在不使用类联系人及其SearchAsync方法的情况下获取联系人是否可行?我继续解释我的问题。
我有一个ObservableCollection
private ObservableCollection<ContactPictureItemModel> _ContactPictures;
是ContactPictureItemModel,就像这样
public class ContactPictureItemModel
{
private string _Email;
private byte[] _Picture;
private string _DisplayName;
public ContactPictureItemModel(string email, byte[] picture, string displayName)
{
this._Email = email;
this._Picture = picture;
this._DisplayName = displayName;
}
public string Email
{
get { return _Email; }
set { _Email = value; }
}
public byte[] Picture
{
get { return _Picture; }
set { _Picture = value; }
}
public string DisplayName
{
get { return _DisplayName; }
set { _DisplayName = value; }
}
}
此ObservableCollection中的每个对象代表一个联系人图片,每当用户从EmailAddressChooserTask中选择一个联系人时,该应用程序已“缓存”。
调用此方法时我需要
public ContactPictureItemModel GetContactPictureItem(string email, string displayName)
{
ContactPictureItemModel contactPictureResult;
foreach (ContactPictureItemModel contact in ContactPictures)
{
if (email.Equals(contact.Key))
{
contactPictureResult = contact;
break;
}
}
if (contactPictureResult == null)
{
//Retrieve contact using "email" parameter
}
return contactPictureResult;
}
并且在ObservableCollection中找不到联系人,以便能够使用参数“email”和“displayName”获取联系,而无需使用任何异步任务。我需要该函数检索ContactPictureItemModel对象。
这可能吗?
谢谢!
答案 0 :(得分:0)
无法同步访问联系人,因为它没有API。
您可以在“加载”状态下创建视图模型,然后在异步方法完成时“填充”。只需确保模型类实现INotifyPropertyChanged
答案 1 :(得分:0)
感谢Richard Szalay,我找到了解决方案。我将解释它,以帮助每个人在这些问题中像我一样(对于Java表示法感到遗憾,代码更短)
这些私有字段的对象代表联系人及其图片
public class ParticipantItemModel {
private string _Email;
private string _DisplayName;
private bool _Paid;
[XmlIgnore]
private BitmapImage _ContactPicture;
[...]
}
每个私人领域都有自己的财产来获取和设定他的价值。喜欢这个
public string Email {
get { return _Email; }
set { _Email = value; }
}
在处理_ContactPicture时,它的属性有点特殊。为了获取它的值,如果_ContactPicture为null并且图片没有缓存到ObservableCollection中,我使用Contacts.SearchAsync任务搜索联系人并返回“空图像”。找到联系人后(尽管已经加载了视图),我将属性ContactPicture设置为正确的图像,引发了PropertyChangedEventArgs事件(正如您在其setter属性中看到的那样)
[XmlIgnore]
public BitmapImage ContactPicture
{
get {
if (_ContactPicture != null) {
return _ContactPicture;
} else {
BitmapImage contactPictureSource = App.ContactPictures.GetContactPicture(Email, DisplayName);
if (contactPictureSource != null) {
return contactPictureSource;
} else {
Contacts contacts = new Contacts();
contacts.SearchCompleted += new EventHandler<ContactsSearchEventArgs>(contacts_SearchCompleted);
contacts.SearchAsync(DisplayName, FilterKind.DisplayName, Email);
return new BitmapImage();
}
}
}
set {
_ContactPicture = value;
//When _ContactPicture is setted, an event is raised by calling to NotifyPropertyChanged()
NotifyPropertyChanged("ContactPicture");
}
}
void contacts_SearchCompleted(object sender, ContactsSearchEventArgs e) {
Contact contact = null;
foreach (var result in e.Results) {
foreach (ContactEmailAddress contactEmail in result.EmailAddresses) {
if (Email.Equals(contactEmail.EmailAddress)) {
contact = result;
this.ContactPicture = GetSourceImageFromContactPicture(contact.GetPicture());
break;
}
}
}
}
}
此外,必须实现INotifyPropertyChanged接口才能引发事件PropertyChangedEventArgs。此事件将使应用程序知道元素(联系人的图片)已更改,并将使用绑定数据刷新
public class ParticipantItemModel : INotifyPropertyChanged {
[...]
// Declare the PropertyChanged event
public event PropertyChangedEventHandler PropertyChanged;
// NotifyPropertyChanged will raise the PropertyChanged event passing the
// source property that is being updated.
public void NotifyPropertyChanged(string propertyName)
{
if (PropertyChanged != null)
{
PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
}
}
结果,显示的联系人没有图片,但几乎自动加载图片。
我希望它有所帮助