Issue 1:
After upgrading Flutter, when I build my app I started getting following error :

Execution failed for task ':app:processDebugManifest'. [ +5 ms] >
Manifest merger failed : Attribute
meta-data#android.support.VERSION@value value=(25.4.0) from
[com.android.support:appcompat-v7:25.4.0] AndroidManifest.xml:28:13-35
[ +23 ms] is also present at
[com.android.support:support-v4:26.1.0] AndroidManifest.xml:28:13-35
value=(26.1.0). [ +8 ms] Suggestion: add
'tools:replace="android:value"' to <meta-data> element at
AndroidManifest.xml:26:9-28:38 to override.

As explained in https://stackoverflow.com/questions/43140059/add-toolsreplace-androidvalue-to-meta-data-element-at-androidmanifest and

https://stackoverflow.com/questions/43280871/android-getting-manifest-merger-failed-error-after-updating-to-a-new-version/44931003 SO answers i added the

configurations.all {
resolutionStrategy.eachDependency { DependencyResolveDetails details ->
def requested = details.requested
if (requested.group == 'com.android.support') {
if (!requested.name.startsWith("multidex")) {
details.useVersion '25.4.0'
}
}
}
}

to my app folder build.gradle :

def localProperties = new Properties()
def localPropertiesFile = rootProject.file('local.properties')
if (localPropertiesFile.exists()) {
localPropertiesFile.withReader('UTF-8') { reader ->
localProperties.load(reader)
}
}

def flutterRoot = localProperties.getProperty('flutter.sdk')
if (flutterRoot == null) {
throw new GradleException("Flutter SDK not found. Define location with flutter.sdk in the local.properties file.")
}

apply plugin: 'com.android.application'
apply from: "$flutterRoot/packages/flutter_tools/gradle/flutter.gradle"

android {
compileSdkVersion 27

lintOptions {
disable 'InvalidPackage'
}

defaultConfig {
// TODO: Specify your own unique Application ID (https://developer.android.com/studio/build/application-id.html).
applicationId "com.yourcompany.chatapp"
minSdkVersion 16
targetSdkVersion 27
versionCode 1
versionName "1.0"
testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
}

buildTypes {
release {
// TODO: Add your own signing config for the release build.
// Signing with the debug keys for now, so `flutter run --release` works.
signingConfig signingConfigs.debug
}
}
}

flutter {
source '../..'
}

dependencies {
testImplementation 'junit:junit:4.12'
androidTestImplementation 'com.android.support.test:runner:1.0.1'
androidTestImplementation 'com.android.support.test.espresso:espresso-core:3.0.1'
}
configurations.all {
resolutionStrategy.eachDependency { DependencyResolveDetails details ->
def requested = details.requested
if (requested.group == 'com.android.support') {
if (!requested.name.startsWith("multidex")) {
details.useVersion '25.4.0'
}
}
}
}
apply plugin: 'com.google.gms.google-services'

Now whenever i run my app i get the following Error :

Error -32601 received from application: Method not found

I have tried by running flutter clean, the error still persists.

Here is output of flutter doctor :

Doctor summary (to see all details, run flutter doctor -v):
[√] Flutter (Channel beta, v0.3.1, on Microsoft Windows [Version 10.0.16299.371], locale en-US)
[√] Android toolchain - develop for Android devices (Android SDK 28.0.0-rc1)
[√] Android Studio (version 3.1)
[√] Connected devices (1 available)

• No issues found!

Issue 2:
pressing 'r' results in error

Error -32601 received from application: Method not found
Hot reload was rejected:
'package:flutter/src/semantics/semantics.dart': malformed type: line 2126 pos 17: cannot resolve class 'SemanticsFlag' from 'SemanticsConfiguration'
void _setFlag(SemanticsFlag flag, bool value) {
^

C:\src\flutter\flutter\examples\flutter_gallery [master ≡ +4 ~3 -0 !]> ..\..\bin\flutter run
Running "flutter packages get" in flutter_gallery... 3.4s
Launching lib/main.dart on Pixel in debug mode...
Initializing gradle... 2.7s
Resolving dependencies... 14.2s
Running 'gradlew assembleDebug'... 20.2s
Built build\app\outputs\apk\app-debug.apk (28.8MB).
Installing build\app\outputs\apk\app.apk... 16.1s
I/FlutterActivityDelegate( 2563): onResume setting current activity to this
Syncing files to device Pixel... 4.5s

🔥 To hot reload your app on the fly, press "r". To restart the app entirely, press "R".
An Observatory debugger and profiler on Pixel is available at: http://127.0.0.1:8100/
For a more detailed help message, press "h". To quit, press "q".

Initializing hot reload...
Error -32601 received from application: Method not found
Hot reload was rejected:
'package:flutter/src/semantics/semantics.dart': malformed type: line 2126 pos 17: cannot resolve class 'SemanticsFlag' from 'SemanticsConfiguration'
void _setFlag(SemanticsFlag flag, bool value) {
^

Try again after fixing the above error(s).
Application finished.
Terminate batch job (Y/N)? y
C:\src\flutter\flutter\examples\flutter_gallery [master ≡ +4 ~3 -0 !]> ..\..\bin\flutter doctor
Doctor summary (to see all details, run flutter doctor -v):
[√] Flutter (on Microsoft Windows [Version 10.0.14393], locale en-US, channel master)
[√] Android toolchain - develop for Android devices (Android SDK 27.0.1)
[√] Android Studio (version 3.0)
[√] IntelliJ IDEA Ultimate Edition (version 2017.3)
[√] Connected devices

• No issues found!
C:\src\flutter\flutter\examples\flutter_gallery [master ≡ +4 ~3 -0 !]> git reflog -1
83e0ca24f (HEAD -> master, upstream/master, origin/master, origin/HEAD) HEAD@{0}: pull upstream master: Fast-forward