SpannableString添加ImageSpan居中處理

Android圖文混排可以通過SpannableString來實現，但是imageSpan只提供了兩種對齊方式：ALIGN_BOTTOM，ALIGN_BASELINE兩種方式，並沒有居中對齊方式。

自定義ImageSpan

public class CenterImageSpan extends ImageSpan {

    public CenterImageSpan(Drawable drawable) {
        super(drawable);

    }

    public CenterImageSpan(Bitmap bitmap) {
        super(bitmap);
    }

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

        Drawable b = getDrawable();
        Paint.FontMetricsInt fm = paint.getFontMetricsInt();
        int transY = (y + fm.descent + y + fm.ascent) / 2 - b.getBounds().bottom / 2;//計算y方向的位移
        canvas.save();
        canvas.translate(x, transY);//繪製圖片位移一段距離
        b.draw(canvas);
        canvas.restore();
    }
}

使用方式

 
  if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
  			   //創建SpannableString對象
               val sp = SpannableString("Test String")
             
  				//拿到所加圖片的drawable對象
                val drawable =context.getDrawable(R.drawable.iv_to_add)
                drawable.setBounds(0, 0, drawable.minimumWidth, drawable.minimumHeight)
				
				//給SpannableString設置ImageSpan
                val imageSpan = CenterImageSpan(drawable)
                sp.setSpan(imageSpan, sp.length - 1, sp.length, ImageSpan.ALIGN_BASELINE)
    
    			textview.text=sp
     }