Mobile Development Workshop DAY 2: INTRODUCTION TO JAVA

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1 Mobile Development Workshop DAY 2: INTRODUCTION TO JAVA

2 Overview Morning session For loops Strings and collections Graphical User Interfaces

3 Recap Last time we covered Java the programming language and the Java Virtual Machine Data and variables Mathematical, comparison, and logical operations If statements Conditional statements Objects, classes, and methods

4 Slot Machine Algorithm Ask the user to play the game or quit If the user decides to play Generate 3 random numbers If all 3 numbers match, display the message Jackpot If any two numbers match, display the message Matched 2 Otherwise, display the message Sorry. Better luck next time Repeat until the user quits

5 The for Statement A for statement executes the body of a loop a fixed number of times. Example for (count = 1; count <= 10; count++) System.out.println(count);

6 The for Statement Syntax for (Initialization, Condition, Update) Body_Statement Body_Statement can be either a simple statement or a compound statement in {}. Corresponding while statement Initialization while (Condition) Body_Statement_Including_Update

7 The for Statement

8 Exercise resrever gnirts Learn about string methods Utilize a for loop

9 Graphical User Interfaces Graphical User Interfaces (GUIs) give users a visual representation of a program s interface The help communicate how a user can navigate the app as well as ways to perform common actions It s important that developers conform to a visual language with which users are familiar Reduces cognitive load Creates more intuitive user experience Makes programmers lives easier

10 Event-driven programming GUI applications usually involve event driven programming This is when aspects or your program may not be executed until some event occurs Even-driven programs are generally more complex because we have more things to consider (things like event order and variable scope)

11 Building GUI applications in Java Java has many facilities for building GUIs Many based on the Java Foundation Classes Swing is a very common toolkit used today to build user interfaces

12 The basics Start with a JFrame object This is your main window It will contain other components that comprise your user interface By default jframe objects are invisible You ll want to change that property once you ve build your interface Be default jframe objects are compact You can specify a fixed size, or have the frame adjust automatically to snugly wrap its children

13 Events and event handling Events can be triggered in a program by user action on the interface When an event occurs, it will have a specific target component Some components display default behavior (usually visual) when it receives an event You can override or augment this behavior by implementing an event handler

14 Implementing event listeners Some events can target any component, and can therefore have those events handled Some events only target certain components

15 Common Swing components Common button types Common text field types Other Swing components

16 Swing layouts Containers (such as a JFrame or JPanel) must be told how to lay out their children This is accomplished by using a layout Containers have default layouts, but you may want to change them

17 Swing layouts

18 Simple Slot Machine 2.0 Extend original slot machine utilizing GUI components