MvvmCross Android EditText绑定不更新屏幕

Question

我发现当使用MvvmCross版本3.5.1启用"不要保持活动"开发人员设置时,Mvvm Cross EditText绑定无法正常工作的情况.以下是重现的步骤:

1. 使用NuGet的"入门"Mvvm Cross软件包创建一个新的Core&Droid项目.
2. 从NuGet添加ZXing.Net.Mobile PCL组件.

3. 实现ViewModel:

       public class FirstViewModel : MvxViewModel
       {
           private readonly IMobileBarcodeScanner _mobileBarcodeScanner;
   
           public FirstViewModel(IMobileBarcodeScanner mobileBarcodeScanner)
           {
               _mobileBarcodeScanner = mobileBarcodeScanner;
           }
   
           private string _barCode = "";
           public string BarCode
           { 
               get { return _barCode; }
               set { _barCode = value; RaisePropertyChanged(() => BarCode); }
           }
   
           private MvxCommand _scanBarCodeCommand;
           public IMvxCommand ScanBarCodeCommand
           {
               get
               {
                   return _scanBarCodeCommand ?? (_scanBarCodeCommand = new MvxCommand(async () => await OnScanBarCode()));
               }
           }
   
           private async Task OnScanBarCode()
           {
               var result = await _mobileBarcodeScanner.Scan();
               if (result != null && !string.IsNullOrEmpty(result.Text))
               {
                   InvokeOnMainThread(() =>
                   {
                       BarCode = result.Text;
                   });
               }
           }
       }
   

4. 实现视图:

   <?xml version="1.0" encoding="utf-8"?>
   <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
       xmlns:local="http://schemas.android.com/apk/res-auto"
       android:orientation="vertical"
       android:layout_width="fill_parent"
       android:layout_height="fill_parent">
       <EditText
           android:layout_width="fill_parent"
           android:layout_height="wrap_content"
           local:MvxBind="Text BarCode" />
       <Button
           android:layout_width="match_parent"
           android:layout_height="wrap_content"
           android:text="Scan"
           local:MvxBind="Click ScanBarCodeCommand" />
   </LinearLayout>
   

5. 在视图中初始化ZXing.Net.Mobile库:

   [Activity(Label = "View for FirstViewModel")]
   public class FirstView : MvxActivity
   {
       protected override void OnCreate(Bundle bundle)
       {
           base.OnCreate(bundle);
           SetContentView(Resource.Layout.FirstView);
           MobileBarcodeScanner.Initialize(Application);
       }
   }
   

6. 运行应用程序并扫描条形码.如果您没有方便的条形码,您可以使用此Barcodesinc条形码生成器并从显示器进行扫描.扫描的条形码应出现在EditText.

7. 通过添加一个android:id来编辑View XML EditText.

   <?xml version="1.0" encoding="utf-8"?>
   <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
       xmlns:local="http://schemas.android.com/apk/res-auto"
       android:orientation="vertical"
       android:layout_width="fill_parent"
       android:layout_height="fill_parent">
       <EditText
           android:id="@+id/scan_text"
           android:layout_width="fill_parent"
           android:layout_height="wrap_content"
           local:MvxBind="Text BarCode" />
       <Button
           android:layout_width="match_parent"
           android:layout_height="wrap_content"
           android:text="Scan"
           local:MvxBind="Click ScanBarCodeCommand" />
   </LinearLayout>
   

8. 重建并运行应用程序. 现在扫描的条形码没有显示在EditText.唯一的变化是给予EditText和android:id.有谁理解为什么添加android:id会破坏MvvmCross数据绑定？

Answer 1

仅为 TextEdit 添加绑定，而不为 EditText 添加绑定。请参阅此处的实现：https://github.com/MvvmCross/MvvmCross/blob/4.0/Cirrious/Cirrious.MvvmCross.Binding.Droid/MvxAndroidBindingBuilder.cs#L85

您可以添加自定义绑定，如下所述：

• https://www.youtube.com/watch?feature=player_detailpage&v=taBoOenbpiU&t=97s
• http://slodge.blogspot.co.uk/2013/06/n28-custom-bindings-n1-days-of-mvvmcross.html
• MvvmCross UITextField 自定义绑定