Animated Progress Bar in Rust egui — Download Manager App | Ep 15

Animated Progress Bar in Rust egui — Download Manager App

Learn how to create a smooth, animated progress bar in Rust using the egui library, perfect for a download manager interface. This example demonstrates how to display progress, show percentage text, add shimmer animation, and update the UI continuously with state-driven buttons.

Code

use egui::{ProgressBar, Ui};

struct DownloadManager {
  progress: f32,    // current progress from 0.0 to 1.0
  downloading: bool,
}

impl DownloadManager {
  fn ui(&mut self, ui: &mut Ui, ctx: &egui::Context) {
    // Create a progress bar with current progress
    let mut progress_bar = ProgressBar::new(self.progress)
      .show_percentage();  // show progress as "XX%"

    // Animate the progress bar if downloading
    if self.downloading {
      progress_bar = progress_bar.animate(true);
      // Request repaint to update animation continuously
      ctx.request_repaint();
    }

    ui.add(progress_bar);

    // State-driven buttons
    if self.downloading {
      if ui.button("Cancel").clicked() {
        self.downloading = false;
        self.progress = 0.0;
      }
    } else {
      if ui.button("Start Download").clicked() {
        self.downloading = true;
        self.progress = 0.0;
      }
    }

    // Simulate progress increment
    if self.downloading && self.progress < 1.0 {
      self.progress += 0.005;  // increase progress smoothly
    } else if self.progress >= 1.0 {
      self.downloading = false;  // stop when complete
    }
  }
}

Key Points

• Use ProgressBar::new(progress) to create a progress bar with a value between 0.0 and 1.0.
• .show_percentage() adds a textual percentage display inside the progress bar.
• .animate(true) applies a shimmer animation effect to indicate active progress.
• Call ctx.request_repaint() each frame to keep the animation and UI updates smooth and continuous.
• Drive UI state with boolean flags to toggle buttons and progress behavior dynamically during downloads.