Legacy icon does not show when using adaptive icon

I had the same trouble, and solved it by renaming my mipmap-anydpi directory to mipmap-anydpi-v26.

Apparently the ic_launcher.xml file confuses older Android versions, and this hides it from all but O. At any rate, my icons now work on all versions (down to SDK 11, at least).

Solution is to have mipmap-anydpi-v26/ic_launcher.xml for adaptive icons applicable for API level 26 and above and for other API levels put ic_launcher.png (Note: Not ic_launcher.xml) in all mimpap folders.

Explanation:

Here is the basic problem mipmap-anydpi take precedence over all other mipmap-*. So if resource is found in mipmap-anydpi it will always take preference. Now mipmap-anydpi-v26 is a filter above this which says resources from mipmap-anydpi-v26 will always be picked irrespective of devices density only if API level is 26 or more (Oreo).

Now you manifest has android:icon="@mipmap/ic_launcher"

If your device has API level 26 or above android will choose to use mipmap-anydpi-v26/ic_launcher.xml and everything works fine.

The problem happens when API level is less than 26. Android stats looking for resource named ic_launcher. It will never go and search in mipmap-anydpi-v26 because of API level constraint. Next, it would look for the resource in mipmap-anydpi and if not there then the actual density resource Eg. mipmap-mdpi.

Next, you cannot give ic_launcher.xml to android devices less than sdk 26 because it does not know what adaptive icons is.

So the solution is to have mipmap-anydpi-v26/ic_launcher.xml for adaptive icons applicable for API level 26 and above and for other API levels put ic_launcher.png (Note: Not ic_launcher.xml) in all mimpap folders.

I have been faced same issue and resolved as below.

Put your ic_launcher.xml and ic_launcher_round.xml should be in mipmap-anydpi-v26 (make sure you should not have ic_launcher.png/jpg or ic_launcher_round.png/jpg in same folder).

Put your ic_launcher.png should be in mipmap-hdpi/mdpi/xhdpi/xxhdpi/xxxhdpi (make sure you should not have ic_launcher.xml and ic_launcher_round.xml in these same folder).

By doing this, You will not get any errors building/running project.

Hope it helps some one who are same issue...