Android TextView中图文混排设置行间距导致高度不一致问题解决

最近项目中需要实现一个评论带表情的功能，刚开始一切顺利，非常easy，突然有一天发现文字跟表情混排的时候，TextView中图文高度不一致，excuse。。。什么鬼，之前明明测试过图文混排，不存在这个问题啊，然后检查代码，没毛病啊，

android:gravity="center_vertical" 也设置了啊，然后猛然发现一行代码：android:lineSpacingExtra="8sp"，原来是设置了这个行间距导致的。知道问题出在哪了，就好解决了，度娘还是看源码，都OK的啊。
先贴一下对比图

 解决之前的效果图：

 　　

解决之后的效果图：　　

图文混排，不可缺少：SpannableString和ImageSpan，但是阅读源码发现，ImageSpan设置对齐方式只有两种：

  /**
     * A constant indicating that the bottom of this span should be aligned
     * with the bottom of the surrounding text, i.e., at the same level as the
     * lowest descender in the text.
     */
    public static final int ALIGN_BOTTOM = 0;
    
    /**
     * A constant indicating that the bottom of this span should be aligned
     * with the baseline of the surrounding text.
     */
    public static final int ALIGN_BASELINE = 1;
    

要是ImageSpan能提供一个使其内容垂直居中的，问题不就轻松解决了吗，但是它没有提供了，****，再看，源码

ImageSpan是继承DynamicDrawableSpan的，而DynamicDrawableSpan中有两个这样的方法：getSize和draw，

 @Override
    public int getSize(Paint paint, CharSequence text,
                         int start, int end,
                         Paint.FontMetricsInt fm) {
        Drawable d = getCachedDrawable();
        Rect rect = d.getBounds();

        if (fm != null) {
            fm.ascent = -rect.bottom; 
            fm.descent = 0; 

            fm.top = fm.ascent;
            fm.bottom = 0;
        }

        return rect.right;
    }

@Override
    public void draw(Canvas canvas, CharSequence text,
                     int start, int end, float x, 
                     int top, int y, int bottom, Paint paint) {
        Drawable b = getCachedDrawable();
        canvas.save();
        
        int transY = bottom - b.getBounds().bottom;
        if (mVerticalAlignment == ALIGN_BASELINE) {
            transY -= paint.getFontMetricsInt().descent;
        }

        canvas.translate(x, transY);
        b.draw(canvas);
        canvas.restore();
    }

所以我们也可以自定义去实现，最后贴上代码：

import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.Canvas;
import android.graphics.Paint;
import android.graphics.Rect;
import android.graphics.drawable.Drawable;
import android.text.style.ImageSpan;

import java.lang.ref.WeakReference;

/**
 * @Created SiberiaDante
 * @Describe：
 * @Time: 2017/8/18
 * @Email: 994537867@qq.com
 * @GitHub: https://github.com/SiberiaDante
 */

public class CenterAlignImageSpan extends ImageSpan {

    private WeakReference<Drawable> mDrawableRef;

    public CenterAlignImageSpan(Context context, Bitmap bitmap, int verticalAlignment) {
        super(context, bitmap, verticalAlignment);
    }

    public CenterAlignImageSpan(Context context, int resId, int verticalAlignment) {
        super(context, resId, verticalAlignment);
    }

    @Override
    public int getSize(Paint paint, CharSequence text, int start, int end,
                       Paint.FontMetricsInt fontMetricsInt) {
        Drawable drawable = getDrawable();
        Rect rect = drawable.getBounds();
        if (fontMetricsInt != null) {
            Paint.FontMetricsInt fmPaint = paint.getFontMetricsInt();
            int fontHeight = fmPaint.descent - fmPaint.ascent;
            int drHeight = rect.bottom - rect.top;
            int centerY = fmPaint.ascent + fontHeight / 2;

            fontMetricsInt.ascent = centerY - drHeight / 2;
            fontMetricsInt.top = fontMetricsInt.ascent;
            fontMetricsInt.bottom = centerY + drHeight / 2;
            fontMetricsInt.descent = fontMetricsInt.bottom;
        }
        return rect.right;
    }

    @Override
    public void draw(Canvas canvas, CharSequence text, int start, int end, float x, int top, int y,
                     int bottom, Paint paint) {
        Drawable drawable = getCachedDrawable();
        canvas.save();
        Paint.FontMetricsInt fmPaint = paint.getFontMetricsInt();
        int fontHeight = fmPaint.descent - fmPaint.ascent;
        int centerY = y + fmPaint.descent - fontHeight / 2;
        int transY = centerY - (drawable.getBounds().bottom - drawable.getBounds().top) / 2;
        canvas.translate(x, transY);
        drawable.draw(canvas);
        canvas.restore();
    }

    private Drawable getCachedDrawable() {
        WeakReference<Drawable> wr = mDrawableRef;
        Drawable d = null;
        if (wr != null) {
            d = wr.get();
        }

        if (d == null) {
            d = getDrawable();
            mDrawableRef = new WeakReference<>(d);
        }

        return d;
    }
}

最后：

 SpannableString spannableStringCustom = new SpannableString("测试图文混排测试图文混排测试图文混排测试图文混排测试图文混排测试图文混排测试图文混排测试图文混排测试图文混排测试图文混排测试图文混排测试图文混排测试图文混排测试图文混排测试图文混排测试图文混排测试图文混排测试图文混排");
        CenterAlignImageSpan span = new CenterAlignImageSpan(this, R.mipmap.ic_launcher, ImageSpan.ALIGN_BASELINE);//重写的ImageSpan
        spannableStringCustom.setSpan(span, 0, 2, Spannable.SPAN_EXCLUSIVE_EXCLUSIVE);
        textViewCustom.setText(spannableStringCustom);

参考文章：https://segmentfault.com/a/1190000007133405