如何在 Android 的 TextView 中的文本下方添加红色波浪线

Question

我正在尝试在文本中的错误下方添加红色波浪线，例如：

不幸的是，我找不到合适的 *Span 类来包装错误文本。

我应该如何在 Android 中实现这样的功能？

Answer 1

这是一个不涉及资源的解决方案：

public class WavyUnderlineSpan implements LineBackgroundSpan {

private int color;
private int lineWidth;
private int waveSize;

public WavyUnderlineSpan() {
    this(Color.RED, 1, 3);
}

public WavyUnderlineSpan(int color, int lineWidth, int waveSize) {
    this.color = color;
    this.lineWidth = lineWidth;
    this.waveSize = waveSize;
}

@Override
public void drawBackground(Canvas canvas, Paint paint, int left, int right, int top, int baseline, int bottom,
                           CharSequence text, int start, int end, int lnum) {
    Paint p = new Paint(paint);
    p.setColor(color);
    p.setStrokeWidth(lineWidth);

    int width = (int) paint.measureText(text, start, end);
    int doubleWaveSize = waveSize * 2;
    for (int i = left; i < left + width; i += doubleWaveSize) {
        canvas.drawLine(i, bottom, i + waveSize, bottom - waveSize, p);
        canvas.drawLine(i + waveSize, bottom - waveSize, i + doubleWaveSize, bottom, p);
    }
}

}

Answer 2

@bpronin 的代码对我不起作用 - 高分辨率屏幕上的跨度太小，它跨越了整个文本，而不仅仅是跨越了错误。

但按照他的想法，我更新了我的答案，以消除添加资源的需要：

public class ErrorSpan extends DynamicDrawableSpan {

    private int width;
    int lineWidth;
    int waveSize;
    int color;


    public ErrorSpan(Resources resources) {
        this(resources, Color.RED, 1, 3);
    }

    public ErrorSpan(Resources resources, int color, int lineWidth, int waveSize) {
        super(DynamicDrawableSpan.ALIGN_BASELINE);
        // Get the screen's density scale
        final float scale = resources.getDisplayMetrics().density;
        // Convert the dps to pixels, based on density scale
        this.lineWidth = (int) (lineWidth * scale + 0.5f);
        this.waveSize = (int) (waveSize * scale + 0.5f);
        this.color = color;
    }

    @Override
    public Drawable getDrawable() {
        return null;
    }

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


    @Override
    public void draw(Canvas canvas, CharSequence text,
                     int start, int end, float x, 
                     int top, int y, int bottom, Paint paint) {

        Paint p = new Paint(paint);
        p.setColor(color);
        p.setStrokeWidth(lineWidth);

        int doubleWaveSize = waveSize * 2;
        for (int i = (int)x; i < x + width; i += doubleWaveSize) {
            canvas.drawLine(i, bottom, i + waveSize, bottom - waveSize, p);
            canvas.drawLine(i + waveSize, bottom - waveSize, i + doubleWaveSize, bottom, p);
        }
        canvas.drawText(text.subSequence(start, end).toString(), x, y, paint);
    }
}