Android: 'dp' to 'px' conversion?

Question

I am reading this article: http://developer.android.com/guide/practices/screens_support.html

It says that the formula Android uses to convert between a dp unit to a px unit is the following:

    px = dp * (dpi / 160)

The article also gives an example when the dpi is 240, which gives us px = 1.5 (I'm calculating for one single dp pixel)

However, what exactly does 1.5 mean here? Once the px units are actually the physical device pixels, will Android draw 1 or 2 pixels?

Answer 1

It depends on the context.

If the dp value is used in a context that implies size, like the android:layout_width attribute, the logic described for Resources.getDimensionPixelSize() will be used. That is, the px value will be rounded to the nearest integer value, with the special case that if px > 0, then the actual value will be at least 1.

If the dp value is used in a context that implies offset, like the android:insetLeft attribute of the Inset Drawable, the logic described for Resources.getDimensionPixelOffset() will be used. That is, the px value will simply be truncated to an integer value.

Sometimes the unmodified floating point value is used, such as for the android:dashWidth attribute of the <stroke/> tag in a Shape Drawable, but this is pretty rare. Usually either the size or the offset logic is used, even if the floating point value could be used.

Answer 2

If what I've read is correct, 1.5px means the single '1' pixel is a color specified, and the .5 of a pixel surrounding it will be a blend with the '1' pixel and a pixel next to it.

E.g.

| A | AB | B |

A is 1.5px and B is 1.5x, therefore the pixel in-between is a mixture of both.

So using that, two pixels next to each other will be blended together e.g with a 1px display

| X | Y |

Now with a 1.5px display:

| XY | YX | It becomes mix of both! but the pixel set as X will be more X than the pixel set as Y