我们应该使用准确的DPI号码来实现多种屏幕尺寸吗？

Question

I know we have some standard of DPI that we can use it for support multiple screen size in an like :

ldpi (low) ~120dpi
mdpi (medium) ~160dpi
hdpi (high) ~240dpi
xhdpi (extra-high) ~320dpi
xxhdpi (extra-extra-high) ~480dpi
xxxhdpi (extra-extra-extra-high) ~640dpi

But when I calculate for some real device, eg LG G3 - it has DPI is 538.

So my question is do we need to use that exactly DPI number for scale the image,... or just let it be one of xxhdpi ( 480dpi ) or xxxhdpi ( 640dpi ).

Answer 1

For my opinion, I think you shouldn't care about information dpi of devices. You should only focus to provide images, size (dp,sp) etc for some type of screens :

ldpi (low) ~120dpi

mdpi (medium) ~160dpi

hdpi (high) ~240dpi

xhdpi (extra-high) ~320dpi

xxhdpi (extra-extra-high) ~480dpi

xxxhdpi (extra-extra-extra-high) ~640dpi

========================================================================= Example: As you maybe known that 1 px = dp (dpi/160)

So if you have an image with size is 32 x 32 px on screen 160 dpi. It's mean your image get size 32 x 32 dp.

Now you want to scale it on xxhdpi (extra-extra-high) ~480dpi.

On xxhdpi (extra-extra-high) ~480dpi : 1 px = dp(480/160) = 3dp

Then you only need to provide another image with size 32*3 x 32*3 px = 96 x 96 px

Answer 2

You just have to provide the right assets and android will take care of the rest. You can check the documentation for more details.

The Android system helps your application achieve density independence in two ways:

1. The system scales dp units as appropriate for the current screen density
2. The system scales drawable resources to the appropriate size, based on the current screen density, if necessary

So in your case its better to provide both the assets. At runtime, the system uses the appropriate resources for your application, based on the generalized size or density of the current device screen.