I UV unwrapped my mesh, but the image texture doesn't show in my object I just created a 3D model of a barrel and UV unwarped. That thing below is the screenshot of the UV image editor.


Then I clicked new button below the UV image editors window and gave a name barrel and unchecked the alpha option, and selected blank to color fill option then clicked ok. then I changed the viewport to texture mode. I can't see the color grid texture on my object. Image below.


i am using blender 2.78n thanks in advance for any help.
UV unwrapping just deals with the coordinates for the mapping of a texture it does not assign the image to the material automagically.

In order to have an image be part of the material, you need to edit the material add an image texture node and connect the color output to the color input socket of the shader, then the UV coordinates as vector for the mapping.