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IT 372 -- Apr 28, 2025

Review Exercises

1. How do you add a new activity to an Android project?
   Answer: right click on app in the Project Explorer. Then select
        New >> Activity >> Empty Views Activity
   Then enter the name of the new activity, leave the Generate a Layout file checked, but leave Launcher activity unchecked. Click Finish.
2. How are the Intent and a Bundle objects used?
   Answer: an Intent object is used to create a new activity; values can be inserted into the Intent object to be obtained by the target activity, for example like this:
   

   intent.putExtra(key, value);
   

   A Bundle object stores information immediately before an app is destroyed, for example when the emulator is rotated. For example, information is stored in a bundle like this:
   

   savedInstanceState.putInt(key, value); 

3. Create an Android app named Greeter with three activities named MainActivity, Greeter2Activity, and Greeter3Activity. MainActivity displays the greeting
   

   Hello, how are you?
   Click for next activity.
   

   Greeter2Activity displays the message
   

   I'm fine, thank you, and you?
   Click for next activity.
   

   Greeter3Activity displays the message
   

   I'm fine too, thanks.
   Click for main activity.
   

   Implement the onClick event handlers with lambda functions (Method 4).
   Ans: Here are the source code files:
   activity_main.xml   MainActivity.java
   activity_greeter2.xml  Greeter2Activity.java
   activity_greeter3.xml  Greeter3Activity.java
4. What does a ConstraintLayout constraint look like?

Writing to the Logcat Window

• Recall that System.out.println writes to the Logcat window.
• A preferred way to write to the Logcat window is using the Log.i (informational) method.  Here is a sample Log.i method call:
  

  Log.i("001", "This is a test.");
  

  "001" is the tag; "This is a test." is the informational message.
• Before running the an app with calls to Log.i, check that the log filter is set to package:mine. Change it by clicking the funnel shaped Show History icon on the top of the Logcat window if necessary. Clear the Logcat window with the trash can Clear Logcat icon on the left of the Logcat window before running the app.
• These are the available Log methods for writing to the Logcat window:
  

  Method	Signature	Meaning
  Log.d	(String, String)	Debug
  Log.e	(String, String)	Error
  Log.i	(String, String)	Information
  Log.v	(String, String)	Verbose
  Log.w	(String, String)	Warning

• Create a new Android app. Put this statement at the end of the onCreate method:
  

  Log.i("001", "This is a test.");
  

  Run the app; find the message with tag "001" in the Logcat window.

The Android Studio IDE

• Locate these Android Studio windows:
      Project   Code   Layout Design   Layout Text   Attributes
      Palette   Component Tree   Terminal   Logcat
• Locate these buttons in the Main Menu (upper left) by hovering over them with the mouse and reading the tooltips.
      Build Project   |   Run 'app'   |   Debug  |   Stop 'app'  | 
      Sync Project with Gradle Files   |  Device Manager  | 
      SDK Manager  |  Project Settings  | 
• Locate these buttons above the Layout Design Window:
      Select Design Surface   |    Orientation for Preview   | 
      Zoom In  |  Zoom to Fit Screen

Practice Problems

1. Create an Android app with project name DonorInfo and two activities MainActivity and DisplayActivity. The MainActivity layout should have two EditText widgets for entering donor name and donation amount and a submit button. Use an ArrayList collection to record the names and amounts. When the button is clicked, record the name and amount in the arraylist, then display all of the information in the array in an EditText widget located in the DisplayActivity. Create a string to put in the Intent object, something like this:
   

   "Tom,2000.00;Anna,1500.00;Terry,2300"
   

   Answer: Here are the resulting source code files:
       activity_main.xml  MainActivity.java  activity_display.xml
       DisplayActivity.java  Donation.java  strings.xml