MvvmCross Android EditText绑定不更新屏幕

本文关键字:更新 屏幕 绑定 Android EditText MvvmCross | 更新日期: 2023-09-27 18:09:08

我发现当使用MvvmCross版本3.5.1启用"不保留活动"开发人员设置时,MvvmCross EditText绑定无法正常工作。下面是复制的步骤:

  1. 创建一个新的核心&使用NuGet的"Getting Started"Mvvm交叉包的Droid项目。
  2. 从NuGet中添加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View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。你可以使用这个条形码设计条形码生成器和扫描从您的显示器,如果你没有任何条形码的便利。扫描后的条形码应出现在EditText .
  7. 通过向EditText添加android:id来编辑View XML。

    <?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。现在扫描的条形码在EditText中不显示。唯一的变化是给出EditTextandroid:id。有人明白为什么添加android:id会破坏MvvmCross数据绑定吗?

MvvmCross Android EditText绑定不更新屏幕

仅为texttedit添加绑定而不为EditText添加绑定。查看这里的实现: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,如下所示:

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