MvvmCross:更改 MonoDroid 上绑定的更新源触发器属性 [英] MvvmCross: change update source trigger property of binding on MonoDroid

问题描述

我想在 Droid EditText 视图上将默认绑定触发器从 PropertyChanged 更改为 LostFocus:

I will like to change the default binding trigger from PropertyChanged to LostFocus on a Droid EditText view:

 <EditText
                android:layout_width="fill_parent"
                android:layout_gravity="center"
                android:textSize="16dp"
                android:minWidth="168dp"
                local:MvxBind="Text SelectedCode, UpdateSourceTrigger=LostFocus" />

但我无法从 Wiki

我知道这在框架内是可能的，但找不到参考.

I know this is possible within the framework but cannot find the reference.

想法?

TIA.

推荐答案

绑定语法不提供UpdateSourceTrigger

改变触发机制的唯一方法是:

The only ways to change the triggering mechanism are:

• 提供自定义绑定
• 或提供自定义控件

我会选择自定义绑定 - 类似于:

I'd go for custom binding - something like:

public class MvxEditTextFocusChangeTextSpecialTargetBinding
    : MvxAndroidTargetBinding
{
    protected EditText EditText
    {
        get { return (EditText)Target; }
    }

    private bool _subscribed;

    public MvxEditTextFocusChangeTextSpecialTargetBinding(EditText view)
        : base(view)
    {
    }

    protected override void SetValueImpl(object target, object value)
    {
        var editText = EditText;
        if (editText == null)
            return;

        value = value ?? string.Empty;
        editText.Text = value.ToString();
    }

    public override MvxBindingMode DefaultMode
    {
        get { return MvxBindingMode.TwoWay; }
    }

    public override void SubscribeToEvents()
    {
        var editText = EditText;
        if (editText == null)
            return;

        editText.FocusChange += HandleFocusChange;
        _subscribed = true;
    }

    private void HandleFocusChange(object sender, View.FocusChangeEventArgs e)
    {
        var editText = EditText;
        if (editText == null)
            return;

        if (!e.HasFocus)
            FireValueChanged(editText.Text);
    }

    public override Type TargetType
    {
        get { return typeof(string); }
    }

    protected override void Dispose(bool isDisposing)
    {
        if (isDisposing)
        {
            var editText = EditText;
            if (editText != null && _subscribed)
            {
                editText.FocusChange -= HandleFocusChange;
                _subscribed = false;
            }
        }
        base.Dispose(isDisposing);
    }
}

注册使用:

registry.RegisterCustomBindingFactory<EditText>("FocusText",
                                                        textView => new MvxEditTextFocusChangeTextSpecialTargetBinding(textView));

然后用作:

 local:MvxBind="FocusText VMProperty"

有关自定义绑定的更多信息，请参阅 N=28 教程 - http://slodge.blogspot.co.uk/2013/06/n28-custom-bindings-n1-days-of-mvvmcross.html

For more on custom bindings, see the N=28 tutorial - http://slodge.blogspot.co.uk/2013/06/n28-custom-bindings-n1-days-of-mvvmcross.html

这篇关于MvvmCross:更改 MonoDroid 上绑定的更新源触发器属性的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！