Question

好吧，所以我设置了一个全包控制来接受扫描输入，然后在文本被更改时执行一些功能。我在EditText上实现了ITextWatcher，当我导航到带有该控件的片段时，我收到错误。这是控件中的必要元素

public class ScannerEditText : EditText, View.IOnKeyListener, View.IOnFocusChangeListener, ITextWatcher
{
    private void Init()
    {
        this.Focusable = true;
        this.FocusableInTouchMode = true;
        //this.SetOnKeyListener(this);
        this.AddTextChangedListener(this);
        //this.OnFocusChangeListener = this;
    }

    private Timer _refreshTimer = null;
    private string _priorText = null;

    public ScannerEditText(Context context)
        : base(context)
    {
        this.Init();
    }

    public ScannerEditText(Context context, IAttributeSet attrs)
        :base(context, attrs)
    {
        this.Init();
    }

    public ScannerEditText(Context context, IAttributeSet attrs, int defStyleAttr)
        :base(context, attrs, defStyleAttr)
    {
        this.Init();
    }

    public ScannerEditText(Context context, IAttributeSet attrs, int defStyleAttr, int defStyleRes)
        :base(context, attrs, defStyleAttr, defStyleRes)
    {
        this.Init();
    }

    void ITextWatcher.AfterTextChanged(IEditable s)
    {
        if (this._refreshTimer != null) this._refreshTimer.Dispose();
        this._refreshTimer = new Timer(delegate (object state)
        {
            this._refreshTimer = null;
            OnUpdateData(this, new EventArgs());
        }, false, 500, 0);
    }

    void ITextWatcher.BeforeTextChanged(ICharSequence s, int start, int count, int after)
    {
        this._priorText = s.ToString();
    }

    void ITextWatcher.OnTextChanged(ICharSequence s, int start, int before, int count)
    {
        string newText = s.ToString();

        //if isEmpty do not advance
        if (string.IsNullOrWhiteSpace(newText))
            return;

        if (newText.Length < this._priorText.Length)
        {
            //if 1 character deleted do not advance
            if (newText == this._priorText.Substring(0, this._priorText.Length - 1))
                return;
        }
        else if (this._priorText.Length < newText.Length)
        {
            //if 1 character added do not advance
            if (newText.Substring(0, newText.Length - 1) == this._priorText)
                return;
        }

        UIUtil.HideKeyboard((Activity)this.Context, (View)this);

        ((View)this.Parent).FindViewById<EditText>(this.NextFocusRightId).RequestFocus();
    }
}

然后我导航到此控件的任何片段并获得以下错误： System.NotSupportedException：无法从原生句柄激活AndroidMobileBarcodeForMieTrakAPI.Xamarin.Controls.ScannerEditText类型的实例

现在，如果我删除了ITextWatcher接口并且实现了其他所有工作

我在搜索之后所看到的一切主要是java，它有点不同，它会覆盖成员而不是实现它们。

Answer 1

您需要使用IntPtr和JniHandleOwnership公开构造函数：

protected ScannerEditText(IntPtr javaReference, JniHandleOwnership transfer)
    : base(javaReference, transfer)
{
}

在EditText上实现ITextWatcher会引发错误

1 个答案: