content: /*
   * Copyright (C) 2016 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.dragndrop;
  
  import android.graphics.PointF;
  import android.os.SystemClock;
  import android.view.DragEvent;
  import android.view.MotionEvent;
  import android.view.VelocityTracker;
  import android.view.ViewConfiguration;
  
  import com.android.launcher3.ButtonDropTarget;
  import com.android.launcher3.DropTarget;
  import com.android.launcher3.Launcher;
  import com.android.launcher3.R;
  import com.android.launcher3.util.FlingAnimation;
  
  /**
   * Utility class to manage fling to delete action during drag and drop.
   */
  public class FlingToDeleteHelper {
  
      private static final float MAX_FLING_DEGREES = 35f;
  
      private final Launcher mLauncher;
      private final int mFlingToDeleteThresholdVelocity;
  
      private ButtonDropTarget mDropTarget;
      private VelocityTracker mVelocityTracker;
  
      public FlingToDeleteHelper(Launcher launcher) {
          mLauncher = launcher;
          mFlingToDeleteThresholdVelocity = launcher.getResources()
                  .getDimensionPixelSize(R.dimen.drag_flingToDeleteMinVelocity);
      }
  
      public void recordMotionEvent(MotionEvent ev) {
          if (mVelocityTracker == null) {
              mVelocityTracker = VelocityTracker.obtain();
          }
          mVelocityTracker.addMovement(ev);
      }
  
      /**
       * Same as {@link #recordMotionEvent}. It creates a temporary {@link MotionEvent} object
       * using {@param event} for tracking velocity.
       */
      public void recordDragEvent(long dragStartTime, DragEvent event) {
          final int motionAction;
          switch (event.getAction()) {
              case DragEvent.ACTION_DRAG_STARTED:
                  motionAction = MotionEvent.ACTION_DOWN;
                  break;
              case DragEvent.ACTION_DRAG_LOCATION:
                  motionAction = MotionEvent.ACTION_MOVE;
                  break;
              case DragEvent.ACTION_DRAG_ENDED:
                  motionAction = MotionEvent.ACTION_UP;
                  break;
              default:
                  return;
          }
          MotionEvent emulatedEvent = MotionEvent.obtain(dragStartTime, SystemClock.uptimeMillis(),
                  motionAction, event.getX(), event.getY(), 0);
          recordMotionEvent(emulatedEvent);
          emulatedEvent.recycle();
      }
  
      public void releaseVelocityTracker() {
          if (mVelocityTracker != null) {
              mVelocityTracker.recycle();
              mVelocityTracker = null;
          }
      }
  
      public DropTarget getDropTarget() {
          return mDropTarget;
      }
  
      public Runnable getFlingAnimation(DropTarget.DragObject dragObject) {
          PointF vel = isFlingingToDelete();
          if (vel == null) {
              return null;
          }
          return new FlingAnimation(dragObject, vel, mDropTarget, mLauncher);
      }
  
      /**
       * Determines whether the user flung the current item to delete it.
       *
       * @return the vector at which the item was flung, or null if no fling was detected.
       */
      private PointF isFlingingToDelete() {
          if (mDropTarget == null) {
              mDropTarget = (ButtonDropTarget) mLauncher.findViewById(R.id.delete_target_text);
          }
          if (mDropTarget == null || !mDropTarget.isDropEnabled()) return null;
          ViewConfiguration config = ViewConfiguration.get(mLauncher);
          mVelocityTracker.computeCurrentVelocity(1000, config.getScaledMaximumFlingVelocity());
          PointF vel = new PointF(mVelocityTracker.getXVelocity(), mVelocityTracker.getYVelocity());
          float theta = MAX_FLING_DEGREES + 1;
          if (mVelocityTracker.getYVelocity() < mFlingToDeleteThresholdVelocity) {
              // Do a quick dot product test to ensure that we are flinging upwards
              PointF upVec = new PointF(0f, -1f);
              theta = getAngleBetweenVectors(vel, upVec);
          } else if (mLauncher.getDeviceProfile().isVerticalBarLayout() &&
                  mVelocityTracker.getXVelocity() < mFlingToDeleteThresholdVelocity) {
              // Remove icon is on left side instead of top, so check if we are flinging to the left.
              PointF leftVec = new PointF(-1f, 0f);
              theta = getAngleBetweenVectors(vel, leftVec);
          }
          if (theta <= Math.toRadians(MAX_FLING_DEGREES)) {
              return vel;
          }
          return null;
      }
  
      private float getAngleBetweenVectors(PointF vec1, PointF vec2) {
          return (float) Math.acos(((vec1.x * vec2.x) + (vec1.y * vec2.y)) /
                  (vec1.length() * vec2.length()));
      }
  }
  