Perflutter

Performance when building in Flutter is why it is named Perflutter as one word. Perflutter is a lightweight Flutter package to inspect real navigation performance in-app. It helps you detect dropped frames, estimate FPS, observe memory peaks, and understand user journey flow screen by screen.

Why This Package

Smoothness is part of product quality. When frames drop:

• animations stutter
• gestures feel delayed
• users feel the app is "heavy" or unstable

Perflutter gives you live, session-level evidence for where performance pressure happens, so you can fix real bottlenecks faster.

Why Frames Matter

Flutter renders continuously. If UI work or raster work exceeds the frame budget, that frame misses target refresh timing and appears as jank.

• at 60Hz, budget is about 16.67ms
• at 120Hz, budget is about 8.33ms
• more dropped frames means less smooth experience

This is an early indicator that expensive work is happening on the wrong thread or at the wrong time.

How Perflutter Works

1. PerflutterNavigatorObserver listens to route and tab changes.
2. PerflutterTracker starts a screen record for the active route.
3. Flutter FrameTiming samples are collected for the current screen.
4. Frame, dropped-frame, and memory stats are aggregated.
5. PerflutterTrigger opens a full report overlay on top of your app.

Installation

Add dependency:

dependencies:
  perflutter: ^0.0.5

Setup Step By Step

1) Add Navigator Observer

import 'package:perflutter/perflutter.dart';

MaterialApp(
  navigatorObservers: [
    PerflutterNavigatorObserver(),
  ],
  home: HomePage(),
);

For MaterialApp.router / AutoRoute:

MaterialApp.router(
  routerConfig: _appRouter.config(
    navigatorObservers: () => [
      PerflutterNavigatorObserver(),
    ],
  ),
);

2) Wrap App With Trigger

import 'package:perflutter/perflutter.dart';

MaterialApp(
  builder: (context, child) {
    return PerflutterTrigger(
      triggerMode: PerflutterTriggerMode.floatingButton,
      child: child ?? const SizedBox.shrink(),
    );
  },
);

3) Open Report

• floatingButton: tap the floatingButton

or

• longPress: long-press anywhere to open

Configurable Attributes

PerflutterTrigger parameters

• child (Widget, required): your app content.
• enabled (bool, optional, default true): enables/disables the whole feature.
• triggerMode (PerflutterTriggerMode?, optional): access entry mode.
  • PerflutterTriggerMode.floatingButton
  • PerflutterTriggerMode.longPress

Example:

PerflutterTrigger(
  enabled: true,
  triggerMode: PerflutterTriggerMode.floatingButton,
  child: child ?? const SizedBox.shrink(),
)

Other public API you may use directly

• PerflutterNavigatorObserver(): attach to navigator observers for route tracking.
• PerflutterReportScreen(onClose: ...): report widget with optional close callback.

Trigger Behavior

• Floating trigger is draggable (onPanUpdate) so you can move it away from important UI.
• Floating trigger uses opacity (0.5) so it does not heavily hide content.
• Trigger mode can be changed from report Settings at runtime.
• Report opens as an overlay screen on top of current app content.

Production Note

Disable Perflutter in production builds.

Recommended pattern:

import 'package:flutter/foundation.dart';
import 'package:perflutter/perflutter.dart';

MaterialApp(
  navigatorObservers: kDebugMode ? [PerflutterNavigatorObserver()] : const [],
  builder: (context, child) {
    return PerflutterTrigger(
      enabled: kDebugMode,
      triggerMode: PerflutterTriggerMode.floatingButton,
      child: child ?? const SizedBox.shrink(),
    );
  },
);

This keeps performance instrumentation for development/testing only.

Report Screen Overview

The report contains:

1. Session Overview
2. Sort + Collect controls
3. Per-screen cards
4. Device System Info
5. Journey Breadcrumb

On every open, the first screen card is expanded by default for quick inspection.

Session Overview Numbers

• Session Time: how long the current tracking session has been running.
• Total Screen Visits: how many screen visits were tracked in this session.
• Total Frames: all rendered frames captured during the session.
• Dropped Frames: frames that missed smooth rendering targets.
• Frames Health %: overall smoothness score for the session.
• FPS (avg): average rendered frames per second for the session.
• Max Memory: highest memory usage observed in the session.

Per-Screen Card Numbers

Each screen card shows:

• screen name
• duration for that visit (or aggregated duration in collect mode)
• estimated FPS
• frame health
• total frames
• dropped frames
• peak memory
• total visits (xN) only when collect mode is enabled

Color Meaning

Performance color (by drop rate):

• green: < 5%
• orange: 5% to < 15%
• red: >= 15%

Memory color (by MB):

• green: < 350
• orange: 350 to < 600
• red: >= 600

Sort And Collect

Sort:

• Latest: newest entries first
• Low Perf: highest dropped-frame ratio first

Collect button:

• Collect (off): show each visit separately
• Collected (on): merge same screen names into one aggregated card
• in collected mode, visits are merged and Total Visits is shown
• collect toggle state is kept during the current app session

Journey Breadcrumb

Journey section shows navigation order for the session, like:

Home > HeavyScreen > NormalScreen

Use it to correlate performance issues with the user path that led to them.

Device System Info

Shows current device descriptor:

• Android: manufacturer + model + Android version
• iOS: device name + system name + system version

This helps you compare performance behavior by device class and OS version.

All Buttons Explained

• Trigger FAB: open report
• Close (X): close report and return to app
• Refresh: reset tracking session data
• Settings: switch trigger mode (Floating Button / Long Press)
• Sort chips: change ordering
• Collect chip: toggle per-visit vs per-screen aggregation

Example App In This Repository

The demo app (example/lib/main.dart) includes:

Normal Screen: Moderate rendering workload.	Heavy Screen: Raster-heavy animated layers with stress levels.

Use them to validate that metrics react clearly to lighter vs heavier rendering pressure.