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this can help you determine if an object fails to hit test. |
this might happen if the object falls outside the bounds of its parent |
and thus not considered for hit testing in the first place. |
if you’re trying to debug compositor layers, consider using the following flags. |
use the debugPaintLayerBordersEnabled flag to find the boundaries |
of each layer. this flag results in outlining each layer’s bounds in orange. |
use the debugRepaintRainbowEnabled flag to display a repainted layer. |
whenever a layer repaints, it overlays with a rotating set of colors. |
any function or method in the flutter framework that starts with |
debug... only works in debug mode. |
<topic_end> |
<topic_start> |
debug animation issues |
info note |
to debug animations with the least effort, slow them down. |
to slow down the animation, |
click slow animations in DevTools’ inspector view. |
this reduces the animation to 20% speed. |
if you want more control over the amount of slowness, |
use the following instructions. |
set the timeDilation variable (from the scheduler |
library) to a number greater than 1.0, for instance, 50.0. |
it’s best to only set this once on app startup. if you |
change it on the fly, especially if you reduce it while |
animations are running, it’s possible that the framework |
will observe time going backwards, which will probably |
result in asserts and generally interfere with your efforts. |
<topic_end> |
<topic_start> |
debug performance issues |
info note |
you can achieve similar results to some of these debug |
flags using DevTools. some of the debug flags provide little benefit. |
if you find a flag with functionality you would like to add to DevTools, |
file an issue. |
flutter provides a wide variety of top-level properties and functions |
to help you debug your app at various points along the |
development cycle. |
to use these features, compile your app in debug mode. |
the following list highlights some of flags and one function from the |
rendering library for debugging performance issues. |
to set these flags either: |
you can generate stack traces on demand as well. |
to print your own stack traces, add the debugPrintStack() |
function to your app. |
<topic_end> |
<topic_start> |
trace dart code performance |
info note |
you can use the DevTools timeline events tab to perform traces. |
you can also import and export trace files into the timeline view, |
but only files generated by DevTools. |
to perform custom performance traces and |
measure wall or CPU time of arbitrary segments of dart code |
like android does with systrace, |
use dart:developer timeline utilities. |
wrap the code you want to measure in timeline methods. |
<code_start> |
import 'dart:developer'; |
void main() { |
Timeline.startSync('interesting function'); |
// iWonderHowLongThisTakes(); |
Timeline.finishSync(); |
} |
<code_end> |
to ensure that the runtime performance characteristics closely match that |
of your final product, run your app in profile mode. |
<topic_end> |
<topic_start> |
add performance overlay |
info note |
you can toggle display of the performance overlay on |
your app using the performance overlay button in the |
flutter inspector. if you prefer to do it in code, |
use the following instructions. |
to enable the PerformanceOverlay widget in your code, |
set the showPerformanceOverlay property to true on the |
MaterialApp, CupertinoApp, or WidgetsApp |
constructor: |
<topic_end> |
<topic_start> |
example 10 |
<code_start> |
import 'package:flutter/material.dart'; |
class MyApp extends StatelessWidget { |
const MyApp({super.key}); |
@override |
widget build(BuildContext context) { |
return MaterialApp( |
showPerformanceOverlay: true, |
title: 'my awesome app', |
theme: ThemeData( |
colorScheme: ColorScheme.fromSeed(seedColor: Colors.deepPurple), |
), |
home: const MyHomePage(title: 'my awesome app'), |
); |
} |
} |
<code_end> |
(if you’re not using MaterialApp, CupertinoApp, |
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