cardCornerRadius shows error

Thanks all for trying to solve the question. At last I got the answer for my question:

1. Import the card view and recycle view separately from sdk/extras/v7/cardview
2. sdk/extras/v7/recycleview
3. right click on the imported projects go to properties and check the library box.
4. Now go the main project where you are working and add these two libraries by right clicking on the project go to properties-->android(left side)-->click add(library) (right bottom side) and the required libraries.

implementation 'com.android.support:cardview-v7:27.1.1'
implementation 'com.android.support:appcompat-v7:27.1.1'
implementation 'com.android.support:design:27.1.1'

Above is sufficient.

Add these dependencies to build.gradle.
Use the keyword implementation instead of compile as it has been deprecated

implementation 'com.android.support:cardview-v7:26.1.0' 
implementation 'com.android.support:appcompat-v7:26.1.0'

then use

app:cardCornerRadius="5dp" 

instead of

card_view:cardCornerRadius="5dp"

This worked for me

app:cardCornerRadius="5dp"
app:cardElevation="2dp"