Android: Convert points to pixels

Question

I have been using the pt unit in XML files. Now I need to set the width of an element at runtime. How can I set the width by points so that it is the same unit I have been using everywhere else. I assume I will need to multiply by resolution and dpi. A code sample would be best.

Please see my post regarding converting Points to Pixels http://systemdotrun.blogspot.co.uk/2014/09/whats-point-in-font-sizing.html? — Dori, Oct 06 '14 at 18:17
The blog linked in the above comment has moved to https://doridori.github.io/Whats-the-Point-(in-fonts-sizing) — digawp, Sep 26 '18 at 06:22

score 11 · Accepted Answer · answered Jan 20 '11 at 16:45

11

First you should really read the following in-depth article from the Android Developer Documentation :

http://developer.android.com/guide/practices/screens_support.html

Right in the middle you'll find the following under the title :

Do not use hard-coded pixel values in your code

// Convert the dps to pixels
final float scale = getContext().getResources().getDisplayMetrics().density;
mGestureThreshold = (int) (GESTURE_THRESHOLD_DP * scale + 0.5f);

answered Jan 20 '11 at 16:45

Yahel

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Why is there a "+ 0.5f" in the second line? Magic number in that example or is it needed to correctly convert pixels to dp? – C0deAttack Jan 20 '11 at 17:08
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Rounds to the nearest whole when the expression is converted to integer. – Blrfl Jan 20 '11 at 18:23
...because otherwise you might end up with 0 pixels... :) – Zordid Apr 04 '14 at 12:32
If you are using float and not casting to int, then adding the 0.5f is not necessary. – ThomasW Mar 25 '19 at 06:03

score 1 · Answer 2 · answered Jan 20 '11 at 16:42

1

You can use dip instead of pt

answered Jan 20 '11 at 16:42

Aman Alam

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I am using pt instead of dip because it makes more sense to the non programmers. If somebody asks how big that is I can say 12 points and they can know what that is. If I say pixels then they may not realize the Android pixels are much smaller then they are on PC and if I say dips then they will be faced with a new word. All that aside. Can I use dip at runtime? Can I convert pt to dip? – 700 Software Jan 20 '11 at 16:47
With regards to your dip at runtime question. Yes you can, but you have to convert Pixels to DPs by multiplying the pixels with the screens scale factor which you can get with context().getResources().getDisplayMetrics().density. – C0deAttack Jan 20 '11 at 17:05

Android: Convert points to pixels

2 Answers2