Align text around ImageSpan center vertical
After reading the source code of TextView, I think we can use the baseLine of eache text line which is "y". And it will work even if you set lineSpaceExtra.
public class VerticalImageSpan extends ImageSpan {
public VerticalImageSpan(Drawable drawable) {
super(drawable);
}
/**
* update the text line height
*/
@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;
}
/**
* see detail message in android.text.TextLine
*
* @param canvas the canvas, can be null if not rendering
* @param text the text to be draw
* @param start the text start position
* @param end the text end position
* @param x the edge of the replacement closest to the leading margin
* @param top the top of the line
* @param y the baseline
* @param bottom the bottom of the line
* @param paint the work paint
*/
@Override
public void draw(Canvas canvas, CharSequence text, int start, int end,
float x, int top, int y, int bottom, Paint paint) {
Drawable drawable = getDrawable();
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();
}
}
ImageSpan imageSpan = new ImageSpan(d, ImageSpan.ALIGN_BOTTOM) {
public void draw(Canvas canvas, CharSequence text, int start,
int end, float x, int top, int y, int bottom,
Paint paint) {
Drawable b = getDrawable();
canvas.save();
int transY = bottom - b.getBounds().bottom;
// this is the key
transY -= paint.getFontMetricsInt().descent / 2;
canvas.translate(x, transY);
b.draw(canvas);
canvas.restore();
}
};
It might be a bit late but I've found a way to do it, no matter the image size. You need to create a class extending ImageSpan and override the methods getSize() and getCachedDrawable() (we don't need to change the last one, but this method from DynamicDrawableSpan is private and cannot be accessed in another way from the child class). In getSize(...), you can then redefined the way DynamicDrawableSpan set the ascent/top/descent/bottom of the line and achieve what you want to do.
Here's my class example:
import android.graphics.Canvas;
import android.graphics.Paint;
import android.graphics.Rect;
import android.graphics.drawable.Drawable;
import android.text.style.DynamicDrawableSpan;
import android.text.style.ImageSpan;
import java.lang.ref.WeakReference;
public class CenteredImageSpan extends ImageSpan {
// Extra variables used to redefine the Font Metrics when an ImageSpan is added
private int initialDescent = 0;
private int extraSpace = 0;
public CenteredImageSpan(final Drawable drawable) {
this(drawable, DynamicDrawableSpan.ALIGN_BOTTOM);
}
public CenteredImageSpan(final Drawable drawable, final int verticalAlignment) {
super(drawable, verticalAlignment);
}
@Override
public void draw(Canvas canvas, CharSequence text,
int start, int end, float x,
int top, int y, int bottom, Paint paint) {
getDrawable().draw(canvas);
}
// Method used to redefined the Font Metrics when an ImageSpan is added
@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) {
// Centers the text with the ImageSpan
if (rect.bottom - (fm.descent - fm.ascent) >= 0) {
// Stores the initial descent and computes the margin available
initialDescent = fm.descent;
extraSpace = rect.bottom - (fm.descent - fm.ascent);
}
fm.descent = extraSpace / 2 + initialDescent;
fm.bottom = fm.descent;
fm.ascent = -rect.bottom + fm.descent;
fm.top = fm.ascent;
}
return rect.right;
}
// Redefined locally because it is a private member from DynamicDrawableSpan
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;
}
private WeakReference<Drawable> mDrawableRef;
}
Let me know if you have any trouble with that class!
My answer tweaks the first answer. Actually I have tried both two methods above, and I don't think they are really center vertical. It would make the drawable more center if it's placed in between ascent and descent, rather than top and bottom. So as to the second answer, it aligns the center of the drawable to the baseline of the text, rather than the center of that text. Here's my solution:
public class CenteredImageSpan extends ImageSpan {
private WeakReference<Drawable> mDrawableRef;
public CenteredImageSpan(Context context, final int drawableRes) {
super(context, drawableRes);
}
@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();
// keep it the same as paint's fm
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) {
Drawable b = getCachedDrawable();
canvas.save();
int drawableHeight = b.getIntrinsicHeight();
int fontAscent = paint.getFontMetricsInt().ascent;
int fontDescent = paint.getFontMetricsInt().descent;
int transY = bottom - b.getBounds().bottom + // align bottom to bottom
(drawableHeight - fontDescent + fontAscent) / 2; // align center to center
canvas.translate(x, transY);
b.draw(canvas);
canvas.restore();
}
// Redefined locally because it is a private member from DynamicDrawableSpan
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;
}
}
I also rewrite getSize to keep the FontMetrics of drawable the same as other text, otherwise the parent view won't wrap the content correctly.