Xamarin形成Picker结合

Question

我想实现一个简单的选择器XAML绑定到3标签，当我从选择器中选择一个值时，标签将自动填充(数据来自SQLite)。以下是我所拥有的：

 <Picker x:Name="ListJobs" Title="Select Job"  ItemsSource="{Binding options}" ItemDisplayBinding="{Binding JobNo}" SelectedItem="{Binding SelectedJobs}"/>

 <Label Text="{Binding JobsId}" IsVisible="True" x:Name="TxtId"/>
 <Label Text="{Binding name}" IsVisible="True" x:Name="TxtName"/>
 <Label Text="{Binding location}" IsVisible="True" x:Name="TxtLoc"/>

模型

public class Jobs
{
public string JobsId {get;set;}
public string name {get;set;}
public string location {get;set;}

public Jobs(){}
}

代码背后：

protected override OnAppearing()
{
 jobsInfo = (List<Jobs>) GetJob();
foreach (var item in jobsInfo)
{
  Jobs options = new Jobs
{
  JobsId = item.JobsId,
  name = item.name,
  location = item.location
};
BindingContext = options;
}
}
 private IEnumerable<Jobs> GetJobsInfo()
        {
            var db = _connection.Table<Jobs>();
            return db.ToList();
        }

我会从选择器(如下拉列表)中选择并填充标签。

Answer 1

首先，代码中有一些错误。

1.在遍历循环(从db获得的数据)时，选项总是用新数据更新(因此它使用最后一个对象生成)，并将其设置为BindingContext。您应该在这里设置一个modelView，而不是一个模型。

2.选择器的itemSource必须是一个list，但是您在这里设置了一个模型。

3.视图模型必须实现INotifyPropertyChanged来通知更改。

我认为你最需要理解的不是这个选择，而是如何使用绑定。

可弯曲性质

数据绑定基础

从数据绑定到MVVM

好吧，让我们回到这个案子。你需要的是这里

我简化了演示，您可以参考它。

• XAML
• 模型和ViewModel： 公共类作业{公共字符串JobsId { get；set；}公共字符串名称{ get；set；}公共字符串位置{ get；set；}公共类RootModel : INotifyPropertyChanged { List jobList；公共列表jobList { get {返回jobList；} set { if (jobList =值){ JobList =值；OnPropertyChanged()；}}就业selectedJob；公共作业SelectedJob { get {返回selectedJob；} set { if (selectedJob = value) { selectedJob = value；OnPropertyChanged()；}公共事件PropertyChangedEventHandler PropertyChanged；受保护的虚拟空OnPropertyChanged(CallerMemberName string propertyName = null) { PropertyChangedEventHandler处理程序= PropertyChanged；if (处理程序!=空){处理程序(此，新的PropertyChangedEventArgs(propertyName))；}}
• 代码背后： 公共MainPage() { InitializeComponent()；this.BindingContext =新RootModel { JobList = GetJobsInfo() }；}私有列表GetJobsInfo() { var db = _connection.Table()；返回db.ToList()；}
• 我的测试：

​

Answer 2

XAML：

<Picker x:Name="ListJobs" Title="Select Job" ItemsSource="{Binding AllJobs}"
        ItemDisplayBinding="{Binding Name}" SelectedItem="{Binding SelectedJob}"/>
<Label Text="{Binding SelectedJob.JobId}" IsVisible="True" x:Name="TxtId"/>
<Label Text="{Binding SelectedJob.Name}" IsVisible="True" x:Name="TxtName"/>
<Label Text="{Binding SelectedJob.Location}" IsVisible="True" x:Name="TxtLoc"/>

型号：

public class Job
{
    public string JobId { get; set; }
    public string Name { get; set; }
    public string Location {get; set; }
}

public class JobModel
{
    public List<Job> AllJobs { get; set; }
    public Job SelectedJob { get; set; }
}

代码背后：

protected override OnAppearing()
{
    BindingContext = new JobsModel {
        AllJobs = GetJobs()
    };
}

private List<Jobs> GetJobs()
{
    var db = _connection.Table<Jobs>();
    return db.ToList();
}

Answer 3

         //How to add picker or dropdownlist in Xamarin forms and bind text ?
    
    
    //we will be using Picker Properties -> pickername.ItemsSource and pickername.SelectedItem
    //In above line pickername is the x:Name given to picker 
    
    
    //page.xaml 
    
               <Frame CornerRadius="5" HeightRequest="50"  Padding="0">
                    <StackLayout Orientation="Horizontal">
                        <controls:BorderlessPicker
                                                x:Name="Pickdoctype" 
                                                ItemDisplayBinding="{Binding text}"
                                                SelectedIndexChanged="Pickdoctype_SelectedIndexChanged"
                                                HorizontalOptions="FillAndExpand"                                                                     
                                                Title="Enter Document Type"
                                                FontSize="20" 
                                                TextColor="Gray">
                        </controls:BorderlessPicker>
                        <ImageButton BackgroundColor="Transparent" Padding="0">
                            <ImageButton.Source>
                                <FontImageSource Glyph="&#xf0d7;" Size="25" 
                                                          FontFamily="{StaticResource FontAwesomeSolid}"
                                                          Color="Gray"></FontImageSource>
                            </ImageButton.Source>
                        </ImageButton>
                    </StackLayout>
                </Frame>
                
                
                
     //page.xaml.cs


      
            //Picker Get API
            var responseUserData = await httpService.Get("manageDocument/documentType/documentType/" + UserID);
            if (responseUserData.IsSuccessStatusCode)
            {
                var responseUserDataString = await responseUserData.Content.ReadAsStringAsync();
                var myDeserializedClass = JsonConvert.DeserializeObject<List<DocumentTypeModel>>(responseUserDataString);
                Pickdoctype.ItemsSource = myDeserializedClass;
               
            }
              
              
              
            //Get Picker value functionality
            private void Pickdoctype_SelectedIndexChanged(object sender, EventArgs e)
            {
                try
                {
                    DocumentTypeModel selectedItem = (DocumentTypeModel)Pickdoctype.SelectedItem;
                    string PickerValue = selectedItem.value;
                    string PickerText = selectedItem.text;
                }
                catch (Exception ex)
                {

                }
            }
    
    
    //Create a model class 
    
         public class DocumentTypeModel
        {
            public string masterName { get; set; }
            public string text { get; set; }
            public string value { get; set; }
        }