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other resources |
you might find the following docs useful: |
<topic_end> |
<topic_start> |
debug flutter apps from code |
this guide describes which debugging features you can enable in your code. |
for a full list of debugging and profiling tools, check out the |
debugging page. |
info note |
if you are looking for a way to use GDB to remotely debug the |
flutter engine running within an android app process, |
check out flutter_gdb. |
<topic_end> |
<topic_start> |
add logging to your application |
info note |
you can view logs in DevTools’ logging view |
or in your system console. this sections |
shows how to set up your logging statements. |
you have two options for logging for your application. |
import dart:io and invoking methods on |
stderr and stdout. for example: |
<code_start> |
stderr.writeln('print me'); |
<code_end> |
if you output too much at once, then android might discard some log lines. |
to avoid this outcome, |
use debugPrint() from flutter’s foundation library. |
this wrapper around print throttles the output to avoid the android kernel |
dropping output. |
you can also log your app using the dart:developer log() function. |
this allows you to include greater granularity and more information |
in the logging output. |
<topic_end> |
<topic_start> |
example 1 |
<code_start> |
import 'dart:developer' as developer; |
void main() { |
developer.log('log me', name: 'my.app.category'); |
developer.log('log me 1', name: 'my.other.category'); |
developer.log('log me 2', name: 'my.other.category'); |
} |
<code_end> |
you can also pass app data to the log call. |
the convention for this is to use the error: named |
parameter on the log() call, JSON encode the object |
you want to send, and pass the encoded string to the |
error parameter. |
<topic_end> |
<topic_start> |
example 2 |
<code_start> |
import 'dart:convert'; |
import 'dart:developer' as developer; |
void main() { |
var myCustomObject = MyCustomObject(); |
developer.log( |
'log me', |
name: 'my.app.category', |
error: jsonEncode(myCustomObject), |
); |
} |
<code_end> |
DevTool’s logging view interprets the JSON encoded error parameter |
as a data object. |
DevTool renders in the details view for that log entry. |
<topic_end> |
<topic_start> |
set breakpoints |
you can set breakpoints in DevTools’ debugger or |
in the built-in debugger of your IDE. |
to set programmatic breakpoints: |
insert programmatic breakpoints using the debugger() statement. |
this statement takes an optional when argument. |
this boolean argument sets a break when the given condition resolves to true. |
example 3 illustrates this. |
<topic_end> |
<topic_start> |
example 3 |
<code_start> |
import 'dart:developer'; |
void someFunction(double offset) { |
debugger(when: offset > 30); |
// ... |
} |
<code_end> |
<topic_end> |
<topic_start> |
debug app layers using flags |
each layer of the flutter framework provides a function to dump its |
current state or events to the console using the debugPrint property. |
info note |
all of the following examples were run as macOS native apps on |
a MacBook pro m1. these will differ from any dumps your |
development machine prints. |
lightbulb tip |
each render object in any tree includes the first five |
hexadecimal digits of its hashCode. |
this hash serves as a unique identifier for that render object. |
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