Xamarin：无法从带有链接的 TextView 中检索 URLSpan答案

【问题标题】：Xamarin: Unable to retrieve URLSpans from a TextView with linksXamarin：无法从带有链接的 TextView 中检索 URLSpan
【发布时间】：2018-01-12 14:00:25
【问题描述】：

我正在尝试从 Xamarin 项目中的 textView 中删除链接下划线。以下 sn-p 在 java 项目中运行良好：

    textView.setText("You must agree to our terms and conditions");

    Pattern pattern1 = Pattern.compile("terms and conditions");
    Linkify.addLinks(textView, pattern1, "http://www.someLink.com", null, new Linkify.TransformFilter() {
        @Override
        public String transformUrl(Matcher match, String url) {
            return "";
        }
    });

    Spannable s = new SpannableString(textView.getText());
    URLSpan[] spans = s.getSpans(0, s.length(), URLSpan.class);
    for (URLSpan span: spans) {
        int start = s.getSpanStart(span);
        int end = s.getSpanEnd(span);
        NoUnderline noUnderline = new NoUnderline();
        s.setSpan(noUnderline, start, end, 0);
    }
    textView.setText(s);

现在，在 C# 中翻译完全相同的代码，我得出以下结论：

        TextView.Text = "You must agree to our terms and conditions";

        Java.Util.Regex.Pattern termsAndConditionsMatcher = Java.Util.Regex.Pattern.Compile("terms and conditions");
        Linkify.AddLinks(TextView, termsAndConditionsMatcher, "https://www.someLink.com/", null, new EmptyLinkTransformer());

        var spannable = new SpannableString(TextView.Text);
        var spans = spannable.GetSpans(0, spannable.Length(), Java.Lang.Class.FromType(typeof(URLSpan)));

        var urlSpans = new URLSpan[spans.Length];
        for (var i = 0; i < urlSpans.Length; i++)
        {
            urlSpans[i] = spans[i] as URLSpan;
        }

        foreach (URLSpan span in urlSpans)
        {
            int start = spannable.GetSpanStart(span);
            int end = spannable.GetSpanEnd(span);
            var updated = new NoUnderlineSpan();
            spannable.SetSpan(updated, start, end, 0);
        }

        TextView.TextFormatted = spannable;

问题是 spannable.GetSpans(0, spannable.Length(), Java.Lang.Class.FromType(typeof(URLSpan))) 返回 0 个元素，即使我看到了链接在 UI 上被着色和下划线。

This 和this 的帖子表明我正确使用了该方法。我在这里做错了吗？

【问题讨论】：

标签： c# android xamarin.android

【解决方案1】：

Xamarin：无法从带有链接的 TextView 中检索 URLSpans

这里有一个解决方法：您可以使用ClickableSpan 而不是URLSpan 来实现相同的功能。

自定义 ClickableSpan 类并覆盖 UpdateDrawState 以从超链接 TextView 中删除下划线：

class MyClickableSpan : ClickableSpan
{
    private MainActivity mainActivity;

    public MyClickableSpan(MainActivity mainActivity)
    {
        this.mainActivity = mainActivity;
    }

    public override void OnClick(View widget)
    {
        Intent browserIntent = new Intent(Intent.ActionView, Uri.Parse("http://www.somelink.com/"));
        mainActivity.StartActivity(browserIntent);
    }

    public override void UpdateDrawState(TextPaint ds)
    {
        base.UpdateDrawState(ds);
        ds.Color = Color.Red;
        ds.UnderlineText = false;
    }
}

使用时：

TextView textview = FindViewById<TextView>(Resource.Id.Terms);

//You need add this line
textview.MovementMethod = LinkMovementMethod.Instance;

//This is the Text of TextView
SpannableString ss1 = new SpannableString("You must agree to our terms and conditions");

//22 means start position, ss1.Length() means end position
ss1.SetSpan(new MyClickableSpan(this), 22, ss1.Length(), SpanTypes.ExclusiveExclusive);

//set text for your TextView
textview.TextFormatted = ss1;

【讨论】：

【解决方案2】：

您可以使用以下代码从 TextView 获取现有跨度

TextView mytextview = ....;

var spans = Android.Text.SpannableFactory.Instance.NewSpannable(mytextview.TextFormatted);

foreach (URLSpan span in spans.GetSpans(0, mytextview.Text.Length, Java.Lang.Class.FromType(typeof(URLSpan))))
{
    //Use an Android.Text.SpannableStringBuilder to build your new spannabletext
    var ssb = new Android.Text.SpannableStringBuilder();
    //Do your business here.
}

//Then set your text to your TextView
mytextview.SetText(ssb, TextView.BufferType.Spannable);

如果您想再次从 textview 中获取 span，只需再次执行相同的代码即可。

【讨论】：