MVVMCross for android - how to do binding in code?

问题:

I want to use MVVMCross, however for my android application I also want to use other libraries (sliding menu and action bar) which require me to inherit my activity classes from their custom class. This prevents me from inheriting MvxActivity, but I noticed that in MVVMCross for iOS, you can do all your bindings in code (see https://github.com/slodge/NPlus1DaysOfMvvmCross/blob/master/N-00-FirstDemo/FirstDemo.Touch/Views/FirstView.cs)

var set = this.CreateBindingSet<FirstView, FirstViewModel>();
set.Bind(textEditFirst).To(vm => vm.FirstName);
set.Bind(textEditSecond).To(vm => vm.LastName);
set.Bind(labelFull).To(vm => vm.FullName);
set.Apply();

Is there any way to do that in Android?

回答1:

Yes - you can use fluent bindings in Android if you want to.

Exactly the same code should work.

You'll need to get references to the ui controls using FindViewById<Type>(), then you can bind them.

For example, in TipCalc you can add identified controls like:

    <EditText
       android:id="@+id/FluentEdit"
       android:layout_width="fill_parent"
       android:layout_height="wrap_content"
       android:inputType="number"
       android:textSize="24dp"
       android:gravity="right"
     />

and then implement binding using:

    protected override void OnViewModelSet()
    {
        SetContentView(Resource.Layout.View_Tip);

        var edit = this.FindViewById<EditText>(Resource.Id.FluentEdit);

        var set = this.CreateBindingSet<TipView, TipViewModel>();
        set.Bind(edit).To(vm => vm.SubTotal);
        set.Apply();

        // for non-default properties use 'For':
        // set.Bind(edit).For(ed => ed.Text).To(vm => vm.SubTotal);

        // you can also use:
        //   .WithConversion("converter", "optional parameter")
        //   .OneTime(), .OneWay() or .TwoWay()
    }

Additionally, you can convert any FooActivity into a data-binding MvxFooActivity by:

• inheriting from FooActivity to provide events from lifetime events in an EventSourceFooActivity
• inheriting from EventSourceFooActivity to provide a datacontext in an MvxFooActivity
• you can then write your code inside activities inheriting from MvxFooActivity

To see, the code required, see:

• https://github.com/slodge/MvvmCross/blob/v3/Cirrious/Cirrious.MvvmCross.Droid.Fragging/MvxEventSourceFragmentActivity.cs
• https://github.com/slodge/MvvmCross/blob/v3/Cirrious/Cirrious.MvvmCross.Droid.Fragging/MvxFragmentActivity.cs

You'll see the same code in all the mvx adapted Activities - MvxActivity, MvxTabActivity, ... There is a little cut-and-paste here, but as much code as possible is place in shared extension methods.

In previous versions, people have used this technique to bind monogame and google ads activities - eg see Insert a Monogame view inside MvvmCross monodroid Activity