Xcode 8 Recommend Me to Change the Min iOS Deployment Target from 7.1 to 8.0

iOS simulator showing different sizes on 7.1 than 8.0

@rmaddy is right.

You need to set a splash image instead of using the LaunchScreen.xib.
Go to your project settings -> target -> App Icons and Launch Images, change "Lauch Images Source" by clicking "Use Asset Catalog", select Images.

you need to change this
select "images"
final result

The iOS deployment target 'IPHONEOS_DEPLOYMENT_TARGET' is set to 8.0, in Flutter How can I change the minimum IOS Deploying Target

I solve it with this code, thanks!
At the end of the PodFile

post_install do |installer|
  installer.pods_project.targets.each do |target|
    target.build_configurations.each do |config|
      config.build_settings.delete 'IPHONEOS_DEPLOYMENT_TARGET'
    end
  end
end

What does deployment target mean?

Lets say you have set minimum deployment target to iOS 9.
This means your application is compatible for iOS 9 and above devices.

The application won't run on below 9.0 devices but can run on any iOS version greater than iOS 9.0.

Minimal Deployment target available for new publishings in the App Store

Yes, you can still publish an application with a deployment target of iOS >8.0. All that matters is whether your app is built with the iOS 12 SDK (basically, if you're building with Xcode 10, it's a given).

Xcode iOS deployment target check?

You can check your deployment target version via __IPHONE_OS_VERSION_MIN_REQUIRED macro and compare it to some sdk version, e.g. to make sure that your deployment target is 4.0 put the following lines somewhere:

#if  __IPHONE_OS_VERSION_MIN_REQUIRED != __IPHONE_4_0

#error wrong deployment target - should be 4.0

#endif