Instrument Rental — Android App (Kotlin)

A clean, two-screen Android app for renting musical instruments. Users browse instruments, pick a color, select a rental duration, and confirm the borrow. The app follows Material Design, passes data between screens using Intents + Parcelable, returns results with onActivityResult, and surfaces feedback with Snackbar/Toast. Automated UI checks are written with Espresso.

Table of Contents

• Features
• Screens
• Architecture
• Data Flow
• UI/UX Choices
• Validation & Error Handling
• Testing
• Project Structure
• Requirements
• Quick Start
• Usage
• Roadmap
• Credits
• License

Features

• Browse instruments with image, name, description, rating, and credits per month.
• Select options: color via RadioGroup + RadioButton; rating via RatingBar.
• Borrow flow: enter duration (months), validate inputs, and confirm.
• Credit tracking: show current credit; block actions when credits are insufficient.
• Responsive feedback:
  • Snackbar for actionable errors near the source control.
  • Toast for quick confirmations/cancellations.
• Data passing: Parcelable model moves instrument data between activities.
• Round-trip result: return updated credit to the browser screen with onActivityResult.
• Automated UI tests with Espresso: navigation, browsing, validation, and credit updates.

Screens

• Welcome / Get Started → CTA that launches browsing.
• Instrument Browser → Next/Prev browsing; shows details, rating, and color options; “Borrow”.
• Borrow Details → Selected instrument recap, duration input, Confirm / Cancel.

Add your screenshots here once you export them from the report:

• images/welcome.png
• images/browse.png
• images/borrow.png

Architecture

A simple two-activity flow with clear responsibilities.

Layer	Responsibility	Key Pieces
UI	Material components, layout XML	ConstraintLayout, LinearLayout, ImageView, TextView, Button, RatingBar, RadioGroup
Data Model	Parcelable instrument payload	data class Instrument(...): Parcelable
Navigation	Screen-to-screen and result return	Intent, putExtra, startActivityForResult, onActivityResult
Feedback	User messages	Snackbar (errors, validation), Toast (confirm/info)
Tests	UI automation	Espresso test cases (navigation/browse/validate/credit)

Data Flow

flowchart LR
  A[Welcome<br/>Get Started] --> B[Browser<br/>Instrument details]
  B -->|Borrow| C[Borrow Details<br/>Duration + Confirm]
  C -->|Confirm OK| D{Enough credits?}
  D -->|No| E[Snackbar: Not enough credit]
  D -->|Yes| F[Update credit<br/>Toast confirm]
  F --> G[Return result to Browser]
  G --> B
  C -->|Cancel| H[Toast cancel] --> B

Loading

Parcelable Model (example)

@Parcelize
data class Instrument(
  val name: String,
  val description: String,
  val price: Int,          // credits per month
  val rating: Float,
  val colorOptions: List<String>,
  val imageRes: Int
) : Parcelable

Passing Data and Returning Results (example)

// Browser → Borrow Details
val intent = Intent(this, BorrowDetailsActivity::class.java).apply {
  putExtra("instrument", currentInstrument)
  putExtra("currentCredit", currentCredit)
  putExtra("selectedColor", selectedColor)
}
startActivityForResult(intent, REQUEST_BORROW)

// Borrow Details → Browser (after confirm)
val result = Intent().putExtra("updatedCredit", newCredit)
setResult(Activity.RESULT_OK, result)
finish()

// Browser receives result
override fun onActivityResult(req: Int, res: Int, data: Intent?) {
  super.onActivityResult(req, res, data)
  if (req == REQUEST_BORROW && res == Activity.RESULT_OK) {
    currentCredit = data?.getIntExtra("updatedCredit", currentCredit) ?: currentCredit
    creditView.text = "Credit: $currentCredit"
  }
}

UI/UX Choices

• Material Design styling for buttons, text, spacing, and consistent theming.
• ConstraintLayout as the default for flexible responsive positioning.
• LinearLayout for simple vertical/horizontal sections where appropriate.
• Contextual messaging: use Snackbar for input/validation issues placed near the control; Toast for short success info.

Validation & Error Handling

• Duration checks: required, positive integer.
• Color required: block proceed if no color is chosen (Snackbar prompt).
• Credit guard: compare duration * price against currentCredit; show Snackbar when insufficient.
• Success & cancel: confirm with Toast.

Testing

Automated UI tests with Espresso cover:

• Navigation: welcome → browser → borrow → back with result.
• Browsing: “Next” updates instrument name/description/image/price correctly.
• Validation: empty/invalid duration and missing color show Snackbar.
• Credit handling: confirming a borrow deducts credits and returns updated value.

Example navigation test (sketch):

@Test fun navigationWorks() {
  onView(withId(R.id.getStarted)).perform(click())
  onView(withId(R.id.instrumentDetailsLayout)).check(matches(isDisplayed()))
  onView(withId(R.id.nextButton)).perform(click())
  onView(withId(R.id.borrowButton)).perform(click())
  onView(withId(R.id.borrowDetailsLayout)).check(matches(isDisplayed()))
}

Project Structure

/app
  src/main/java/...
    ui/
      MainActivity        # Welcome / Get Started
      BrowserActivity     # Browse instruments (a.k.a. MainActivity2 in report)
      BorrowDetailsActivity
    model/
      Instrument.kt       # Parcelable data class
    util/
      Extensions.kt       # (optional helpers)
  src/androidTest/java/... # Espresso tests
  src/main/res/
    layout/               # XML layouts (ConstraintLayout/LinearLayout)
    drawable/             # icons / images
    values/               # colors, styles (Material theme), strings

Requirements

• Android Studio (latest stable)
• Kotlin plugin (bundled)
• Android SDK + emulator/device

Quick Start

# Clone
git clone https://github.com/your-username/instrument-rental-android.git
cd instrument-rental-android

# Open with Android Studio
# Build → Run on emulator or device

Usage

1. Launch app and tap Get Started.
2. Browse instruments with Next; pick a Color.
3. Tap Borrow, enter Duration (months), Confirm.
4. If credits are enough → success Toast; credit is deducted and shown back on the browser screen.
   If not enough → Snackbar explains what’s missing.

Roadmap

• Login/profile to persist credit and history.
• Animated transitions and richer UI states.
• Instrument search/filter and favorites.
• Local persistence (Room) or remote backend (Firebase) for real data.

Credits

• Built with Kotlin, Android Studio, Material Design, and Espresso.
• Wireframes created in Figma.
• Report, sketches, and code screenshots informed this README.

License

MIT.