我正在编写一个Xamarin PCL应用程序,但是我一直遇到这个错误:
System.Reflection.TargetInvocationException: 目标调用的异常。
有时也会出现以下错误:
System.Reflection.TargetInvocationException: <超时获取异常详情>
当我点击在XAML中绑定到OptionClick行的图像并且在C#中是 new Command((sender) => ShowOptionActions(message.Id, message.Sender_Id, sender))
时,才会出现此错误。我尝试将其更改为DisplayAlert而不是该方法,但无论我放什么都会在单击它时出现错误。
它只出现在Android上,对于iOS它运行正常。它们都使用相同的代码。
我的ObjectMessage类是:
public class MessageObject : INotifyPropertyChanged
{
private int Id = -1;
private Command optionCommandValue;
private string bodyValue = String.Empty;
private Color bodyColorValue = Color.Black;
private string likeImageSource = String.Empty;
private Command likeCommandValue;
private string timestampValue = String.Empty;
private Boolean showBannersValue = true;
public event PropertyChangedEventHandler PropertyChanged;
private void NotifyPropertyChanged([CallerMemberName] String propertyName = "")
{
PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
}
private MessageObject(int id, Command optionCommand, string body, string likeImage, Command likeCommand, string timestamp)
{
Id = id;
optionCommandValue = optionCommand;
bodyValue = body;
bodyColorValue = Color.Black;
likeImageSource = likeImage;
likeCommandValue = likeCommand;
timestampValue = timestamp;
showBannersValue = true;
}
public static MessageObject CreateMessage(int id, Command optionCommand, string body, string likeImage, Command likeCommand, string timestamp)
{
return new MessageObject(id, optionCommand, body, likeImage, likeCommand, timestamp);
}
public int ID
{
get
{
return this.Id;
}
}
public Command OptionClick
{
get
{
return this.optionCommandValue;
}
set
{
if (value != this.optionCommandValue)
{
this.optionCommandValue = value;
NotifyPropertyChanged();
}
}
}
public string Body
{
get
{
return this.bodyValue;
}
set
{
if (value != this.bodyValue)
{
this.bodyValue = value;
NotifyPropertyChanged();
}
}
}
public Color BodyColor
{
get
{
return this.bodyColorValue;
}
set
{
if (value != this.bodyColorValue)
{
this.bodyColorValue = value;
NotifyPropertyChanged();
}
}
}
public string LikeImageSource
{
get
{
return this.likeImageSource;
}
set
{
if (value != this.likeImageSource)
{
this.likeImageSource = value;
NotifyPropertyChanged();
}
}
}
public Command LikeClick
{
get
{
return this.likeCommandValue;
}
set
{
if (value != this.likeCommandValue)
{
this.likeCommandValue = value;
NotifyPropertyChanged();
}
}
}
public string Timestamp
{
get
{
return this.timestampValue;
}
set
{
if(value != this.timestampValue)
{
this.timestampValue = value;
NotifyPropertyChanged();
}
}
}
public Boolean ShowBanners
{
get
{
return this.showBannersValue;
}
set
{
if (value != this.showBannersValue)
{
this.showBannersValue = value;
NotifyPropertyChanged();
}
}
}
}
我使用以下代码创建一个MessageObject:
MessageObject mo = MessageObject.CreateMessage(
message.Id,
new Command((sender) => ShowOptionActions(message.Id, message.Sender_Id, sender)),
message.Body,
message.Liked == 0 ? "like_icon.png" : "liked_icon.png",
new Command((sender) => LikeMessageClick(message.Id, sender)),
dateFormat.ToString("MMMM dd, yyyy HH:mm"));
我的XAML代码是
<ContentPage.Content>
<StackLayout BackgroundColor="#7ed6df">
<local:PostListView x:Name="MessageView" HasUnevenRows="True" IsPullToRefreshEnabled="True" Refreshing="MessageView_Refreshing" SeparatorVisibility="None" BackgroundColor="#7ed6df">
<ListView.ItemTemplate>
<DataTemplate>
<local:PostViewCell>
<StackLayout>
<StackLayout x:Name="MessageLayout" BackgroundColor="White" Margin="10, 10, 10, 10" Padding="10, 10, 15, 10">
<Image Source="options_icon.png" HeightRequest="18" HorizontalOptions="End" Margin="5, 0, 5, 0" IsVisible="{Binding ShowBanners}">
<Image.GestureRecognizers>
<TapGestureRecognizer Command="{Binding OptionClick}" CommandParameter="{Binding .}"/>
</Image.GestureRecognizers>
</Image>
<Label Text="{Binding Body}" HorizontalOptions="CenterAndExpand" TextColor="{Binding BodyColor}" FontSize="15" Margin="0, 10, 0, 10"/>
<StackLayout x:Name="MessageFooter" Orientation="Horizontal" IsVisible="{Binding ShowBanners}">
<Image x:Name="LikeSource" Source="{Binding LikeImageSource}" HeightRequest="20" HorizontalOptions="StartAndExpand" Margin="0, 0, 10, 0">
<Image.GestureRecognizers>
<TapGestureRecognizer Command="{Binding LikeClick}" CommandParameter="{Binding .}"/>
</Image.GestureRecognizers>
</Image>
<Label Text="{Binding Timestamp}" TextColor="Black" FontSize="10" HorizontalOptions="EndAndExpand"/>
</StackLayout>
</StackLayout>
</StackLayout>
</local:PostViewCell>
</DataTemplate>
</ListView.ItemTemplate>
</local:PostListView>
</StackLayout>
</ContentPage.Content>
我的完整堆栈跟踪在这里
编辑:
我为一个新项目添加了一个新的TapGesture,但它也有同样的问题。
OptionClick = new Command(() => page.DisplayAlert("ok", "ok", "ok"))
- Christo NelOptionClick
的定义以及异常的堆栈跟踪吗?(请勿作为评论,编辑问题) - Sven-Michael Stübe