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dart runtimes and compilers support the combination of
two critical features for flutter: a JIT-based fast
development cycle that allows for shape changing and
stateful hot reloads in a language with types,
plus an Ahead-of-Time compiler that emits efficient
ARM code for fast startup and predictable performance of
production deployments.
in addition, we have the opportunity to work closely
with the dart community, which is actively investing
resources in improving dart for use in flutter. for
example, when we adopted dart,
the language didn’t have an ahead-of-time
toolchain for producing native binaries,
which is instrumental in achieving predictable,
high performance, but now the language does because the dart team
built it for flutter. similarly, the dart VM has
previously been optimized for throughput but the
team is now optimizing the VM for latency, which is more
important for flutter’s workload.
dart scores highly for us on the following primary criteria:
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can flutter run any dart code?
flutter can run dart code that doesn’t directly or
transitively import dart:mirrors or dart:html.
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how big is the flutter engine?
in march 2021, we measured the download size of a
minimal flutter app (no material components,
just a single center widget, built with flutter build
apk --split-per-abi), bundled and compressed as a release APK,
to be approximately 4.3 MB for ARM32, and 4.8 MB for ARM64.
on ARM32, the core engine is approximately 3.4 MB
(compressed), the framework + app code is approximately
765 KB (compressed), the LICENSE file is 58 KB
(compressed), and necessary java code (classes.dex)
is 120 KB (compressed).
in ARM64, the core engine is approximately 4.0 MB
(compressed), the framework + app code is approximately
659 KB (compressed), the LICENSE file is 58 KB
(compressed), and necessary java code (classes.dex)
is 120 KB (compressed).
these numbers were measured using apkanalyzer,
which is also built into android studio.
on iOS, a release IPA of the same app has a download
size of 10.9 MB on an iPhone x, as reported by apple’s
app store connect. the IPA is larger than the APK mainly
because apple encrypts binaries within the IPA, making the
compression less efficient (see the
iOS app store specific considerations
section of apple’s QA1795).
info note
the release engine binary used to include LLVM IR (bitcode).
however, apple deprecated bitcode in xcode 14 and removed support,
so it has been removed from the flutter 3.7 release.
of course, we recommend that you measure your own app.
to do that, see measuring your app’s size.
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how does flutter define a pixel?
flutter uses logical pixels,
and often refers to them merely as “pixels”.
flutter’s devicePixelRatio expresses the ratio
between physical pixels and logical CSS pixels.
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capabilities
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what kind of app performance can i expect?
you can expect excellent performance. flutter is
designed to help developers easily achieve a constant 60fps.
flutter apps run using natively compiled code—no
interpreters are involved.
this means that flutter apps start quickly.
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<topic_start>
what kind of developer cycles can i expect? how long between edit and refresh?
flutter implements a hot reload developer cycle. you can expect
sub-second reload times, on a device or an emulator/simulator.
flutter’s hot reload is stateful so the app state
is retained after a reload. this means you can quickly iterate
on a screen deeply nested in your app, without starting
from the home screen after every reload.
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<topic_start>
how is hot reload different from hot restart?
hot reload works by injecting updated source code files
into the running dart VM (virtual machine). this doesn’t
only add new classes, but also adds methods and fields
to existing classes, and changes existing functions.
hot restart resets the state to the app’s initial state.
for more information, see hot reload.
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<topic_start>
where can i deploy my flutter app?
you can compile and deploy your flutter app to iOS, android,
web, and desktop.
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