Publish/subscribe pattern which allows a number of observer objects to see an event.Īllows an object to alter its behavior when its internal state changes.Īllows one of a family of algorithms to be selected on-the-fly at runtime.ĭefines the skeleton of an algorithm as an abstract class, allowing its subclasses to provide concrete behavior. Provides the ability to restore an object to its previous state (undo). Provides a placeholder for another object to control access, reduce cost, and reduce complexity.ĭelegates commands to a chain of processing objects.Ĭreates objects which encapsulate actions and parameters.Īccesses the elements of an object sequentially without exposing its underlying representation.Īllows loose coupling between classes by being the only class that has detailed knowledge of their methods. Reduces the cost of creating and manipulating a large number of similar objects. Provides a simplified interface to a large body of code. Restricts object creation for a class to only one instance.Īllows classes with incompatible interfaces to work together by wrapping its own interface around that of an already existing class.ĭecouples an abstraction from its implementation so that the two can vary independently.Ĭomposes zero-or-more similar objects so that they can be manipulated as one object.ĭynamically adds/overrides behaviour in an existing method of an object. Groups object factories that have a common theme.Ĭonstructs complex objects by separating construction and representation.Ĭreates objects without specifying the exact class to create.Ĭreates objects by cloning an existing object. Copy and paste the following code into the file just above the tag. Open the strings.xml file from the values directory. If there is a default Hello World TextView, delete the TextView and move to the next step. To change the layout open the activity_main.xml in the XML editor and replace the RelativeLayout by FrameLayout as shown here. Generally, FrameLayout should be used to hold a single child view, because it can be difficult to organize child views in a way that's scalable to different screen sizes without the children overlapping each other. FrameLayout is designed to block out an area on the screen to display a single item.
Therefore, the parent layout is changed to the FrameLayout. Almost always ListView covers the entire screen of your application.
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