[shared_preferences] Replace AsyncTask class with AsyncHandler to handle async task for Android

packages/shared_preferences/shared_preferences/android/src/main/java/io/flutter/plugins/sharedpreferences/AsyncHandler.java

@@ -0,0 +1,75 @@
+package io.flutter.plugins.sharedpreferences;
+
+import android.os.Handler;
+import android.os.Looper;
+import java.util.Iterator;
+import java.util.ServiceLoader;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.concurrent.ThreadFactory;
+
+/** Helper class to handle async tasks */
+class AsyncHandler {
+  private ExecutorService executorService;
+
+  private final Handler handler;
+
+  public AsyncHandler() {
+    Iterator<ExecutorService> executorServiceIterator =
+        ServiceLoader.load(ExecutorService.class).iterator();
+    if (executorServiceIterator.hasNext()) {
+      executorService = executorServiceIterator.next();
+    } else {
+      executorService =
+          Executors.newSingleThreadExecutor(
+              new ThreadFactory() {
+                @Override
+                public Thread newThread(Runnable r) {
+                  Thread thread = new Thread(r, "SharedPreferencesAsync");
+                  thread.setDaemon(true);
+                  return thread;
+                }
+              });
+    }
+    handler = new Handler(Looper.getMainLooper());
+  }
+
+  public <R> void executeAsync(
+      final Callable<R> executeInBackground, final Callback<R> resultCallback) {
+    executorService.execute(
+        new Runnable() {
+          @Override
+          public void run() {
+            try {
+              final R result = executeInBackground.call();
+              handler.post(
+                  new Runnable() {
+                    @Override
+                    public void run() {
+                      resultCallback.onComplete(result);
+                    }
+                  });
+            } catch (final Exception ex) {
+              handler.post(
+                  new Runnable() {
+                    @Override
+                    public void run() {
+                      resultCallback.onError(ex);
+                    }
+                  });
+            }
+          }
+        });
+  }
+
+  public interface Callback<R> {
+    void onError(Exception e);
+
+    void onComplete(R result);
+  }
+
+  public interface Callable<V> {
+
+    V call() throws Exception;
+  }
+}

packages/shared_preferences/shared_preferences/android/src/main/java/io/flutter/plugins/sharedpreferences/MethodCallHandlerImpl.java

@@ -6,7 +6,6 @@
 
 import android.content.Context;
 import android.content.SharedPreferences;
-import android.os.AsyncTask;
 import android.util.Base64;
 import io.flutter.plugin.common.MethodCall;
 import io.flutter.plugin.common.MethodChannel;
@@ -38,12 +37,15 @@ class MethodCallHandlerImpl implements MethodChannel.MethodCallHandler {
 
   private final android.content.SharedPreferences preferences;
 
+  private final AsyncHandler asyncHandler;
+
   /**
    * Constructs a {@link MethodCallHandlerImpl} instance. Creates a {@link
    * android.content.SharedPreferences} based on the {@code context}.
    */
   MethodCallHandlerImpl(Context context) {
     preferences = context.getSharedPreferences(SHARED_PREFERENCES_NAME, Context.MODE_PRIVATE);
+    asyncHandler = new AsyncHandler();
   }
 
   @Override
@@ -118,17 +120,24 @@ public void onMethodCall(MethodCall call, MethodChannel.Result result) {
 
   private void commitAsync(
       final SharedPreferences.Editor editor, final MethodChannel.Result result) {
-    new AsyncTask<Void, Void, Boolean>() {
-      @Override
-      protected Boolean doInBackground(Void... voids) {
-        return editor.commit();
-      }
+    asyncHandler.executeAsync(
+        new AsyncHandler.Callable<Boolean>() {
+          @Override
+          public Boolean call() {
+            return editor.commit();
+          }
+        },
+        new AsyncHandler.Callback<Boolean>() {
+          @Override
+          public void onError(Exception e) {
+            result.error(e.getClass().getName(), e.getLocalizedMessage(), e.getMessage());
+          }
 
-      @Override
-      protected void onPostExecute(Boolean value) {
-        result.success(value);
-      }
-    }.execute();
+          @Override
+          public void onComplete(Boolean resultValue) {
+            result.success(resultValue);
+          }
+        });
   }
 
   private List<String> decodeList(String encodedList) throws IOException {