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Android Layout Worksheet: Mastering activity_main.xml Design

Objective: Teach students a template-driven, pattern-based methodology for designing, troubleshooting, and structuring Android layout XML files, particularly activity_main.xml.

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📌 Why Follow a Pattern-Driven Layout Design?

Most students copy-paste XML without understanding why it works. The Android MOJO approach helps break down layout design into repeatable patterns, ensuring: ✅ Modularity – Layouts are reusable and scalable. ✅ Consistency – Standardized structures improve efficiency. ✅ Troubleshooting Readiness – Debugging becomes structured, not trial-and-error.

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📌 Part 1: The MOJO Layout Framework

🛠 Step 1: Android Layout Checklist

Before writing any layout XML, ask yourself: ✔ Which UI container is best? → LinearLayout, ConstraintLayout, FrameLayout? ✔ What alignment do components need? → Horizontal, Vertical, Relative? ✔ Are margins and padding standardized? ✔ Are text sizes, colors, and dimensions in res/values/?

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📌 Part 2: Layout XML Pattern (MOJO Standard Template)

Use this template to structure any Android layout file effectively.

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🛠 Template: activity_main.xml (Standard MOJO Layout)

<?xml version="1.0" encoding="utf-8"?>

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"

android:layout_width="match_parent"

android:layout_height="match_parent"

android:padding="16dp"

android:orientation="vertical">

<TextView

android:id="@+id/headerText"

android:layout_width="match_parent"

android:layout_height="wrap_content"

android:text="@string/header_title"

android:textSize="24sp"

android:textStyle="bold"

android:gravity="center"

android:layout_marginBottom="16dp"/>

<EditText

android:id="@+id/usernameEditText"

android:layout_width="match_parent"

android:layout_height="wrap_content"

android:hint="@string/enter_username"

android:inputType="textPersonName"

android:layout_marginBottom="8dp" />

<EditText

android:id="@+id/emailEditText"

android:layout_width="match_parent"

android:layout_height="wrap_content"

android:hint="@string/enter_email"

android:inputType="textEmailAddress"

android:layout_marginBottom="16dp" />

<Button

android:id="@+id/submitButton"

android:layout_width="match_parent"

android:layout_height="wrap_content"

android:text="@string/submit_button"

android:layout_marginTop="8dp" />

<Button

android:id="@+id/cancelButton"

android:layout_width="match_parent"

android:layout_height="wrap_content"

android:text="@string/cancel_button"

android:layout_marginTop="8dp" />

</LinearLayout>

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📌 Part 3: Understanding the Template

This layout follows MOJO design principles:

1️⃣ Container Choice (LinearLayout)

Best for simple vertical stacking of elements.

Alternative? Use ConstraintLayout for complex UI.

2️⃣ Padding & Margins

android:padding="16dp" → Ensures a uniform outer margin.

android:layout_marginBottom="8dp" → Spacing between elements.

3️⃣ Text Standardization

Text size uses sp (textSize="24sp").

Text values are referenced from strings.xml, not hardcoded.

4️⃣ Input Fields

Uses android:hint="@string/enter_username" to prompt the user.

android:inputType="textPersonName" ensures proper keyboard format.

5️⃣ Button Actions

@+id/submitButton → This ID is referenced in Kotlin code.

Stacked buttons should have uniform spacing (layout_marginTop="8dp").

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📌 Part 4: Customizing the Template

🛠 Step 2: Modify and Implement a Custom Layout

🎯 Exercise: Create a Login Screen

Modify the provided template to create a Login Page: ✅ Use ConstraintLayout instead of LinearLayout. ✅ Add a Password Field (inputType="textPassword"). ✅ Add a "Forgot Password?" TextView (align below Password field). ✅ Place Login Button centered on screen.

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🛠 Custom activity_login.xml (MOJO Login Screen)

<?xml version="1.0" encoding="utf-8"?>

<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"

android:layout_width="match_parent"

android:layout_height="match_parent"

android:padding="16dp">

<EditText

android:id="@+id/usernameEditText"

android:layout_width="0dp"

android:layout_height="wrap_content"

android:hint="@string/enter_username"

android:inputType="textPersonName"

app:layout_constraintTop_toTopOf="parent"

app:layout_constraintStart_toStartOf="parent"

app:layout_constraintEnd_toEndOf="parent"

android:layout_marginTop="50dp"/>

<EditText

android:id="@+id/passwordEditText"

android:layout_width="0dp"

android:layout_height="wrap_content"

android:hint="@string/enter_password"

android:inputType="textPassword"

app:layout_constraintTop_toBottomOf="@id/usernameEditText"

app:layout_constraintStart_toStartOf="parent"

app:layout_constraintEnd_toEndOf="parent"

android:layout_marginTop="12dp"/>

<TextView

android:id="@+id/forgotPasswordText"

android:layout_width="wrap_content"

android:layout_height="wrap_content"

android:text="@string/forgot_password"

android:textColor="@android:color/holo_blue_light"

android:textStyle="bold"

app:layout_constraintTop_toBottomOf="@id/passwordEditText"

app:layout_constraintStart_toStartOf="parent"

app:layout_constraintEnd_toEndOf="parent"

android:layout_marginTop="8dp"/>

<Button

android:id="@+id/loginButton"

android:layout_width="wrap_content"

android:layout_height="wrap_content"

android:text="@string/login"

app:layout_constraintTop_toBottomOf="@id/forgotPasswordText"

app:layout_constraintStart_toStartOf="parent"

app:layout_constraintEnd_toEndOf="parent"

android:layout_marginTop="20dp"/>

</androidx.constraintlayout.widget.ConstraintLayout>

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📌 Part 5: Debugging & Fixing Layout Issues

🛠 Step 3: Common Errors and Fixes

Table 1

Table 1

Issue

Fix

❌ Elements not displaying

Ensure layout_width and layout_height are set correctly (match_parent or wrap_content).

❌ Overlapping views

Use margin and padding to space elements correctly.

❌ Wrong keyboard type

Ensure correct inputType (textPassword, textEmailAddress, etc.).

❌ Text not translating

Check if text is in strings.xml.

❌ Buttons too small

Set android:layout_width="match_parent" for full-width buttons.

There are no rows in this table

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🚀 Summary: Mastering activity_main.xml the MOJO Way

Using the Android MOJO approach, students don’t just copy-paste XML—they follow a structured methodology to: ✅ Select the correct layout container (LinearLayout vs. ConstraintLayout). ✅ Apply consistent spacing using padding/margin. ✅ Reference UI text from strings.xml for maintainability. ✅ Debug layout issues efficiently using a systematic approach.

🔥 Next Step: Move to Fragments & Modular UI Design to enhance reusability and dynamic layouts! 🚀

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