Android Instagram喜欢文字贴纸背景

Question

我正在尝试在应用中实现类似Instagram文字贴纸的背景。我正在尝试使用Spannable实现它。我根据此stack overflow question

使用了以下代码

import android.graphics.Canvas;
import android.graphics.Paint;
import android.graphics.Path;
import android.graphics.RectF;
import android.text.style.LineBackgroundSpan;

public class BackgroundColorSpan implements LineBackgroundSpan {
private float padding;
private float radius;

private RectF rect = new RectF();
private Paint paint = new Paint();
private Paint paintStroke = new Paint();
private Path path = new Path();

private float prevWidth = -1f;
private float prevLeft = -1f;
private float prevRight = -1f;
private float prevBottom = -1f;
private float prevTop = -1f;


public BackgroundColorSpan(int backgroundColor,
                           float padding,
                           float radius) {
    this.padding = padding;
    this.radius = radius;

    paint.setColor(backgroundColor);
    //paintStroke.setStyle(Paint.Style.STROKE);
    //paintStroke.setStrokeWidth(5f);
    paintStroke.setColor(backgroundColor);
}

@Override
public void drawBackground(
                final Canvas c,
                final Paint p,
                final int left,
                final int right,
                final int top,
                final int baseline,
                final int bottom,
                final CharSequence text,
                final int start,
                final int end,
                final int lnum) {

    float width = p.measureText(text, start, end) + 2f * padding;
    float shift = (right - width) / 2f;

    rect.set(shift, top, right - shift, bottom);

    if (lnum == 0) {
        c.drawRoundRect(rect, radius, radius, paint);
    } else {
        path.reset();
        float dr = width - prevWidth;
        float diff = -Math.signum(dr) * Math.min(2f * radius, Math.abs(dr/2f))/2f;
        path.moveTo(
                        prevLeft, prevBottom - radius
        );

        path.cubicTo(
                        prevLeft, prevBottom - radius,
                        prevLeft, rect.top,
                        prevLeft + diff, rect.top
        );
        path.lineTo(
                        rect.left - diff, rect.top
        );
        path.cubicTo(
                        rect.left - diff, rect.top,
                        rect.left, rect.top,
                        rect.left, rect.top + radius
        );
        path.lineTo(
                        rect.left, rect.bottom - radius
        );
        path.cubicTo(
                        rect.left, rect.bottom - radius,
                        rect.left, rect.bottom,
                        rect.left + radius, rect.bottom
        );
        path.lineTo(
                        rect.right - radius, rect.bottom
        );
        path.cubicTo(
                        rect.right - radius, rect.bottom,
                        rect.right, rect.bottom,
                        rect.right, rect.bottom - radius
        );
        path.lineTo(
                        rect.right, rect.top + radius
        );
        path.cubicTo(
                        rect.right, rect.top + radius,
                        rect.right, rect.top,
                        rect.right + diff, rect.top
        );
        path.lineTo(
                        prevRight - diff, rect.top
        );
        path.cubicTo(
                        prevRight - diff, rect.top,
                        prevRight, rect.top,
                        prevRight, prevBottom - radius
        );
        path.cubicTo(
                        prevRight, prevBottom - radius,
                        prevRight, prevBottom,
                        prevRight - radius, prevBottom

        );
        path.lineTo(
                        prevLeft + radius, prevBottom
        );
        path.cubicTo(
                        prevLeft + radius, prevBottom,
                        prevLeft, prevBottom,
                        prevLeft, rect.top - radius
        );
        c.drawPath(path, paintStroke);
    }

    prevWidth = width;
    prevLeft = rect.left;
    prevRight = rect.right;
    prevBottom = rect.bottom;
    prevTop = rect.top;
}

}

上面的代码工作正常，但仅适用于居中对齐的文本。如何修改此类以更改文本对齐方式？