过程

1. 计算字符串绘制成图片时的图片大小
2. 创建位图
3. 绘制位图

代码

    public static Bitmap fromText(float textSize, String text) {
        Paint paint = new Paint();
        paint.setTextSize(textSize);
        paint.setTextAlign(Paint.Align.LEFT);
        paint.setColor(Color.BLACK);

        Rect bound = new Rect();
        paint.getTextBounds(text, 0, text.length(), bound);

        Paint.FontMetrics fm = paint.getFontMetrics();

        int width = bound.width() + 6;
        int height = bound.height() + 4;

        Bitmap bitmap = Bitmap.createBitmap(width, height, Bitmap.Config.ARGB_8888);
        Canvas canvas = new Canvas(bitmap);
        canvas.drawText(text, 0, height + fm.top - fm.ascent, paint);
        canvas.save();

        return bitmap;
    }

示例

将货币符号转成位图显示在控件左侧，将金额作为控件的文本值，可以使控件更好的表示金钱的概念

Currency currency = Currency.getInstance("USD");
Bitmap bitmap = fromText(36, currency.getSymbol());
Drawable drawable = new BitmapDrawable(bitmap);
drawable.setBounds(0, 0, drawable.getMinimumWidth(), drawable.getMinimumHeight());
view.setCompoundDrawables(drawable , null, null, null);