Field Trip #26

Create a Find a Word Puzzle in JavaBy Keith Lynn

JPanel

A JPanel is a lightweight container that can be placed inside of other containers

It can have its own layout For this app, we will make the layout of a

JPanel a grid

JApplet

A JApplet is a top-level container in Java We will use the JApplet to contain two Jpanels The first JPanel will contain letters The second JPanel will contain words In order to load a JApplet, we create an HTML

document The HTML document must contain an applet

tag The applet tag must contain the applet's name,

width, and height

LayoutManager

A LayoutManager defines how components will be placed onto a screen

There are built-in layout managers in Java FlowLayout will put components in a row GridLayout will put components in a grid In this app, we will create a Jpanel to hold

letters in buttons and put the buttons in a grid

String

A String is a collection of individual characters We can obtain the character at a certain

position in a String with the method charAt(int) The first character in a String is at position 0 We can determine the length of the String with

the length() method We can concatenate characters to String with

the += operator We can compare the content of two Strings with

the equals or equalsIgnoreCase methods

Character

A character is a single character There is a special relationship between chars

and ints in Java If you treat a char like an int, it is converted to

its ASCII equivalent

Events Events can be detected and acted on by

creating listeners In this app, we will have three different kind of

event listeners We will attach an ActionListener to a single

button that will start the puzzle For each button in the grid, we will attach both a

MouseListener and MouseMotionListener The MouseListener will be use to determine

when we let up on the mouse The MouseMotionListener will be use to

determine when we drag the mouse

Color

In this app, when a word has been found, we will change the background color of the button to red

We will change the text color to white

Fonts

Fonts allows us to change the appearance of text

We will display a list of words the user will find When a user correctly finds one, the font of the

word will be changed to strikethrough

Arrays

Arrays are a collection of elements of the same type

In this app, we will consider what is actually a 2 dimensional array

Java doesn't directly support 2 dimensional arrays so we will create an array of arrays

The array will hold all of the buttons The buttons contain letters

Subclasses

In this app, we will also make use of the ability to create subclasses

If a class is not declared final, then we can create a new class called a subclass

We can add additional functionality to the subclass

The game

The idea behind the game to choose randomly words from a list

We create a grid of 400 letters and randomly choose locations to place those words in the grid

After we have placed those words, we fill the other buttons in with random letters

The words hidden are displayed in a list

The game, cont'd

The player will search through the grid trying to locate the words

When a player thinks they have found the word, they will hold down the mouse on the first letter and drag the mouse to the last letter

When the player begins dragging the mouse, a MouseMotionEvent is fired

We record the buttons that the user drags the mouse over

The game, cont'd

When the user lets up on the mouse, a MouseEvent is fired

We then collect the letters from the buttons the user selected

We create a String from the letters and check to see if it is in the list

If it is, then we change the font of the word to strikethrough

If the user wants to start over, we provide a button to reset the grid