Warnings unchecked or unsafe

[kikoba]

When compiling any code (example included) I get these warnings: if I clean build folder

Note: Some input files use unchecked or unsafe operations.
Note: Recompile with -Xlint:unchecked for details.

the warnings are for:

...build\barcode_scan\generated\source\proto\release\javalite\de\mintware\barcode_scan\AndroidConfigurationOuterClass.java:396: warning: [unchecked] unchecked call to DefaultInstanceBasedParser(T) as a member of the raw type DefaultInstanceBasedParser
                PARSER = new DefaultInstanceBasedParser(DEFAULT_INSTANCE);
                         ^
  where T is a type-variable:
    T extends GeneratedMessageLite<T,?> declared in class DefaultInstanceBasedParser
... 
build\barcode_scan\generated\source\proto\release\javalite\de\mintware\barcode_scan\AndroidConfigurationOuterClass.java:396: warning: [unchecked] unchecked conversion
                PARSER = new DefaultInstanceBasedParser(DEFAULT_INSTANCE);
                         ^
  required: Parser<AndroidConfiguration>
  found:    DefaultInstanceBasedParser
...
build\barcode_scan\generated\source\proto\release\javalite\de\mintware\barcode_scan\Protos.java:645: warning: [unchecked] unchecked conversion
                PARSER = new DefaultInstanceBasedParser(DEFAULT_INSTANCE);
                         ^
  required: Parser<AndroidConfiguration>
  found:    DefaultInstanceBasedParser
...
build\barcode_scan\generated\source\proto\release\javalite\de\mintware\barcode_scan\ScanResultOuterClass.java:884: warning: [unchecked] unchecked call to DefaultInstanceBasedParser(T) as a member of the raw type DefaultInstanceBasedParser
                PARSER = new DefaultInstanceBasedParser(DEFAULT_INSTANCE);
                         ^
  where T is a type-variable:
    T extends GeneratedMessageLite<T,?> declared in class DefaultInstanceBasedParser
erClass.java:884: warning: [unchecked] unchecked conversion
                PARSER = new DefaultInstanceBasedParser(DEFAULT_INSTANCE);
                         ^
  required: Parser<ScanResult>
  found:    DefaultInstanceBasedParser

...more others similar.

is it possible to remove them? I use Android.

[√] Flutter (Channel stable, 1.22.0, on Microsoft Windows [Versione 10.0.19041.508], locale it-IT)
[√] Android toolchain - develop for Android devices (Android SDK version 29.0.2)
[√] Android Studio (version 4.0)