CMPT 381 Assignment 6: Text Prediction solution




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In this assignment, you will work with soft keyboards and text models to develop a predictive keyboard for Java coding, using JavaFX.
Part 1: A Coding Soft Keyboard in JavaFX
Using JavaFX, build the on-screen keyboard pictured at right.
Interface requirements:
 The UI consists of several JavaFX Buttons (one for each keyboard key), and
one entry box below the keyboard.
Interaction requirements:
 When the user clicks on a key button, that symbol is added to the entry box
at the bottom of the window (unless the key is Delete or Shift)
 When the user clicks Delete, the rightmost character is deleted
 When the user clicks Shift, all letters change to upper case (see lower
picture); the letters stay in upper case until the Shift key is clicked again.
 Shift has no effect on the number or symbol keys
Software requirements:
 All keyboard keys should be implemented as JavaFX Buttons
 Although it is possible to do the keyboard layout one button at a time, it will
be much simpler to do it algorithmically
 Build the keyboard UI, and handle button events, within the main JavaFX
application class
 Implement method “changeCase( )” to change from upper to lower case
 You do *not* need to use an MVC architecture for the application
Resources for part 1:
 JavaFX layout tutorial:
Part 2: Modeling and Predicting Java Code
In the second part of the assignment, you will add capabilities to your system from Part 1 that process a directory of Java source files
(to build a model of Java code), and that provide word-level predictions in the interface based on what the user has typed.
Additional interface requirements:
 Add UI components to the top of the interface to show the top three
suggestions from the predictor (see picture at right)
Additional interaction requirements:
 As the user types on the soft keyboard, the system generates predictions
based on what has been typed so far. For example, in the system shown at
right, the user has typed “Box” on the soft keyboard, and the top predictions
are shown above the keyboard (“Box”, “BoxModel”, and “BoxCommand”). In
addition, the suggestion UI shows the number of times that the suggestion
appears in the trie structure (see below) – for example, “Box” was seen 18
times in the training data.
 Any change to the entered text (including changes resulting from the Delete button) regenerate a new prediction.
 Clicking on any of the suggestions copies the suggestion into the entry box
Additional software requirements:
 Add classes Trie and TrieNode, based on the example in the moodle Examples folder. The trie structure will hold the model of
Java code that will allow you to make predictions
 To build the trie:
o Read in all of the Java source files from the BoxFX example (on moodle)
o Split the text into words using the following characters as delimiters: space, round brackets, period, and comma.
o Add each word to the trie
 Add class Candidate to hold a candidate word and its frequency
 Write method public ArrayList getCandidates(String prefix) in class Trie (you will also need
subsidiary methods in class TrieNode):
o Traverse the trie using the current prefix string (i.e., what the user has typed so far)
o Create Candidate objects for each complete word below this point in the trie (with their frequencies)
 Write method public void getSuggestions(String prefix) in the application class. This method will be called
whenever the text in the entry box changes, and will put the top three suggestions (sorted by frequency) into the suggestions UI
Resources for part 2:
 Trie example code: on the moodle in the Examples directory
 BoxFX code: on the moodle in the Examples directory
 Trie on Wikipedia:
This assignment is to be completed individually; each student will hand in an assignment.
What and Where to hand in
 JavaFX: a zip file of your NetBeans project folder for either part 1 (if that is as much as you have completed) or part 2. If you
have completed part 2, you do not have to hand in a project file for part 1.
 A readme.txt file that indicates exactly what the marker needs to do to run your code. (Systems for 381 should never require
the marker to install external libraries).
 Hand in your two files (one zip and one readme.txt) to the link on the course Moodle.
Marks will be given for producing a system that meets the requirements above, and compiles and runs without errors. Note that no
late assignments will be allowed, and no extensions will be given, without medical reasons.