[various] Scrubs pre-SDK-21 Android code (#9112)

- Removes any annotations or runtime checks related to Android API 20 or 21, as 21 is the minimum API version supported by the versions of Flutter these plugins support.
- Removes comment/README references to limitations for <21.
- Updates READMEs for app-facing packages to reflect the current support levels.

Fixes flutter/flutter#157106

## Pre-Review Checklist

[^1]: Regular contributors who have demonstrated familiarity with the repository guidelines only need to comment if the PR is not auto-exempted by repo tooling.

Author: stuartmorgan-g

packages/camera/camera_android/android/src/test/java/io/flutter/plugins/camera/CameraTest.java

@@ -663,7 +663,7 @@ public void setDescriptionWhileRecording_errorsWhenUnsupported() {
     camera.mediaRecorder = mockMediaRecorder;
     camera.recordingVideo = true;
     camera.videoRenderer = mockVideoRenderer;
-    SdkCapabilityChecker.SDK_VERSION = Build.VERSION_CODES.LOLLIPOP;
+    SdkCapabilityChecker.SDK_VERSION = Build.VERSION_CODES.N;
 
     final CameraProperties newCameraProperties = mock(CameraProperties.class);
     assertThrows(

packages/camera/camera_android/example/android/build.gradle

@@ -30,7 +30,8 @@ tasks.register("clean", Delete) {
 gradle.projectsEvaluated {
     project(":camera_android") {
         tasks.withType(JavaCompile) {
-            options.compilerArgs << "-Xlint:all" << "-Werror"
+            // Ignore classfile due to https://issuetracker.google.com/issues/342067844
+            options.compilerArgs << "-Xlint:all" << "-Werror" << "-Xlint:-classfile"
         }
     }
 }

packages/espresso/CHANGELOG.md

@@ -1,3 +1,7 @@
+## 0.4.0+7
+
+* Removes obsolete code related to supporting SDK <21.
+
 ## 0.4.0+6
 
 * Updates compileSdk 34 to flutter.compileSdkVersion.

packages/espresso/README.md

@@ -4,7 +4,7 @@ Provides bindings for Espresso tests of Flutter Android apps.
 
 |             | Android |
 |-------------|---------|
-| **Support** | SDK 16+ |
+| **Support** | SDK 21+ |
 
 ## Installation
 

packages/espresso/android/build.gradle

@@ -26,7 +26,7 @@ android {
     compileSdk = flutter.compileSdkVersion
 
     defaultConfig {
-        minSdkVersion 19
+        minSdkVersion 21
         testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
     }
 

packages/espresso/pubspec.yaml

@@ -3,7 +3,7 @@ description: Java classes for testing Flutter apps using Espresso.
   Allows driving Flutter widgets from a native Espresso test.
 repository: https://github.com/flutter/packages/tree/main/packages/espresso
 issue_tracker: https://github.com/flutter/flutter/issues?q=is%3Aissue+is%3Aopen+label%3A%22p%3A+espresso%22
-version: 0.4.0+6
+version: 0.4.0+7
 
 environment:
   sdk: ^3.6.0

packages/file_selector/file_selector/CHANGELOG.md

@@ -1,5 +1,6 @@
 ## NEXT
 
+* Updates README to indicate that Andoid SDK <21 is no longer supported.
 * Updates minimum supported SDK version to Flutter 3.22/Dart 3.4.
 
 ## 1.0.3

packages/file_selector/file_selector/README.md

@@ -8,7 +8,7 @@ A Flutter plugin that manages files and interactions with file dialogs.
 
 |             | Android | iOS     | Linux | macOS  | Web | Windows     |
 |-------------|---------|---------|-------|--------|-----|-------------|
-| **Support** | SDK 19+ | iOS 12+ | Any   | 10.14+ | Any | Windows 10+ |
+| **Support** | SDK 21+ | iOS 12+ | Any   | 10.14+ | Any | Windows 10+ |
 
 ## Setup
 
@@ -114,9 +114,7 @@ pass different `XTypeGroup`s based on `Platform`.
 | Choose a single file   | Pick a file/image                  | ✔️       | ✔️       | ✔️        | ✔️       | ✔️          | ✔️          |
 | Choose multiple files  | Pick multiple files/images         | ✔️       | ✔️       | ✔️        | ✔️       | ✔️          | ✔️          |
 | Choose a save location | Pick a directory to save a file in | ❌       | ❌       | ✔️        | ✔️       | ✔️          | ❌          |
-| Choose a directory     | Pick a directory and get its path  | ✔️†       | ❌       | ✔️        | ✔️       | ✔️          | ❌          |
-
-† Choosing a directory is no supported on versions of Android before SDK 21 (Lollipop).
+| Choose a directory     | Pick a directory and get its path  | ✔️       | ❌       | ✔️        | ✔️       | ✔️          | ❌          |
 
 [example]:./example
 [entitlement]: https://docs.flutter.dev/desktop#entitlements-and-the-app-sandbox

packages/file_selector/file_selector_android/CHANGELOG.md

@@ -1,3 +1,7 @@
+## 0.5.1+14
+
+* Removes obsolete code related to supporting SDK <21.
+
 ## 0.5.1+13
 
 * Updates compileSdk 34 to flutter.compileSdkVersion.

packages/file_selector/file_selector_android/android/build.gradle

@@ -31,7 +31,7 @@ android {
     }
 
     defaultConfig {
-        minSdkVersion 19
+        minSdkVersion 21
     }
 
     dependencies {