Android SpannableString 设置部分文本后面的背景

Question

我想创建与此图片类似的东西：

我成功地使用 SpannableStringBuilder 创建了除橙色圆角矩形之外的所有内容。我可以使用 BackgroundColorSpan 将背景设置为该颜色，但我找不到使其变圆的方法。我有什么想法可以实现这一目标吗？

提前致谢！

编辑： 我正在使用 Xamarin.Android，但这是我的代码：

stringBuilder.SetSpan(new BackgroundColorSpan(Application.Context.Resources.GetColor(Resource.Color.orangeColor)), stringBuilder.Length() - length, stringBuilder.Length(), SpanTypes.ExclusiveExclusive);

Answer 1

如果有人对 Roosevelt 的代码示例有困难（我确实有困难，可能是因为它是 Xamarin.Android？），这里有一个更基本的 Android java 版本的翻译：

    public class RoundedBackgroundSpan extends ReplacementSpan {

        private static int CORNER_RADIUS = 8;
        private int backgroundColor = 0;
        private int textColor = 0;

        public RoundedBackgroundSpan(Context context) {
            super();
            backgroundColor = context.getResources().getColor(R.color.gray);
            textColor = context.getResources().getColor(R.color.white);
        }

        @Override
        public void draw(Canvas canvas, CharSequence text, int start, int end, float x, int top, int y, int bottom, Paint paint) {
            RectF rect = new RectF(x, top, x + measureText(paint, text, start, end), bottom);
            paint.setColor(backgroundColor);
            canvas.drawRoundRect(rect, CORNER_RADIUS, CORNER_RADIUS, paint);
            paint.setColor(textColor);
            canvas.drawText(text, start, end, x, y, paint);
        }

        @Override
        public int getSize(Paint paint, CharSequence text, int start, int end, Paint.FontMetricsInt fm) {
            return Math.round(paint.measureText(text, start, end));
        }

        private float measureText(Paint paint, CharSequence text, int start, int end) {
            return paint.measureText(text, start, end);
        }
    }

为了使用，以下代码段取自 Activity，基本上在每个标签字符串周围放置一个漂亮的圆角背景，并在每个标签之间放置一个空间缓冲区。请注意，注释掉的行只是放入背景颜色，这不会产生漂亮的外观......

    SpannableStringBuilder stringBuilder = new SpannableStringBuilder();

    String between = "";
    for (String tag : eventListing.getTags()) {
       stringBuilder.append(between);
       if (between.length() == 0) between = "  ";
       String thisTag = "  "+tag+"  ";
       stringBuilder.append(thisTag);
       stringBuilder.setSpan(new RoundedBackgroundSpan(this), stringBuilder.length() - thisTag.length(), stringBuilder.length() - thisTag.length() + thisTag.length(), Spanned.SPAN_EXCLUSIVE_EXCLUSIVE);
       //stringBuilder.setSpan(new BackgroundColorSpan(getResources().getColor(R.color.gray)), stringBuilder.length() - thisTag.length(), stringBuilder.length(), Spanned.SPAN_EXCLUSIVE_EXCLUSIVE);
    }

    TextView tv = new TextView(this);
    tv.setText(stringBuilder);

Answer 2

根据 pskink 的建议，我设法解决了我的问题。 这是我的课：

public class RoundedBackgroundSpan : ReplacementSpan
{
    public override void Draw(Canvas canvas, ICharSequence text, int start, int end, float x, int top, int y, int bottom, Paint paint)
    {
        var rect = new RectF(x, top, x + MeasureText(paint, text, start, end), bottom);
        paint.Color = Application.Context.Resources.GetColor(Resource.Color.nextTimeBackgroundColor);
        canvas.DrawRoundRect(rect, Application.Context.Resources.GetDimensionPixelSize(Resource.Dimension.localRouteDetailsRoundRectValue), Application.Context.Resources.GetDimensionPixelSize(Resource.Dimension.localRouteDetailsRoundRectValue), paint);
        paint.Color = Application.Context.Resources.GetColor(Resource.Color.nextTimeTextColor);
        canvas.DrawText(text, start, end, x, y, paint);
    }

    public override int GetSize(Paint paint, ICharSequence text, int start, int end, Paint.FontMetricsInt fm)
    {
        return Math.Round(MeasureText(paint, text, start, end));
    }

    private float MeasureText(Paint paint, ICharSequence text, int start, int end)
    {
        return paint.MeasureText(text, start, end);
    }
}

使用示例：

var stringBuilder = new SpannableStringBuilder();
var stringToAppend = "hello world";
stringBuilder.Append(stringToAppend);
stringBuilder.SetSpan(new RoundedBackgroundSpan(), stringBuilder.Length() - stringToAppend.Length, stringBuilder.Length(), SpanTypes.ExclusiveExclusive);

Answer 3

只有一个词：ReplacementSpan

Answer 4

如果您的用例需要单个字符的圆形背景，您可以替换

draw(..)

方法来绘制圆形：

@Override
    public void draw(Canvas canvas, CharSequence text, int start, int end, float x, int top, int y, int bottom, Paint paint) {
        paint.setColor(backgroundColor);
        canvas.drawCircle(x, y, cornerRadius, paint);
        paint.setColor(textColor);
        canvas.drawText(text, start, end, x, y, paint);
    }

适用于突出显示列表中的计数。