Generate a Mobile App UI from a Sketch in Minutes

TL;DR: Replay allows you to generate fully functional mobile app UIs from screen recordings, leveraging behavior analysis for accurate and efficient code generation.

Stop Designing, Start Recording: Mobile App UI in Minutes#

Building mobile app UIs is often a tedious process involving iterative design cycles, complex prototyping, and painstaking code implementation. What if you could skip the static design phase and directly translate a user's intended flow into a working application? That's the promise of behavior-driven code generation, and Replay is leading the charge.

Traditional methods like Figma-to-code or screenshot-to-code have limitations. They rely on static images, lacking the crucial context of user interaction and intent. Replay analyzes video, the ultimate source of truth for understanding user behavior. By capturing screen recordings of your desired app flow, Replay reconstructs a functional UI, dramatically reducing development time.

The Problem with Static Designs#

While tools like Figma and Adobe XD are powerful for visual design, they represent a single point in time. They don't inherently capture the nuances of user interaction:

• •Button presses and navigation patterns
• •Data input and form submissions
• •Dynamic content updates and animations

These interactions are critical for a functional UI, and manually translating them from a design document to code is time-consuming and error-prone.

Behavior-Driven Reconstruction: Video as the Source of Truth#

Replay introduces a paradigm shift: Behavior-Driven Reconstruction. Instead of relying on static designs, Replay uses video recordings of user interactions as the primary input. This approach offers several key advantages:

• •Captures User Intent: Replay analyzes the video to understand what the user is trying to accomplish, not just what they see on the screen.
• •Handles Dynamic Content: Video inherently captures dynamic content changes, allowing Replay to generate code that accurately reflects these changes.
• •Eliminates Design Ambiguity: Video provides a clear and unambiguous representation of the desired UI behavior, reducing the risk of misinterpretation during development.

How Replay Works: From Video to Code#

Replay leverages advanced AI, specifically Gemini, to analyze video recordings and generate functional UI code. The process can be broken down into the following steps:

1. •Video Capture: Record a video of the desired mobile app flow. This could be a walkthrough of an existing app, a demonstration of a prototype, or even a sketch brought to life with simple interactions.
2. •Upload and Analysis: Upload the video to Replay. The engine then analyzes the video, identifying UI elements, user interactions, and data flow.
3. •Code Generation: Replay generates clean, well-structured code based on the video analysis. This includes UI components, event handlers, and data bindings.
4. •Customization and Integration: Customize the generated code to fit your specific needs. Replay supports style injection and integrates seamlessly with popular backend platforms like Supabase.

Building a Simple To-Do App UI with Replay#

Let's walk through a simplified example of generating a To-Do app UI using Replay. Imagine you've recorded a video of yourself:

1. •Opening a blank app screen.
2. •Typing "Buy groceries" into a text field.
3. •Tapping an "Add" button.
4. •Seeing "Buy groceries" appear in a list.
5. •Tapping a checkbox next to "Buy groceries".
6. •Seeing the item visually marked as completed.

Here's how Replay would translate this video into code:

Step 1: Video Upload and Processing#

Upload the recorded video to the Replay platform. Replay will analyze the video, identifying key UI elements like text fields, buttons, lists, and checkboxes. It will also recognize user interactions like text input, button taps, and checkbox selections.

Step 2: Code Generation and Customization#

Replay generates the following React code (or similar, depending on your chosen framework):

typescript
// Generated by Replay
import React, { useState } from 'react';

interface TodoItem {
  text: string;
  completed: boolean;
}

const App = () => {
  const [todos, setTodos] = useState<TodoItem[]>([]);
  const [newTodo, setNewTodo] = useState('');

  const handleInputChange = (event: React.ChangeEvent<HTMLInputElement>) => {
    setNewTodo(event.target.value);
  };

  const handleAddTodo = () => {
    if (newTodo.trim() !== '') {
      setTodos([...todos, { text: newTodo, completed: false }]);
      setNewTodo('');
    }
  };

  const handleToggleComplete = (index: number) => {
    const updatedTodos = [...todos];
    updatedTodos[index].completed = !updatedTodos[index].completed;
    setTodos(updatedTodos);
  };

  return (
    <div>
      <input
        type="text"
        value={newTodo}
        onChange={handleInputChange}
        placeholder="Add a new todo"
      />
      <button onClick={handleAddTodo}>Add</button>
      <ul>
        {todos.map((todo, index) => (
          <li key={index}>
            <input
              type="checkbox"
              checked={todo.completed}
              onChange={() => handleToggleComplete(index)}
            />
            <span style={{ textDecoration: todo.completed ? 'line-through' : 'none' }}>
              {todo.text}
            </span>
          </li>
        ))}
      </ul>
    </div>
  );
};

export default App;

💡 Pro Tip: Replay intelligently names variables and functions based on the context observed in the video, making the generated code more readable and maintainable.

Step 3: Style Injection#

Replay also allows you to inject styles based on the visual elements in the video. For example, you might want to match the font, colors, and spacing of the original design. Replay provides a mechanism to define CSS rules that are automatically applied to the generated UI.

Replay vs. Traditional Methods: A Comparison#

Here's a comparison of Replay with other popular UI generation methods:

📝 Note: While Figma-to-code tools are useful for translating static designs, they struggle to capture the dynamic aspects of user interaction. Screenshot-to-code tools are even more limited, as they only capture a single visual state.

Addressing Common Concerns#

• •Video Quality: Replay works best with clear, well-lit videos. However, it can still handle videos with some noise and imperfections.
• •Complex Interactions: For highly complex interactions, it may be necessary to break down the video into smaller segments.
• •Code Customization: While Replay generates functional code, you'll likely need to customize it to fit your specific application architecture and styling preferences.

⚠️ Warning: Replay is not a replacement for skilled developers. It's a powerful tool that accelerates the UI development process, but it still requires human oversight and customization.

Product Flow Maps#

Beyond individual UI components, Replay can also generate product flow maps based on the video analysis. This allows you to visualize the user's journey through the app and identify potential bottlenecks or areas for improvement.

Frequently Asked Questions#

Is Replay free to use?#

Replay offers a free tier with limited features. Paid plans are available for more advanced features and higher usage limits. Check the Replay pricing page for the latest details.

How is Replay different from v0.dev?#

v0.dev primarily focuses on generating UI components based on text prompts. Replay, on the other hand, analyzes video recordings to understand user behavior and generate complete UI flows. Replay excels at capturing the dynamic aspects of user interaction, while v0.dev is better suited for generating static UI elements based on textual descriptions.

What frameworks does Replay support?#

Replay currently supports React, Vue, and Angular. Support for other frameworks is planned for future releases.

Can Replay handle animations and transitions?#

Yes, Replay can analyze animations and transitions in the video and generate corresponding code.

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Ready to try behavior-driven code generation? Get started with Replay - transform any video into working code in seconds.