计算不同屏幕的dp以支持多个屏幕

Question

I know there are many questions like this, I have read many blogs and questions on this and I am not satisfied by what I have understand.

I want to support multiple screens and resolutions like hdpi, xxxhdpi etc. And i am using dimens.xml for this purpose. But m still unclear about how to calculate exact dp value for different screens.

For example if 48dp x 48dp ImageView is proper for hdpi device, what values should i define for xxhdpi device? Is there any fixed calulation just like there is for drawable images?

I am using these folder for trying to support multiple screens :

values-sw320dp-hdpi
values-sw320dp-xhdpi/xxhdpi/xxxhdpi

There are few problems I am facing currently

• Though defining values in respective dimens.xml works almost for most of the devices, there are few devices which takes wrong values

For example I have Lg optimus G that is xhdpi device, but it reads values from values-sw320dp-xxxhdpi 's dimens.xml instead of xhdpi one

• I am not able to calculate the exact value for each resolution (hdpi,xhdpi etc), so the view which looks perfect in hdpi device, seems little large or small in xxxhdpi as I can't guess the value like if hdpi view size is 48dp then xxxhdpi should be of 64dp or something as I don't know the exact approach.

Also while searching for supporting different screens, I read many times about calculating dp at runtime based on density or calulating pixels etc.

I am too confused about all this. Please help me in understanding and learning the proper way of making responsive apps.

Answer 1

You can use resource qualifiers to specify different sizes for Views.

If you want the width of an ImageView to vary based on the size of the screen, create a new dimension in your dimens.xml file called image_view_width (for example).

This then essentially creates a copy of the dimens.xml but adding the 'Size' qualifier. This will create another version of the dimens.xml file, and any device that meets your specified qualifications will use that version of dimens.xml . You then add image_view_width to this new file and give it a different (smaller/bigger) value. You can do this as many times as you want and with as many different qualifiers as you want.

Finally, when you want to use this value in your layouts, you only have to type:

android:layout_width="@dimen/image_view_width"

and android will do the rest for you.

Hope this helps!