Refactor HandlerInjector to SettingsLib

- Plan to share the HandlerInjector class to System UI.

Bug: 194186477
Test: manual test
make RunSettingsLibRoboTests ROBOTEST_FILTER=HandlerInjectorTest

Change-Id: Iedec9c9372f32d26ba3b99ec656f8b962731a1f2

packages/SettingsLib/src/com/android/settingslib/utils/HandlerInjector.java

@@ -0,0 +1,41 @@
+/*
+ * Copyright (C) 2021 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.settingslib.utils;
+
+import android.os.Handler;
+
+/**
+ * Wrapper the {@link android.os.Handler} for testing compatibility.
+ */
+public class HandlerInjector {
+
+    protected final Handler mHandler;
+
+    public HandlerInjector(Handler handler) {
+        mHandler = handler;
+    }
+
+    /**  Wrapper the {@link android.os.Handler#postDelayed} for testing compatibility. */
+    public void postDelayed(Runnable runnable, long delayMillis) {
+        mHandler.postDelayed(runnable, delayMillis);
+    }
+
+    /**  Wrapper the {@link android.os.Handler#removeCallbacks} for testing compatibility. */
+    public void removeCallbacks(Runnable runnable) {
+        mHandler.removeCallbacks(runnable);
+    }
+}

packages/SettingsLib/tests/robotests/src/com/android/settingslib/utils/HandlerInjectorTest.java

@@ -0,0 +1,64 @@
+/*
+ * Copyright (C) 2021 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.settingslib.utils;
+
+import static org.mockito.Mockito.verify;
+
+import android.os.Handler;
+
+import org.junit.Before;
+import org.junit.Rule;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.mockito.Mock;
+import org.mockito.junit.MockitoJUnit;
+import org.mockito.junit.MockitoRule;
+import org.robolectric.RobolectricTestRunner;
+
+@RunWith(RobolectricTestRunner.class)
+public class HandlerInjectorTest {
+
+    public static final long TEST_DELAY_MILLIS = 0L;
+
+    @Rule
+    public final MockitoRule mMockitoRule = MockitoJUnit.rule();
+    @Mock
+    public Handler mHandler;
+    @Mock
+    public Runnable mRunnable;
+
+    private HandlerInjector mHandlerInjector;
+
+    @Before
+    public void setUp() {
+        mHandlerInjector = new HandlerInjector(mHandler);
+    }
+
+    @Test
+    public void postDelayed_doByMainThreadHandler() {
+        mHandlerInjector.postDelayed(mRunnable, TEST_DELAY_MILLIS);
+
+        verify(mHandler).postDelayed(mRunnable, TEST_DELAY_MILLIS);
+    }
+
+    @Test
+    public void removeCallbacks_doByMainThreadHandler() {
+        mHandlerInjector.removeCallbacks(mRunnable);
+
+        verify(mHandler).removeCallbacks(mRunnable);
+    }
+}