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/*
* 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.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);
}
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()));
}
}
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