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click open.
error important
do not use the new > project from existing sources
option for flutter projects.
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editing code and viewing issues
the flutter plugin performs code analysis that enables the following:
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running and debugging
info note
you can debug your app in a few ways.
the instructions below describe features available in android
studio and IntelliJ. for information on launching DevTools,
see running DevTools from android studio in the
DevTools docs.
running and debugging are controlled from the main toolbar:
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selecting a target
when a flutter project is open in the IDE, you should see a set of
flutter-specific buttons on the right-hand side of the toolbar.
info note
if the run and debug buttons are disabled, and no targets are listed,
flutter has not been able to discover any connected iOS or
android devices or simulators.
you need to connect a device, or start a simulator, to proceed.
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run app without breakpoints
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run app with breakpoints
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fast edit and refresh development cycle
flutter offers a best-in-class developer cycle enabling you to see the effect
of your changes almost instantly with the stateful hot reload feature.
to learn more, check out hot reload.
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show performance data
info note
to examine performance issues in flutter, see the
timeline view.
to view the performance data, including the widget rebuild
information, start the app in debug mode, and then open
the performance tool window using
view > tool windows > flutter performance.
to see the stats about which widgets are being rebuilt, and how often,
click show widget rebuild information in the performance pane.
the exact count of the rebuilds for this frame displays in the second
column from the right. for a high number of rebuilds, a yellow spinning
circle displays. the column to the far right shows how many times a
widget was rebuilt since entering the current screen.
for widgets that aren’t rebuilt, a solid grey circle displays.
otherwise, a grey spinning circle displays.
the app shown in this screenshot has been designed to deliver
poor performance, and the rebuild profiler gives you a clue
about what is happening in the frame that might cause poor
performance. the widget rebuild profiler is not a diagnostic
tool, by itself, about poor performance.
the purpose of this feature is to make you aware when widgets are
rebuilding—you might not realize that this is happening when just
looking at the code. if widgets are rebuilding that you didn’t expect,
it’s probably a sign that you should refactor your code by splitting
up large build methods into multiple widgets.
this tool can help you debug at least four common performance issues:
the whole screen (or large pieces of it) are built by a single
StatefulWidget, causing unnecessary UI building. split up the
UI into smaller widgets with smaller build() functions.
offscreen widgets are being rebuilt. this can happen, for example,
when a ListView is nested in a tall column that extends offscreen.
or when the RepaintBoundary is not set for a list that extends
offscreen, causing the whole list to be redrawn.
the build() function for an AnimatedBuilder draws a subtree that
does not need to be animated, causing unnecessary rebuilds of static
objects.
an opacity widget is placed unnecessarily high in the widget tree.
or, an opacity animation is created by directly manipulating the
opacity property of the opacity widget, causing the widget itself
and its subtree to rebuild.
you can click on a line in the table to navigate to the line
in the source where the widget is created. as the code runs,
the spinning icons also display in the code pane to help you
visualize which rebuilds are happening.
note that numerous rebuilds doesn’t necessarily indicate a problem.
typically you should only worry about excessive rebuilds if you have
already run the app in profile mode and verified that the performance
is not what you want.
and remember, the widget rebuild information is only available in
a debug build. test the app’s performance on a real device in a profile
build, but debug performance issues in a debug build.
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editing tips for flutter code
if you have additional tips we should share, let us know!
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