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play-store-based implementation that the validator checks for.
the validator detects any new, changed, or removed
loading units generated by gen_snapshot.
the current generated loading units are tracked in your
<projectdirectory>/deferred_components_loading_units.yaml file.
this file should be checked into source control to ensure that
changes to the loading units by other developers can be caught.
the validator also checks for the following in the
android directory:
<projectdir>/android/app/src/main/res/values/strings.xml
an entry for every deferred component mapping the key
${componentname}name to ${componentname}.
this string resource is used by the AndroidManifest.xml
of each feature module to define the dist:title property.
for example:
<projectdir>/android/<componentname>
an android dynamic feature module for
each deferred component exists and contains a build.gradle
and src/main/AndroidManifest.xml file.
this only checks for existence and does not validate
the contents of these files. if a file does not exist,
it generates a default recommended one.
<projectdir>/android/app/src/main/res/values/androidmanifest.xml
contains a meta-data entry that encodes
the mapping between loading units and component name the
loading unit is associated with. this mapping is used by the
embedder to convert dart’s internal loading unit id
to the name of a deferred component to install. for example:
the gen_snapshot validator won’t run until the prebuild
validator passes.
for each of these checks,
the tool produces the modified or new files
needed to pass the check.
these files are placed in the
<projectdir>/build/android_deferred_components_setup_files directory.
it is recommended that the changes be applied by
copying and overwriting the same files in the
project’s android directory. before overwriting,
the current project state should be committed to
source control and the recommended changes should be
reviewed to be appropriate. the tool won’t make any
changes to your android/ directory automatically.
once the available
loading units are generated and logged in
<projectdirectory>/deferred_components_loading_units.yaml,
it is possible to fully configure the pubspec’s
deferred-components section so that the loading units
are assigned to deferred components as desired.
to continue with the box example, the generated
deferred_components_loading_units.yaml file would contain:
the loading unit id (‘2’ in this case) is used
internally by dart, and can be ignored.
the base loading unit (id ‘1’) is not listed
and contains everything not explicitly contained
in another loading unit.
you can now add the following to pubspec.yaml:
to assign a loading unit to a deferred component,
add any dart lib in the loading unit into the
libraries section of the feature module.
keep the following guidelines in mind:
loading units should not be included
in more than one component.
including one dart library from a
loading unit indicates that the entire loading
unit is assigned to the deferred component.
all loading units not assigned to
a deferred component are included in the base component,
which always exists implicitly.
loading units assigned to the same
deferred component are downloaded, installed,
and shipped together.
the base component is implicit and
need not be defined in the pubspec.
assets can also be included by adding
an assets section in the deferred component configuration:
an asset can be included in multiple deferred components,
but installing both components results in a replicated asset.
assets-only components can also be defined by omitting the
libraries section. these assets-only components must be
installed with the DeferredComponent utility class in
services rather than loadLibrary().
since dart libs are packaged together with assets,
if a dart library is loaded with loadLibrary(),
any assets in the component are loaded as well.
however, installing by component name and the services utility
won’t load any dart libraries in the component.
you are free to include assets in any component,
as long as they are installed and loaded when they
are first referenced, though typically,
assets and the dart code that uses those assets
are best packed in the same component.
manually add all deferred components
that you defined in pubspec.yaml into the
android/settings.gradle file as includes.
for example, if there are three deferred components
defined in the pubspec named, boxComponent, circleComponent,
and assetComponent, ensure that android/settings.gradle
contains the following:
repeat steps 3.1 through 3.6 (this step)
until all validator recommendations are handled and the tool