Untitled Quiz

User Interface Components

• Action Bar: Contains a menu of common actions at the top of the app.
• Notification Area: Displays the topmost system menu and icons for alerts.
• Android Widgets: Various UI components such as:
  • Analog/Digital Clock, Button, Checkbox, Date/Time Picker
  • EditText, Gallery, ImageView/Button, ProgressBar
  • RadioButton, Spinner, TextView, MapView, WebView

Designing a User Interface

• XML layout files (e.g., activity_main.xml) are used to define UI components.
• Widgets can be dragged from the Palette to a preview image for layout design.
• Properties for each widget can be set in the Properties panel.

Events and Event-Driven Programming

• Events: Stimuli such as mouse motion, key presses, timers, and network data.
• Event-driven programming relies on user actions to control program flow and is common in graphical applications.
• To respond to events:
  • Create methods known as "listener" methods to handle specific events.
  • Attach these methods to GUI widgets in the design view.

Setting an Event Listener

• Select the widget in Design view, find the onClick property, and specify the method name.
• Switch to Text view to locate the XML for the button and create the method for the click action.

View Objects

• Each widget corresponds to a Java object that is a subclass of the View class.
• View objects have various methods to get and set properties like background, ID, margins, padding, and visibility.
• Example method for a Button’s text: public String getText() and public void setText(String text).

Accessing Widgets in Java Code

• Assign a unique ID value to each widget in Design view.
• Use findViewById to access the widget in Java, casting it to the correct type (e.g., Button, TextView).
• Example function to handle button click events: sets text in a TextView.

Exercise: Number Game

• Concept for "Bigger Number" game:
  • User compares two numbers by selecting corresponding buttons.
  • Displays "correct" or "incorrect" messages after each guess.
  • Scoring system awards points for correct answers and penalizes for incorrect answers.

Displaying Toast Messages

• Use Toast.makeText to display short messages for user feedback.
• Toast duration can be set to LENGTH_SHORT or LENGTH_LONG.
• Toasts are used for brief status updates but should not be relied on for critical information.

Resource Files Structure

• drawable/: Stores images.
• layout/: Contains descriptions of the GUI layout.
• menu/: Defines overall app menu options.
• values/: Holds constant values and arrays including strings for localization data and styles for visual appearance.

Gradle Build System

• Gradle manages build/compile processes for Android projects.
• The build.gradle file serves as the main configuration file for project builds.

Virtual Devices (AVDs)

• AVDs allow for running projects in an emulator, simulating various Android devices.
• When running a project in Android Studio, the app builds, installs, and loads on the virtual device.
• Alternatively, apps can be tested directly on actual Android devices for better performance but require physical connectivity to a development PC.

Top-Down Design Approach

• Emphasizes starting from app design and learning required skills to build that app.
• Example application: the "Bigger Number" game incorporates user interaction through buttons to select the bigger number among two provided options.

Android Terminology

• Activity: A single screen in an app, fundamental GUI component.
• View: Elements displayed in an activity, including widgets and layouts.
• Widget: GUI controls such as buttons and text fields.
• Layout: An invisible container managing positions and sizes of widgets.
• Event: Actions triggered by user interactions with widgets.