Add haptic effect for the seekbar in Settings 3/n.

- in Pointer speed, perform haptic feedback as the seekbar's progress value is updated.
- screenshot, https://screenshot.googleplex.com/997TwHNc4TJtsG7

Bug: 174109628
Test: make -j42 RunSettingsRoboTests ROBOTEST_FILTER=PointerSpeedPreferenceTest
Change-Id: I385f290ae8ca39944eaeb054298db45da6acab4c

src/com/android/settings/PointerSpeedPreference.java

@@ -16,6 +16,8 @@
 
 package com.android.settings;
 
+import static android.view.HapticFeedbackConstants.CLOCK_TICK;
+
 import android.content.ContentResolver;
 import android.content.Context;
 import android.database.ContentObserver;
@@ -37,6 +39,7 @@ public class PointerSpeedPreference extends SeekBarDialogPreference implements
     private boolean mRestoredOldState;
 
     private boolean mTouchInProgress;
+    private int mLastProgress = -1;
 
     private ContentObserver mSpeedObserver = new ContentObserver(new Handler()) {
         @Override
@@ -76,6 +79,10 @@ public class PointerSpeedPreference extends SeekBarDialogPreference implements
         if (!mTouchInProgress) {
             mIm.tryPointerSpeed(progress + InputManager.MIN_POINTER_SPEED);
         }
+        if (progress != mLastProgress) {
+            seekBar.performHapticFeedback(CLOCK_TICK);
+            mLastProgress = progress;
+        }
     }
 
     public void onStartTrackingTouch(SeekBar seekBar) {

tests/robotests/src/com/android/settings/PointerSpeedPreferenceTest.java

@@ -0,0 +1,58 @@
+/*
+ * Copyright (C) 2020 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.settings;
+
+import static android.view.HapticFeedbackConstants.CLOCK_TICK;
+import static android.view.HapticFeedbackConstants.CONTEXT_CLICK;
+
+import static com.google.common.truth.Truth.assertThat;
+
+import static org.robolectric.Shadows.shadowOf;
+
+import android.content.Context;
+import android.util.AttributeSet;
+import android.widget.SeekBar;
+
+import org.junit.Before;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.robolectric.RobolectricTestRunner;
+import org.robolectric.RuntimeEnvironment;
+
+@RunWith(RobolectricTestRunner.class)
+public class PointerSpeedPreferenceTest {
+
+    private Context mContext;
+    private AttributeSet mAttrs;
+    private SeekBar mSeekBar;
+    private PointerSpeedPreference mPointerSpeedPreference;
+
+    @Before
+    public void setUp() {
+        mContext = RuntimeEnvironment.application;
+        mSeekBar = new SeekBar(mContext, mAttrs);
+        mPointerSpeedPreference = new PointerSpeedPreference(mContext, mAttrs);
+    }
+
+    @Test
+    public void onProgressChanged_minimumValue_clockTickFeedbackPerformed() {
+        mSeekBar.performHapticFeedback(CONTEXT_CLICK);
+        mPointerSpeedPreference.onProgressChanged(mSeekBar, 0, true);
+
+        assertThat(shadowOf(mSeekBar).lastHapticFeedbackPerformed()).isEqualTo(CLOCK_TICK);
+    }
+}