[url_launcher] Temporarily restore Android 21 support (#9986)

The change to drop API 21-23 support was intended to set the minimum Flutter version to 3.35, but didn't actually do so. This reverts the changes to drop 21-23, so that anyone who got the broken version can update to a working version, and then I'll follow up with a new PR that re-lands the change but with the missed SDK constraint change.

## 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/url_launcher/url_launcher_android/CHANGELOG.md

@@ -1,3 +1,8 @@
+## 6.3.20
+
+* Restore SDK 21-23 support, as the previous change was intended
+  to require Flutter 3.35, but didn't.
+
 ## 6.3.19
 
 * Updates minimum supported SDK version to Flutter 3.35.

packages/url_launcher/url_launcher_android/android/build.gradle

@@ -29,7 +29,7 @@ android {
     compileSdk = flutter.compileSdkVersion
 
     defaultConfig {
-        minSdkVersion 24
+        minSdkVersion 21
         testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
     }
 

packages/url_launcher/url_launcher_android/android/src/main/java/io/flutter/plugins/urllauncher/WebViewActivity.java

@@ -9,6 +9,7 @@
 import android.content.Context;
 import android.content.Intent;
 import android.content.IntentFilter;
+import android.os.Build;
 import android.os.Bundle;
 import android.os.Message;
 import android.provider.Browser;
@@ -19,6 +20,7 @@
 import android.webkit.WebViewClient;
 import androidx.annotation.NonNull;
 import androidx.annotation.Nullable;
+import androidx.annotation.RequiresApi;
 import androidx.annotation.VisibleForTesting;
 import androidx.core.content.ContextCompat;
 import java.util.Collections;
@@ -47,6 +49,7 @@ public void onReceive(Context context, Intent intent) {
 
   private final WebViewClient webViewClient =
       new WebViewClient() {
+        @RequiresApi(Build.VERSION_CODES.N)
         @Override
         public boolean shouldOverrideUrlLoading(WebView view, WebResourceRequest request) {
           view.loadUrl(request.getUrl().toString());
@@ -72,6 +75,17 @@ public boolean shouldOverrideUrlLoading(
               webview.loadUrl(request.getUrl().toString());
               return true;
             }
+
+            /*
+             * This method is deprecated in API 24. Still overridden to support
+             * earlier Android versions.
+             */
+            @SuppressWarnings("deprecation")
+            @Override
+            public boolean shouldOverrideUrlLoading(WebView view, String url) {
+              webview.loadUrl(url);
+              return true;
+            }
           };
 
       final WebView newWebView = new WebView(webview.getContext());

packages/url_launcher/url_launcher_android/pubspec.yaml

@@ -2,7 +2,7 @@ name: url_launcher_android
 description: Android implementation of the url_launcher plugin.
 repository: https://github.com/flutter/packages/tree/main/packages/url_launcher/url_launcher_android
 issue_tracker: https://github.com/flutter/flutter/issues?q=is%3Aissue+is%3Aopen+label%3A%22p%3A+url_launcher%22
-version: 6.3.19
+version: 6.3.20
 
 environment:
   sdk: ^3.7.0