Align text around ImageSpan center vertical

Question

I have an ImageSpan inside of a piece of text. What I've noticed is that the surrounding text is always drawn at the bottom of the text line -- to be more precise, the size of the text line grows with the image but the baseline of the text does not shift upward. When the image is noticeably larger than the text size, the effect is rather unsightly.

Here is a sample, the outline shows bounds of the TextView:

I am trying to have the surrounding text be centered vertically with respect to the image being displayed. Here is the same sample with blue text showing the desired location:

Here are the constraints that I'm bound by:

• I cannot use compound drawables. The images must be able to be shown between words.
• The text may be multiline depending on the content. I have no control over this.
• My images are larger than the surrounding text and I cannot reduce their size. While the sample image above is larger than the actual images (to demonstrate the current behavior), the actual images are still large enough that this problem is noticeable.

I've tried using the android:gravity="center_vertical" attribute on the TextView, but this does not have any effect. I believe this just vertically centers the text lines, but within the text line the text is still drawn at the bottom.

My current train of thought is to create a custom span that shifts the baseline of the text based on the height of the line and the current text size. This span would encompass the entire text, and I would have to compute the intersection with the ImageSpans so I can avoid shifting the images as well. This sounds rather daunting and I'm hoping someone can suggest another approach.

Any and all help is appreciated!

Answer 1

This solution works. I have tested it and am using it for sometime. It doesn't consider the ascent and decent but it Aligns the drawable in the center.

import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Paint;
import android.graphics.Rect;
import android.graphics.drawable.Drawable;
import android.support.annotation.NonNull;
import android.text.style.ImageSpan;

import java.lang.ref.WeakReference;

public class CustomImageSpan extends ImageSpan {

  /**
   * A constant indicating that the center of this span should be aligned
   * with the center of the surrounding text
   */
  public static final int ALIGN_CENTER = -12;
  private WeakReference<Drawable> mDrawable;
  private int mAlignment;

  public CustomImageSpan(Context context, final int drawableRes, int alignment) {
    super(context, drawableRes);
    mAlignment = alignment;
  }

  @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) {
      Paint.FontMetricsInt pfm = paint.getFontMetricsInt();
      fm.ascent = pfm.ascent;
      fm.descent = pfm.descent;
      fm.top = pfm.top;
      fm.bottom = pfm.bottom;
    }
    return rect.right;
  }

  @Override
  public void draw(@NonNull Canvas canvas, CharSequence text,
                   int start, int end, float x,
                   int top, int y, int bottom, @NonNull Paint paint) {
    if (mAlignment == ALIGN_CENTER) {
      Drawable cachedDrawable = getCachedDrawable();
      canvas.save();
      //Get the center point and set the Y coordinate considering the drawable height for aligning the icon vertically
      int transY = ((top + bottom) / 2) - cachedDrawable.getIntrinsicHeight() / 2;
      canvas.translate(x, transY);
      cachedDrawable.draw(canvas);
      canvas.restore();
    } else {
      super.draw(canvas, text, start, end, x, top, y , bottom, paint);
    }
  }

  // Redefined locally because it is a private member from DynamicDrawableSpan
  private Drawable getCachedDrawable() {
    WeakReference<Drawable> wr = mDrawable;
    Drawable d = null;
    if (wr != null) {
      d = wr.get();
    }
    if (d == null) {
      d = getDrawable();
      mDrawable = new WeakReference<>(d);
    }
    return d;
  }
}