System action registration API for SystemUI

Bug: 136286274
Test: atest AccessibilityManagerTest
      atest AccessibilityManagerServiceTest
Change-Id: I6bbdf3627bfc9b39551cc7809dda1cf43d1d6ea4
diff --git a/tests/utils/testutils/Android.bp b/tests/utils/testutils/Android.bp
index f71be7b..a6625ab 100644
--- a/tests/utils/testutils/Android.bp
+++ b/tests/utils/testutils/Android.bp
@@ -22,6 +22,7 @@
     static_libs: [
         "junit",
         "hamcrest-library",
+        "androidx.test.runner",
     ],
 
     libs: [
diff --git a/tests/utils/testutils/java/com/android/server/accessibility/test/MessageCapturingHandler.java b/tests/utils/testutils/java/com/android/server/accessibility/test/MessageCapturingHandler.java
new file mode 100644
index 0000000..bce2ab5
--- /dev/null
+++ b/tests/utils/testutils/java/com/android/server/accessibility/test/MessageCapturingHandler.java
@@ -0,0 +1,118 @@
+/*
+ * Copyright (C) 2016 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.android.server.accessibility.test;
+
+import android.os.Handler;
+import android.os.Looper;
+import android.os.Message;
+import android.util.Pair;
+
+import androidx.test.InstrumentationRegistry;
+
+import java.util.ArrayList;
+import java.util.List;
+
+/**
+ * Utility class to capture messages dispatched through a handler and control when they arrive
+ * at their target.
+ */
+public class MessageCapturingHandler extends Handler {
+    public List<Pair<Message, Long>> timedMessages = new ArrayList<>();
+
+    Handler.Callback mCallback;
+
+    public MessageCapturingHandler(Handler.Callback callback) {
+        this(InstrumentationRegistry.getContext().getMainLooper(), callback);
+    }
+
+    public MessageCapturingHandler(Looper looper, Callback callback) {
+        super(looper);
+        mCallback = callback;
+    }
+
+    /**
+     * Holding messages in queue, but never dispatching.
+     * @see #removeAllMessages()
+     */
+    @Override
+    public boolean sendMessageAtTime(Message message, long uptimeMillis) {
+        timedMessages.add(new Pair<>(Message.obtain(message), uptimeMillis));
+        return super.sendMessageAtTime(message, Long.MAX_VALUE);
+    }
+
+    public void setCallback(Handler.Callback callback) {
+        mCallback = callback;
+    }
+
+    public void sendOneMessage() {
+        Message message = timedMessages.remove(0).first;
+        removeMessages(message.what, message.obj);
+        dispatchMessage(message);
+        removeStaleMessages();
+    }
+
+    public void sendAllMessages() {
+        while (!timedMessages.isEmpty()) {
+            sendOneMessage();
+        }
+    }
+
+    public void sendLastMessage() {
+        Message message = timedMessages.remove(timedMessages.size() - 1).first;
+        removeMessages(message.what, message.obj);
+        dispatchMessage(message);
+        removeStaleMessages();
+    }
+
+    /**
+     * Clear messages sent from this handler in queue.
+     * <p>
+     * If main looper is used, this method should be called in tear down function
+     * to ensure messages isolation between test cases.
+     * </p>
+     */
+    public void removeAllMessages() {
+        if (hasMessages()) {
+            for (int i = 0; i < timedMessages.size(); i++) {
+                Message message = timedMessages.get(i).first;
+                removeMessages(message.what, message.obj);
+            }
+        }
+    }
+
+    public boolean hasMessages() {
+        removeStaleMessages();
+        return !timedMessages.isEmpty();
+    }
+
+    private void removeStaleMessages() {
+        for (int i = 0; i < timedMessages.size(); i++) {
+            Message message = timedMessages.get(i).first;
+            if (!hasMessages(message.what, message.obj)) {
+                timedMessages.remove(i--);
+            }
+        }
+    }
+
+    public void dispatchMessage(Message m) {
+        if (mCallback != null) {
+            mCallback.handleMessage(m);
+            return;
+        }
+        super.dispatchMessage(m);
+    }
+}