[google_sign_in] Fix Android Java warnings (#3762)

Removes lint-baseline.xml, and fixes all resulting warnings. Also fixes some warnings that only show up in the AS linter as opportunistic fixes.

All anonymous object->lambda conversions were auto-generated by the AS auto-fix for those warnings.

Fixed an edge case bug found during warning fixes; the Dart `getTokens` call has an argument that was (I assume accidentally) declared as `bool? shouldRecoverAuth = true` instead of `bool shouldRecoverAuth = true`, which means that while it defaults to `true` if not passed, it can be explicitly passed `null` and will keep that value. This was being passed directly into the method channel, and on the Java side was extracted as a `boolean` which would throw an exception on null.

Part of flutter/flutter#88011

packages/google_sign_in/google_sign_in_android/CHANGELOG.md

@@ -1,3 +1,7 @@
+## 6.1.11
+
+* Fixes Java warnings.
+
 ## 6.1.10
 
 * Sets an explicit Java compatibility version.

packages/google_sign_in/google_sign_in_android/android/build.gradle

@@ -37,7 +37,6 @@ android {
         checkAllWarnings true
         warningsAsErrors true
         disable 'AndroidGradlePluginVersion', 'InvalidPackage', 'GradleDependency'
-        baseline file("lint-baseline.xml")
     }
 
 

packages/google_sign_in/google_sign_in_android/android/src/main/java/io/flutter/plugins/googlesignin/BackgroundTaskRunner.java

@@ -4,6 +4,7 @@
 
 package io.flutter.plugins.googlesignin;
 
+import androidx.annotation.NonNull;
 import com.google.common.util.concurrent.ListenableFuture;
 import com.google.common.util.concurrent.SettableFuture;
 import java.util.concurrent.BlockingQueue;
@@ -31,7 +32,7 @@ public interface Callback<T> {
      * the future is guaranteed not to block). If the future completed with an exception, then
      * {@code get()} will throw an {@code ExecutionException}.
      */
-    void run(Future<T> future);
+    void run(@NonNull Future<T> future);
   }
 
   private final ThreadPoolExecutor executor;
@@ -53,16 +54,9 @@ public BackgroundTaskRunner(int threads) {
    *
    * <p>The callback will be notified on the UI thread.
    */
-  public <T> void runInBackground(Callable<T> task, final Callback<T> callback) {
+  public <T> void runInBackground(@NonNull Callable<T> task, final @NonNull Callback<T> callback) {
     final ListenableFuture<T> future = runInBackground(task);
-    future.addListener(
-        new Runnable() {
-          @Override
-          public void run() {
-            callback.run(future);
-          }
-        },
-        Executors.uiThreadExecutor());
+    future.addListener(() -> callback.run(future), Executors.uiThreadExecutor());
   }
 
   /**
@@ -72,19 +66,16 @@ public void run() {
    * <p>Note: the future will be notified on the background thread. To be notified on the UI thread,
    * use {@link #runInBackground(Callable,Callback)}.
    */
-  public <T> ListenableFuture<T> runInBackground(final Callable<T> task) {
+  public @NonNull <T> ListenableFuture<T> runInBackground(final @NonNull Callable<T> task) {
     final SettableFuture<T> future = SettableFuture.create();
 
     executor.execute(
-        new Runnable() {
-          @Override
-          public void run() {
-            if (!future.isCancelled()) {
-              try {
-                future.set(task.call());
-              } catch (Throwable t) {
-                future.setException(t);
-              }
+        () -> {
+          if (!future.isCancelled()) {
+            try {
+              future.set(task.call());
+            } catch (Throwable t) {
+              future.setException(t);
             }
           }
         });

packages/google_sign_in/google_sign_in_android/android/src/main/java/io/flutter/plugins/googlesignin/Executors.java

@@ -6,6 +6,7 @@
 
 import android.os.Handler;
 import android.os.Looper;
+import androidx.annotation.NonNull;
 import java.util.concurrent.Executor;
 
 /**
@@ -16,7 +17,7 @@
  */
 public final class Executors {
 
-  private static final class UiThreadExecutor implements Executor {
+  static final class UiThreadExecutor implements Executor {
     private static final Handler UI_THREAD = new Handler(Looper.getMainLooper());
 
     @Override
@@ -26,7 +27,7 @@ public void execute(Runnable command) {
   }
 
   /** Returns an {@code Executor} that will post commands to the UI thread. */
-  public static Executor uiThreadExecutor() {
+  public static @NonNull Executor uiThreadExecutor() {
     return new UiThreadExecutor();
   }