Question

我正在做的是将数据传递超过2页。我在导航时将viewmodel分配给下一页。在第二页中，我有一个列表视图，在添加值后没有刷新/更新。

请帮帮我!!

这是我的代码

MyViewModel

.squaredThree {
    width: 20px;    
    margin: 20px auto;
    position: relative;
}

.squaredThree label {
    cursor: pointer;
    position: absolute;
    width: 20px;
    height: 20px;
    top: 0;
    border-radius: 4px;
    box-shadow: inset 0px 1px 1px rgba(0,0,0,0.5), 0px 1px 0px rgba(255,255,255,.4);

    background: -webkit-linear-gradient(top, #222 0%, #45484d 100%);
    filter: progid:DXImageTransform.Microsoft.gradient( startColorstr='#222', endColorstr='#45484d',GradientType=0 );
}

.squaredThree label:after {
    -ms-filter: "progid:DXImageTransform.Microsoft.Alpha(Opacity=0)";
    filter: alpha(opacity=0);
    opacity: 0;
    content: '';
    position: absolute;
    width: 9px;
    height: 5px;
    background: transparent;
    top: 4px;
    left: 4px;
    border: 3px solid #fcfff4;
    border-top: none;
    border-right: none;
    -webkit-transform: rotate(-45deg);
}

.squaredThree label:hover::after {
    -ms-filter: "progid:DXImageTransform.Microsoft.Alpha(Opacity=30)";
    filter: alpha(opacity=30);
    opacity: 0.3;
}

#one input[type=checkbox]:checked + label:after {
    -ms-filter: "progid:DXImageTransform.Microsoft.Alpha(Opacity=100)";
    filter: alpha(opacity=100);
    opacity: 1;
}

#two input[type=checkbox]:checked + label:after {
    -ms-filter: "progid:DXImageTransform.Microsoft.Alpha(Opacity=100)";
    filter: alpha(opacity=100);
    opacity: 1;
}


#three input[type=checkbox]:checked + label:after {
    -ms-filter: "progid:DXImageTransform.Microsoft.Alpha(Opacity=100)";
    filter: alpha(opacity=100);
    opacity: 1;
}

userdetails.xaml

<div id="one">
<div class="squaredThree one">
    <input type="checkbox" value="None" id="squaredThree" name="check" />
    <label for="squaredThree"></label>
</div>
</div>

<div id="two">
<div class="squaredThree">
    <input type="checkbox" value="None" id="squaredThree1" name="check" />
    <label for="squaredThree"></label>
</div>
</div>

<div id="three">
<div class="squaredThree">
    <input type="checkbox" value="None" id="squaredThree" name="check" />
    <label for="squaredThree"></label>
</div>
</div>

userdetails.xaml.cs

public class MyViewModel : INotifyPropertyChanged
    { 
        public string _userName { get; set; }
        public List<family> familyList;
        public List<family> FamilyList
        {
            get { return familyList; }
            set
            {
                familyList = value;
                OnPropertyChanged();
            }
        }       
        public event PropertyChangedEventHandler PropertyChanged;
        public MyViewModel()
        {
            _userName = "Mak";
            familyList = new List<family>();
        }
        public void AddMember(string memberName)
        {
            FamilyList.Add(new family
            {
                name = memberName,
                id = Guid.NewGuid().ToString(),
                username=_userName
            });
        }
 protected virtual void OnPropertyChanged([CallerMemberName] string propertyName = null)
        {
            PropertyChangedEventHandler handler = PropertyChanged;
            if (handler != null)
                handler(this, new PropertyChangedEventArgs(propertyName));
        }
}

FamilyMember.xaml

<cl:BasePage xmlns="http://xamarin.com/schemas/2014/forms" xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml" x:Class="familyinfo.userdetails" xmlns:cl="clr-namespace:familyinfo;assembly=familyinfo">
<Label Font="Roboto-Medium" FontSize="14" Text="{Bindinbg _userName}" />
<Button Clicked="Next_Step" HeightRequest="30" HorizontalOptions="FillAndExpand" BorderRadius="12" Text="NEXT" />
</cl:BasePage>

FamilyMember.xaml.cs

public partial class userdetails : BasePage
    {
        public MyViewModel _myViewModel { get; set; }
        public userdetails()
        {
            InitializeComponent();
            BindingContext = new MyViewModel();
        }
        void Next_Step(object sender, System.EventArgs e)
        {
            _myViewModel =(MyViewModel) this.BindingContext;
            var familyMember = new FamilyMember();
            familyMember.BindingContext = _myViewModel;
            Application.Current.MainPage = new NavPage(registerCar);
         }
     }

Answer 1

我同意Atul：使用ObservableCollection是正确的方法。

解决方法 - 如果您没有机会更改 - 是将ListView的{{1}}设置为ItemSource并返回列表，只要数据发生变化，用户界面需要更新：

null

Answer 2

我刚使用ObservableCollection代替List而且它有效!!

Answer 3

实际上，您必须使用实现INotifyCollectionChanged接口的集合（而不是众所周知的INofifyPropertyChanged）。而这正是ObservableCollection<T>给你的。这就是为什么它像“魔术”一样工作。

在Xamarin Forms中添加值后，ListView不会刷新

3 个答案: