Grid layout (LazyVGrid, LazyHGrid) in iOS Swift - Mini App: Build & Ship

Build: Photo Gallery

A screen that shows a grid of photos using a vertical lazy grid. Each photo is a colored square with a number label. The grid scrolls vertically.

Target UI

Photo Gallery

+-------------------------+
| [1] [2] [3] [4] [5]    |
| [6] [7] [8] [9] [10]   |
| [11][12][13][14][15]   |
| ...                     |
+-------------------------+

Use LazyVGrid with 5 columns

Display 20 colored squares labeled 1 to 20

Each square is 60x60 points with rounded corners

Grid scrolls vertically

Use SwiftUI

Starter Code

iOS Swift

import SwiftUI

struct PhotoGalleryView: View {
    let columns = [
        // TODO: Define 5 grid columns here
    ]
    
    var body: some View {
        ScrollView {
            LazyVGrid(columns: columns) {
                // TODO: Add 20 colored squares with labels
            }
            .padding()
        }
    }
}

struct PhotoGalleryView_Previews: PreviewProvider {
    static var previews: some View {
        PhotoGalleryView()
    }
}

Task 1

Task 2

Task 3

Task 4

Solution

iOS Swift

import SwiftUI

struct PhotoGalleryView: View {
    let columns = Array(repeating: GridItem(.fixed(60), spacing: 10), count: 5)
    
    var body: some View {
        ScrollView {
            LazyVGrid(columns: columns, spacing: 10) {
                ForEach(1...20, id: \.self) { number in
                    ZStack {
                        RoundedRectangle(cornerRadius: 8)
                            .fill(Color(hue: Double(number) / 20.0, saturation: 0.7, brightness: 0.8))
                            .frame(width: 60, height: 60)
                        Text("\(number)")
                            .font(.headline)
                            .foregroundColor(.white)
                    }
                }
            }
            .padding()
        }
    }
}

struct PhotoGalleryView_Previews: PreviewProvider {
    static var previews: some View {
        PhotoGalleryView()
    }
}

We define 5 columns using GridItem(.fixed(60)) to make each column 60 points wide. The LazyVGrid arranges items vertically in these columns. We loop from 1 to 20 to create 20 squares. Each square is a rounded rectangle with a color that changes hue based on the number, making the grid colorful. The number is shown centered in white text. The grid scrolls vertically inside a ScrollView. Padding and spacing keep the layout neat.

Final Result

Completed Screen

Photo Gallery

+------------------------------------------------+
| [ 1 ] [ 2 ] [ 3 ] [ 4 ] [ 5 ]                   |
| [ 6 ] [ 7 ] [ 8 ] [ 9 ] [10 ]                   |
| [11 ] [12 ] [13 ] [14 ] [15 ]                   |
| [16 ] [17 ] [18 ] [19 ] [20 ]                   |
|                                                |
| (scrollable vertically)                         |
+------------------------------------------------+

User can scroll vertically to see all 20 squares

Each square is a colored box with a number label

Grid adjusts spacing evenly with 5 columns

Stretch Goal

Add a toggle button to switch between vertical and horizontal grid layouts using LazyVGrid and LazyHGrid.

💡 Hint

Use a @State variable to track layout mode. Use LazyVGrid for vertical and LazyHGrid for horizontal. Change columns and rows accordingly.

Practice

1. What does LazyVGrid do in SwiftUI?

easy

A. Arranges items vertically in columns

B. Arranges items horizontally in rows

C. Creates a single scrollable list

D. Stacks items on top of each other

Solution

1. Step 1: Understand LazyVGrid purpose

   LazyVGrid arranges views vertically in columns, meaning items fill columns top to bottom.

2. Step 2: Compare with other layouts

   LazyHGrid arranges horizontally in rows, so LazyVGrid is vertical columns.

3. Final Answer:

   Arranges items vertically in columns -> Option A

4. Quick Check:

   LazyVGrid = vertical columns [OK]

Hint: Remember V in LazyVGrid means vertical columns [OK]

Common Mistakes:

• Confusing LazyVGrid with LazyHGrid
• Thinking it stacks items horizontally
• Assuming it creates a list

2. Which of the following is the correct way to define a grid with two flexible columns using LazyVGrid?

easy

A. LazyVGrid(columns: [GridItem(.flexible()), GridItem(.flexible())]) { ... }

B. LazyVGrid(rows: [GridItem(.flexible()), GridItem(.flexible())]) { ... }

C. LazyHGrid(columns: [GridItem(.flexible()), GridItem(.flexible())]) { ... }

D. LazyVGrid(columns: GridItem(.fixed(100))) { ... }

Solution

1. Step 1: Check parameter name for LazyVGrid

   LazyVGrid uses the parameter 'columns' to define its grid structure.

2. Step 2: Verify GridItem array for two flexible columns

   Two GridItem(.flexible()) inside an array means two flexible columns.

3. Final Answer:

   LazyVGrid(columns: [GridItem(.flexible()), GridItem(.flexible())]) { ... } -> Option A

4. Quick Check:

   LazyVGrid uses columns array [OK]

Hint: LazyVGrid needs 'columns' parameter as array [OK]

Common Mistakes:

• Using 'rows' parameter with LazyVGrid
• Confusing LazyHGrid with LazyVGrid
• Passing single GridItem without array

3. What will be the layout result of this code snippet?

LazyHGrid(rows: [GridItem(.fixed(50))]) {
  ForEach(0..<3) { i in
    Text("Item \(i)")
  }
}

medium

A. Three items arranged vertically in one column

B. Three items arranged horizontally in one row with fixed height

C. Three items stacked on top of each other with flexible height

D. Syntax error due to missing columns parameter

Solution

1. Step 1: Understand LazyHGrid with rows parameter

   LazyHGrid arranges items horizontally in rows. Here, rows array has one GridItem with fixed height 50.

2. Step 2: Analyze ForEach producing 3 items

   Three Text views will be placed horizontally in one row, each with height 50.

3. Final Answer:

   Three items arranged horizontally in one row with fixed height -> Option B

4. Quick Check:

   LazyHGrid + rows = horizontal rows [OK]

Hint: LazyHGrid uses rows array to set horizontal rows [OK]

Common Mistakes:

• Thinking LazyHGrid arranges vertically
• Confusing fixed height with width
• Expecting syntax error due to columns

4. Identify the error in this SwiftUI grid code:

LazyVGrid(rows: [GridItem(.flexible())]) {
  Text("Hello")
  Text("World")
}

medium

A. Text views cannot be inside LazyVGrid

B. Missing ForEach loop for multiple items

C. GridItem should be .fixed, not .flexible

D. Using 'rows' parameter instead of 'columns' in LazyVGrid

Solution

1. Step 1: Check parameter name for LazyVGrid

   LazyVGrid requires 'columns' parameter, not 'rows'. Using 'rows' causes error.

2. Step 2: Confirm other parts are valid

   Text views can be inside LazyVGrid; ForEach is optional for multiple views.

3. Final Answer:

   Using 'rows' parameter instead of 'columns' in LazyVGrid -> Option D

4. Quick Check:

   LazyVGrid needs 'columns' parameter [OK]

Hint: LazyVGrid uses 'columns', not 'rows' [OK]

Common Mistakes:

• Confusing rows and columns parameters
• Thinking ForEach is mandatory
• Misunderstanding GridItem types

5. You want to create a grid with 3 columns where the first column is fixed width 100, the second is flexible, and the third is adaptive with minimum 80 width. Which code correctly defines the columns array for LazyVGrid?

hard

A. [GridItem(.adaptive(minimum: 80)), GridItem(.fixed(100)), GridItem(.flexible())]

B. [GridItem(.flexible()), GridItem(.fixed(100)), GridItem(.adaptive(minimum: 80))]

C. [GridItem(.fixed(100)), GridItem(.flexible()), GridItem(.adaptive(minimum: 80))]

D. [GridItem(.fixed(100)), GridItem(.adaptive(minimum: 80)), GridItem(.flexible())]

Solution

1. Step 1: Match column order with requirements

   The first column must be fixed width 100, second flexible, third adaptive minimum 80.

2. Step 2: Check each GridItem in options

   [GridItem(.fixed(100)), GridItem(.flexible()), GridItem(.adaptive(minimum: 80))] matches order: fixed(100), flexible(), adaptive(minimum: 80).

3. Final Answer:

   [GridItem(.fixed(100)), GridItem(.flexible()), GridItem(.adaptive(minimum: 80))] -> Option C

4. Quick Check:

   Order and types must match requirements [OK]

Hint: Order of GridItems matches column order [OK]

Common Mistakes:

• Mixing order of GridItems
• Using wrong GridItem types
• Confusing adaptive with flexible