The Countdown Timer app is a lightweight utility that launches a modal dialog to count down from a user-selected duration (5s, 10s, 15s, or 30s). Once the timer reaches zero, the app plays a confirmation tone and vibration, then shows a dismiss button. This project serves as a basic example of using CountDownTimer, ToneGenerator, and custom Dialog implementation in Android.

Key Features

Selectable Duration: A main screen with a duration picker (chip group) and a start button.
Modal Countdown: A full-screen dialog with circular progress ring, stop/restart buttons, and a confirmation tone during the final 3 seconds.
Haptic Feedback: Vibration on the last 3 seconds and on completion (configurable via shared preferences).
Real-time Updates: UI updates every second to reflect the remaining time.

Getting Started

Prerequisites

Android Studio (Ladybug or newer recommended)
JDK 17
An Android device or emulator running API level 24 or higher.

Building the App

To build the debug APK from the command line:

./gradlew assembleDebug

Running the App

Via Android Studio

Open the project in Android Studio.
Select your target device/emulator.
Click the Run button or press Shift + F10.

Via ADB

First, ensure your device or emulator is connected (adb devices). Then install the debug APK and launch the app:

# Install the debug APK
adb install -r app/build/outputs/apk/debug/app-debug.apk

# Launch the app
adb shell am start -n com.example.countdowntimer.debug/com.example.countdowntimer.MainActivity

Taking a Screenshot via ADB

To capture a screenshot of the app from your host machine:

# Take the screenshot on the device
adb shell screencap -p /sdcard/screenshot.png

# Pull it to your host machine
adb pull /sdcard/screenshot.png screenshots/

Project Structure

app/
├── src/
│   └── main/
│       ├── java/com/example/countdowntimer/
│       │   ├── MainActivity.kt          # Main entry point; duration picker and timer trigger
│       │   ├── CountdownDialog.kt       # Countdown logic, tone, and vibration
│       │   └── CountdownCanvasView.kt   # Custom circular progress ring view
│       ├── res/layout/                  # UI layouts
│       │   ├── activity_main.xml
│       │   └── dialog_countdown.xml
│       └── AndroidManifest.xml          # Application manifest
└── build.gradle                         # App-level build configuration