Using edge effect to trigger spring animation for all apps.

Bug: 72811152
Bug: 72059944

Change-Id: Ied7b51caa2fb48a2fda126d59e4eaf6a35edded3

src/com/android/launcher3/views/SpringRelativeLayout.java

@@ -0,0 +1,157 @@
+/*
+ * Copyright (C) 2018 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.launcher3.views;
+
+import android.content.Context;
+import android.graphics.Canvas;
+import android.support.animation.FloatPropertyCompat;
+import android.support.animation.SpringAnimation;
+import android.support.animation.SpringForce;
+import android.support.annotation.NonNull;
+import android.support.v7.widget.RecyclerView;
+import android.support.v7.widget.RecyclerView.EdgeEffectFactory;
+import android.util.AttributeSet;
+import android.util.Log;
+import android.util.SparseBooleanArray;
+import android.view.View;
+import android.widget.EdgeEffect;
+import android.widget.RelativeLayout;
+
+import static android.support.animation.SpringForce.DAMPING_RATIO_MEDIUM_BOUNCY;
+import static android.support.animation.SpringForce.STIFFNESS_LOW;
+import static android.support.animation.SpringForce.STIFFNESS_MEDIUM;
+
+public class SpringRelativeLayout extends RelativeLayout {
+
+    private static final float STIFFNESS = (STIFFNESS_MEDIUM + STIFFNESS_LOW) / 2;
+    private static final float DAMPING_RATIO = DAMPING_RATIO_MEDIUM_BOUNCY;
+    private static final float VELOCITY_MULTIPLIER = 0.3f;
+
+    private static final FloatPropertyCompat<SpringRelativeLayout> DAMPED_SCROLL =
+            new FloatPropertyCompat<SpringRelativeLayout>("value") {
+
+                @Override
+                public float getValue(SpringRelativeLayout object) {
+                    return object.mDampedScrollShift;
+                }
+
+                @Override
+                public void setValue(SpringRelativeLayout object, float value) {
+                    object.setDampedScrollShift(value);
+                }
+            };
+
+    private final SparseBooleanArray mSpringViews = new SparseBooleanArray();
+    private final SpringAnimation mSpring;
+
+    private float mDampedScrollShift = 0;
+
+    public SpringRelativeLayout(Context context) {
+        this(context, null);
+    }
+
+    public SpringRelativeLayout(Context context, AttributeSet attrs) {
+        this(context, attrs, 0);
+    }
+
+    public SpringRelativeLayout(Context context, AttributeSet attrs, int defStyleAttr) {
+        super(context, attrs, defStyleAttr);
+        mSpring = new SpringAnimation(this, DAMPED_SCROLL, 0);
+        mSpring.setSpring(new SpringForce(0)
+                .setStiffness(STIFFNESS)
+                .setDampingRatio(DAMPING_RATIO));
+    }
+
+    public void addSpringView(int id) {
+        mSpringViews.put(id, true);
+    }
+
+    @Override
+    protected boolean drawChild(Canvas canvas, View child, long drawingTime) {
+        if (mDampedScrollShift != 0 && mSpringViews.get(child.getId())) {
+            canvas.translate(0, mDampedScrollShift);
+            boolean result = super.drawChild(canvas, child, drawingTime);
+            canvas.translate(0, -mDampedScrollShift);
+            return result;
+        }
+        return super.drawChild(canvas, child, drawingTime);
+    }
+
+    private void setDampedScrollShift(float shift) {
+        if (shift != mDampedScrollShift) {
+            mDampedScrollShift = shift;
+            invalidate();
+        }
+    }
+
+    private void finishScrollWithVelocity(float velocity) {
+        mSpring.setStartVelocity(velocity);
+        mSpring.setStartValue(mDampedScrollShift);
+        mSpring.start();
+    }
+
+    public EdgeEffectFactory createEdgeEffectFactory() {
+        return new SpringEdgeEffectFactory();
+    }
+
+    private class SpringEdgeEffectFactory extends EdgeEffectFactory {
+
+        @NonNull @Override
+        protected EdgeEffect createEdgeEffect(RecyclerView view, int direction) {
+            switch (direction) {
+                case DIRECTION_TOP:
+                    return new SpringEdgeEffect(getContext(), +VELOCITY_MULTIPLIER);
+                case DIRECTION_BOTTOM:
+                    return new SpringEdgeEffect(getContext(), -VELOCITY_MULTIPLIER);
+            }
+            return super.createEdgeEffect(view, direction);
+        }
+    }
+
+    private class SpringEdgeEffect extends EdgeEffect {
+
+        private final float mVelocityMultiplier;
+
+        private float mDistance;
+
+        public SpringEdgeEffect(Context context, float velocityMultiplier) {
+            super(context);
+            mVelocityMultiplier = velocityMultiplier;
+        }
+
+        @Override
+        public boolean draw(Canvas canvas) {
+            return false;
+        }
+
+        @Override
+        public void onAbsorb(int velocity) {
+            finishScrollWithVelocity(velocity * mVelocityMultiplier);
+        }
+
+        @Override
+        public void onPull(float deltaDistance, float displacement) {
+            mDistance += deltaDistance * (mVelocityMultiplier / 3f);
+            setDampedScrollShift(mDistance * getHeight());
+        }
+
+        @Override
+        public void onRelease() {
+            mDistance = 0;
+            finishScrollWithVelocity(0);
+        }
+    }
+}