我是否需要使用所有drawable，drawable-mdpi，drawable-hdpi，drawable-xhdpi，drawable-xxhdpi和drawable-xxxhdpi？

Question

I realise that Android will try it's best if it does not find an icon in the required folder but I see someplaces they suggest all of the above and in others they don't include drawable ?

So should I populate drawable as well if all the others are filled with my tab icon images?

Answer 1

If you use a VectorDrawable , you don't need to add a Resource for every density (mdpi, xhdpi etc). VectorDrawable is supported since API 21 (Lollipop) or with Support Library (or AndroidX).

For simple types of images (usually icons), you can avoid creating separate images for each density by using vector graphics. Because vector graphics define the illustration with geometric line paths instead of pixels, they can be drawn at any size without scaling artifacts.

For images (PNG) on the other hand, you must add proper icons for every density because Android will try to scale the images (so they can proportionally occupy same area in all devices). When scaling, the image may become blurred reducing the quality of your UI.

To provide good graphical qualities on devices with different pixel densities, you should provide multiple versions of each bitmap in your app—one for each density bucket, at a corresponding resolution. Otherwise, Android must scale your bitmap so it occupies the same visible space on each screen, resulting in scaling artifacts such as blurring.

You can read more HERE and HERE

EDIT

Maybe, you don't need to duplicate ALL icons. A lot of factors can lead to different experiences such as using wrap_content or a specific dimension to control the icon size or even using a different scaleType in your ImageView . So, maybe, you can start by adding icons for xhdpi or xxhdpi folders only and check your screen in different screen (small display, large displays, low-resolution displays, high-resolution displays etc). Then, you can "duplicate" only the necessary icons... But if your project or APK size is relatively small, don't mind to duplicate the icons.

There's even some online tools to generate the assets for every density from a single PNG such Android Asset Studio website..

Answer 2

If you are adding all resolution drawable icon like :

drawable-mdpi
drawable-hdpi
drawable-xhdpi
drawable-xxhdpi
drawable-xxxdpi

then you need not to add any extra icons on drawable folder because all the device resolution covers under the above drawable folders