Android Action Bar Tutorial

 

The action bar helps access the most important and relevant to current context actions much quicker and easier. Buttons that appear in the action bar are called action buttons, and in case some of them can't fit in the action bar, they are hidden in the action overflow. 

     Action bar also gives a dedicated space in your application to identify users location in the app, which can be very useful if your application has a complex hierarchy. 

Screen Orientation Tutorial

     To make your application more responsive and improve user experience, you should create an alternative layout for landscape orientation, so that when a users device is horizontal the application layout would automatically switch to landscape layout.   
       To do that go to the res/layout directory of your project, right click the layout folder and select New->Android XML File. When a new file wizard opens, give new file the exact same name that is your main layout name (by default it is activity_main.xml) and press next (Picture 1).

Picture 1

Toast Tutorial

          Toast is a simple pop-up notification message, that automatically fades away after a certain amount of time. Toasts are used to notify user of a completion of certain operation, for example, if you are working on a task management application, toast can be used to tell your user that a task has been successfully saved. 

Relative Layout Tutorial

       In RelativeLayout all views are positioned relatively to each other. This means that you can create an EditText element and then create a button and say that you want this button to be positioned to left of the EditText. View can be positioned relatively to its sibling elements or to its parent layout. 

        Many say that RelativeLayout is the hardest to master, but I honesty don't think so at all. RelativeLayout is very flexible and I am sure that if you spend some time just playing around with it, you'll find it very easy to use as well ;)

Linear Layout Tutorial

      Using LinearLayout all layout elements are aligned alongside, horizontally or vertically. In this view group all its children are placed one after another, which means that there can only be one child in each row, regardless of its width.

      Layout's orientation is set using android:orientation attribute. Here are two examples of horizontal and vertical LinearLayout: