To Lecture Notes

IT 372 -- May 12, 2025

Review Questions

1. How do you round off a double value to three digits after the decimal point?
   Answer: Here are two ways to do this:
   

   // Method 1
   double xRounded = Math.round(x * 1000.0) / 1000.0;
   // Method 2
   String xRounded = String.format("%.3f", x); 
   

2. For this problem, use the scheme for finding the UTF-8 encoding for a character, given its hex Unicode code:
   

                 Minimum Maximum Byte 1   Byte 2   Byte 3
                code    code
                point   point
   One byte:    U+0000  U+007F  0xxxxxxx 
   Two bytes:   U+0080  U+07FF  110xxxxx 10xxxxxx 
   Three bytes: U+0800  U+FFFF  1110xxxx 10xxxxxx 10xxxxxx
   

   1. Find the UTF-8 encoding of the character á (a with acute accent).  This character has hex Unicode code E1. Its UTF-8 encoding requires two bytes.
   2. Find the UTF-8 encoding of the character ♯ (music sharp sign). This character has hex Unicode 266F. Its UTF-encoding requires three bytes.
3. Write an app that displays The Raven Poem by Edgar Allen Poe in a textview. Read the poem from the folder res/raw/theraven.txt
   Answer: The layout and Java activity files.
4. Write an app that displays the picture defined by this text file named shapes.txt:
   

   R,50,50,350,100,#DC143C
   O,200,200,300,250,#E9967A
   R,50,350,550,450,#B8860B
   O,500,50,600,100,#00FA9A
   

   R means rectangle, O means oval. The fields are x and y coordinates of the upper left corner, and the width and height of the rectangle or of the bounding rectangle for the ovals. The last field is the hex color code.
   
   Save this data in res/raw/drawing.txt and access it in onCreate like this:
   

   InputStream iStream = getResources( ).
       openRawResource(R.raw.drawing);
   Scanner scanner = new Scanner(iStream); 
   

   Answer: Here are the source code files:
   activity_main.xml  Shape.java  MyView.java  MainActivity.java
5. Look at the DrawRivers Example.
6. How could you use radio buttons to control the radius and color of a circle that you draw using touch event info?

Project 4

• Look at the Project 4 Description.

Introduction to Kotlin

ZooMap App

• Create an Android app named ZooMap
• Create a layout that contains a linear layout, which is 400x400 pixels
• Place the input file zoomap.txt in this Android folder:
  

  app/src/main/res/raw
  

  This map shows the locations of the zoo cages and the animals that live in them.
• Create a MyView class derived from View with an onDraw method that reads the input file zoomap.txt and plots the points according to the x and y coordinates. Multiply the x and y values by 2 before plotting them.
• Instantiate a MyView object and add it to the linear layout.
• Add an onTouch event handler to the MyView object.
• When the object is touched, if the touch location is close to one of the animal cages, look up the id in the input file, and display the id in a toast. Use a HashMap to store the id, x, and y values so that you don't need to read the input file every time that a touch occurs.
• After testing that the toast displays the correct values, instead of showing the toast, pass the id to a new activity.
• The new activity should look up the id in the input file and show the animal and gender in TextView widgets.
• Source code files for the ZooMap app:
  activity_main.xml   activity_details.xml
  MainActivity.java   DetailsActivity.java
  MyView.java   Point.java   zoomap.txt.