居中的ImageSpan

import android.graphics.Bitmap;
import android.graphics.Canvas;
import android.graphics.Paint;
import android.graphics.drawable.Drawable;
import android.support.annotation.NonNull;
import android.text.style.ImageSpan;

public class CenterAlignImageSpan extends ImageSpan {

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

    }

    public CenterAlignImageSpan(Bitmap b) {
        super(b);
    }

    @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();
        //计算y方向的位移
        int transY = (y + fm.descent + y + fm.ascent) / 2 - b.getBounds().bottom / 2;
        canvas.save();
        canvas.translate(x, transY);//绘制图片位移一段距离
        b.draw(canvas);
        canvas.restore();
    }
}

转载：https://www.jianshu.com/p/191dd6b9af1a