Xamarin.Forms:MultiLineLabel不再适用于Android
作者:互联网
在我的Xamarin.Forms项目中,我使用MultiLineLabel在1或2行显示标题,具体取决于文本长度.我基于这个blog来实现这一目标.
所以我有一个MultiLineLabel控件:
public class MultiLineLabel : Label
{
private static int _defaultLineSetting = -1;
public static readonly BindableProperty LinesProperty = BindableProperty.Create(nameof(Lines), typeof(int), typeof(MultiLineLabel), _defaultLineSetting);
public int Lines
{
get { return (int)GetValue(LinesProperty); }
set { SetValue(LinesProperty, value); }
}
}
我使用2个渲染器:
>在iOS上,我保留了给定的渲染器:
public class CustomMultiLineLabelRenderer : LabelRenderer
{
protected override void OnElementChanged(ElementChangedEventArgs<Label> e)
{
base.OnElementChanged(e);
MultiLineLabel multiLineLabel = (MultiLineLabel)Element;
if (multiLineLabel != null && multiLineLabel.Lines != -1)
Control.Lines = multiLineLabel.Lines;
}
}
>在Android上我已经自定义了渲染器:
public class CustomMultiLineLabelRenderer : LabelRenderer
{
protected override void OnElementChanged(ElementChangedEventArgs<Label> e)
{
base.OnElementChanged(e);
MultiLineLabel multiLineLabel = (MultiLineLabel)Element;
if (multiLineLabel != null && multiLineLabel.Lines != -1)
{
Control.Ellipsize = TextUtils.TruncateAt.End;
Control.SetMaxLines(multiLineLabel.Lines);
}
}
}
我在XAML中使用这样的MultiLineLabel:
<StackLayout
Grid.Row="0"
Spacing="0">
<local:MultiLineLabel
Margin="8,6,8,0"
TextColor="{ DynamicResource InverseTextColor }"
Text="{ Binding encart_titre }"
FontSize="{ artina:OnOrientationDouble
Default=16,
PortraitTablet=20,
LandscapeTablet=20 }"
LineBreakMode="TailTruncation"
Lines="2"
Grid.Column="0"
BackgroundColor="Yellow"
/>
</StackLayout>
直到我使用Xamarin.Forms v.2.3.4.247,这在Android上运行良好:
但在更新到最新版本(Xamarin.Forms v.2.4.0.269-pre2)后,它不再按预期工作:
我还试图使用博客上给出的渲染器:
protected override void OnElementChanged(ElementChangedEventArgs<Label> e)
{
base.OnElementChanged(e);
MultiLineLabel multiLineLabel = (MultiLineLabel)Element;
if (multiLineLabel != null && multiLineLabel.Lines != -1)
{
Control.SetSingleLine(false);
Control.SetLines(multiLineLabel.Lines);
}
}
你有什么解释吗?还是另一个建议?在iOS上这很好用.
解决方法:
But after having updated to the latest version (Xamarin.Forms v.2.4.0.269-pre2), it doesn’t longer work as expected:
原因:
我查看了Xamarin.Forms v.2.4.0.269-pre2的源代码.在LabelRenderer的OnElementChange事件中,将调用FormsTextView的SetLineBreakMode,其中包含以下代码:
public static void SetLineBreakMode(this TextView textView, LineBreakMode lineBreakMode)
{
switch (lineBreakMode)
{
case LineBreakMode.NoWrap:
textView.SetMaxLines(1);
textView.SetSingleLine(true);
textView.Ellipsize = null;
break;
case LineBreakMode.WordWrap:
textView.Ellipsize = null;
textView.SetMaxLines(100);
textView.SetSingleLine(false);
break;
case LineBreakMode.CharacterWrap:
textView.Ellipsize = null;
textView.SetMaxLines(100);
textView.SetSingleLine(false);
break;
case LineBreakMode.HeadTruncation:
textView.SetMaxLines(1);
textView.SetSingleLine(true);
textView.Ellipsize = TextUtils.TruncateAt.Start;
break;
case LineBreakMode.TailTruncation:
textView.SetMaxLines(1);
textView.SetSingleLine(true);
textView.Ellipsize = TextUtils.TruncateAt.End;
break;
case LineBreakMode.MiddleTruncation:
textView.SetMaxLines(1);
textView.SetSingleLine(true);
textView.Ellipsize = TextUtils.TruncateAt.Middle;
break;
}
}
如您所见,如果您使用LineBreakMode.TailTruncation,则为textView.SetMaxLines(1);和textView.SetSingleLine(true);将被调用,这将禁用多行功能.(在2.3.4 textView.SetSingleLine(true);不存在).
解:
要解决此问题,您只需在渲染器中添加两行代码:
protected override void OnElementChanged(ElementChangedEventArgs<Xamarin.Forms.Label> e)
{
base.OnElementChanged(e);
MultiLineLabel multiLineLabel = (MultiLineLabel)Element;
if (multiLineLabel != null && multiLineLabel.Lines != -1)
{
Control.SetSingleLine(false);
Control.SetMaxLines(multiLineLabel.Lines);
Control.SetLines(multiLineLabel.Lines);
}
}
标签:android,label,multiline,xamarin-forms,custom-renderer 来源: https://codeday.me/bug/20190608/1196174.html