="Auto"/>
</Grid.ColumnDefinitions>
<Rectangle Grid.RowSpan="3" Fill="{Binding BubbleBackGroundColor}" />
<TextBlock Text="test" Visibility="{Binding GroupMemberVisibility}" FontSize="22" FontFamily="Segoe WP Semibold" Margin="12, 12, 0, 0" />
<TextBlock Grid.Row="2" Text="{Binding Name}" HorizontalAlignment="Right" Margin="0,0,12,6" FontSize="18" />
</Grid>
</Grid>
</DataTemplate>
</phone:LongListSelector.ItemTemplate>
</phone:LongListSelector>
</Grid>
点击标题时,包含元素的长列表选择器滚动到底部。 当元素的值从30-50-100个元素更改时,观察到的时间为20ms,744ms,815ms。 测试是通过诺基亚Lumia 620完成的。
在此示例中,项目模板非常简单,但是在实际情况下,我的项目templates are much more complex
。 因此,在这种情况下, 1753ms for 100 elements
花费的时间为1753ms for 100 elements
。
为什么会有如此巨大的time difference
。 Can this be improved
任何方式Can this be improved
吗?
还有其他人观察到吗?
有解决此问题的解决方法。
从lls提取视口,然后设置视口原点。
要提取视口,我们必须在xaml中添加样式
<Style x:Name="llsMessagesStyle" TargetType="phone:LongListSelector">
<Setter Property="Background" Value="Transparent"/>
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="phone:LongListSelector">
<Grid Background="{TemplateBinding Background}" d:DesignWidth="480" d:DesignHeight="800">
<VisualStateManager.VisualStateGroups>
<VisualStateGroup x:Name="ScrollStates">
<VisualStateGroup.Transitions>
<VisualTransition GeneratedDuration="00:00:00.5"/>
</VisualStateGroup.Transitions>
<VisualState x:Name="Scrolling">
<Storyboard>
<DoubleAnimation Duration="0" To="1" Storyboard.TargetProperty="Opacity" Storyboard.TargetName="VerticalScrollBar"/>
</Storyboard>
</VisualState>
<VisualState x:Name="NotScrolling"/>
</VisualStateGroup>
</VisualStateManager.VisualStateGroups>
<Grid Margin="0">
<ViewportControl x:Name="ViewportControl" HorizontalContentAlignment="Stretch" VerticalAlignment="Bottom" Loaded="ViewPortLoaded"/>
<ScrollBar x:Name="VerticalScrollBar" Style="{StaticResource ChatThemeScrollBarStyle}" Opacity="0" Margin="2 0 2 0" Orientation="Vertical" HorizontalAlignment="Right" Width="5" ValueChanged="vScrollBar1_ValueChanged" />
</Grid>
</Grid>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
在后面的代码中:
ViewportControl llsViewPort;
private void ViewPortLoaded(object sender, RoutedEventArgs e)
{
llsViewPort = sender as ViewportControl;
}
private void ScrollToBottom()
{
if (llsViewPort != null)
llsViewPort.SetViewportOrigin(new System.Windows.Point(0, llsViewPort.Bounds.Height));
}
这样我们就可以实现所需的功能。
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