This is an example of how to make a loading screen in libgdx. It features a loading bar which updates with the progress.
The bar can be animated and is interpolated to make the progress less 'jerky'.
[Video example] 1

Check out the [LoadingScreen.java] 4 file, which is commented.
It relies on the [AssetManager] 6 to load the assets in another thread. This gives it the opportunity to show a responsive screen instead of having the game freeze while assets are being loaded.

First it loads the assets needed to show the loading screen. For this, it is calling AssetManager's finishLoading();
This will make the screen wait until all the loading assets are loaded before moving on.
Then it should tell the AssetManager what to load next.

In the resize() method we are placing all the components.
NOTE: If you check the code you will see that the loadingBar is actually never resized or moved. Instead it is hidden from the beginning, and then showing more and more as the assets are being loaded.

In the render() method AssetManager.update() is being constantly called to make it load the assets. This method will return TRUE when everything is loaded, so then it would be a good time to move on to some other screen. In this example, it moves on to MainMenuScreen after a touch.
The percentage value given by the manager is interpolated to give a more smooth bar. Try changing the value from 0.1f to 1f to see the difference. Or check this [video with no interpolation] 5

[Libgdx] 2
[Vector logo] 3