Wordpress: filter posts by category in pages NOT WORKING?

Question

For over 3 days I am trying to filter posts in certain blog pages by certain categories on my wordpress theme: "Grafika".For example: I create a blog page called "Friends", after that I create a category named "friends" and after that I create 5 posts and I assign the "friends" category to those 5 posts.How can I do that on the "Friends" page to display only the posts from the category "friends".Currently the page shows all my blog posts from all pages.

I have tried many many plugins, query_posts, query_args, shortcut codes in page, modifying template. Actually I have only 1 plugin wich almost fixed my problem.The plugin it's called "wp posts filter".But it doesn't fully work.The problem with this plugin is that I am applying a filter for Home Page and that filter goes to all my pages no matter that for other pages I applyied different filters.This is the plugin link: here

Can somebody give me a REALLY WORKING solution to filter posts display by category on pages ? Thank you very much for reading !

Answer 1

1. Create a new custom page template for your blog
2. Create a customized loop on this page http://pastebin.com/bRLhpGzC
3. change the page template to the one you created, http://imgur.com/4VTpyMw

Answer 2

In your functions.php file of your theme, we can use the pre_get_posts function to alter the query before the page load.

function my_friends_category( $query ) {
    if ( $query->is_page('friends')):
        $query->set( 'cat', 'friends' );
    endif;
}
add_action( 'pre_get_posts', 'my_friends_category' );

This is assume the name of your page is friends otherwise replace it with the id of the page.