如果有人在处理罗斯福的代码示例时遇到困难（我肯定是，也许是因为它是Xamarin.Android？），这是一个更基本的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);
}
}
为了便于使用，以下代码段取自Activity，基本上在每个标签字符串周围放置了一个圆角背景，每个标签之间都有一个空格缓冲区。请注意，注释掉的行仅带有背景色，看起来效果不佳。
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);
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);
}
}
用法示例：
var stringBuilder = new SpannableStringBuilder();
var stringToAppend = "hello world";
stringBuilder.Append(stringToAppend);
stringBuilder.SetSpan(new RoundedBackgroundSpan(), stringBuilder.Length() - stringToAppend.Length, stringBuilder.Length(), SpanTypes.ExclusiveExclusive);
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