CSC 349: The Week beginning Sept. 4

• Homework:
  
  Answer the questions in the quiz found at http://docs.oracle.com/javase/tutorial/java/concepts/QandE/questions.html (All of the answers can be found in the links What is an Object?, What is a Class?, etc found on the upper left hand side of the page. Read them if you don't know the answers.)
  
  In the context of Android programming define the following terms
  • final
  • @Override
  • Gradle
  • Kotlin
  
  Due: Sept. 12
  
  
• Tuesday:
  
  Presentation: Intro to ConstraintLayout
  
  RestCalc.zip The activity_main.xml and MainActivity.java files for a simple restaurant tip calculator app. Some features to notice
  • using a EditText that takes in a decimal number (below is an attribute in xml layout)
    android:inputType="numberDecimal"
  • getting information out of EditText and into a variable declared as a double (in MainActivity.java) The output of the .getText() method has to be converted to a string and then parsed as a double
    double bill = Double.parseDouble(etBill.getText().toString());
  • adding an event method associated with user typing in an EditText
    etBill.addTextChangedListener(new TextWatcher() {
    which requires three methods
    1. public void beforeTextChanged(CharSequence charSequence, int i, int i1, int i2) {
    2. public void onTextChanged(CharSequence charSequence, int i, int i1, int i2) {
    3. public void afterTextChanged(Editable editable) {
  
  
  Lab: Salary Calculation
  Make an app that allows a user to enter two (decimal) numbers, the first an hourly wage and the second a number of hours worked that week. When the user clicks a button, the app should calculate the weekly salary including time-and-a-half for any hours over 40.
  
  30 hours at $10.00 yields 30*10 = $300.00.
  50 hours at $10.00 yields 40*10 + (50-40)*10*1.5 = $550.00
  
  
  • The resulting salary should be displayed with a dollar sign and two decimal places.
  • The result should be cleared out if the user changes either input value.
  • A "toast" should be displayed if the user enters hours greater than 84 saying that the user worked too many hours.
  
  
  Due: Sept. 12
  
  
• Thursday:
  
  RestCalc3.zip The activity_main.xml and MainActivity.java files for a revised version of the restaurant tip calculator app that uses radiobuttons to select the tip amount. Some features to notice
  • In the layout, the RadioButtons and contained with a RadioGroup. The RadioGroup is a container and so has open and close tags; whereas RadioButtons are "singletons" and thus end with />
  • The RadioButtons did not require constraints. Instead they were placed one under the other within the RadioGroup container.
  • In MainActivity.java, we worked first with the RadioGroup
    final RadioGroup rgTip = (RadioGroup) findViewById(R.id.rgTip);
int radio_id = rgTip.getCheckedRadioButtonId();
    
    and only then with the RadioButtons
    
    RadioButton myRad = (RadioButton) findViewById(radio_id);
  • The id obtained from the RadioGroup is -1 if no RadioButton in the group is checked.
  
  
  Lab: Cooking Steak
  Design an app with two sets of radio buttons (each set in its own radio group). Also have a Button and a TextView.
  
  The first set of radio buttons is for the user to choose the "doneness" (Rare, Medium Rare, Medium, Medium Well, Well).
  
  The second set of radio buttons is for the user to choose the thickness in inches (1, 1.25, 1.5, 1.75, 2).
  
  If the "doneness index" is 0 for Rare, 1 for Medium Rare, etc., then the cook time (in minutes)can be calculated as
  
  cook_time = 2 + doneness_index + thickness * 2
  
  When the user clicks the button, determine the doneness and thickness, then calculate and display the cook time.
  
  If the user did not choose a doneness, display a Toast message. Similarly if the user did not choose a thickness, display a Toast message.
  
  If the user changes the doneness or the thickness, then either remove your answer or recalculate your answer.
  
  Due: Sept. 14