To display image, you should use app:srcCompat
like the following.
<ImageView
...
...
...
app:srcCompat="@drawable/resource_name" />
tools:srcCompat
is responsible for showing the files in the preview pane of the IDE. It will not show the image in app.
Another approach to load image would be using Glide or Picasso library. You can find how to use them in their respective readme file.