content: /*
   * 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 static androidx.dynamicanimation.animation.SpringForce.DAMPING_RATIO_MEDIUM_BOUNCY;
  import static androidx.dynamicanimation.animation.SpringForce.STIFFNESS_LOW;
  import static androidx.dynamicanimation.animation.SpringForce.STIFFNESS_MEDIUM;
  
  import android.content.Context;
  import android.graphics.Canvas;
  import android.util.AttributeSet;
  import android.util.SparseBooleanArray;
  import android.view.View;
  import android.widget.EdgeEffect;
  import android.widget.RelativeLayout;
  
  import androidx.annotation.NonNull;
  import androidx.dynamicanimation.animation.DynamicAnimation;
  import androidx.dynamicanimation.animation.FloatPropertyCompat;
  import androidx.dynamicanimation.animation.SpringAnimation;
  import androidx.dynamicanimation.animation.SpringForce;
  import androidx.recyclerview.widget.RecyclerView;
  import androidx.recyclerview.widget.RecyclerView.EdgeEffectFactory;
  
  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);
                  }
              };
  
      protected final SparseBooleanArray mSpringViews = new SparseBooleanArray();
      private final SpringAnimation mSpring;
  
      private float mDampedScrollShift = 0;
      private SpringEdgeEffect mActiveEdge;
  
      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);
      }
  
      public void removeSpringView(int id) {
          mSpringViews.delete(id);
          invalidate();
      }
  
      /**
       * Used to clip the canvas when drawing child views during overscroll.
       */
      public int getCanvasClipTopForOverscroll() {
          return 0;
      }
  
      @Override
      protected boolean drawChild(Canvas canvas, View child, long drawingTime) {
          if (mDampedScrollShift != 0 && mSpringViews.get(child.getId())) {
              int saveCount = canvas.save();
  
              canvas.clipRect(0, getCanvasClipTopForOverscroll(), getWidth(), getHeight());
              canvas.translate(0, mDampedScrollShift);
              boolean result = super.drawChild(canvas, child, drawingTime);
  
              canvas.restoreToCount(saveCount);
  
              return result;
          }
          return super.drawChild(canvas, child, drawingTime);
      }
  
      private void setActiveEdge(SpringEdgeEffect edge) {
          if (mActiveEdge != edge && mActiveEdge != null) {
              mActiveEdge.mDistance = 0;
          }
          mActiveEdge = edge;
      }
  
      protected void setDampedScrollShift(float shift) {
          if (shift != mDampedScrollShift) {
              mDampedScrollShift = shift;
              invalidate();
          }
      }
  
      private void finishScrollWithVelocity(float velocity) {
          mSpring.setStartVelocity(velocity);
          mSpring.setStartValue(mDampedScrollShift);
          mSpring.start();
      }
  
      protected void finishWithShiftAndVelocity(float shift, float velocity,
              DynamicAnimation.OnAnimationEndListener listener) {
          setDampedScrollShift(shift);
          mSpring.addEndListener(listener);
          finishScrollWithVelocity(velocity);
      }
  
      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) {
              setActiveEdge(this);
              mDistance += deltaDistance * (mVelocityMultiplier / 3f);
              setDampedScrollShift(mDistance * getHeight());
          }
  
          @Override
          public void onRelease() {
              mDistance = 0;
              finishScrollWithVelocity(0);
          }
      }
  }