[Slider] Fixed behaviour when Slider is in a scrolling container

Resolves #833

GIT_ORIGIN_REV_ID=86b976f757fb8354ffe502c5acc32b6954890bb9
PiperOrigin-RevId: 286431744

Author: rubensousa

catalog/java/io/material/catalog/slider/SliderFragment.java

@@ -70,6 +70,13 @@ public Fragment createFragment() {
             return new SliderDiscreteDemoFragment();
           }
         });
+    additionalDemos.add(
+        new Demo(R.string.cat_slider_demo_scroll_container_title) {
+          @Override
+          public Fragment createFragment() {
+            return new SliderScrollContainerDemoFragment();
+          }
+        });
     return additionalDemos;
   }
 

catalog/java/io/material/catalog/slider/SliderScrollContainerDemoFragment.java

@@ -0,0 +1,51 @@
+/*
+ * Copyright 2019 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
+ *
+ *     https://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 io.material.catalog.slider;
+
+import io.material.catalog.R;
+
+import android.os.Bundle;
+import androidx.annotation.Nullable;
+import android.view.LayoutInflater;
+import android.view.View;
+import android.view.ViewGroup;
+import android.widget.LinearLayout;
+import com.google.android.material.slider.Slider;
+import io.material.catalog.feature.DemoFragment;
+
+/**
+ * A fragment that displays a list of {@link Slider} inside a ScrollView to showcase how touch
+ * events are handled.
+ */
+public class SliderScrollContainerDemoFragment extends DemoFragment {
+
+  @Override
+  public View onCreateDemoView(
+      LayoutInflater layoutInflater, @Nullable ViewGroup viewGroup, @Nullable Bundle bundle) {
+    View view =
+        layoutInflater.inflate(
+            R.layout.cat_slider_demo_scroll, viewGroup, false /* attachToRoot */);
+    LinearLayout sliderContainer = view.findViewById(R.id.sliderContainer);
+    for (int i = 0; i < 50; i++) {
+      sliderContainer.addView(
+          new Slider(layoutInflater.getContext()),
+          ViewGroup.LayoutParams.MATCH_PARENT,
+          ViewGroup.LayoutParams.WRAP_CONTENT);
+    }
+    return view;
+  }
+}

catalog/java/io/material/catalog/slider/res/layout/cat_slider_demo_scroll.xml

@@ -0,0 +1,32 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!--
+  Copyright 2019 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.
+  -->
+<ScrollView
+    xmlns:android="http://schemas.android.com/apk/res/android"
+    android:layout_width="match_parent"
+    android:layout_height="match_parent">
+
+  <LinearLayout
+    android:id="@+id/sliderContainer"
+      android:layout_width="match_parent"
+      android:layout_height="wrap_content"
+      android:paddingLeft="16dp"
+      android:paddingRight="16dp"
+      android:orientation="vertical">
+
+
+  </LinearLayout>
+</ScrollView>

catalog/java/io/material/catalog/slider/res/values/strings.xml

@@ -18,6 +18,7 @@
   <string name="cat_slider_title" description="Title for the screen that showcases demonstrative usages of the Slider widget">Slider</string>
   <string name="cat_slider_demo_continuous_title" description="Title for the continuous Slider widget demo">Continuous Slider demo</string>
   <string name="cat_slider_demo_discrete_title" description="Title for the discrete Slider widget demo">Discrete Slider demo</string>
+  <string name="cat_slider_demo_scroll_container_title" description="Title for the Slider inside scrolling container demo">Slider in scrolling container demo</string>
 
   <string name="cat_slider_description" description="Body text describing the Slider widget within the design system [CHAR LIMIT=NONE]">
     Sliders let users select from a range of values by moving the slider thumb.

lib/java/com/google/android/material/slider/Slider.java

@@ -52,6 +52,9 @@
 import android.view.InflateException;
 import android.view.MotionEvent;
 import android.view.View;
+import android.view.ViewConfiguration;
+import android.view.ViewGroup;
+import android.view.ViewParent;
 import com.google.android.material.drawable.DrawableUtils;
 import com.google.android.material.internal.DescendantOffsetUtils;
 import com.google.android.material.internal.ThemeEnforcement;
@@ -179,6 +182,8 @@ public class Slider extends View {
 
   @NonNull private TooltipDrawable label;
 
+  private final int scaledTouchSlop;
+
   private int widgetHeight;
   private boolean floatingLabel;
   private int trackHeight;
@@ -187,6 +192,7 @@ public class Slider extends View {
   private int thumbRadius;
   private int haloRadius;
   private int labelPadding;
+  private float touchDownX;
   private OnChangeListener listener;
   private LabelFormatter formatter;
   private boolean thumbIsPressed = false;
@@ -315,6 +321,8 @@ public void onFocusChange(View v, boolean hasFocus) {
 
     // Set up the thumb drawable to always show the compat shadow.
     thumbDrawable.setShadowCompatibilityMode(MaterialShapeDrawable.SHADOW_COMPAT_MODE_ALWAYS);
+
+    scaledTouchSlop = ViewConfiguration.get(context).getScaledTouchSlop();
   }
 
   private void loadResources(@NonNull Resources resources) {
@@ -924,6 +932,12 @@ public boolean onTouchEvent(@NonNull MotionEvent event) {
 
     switch (event.getActionMasked()) {
       case MotionEvent.ACTION_DOWN:
+        // If we're inside a scrolling container,
+        // we should start dragging in ACTION_MOVE
+        if (isInScrollingContainer()) {
+          touchDownX = event.getX();
+          break;
+        }
         getParent().requestDisallowInterceptTouchEvent(true);
         requestFocus();
         thumbIsPressed = true;
@@ -938,6 +952,14 @@ public boolean onTouchEvent(@NonNull MotionEvent event) {
         }
         break;
       case MotionEvent.ACTION_MOVE:
+        if (!thumbIsPressed) {
+          // Check if we're trying to scroll instead of dragging this Slider
+          if (Math.abs(x - touchDownX) < scaledTouchSlop) {
+            return false;
+          }
+          getParent().requestDisallowInterceptTouchEvent(true);
+        }
+        thumbIsPressed = true;
         thumbPosition = position;
         snapThumbPosition();
         updateHaloHotSpot();
@@ -1008,6 +1030,24 @@ private void invalidateTrack() {
     activeTicksPaint.setStrokeWidth(trackHeight / 2.0f);
   }
 
+  /**
+   * If this returns true, we can't start dragging the Slider immediately when we receive a {@link
+   * MotionEvent#ACTION_DOWN}. Instead, we must wait for a {@link MotionEvent#ACTION_MOVE}. Copied
+   * from hidden method of {@link View} isInScrollingContainer.
+   *
+   * @return true if any of this View's parents is a scrolling View.
+   */
+  private boolean isInScrollingContainer() {
+    ViewParent p = getParent();
+    while (p instanceof ViewGroup) {
+      if (((ViewGroup) p).shouldDelayChildPressedState()) {
+        return true;
+      }
+      p = p.getParent();
+    }
+    return false;
+  }
+
   @Override
   protected void drawableStateChanged() {
     super.drawableStateChanged();