Android Open Source - android_app Swipe Dismiss Touch Listener

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License

The source code is released under:

Apache License

Java Source Code

/*
 * ******************************************************************************
 *   Copyright (c) 2014 Google Inc., Gabriele Mariotti.
 */*ww  w  .j ava  2  s . c om*/
 *   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 it.gmariotti.cardslib.library.view.listener;

import android.animation.Animator;
import android.animation.AnimatorListenerAdapter;
import android.animation.ValueAnimator;
import android.app.ListActivity;
import android.app.ListFragment;
import android.view.MotionEvent;
import android.view.VelocityTracker;
import android.view.View;
import android.view.ViewConfiguration;
import android.view.ViewGroup;
import android.widget.AdapterView;
import android.widget.ListView;

/**
 * A {@link View.OnTouchListener} that makes any {@link View} dismissable when the
 * user swipes (drags her finger) horizontally across the view.
 *
 * <p><em>For {@link ListView} list items that don't manage their own touch events
 * (i.e. you're using
 * {@link ListView#setOnItemClickListener(AdapterView.OnItemClickListener)}
 * or an equivalent listener on {@link ListActivity} or
 * {@link ListFragment}, use {@link SwipeDismissListViewTouchListener} instead.</em></p>
 *
 * <p>Example usage:</p>
 *
 * <pre>
 * view.setOnTouchListener(new SwipeDismissTouchListener(
 *         view,
 *         null, // Optional token/cookie object
 *         new SwipeDismissTouchListener.OnDismissCallback() {
 *             public void onDismiss(View view, Object token) {
 *                 parent.removeView(view);
 *             }
 *         }));
 * </pre>
 *
 * <p>This class Requires API level 12 or later due to use of {@link
 * android.view.ViewPropertyAnimator}.</p>
 *
 * @see SwipeDismissListViewTouchListener
 */
public class SwipeDismissTouchListener implements View.OnTouchListener {

    // Cached ViewConfiguration and system-wide constant values
    private int mSlop;
    private int mMinFlingVelocity;
    private int mMaxFlingVelocity;
    private long mAnimationTime;

    // Fixed properties
    private View mView;
    private DismissCallbacks mCallbacks;
    private int mViewWidth = 1; // 1 and not 0 to prevent dividing by zero

    // Transient properties
    private float mDownX;
    private float mDownY;
    private boolean mSwiping;
    private int mSwipingSlop;
    private Object mToken;
    private VelocityTracker mVelocityTracker;
    private float mTranslationX;

    /**
     * The callback interface used by {@link SwipeDismissTouchListener} to inform its client
     * about a successful dismissal of the view for which it was created.
     */
    public interface DismissCallbacks {
        /**
         * Called to determine whether the view can be dismissed.
         */
        boolean canDismiss(Object token);

        /**
         * Called when the user has indicated they she would like to dismiss the view.
         *
         * @param view  The originating {@link View} to be dismissed.
         * @param token The optional token passed to this object's constructor.
         */
        void onDismiss(View view, Object token);
    }

    /**
     * Constructs a new swipe-to-dismiss touch listener for the given view.
     *
     * @param view     The view to make dismissable.
     * @param token    An optional token/cookie object to be passed through to the callback.
     * @param callbacks The callback to trigger when the user has indicated that she would like to
     *                 dismiss this view.
     */
    public SwipeDismissTouchListener(View view, Object token, DismissCallbacks callbacks) {
        ViewConfiguration vc = ViewConfiguration.get(view.getContext());
        mSlop = vc.getScaledTouchSlop();
        mMinFlingVelocity = vc.getScaledMinimumFlingVelocity() * 16;
        mMaxFlingVelocity = vc.getScaledMaximumFlingVelocity();
        mAnimationTime = view.getContext().getResources().getInteger(
                android.R.integer.config_shortAnimTime);
        mView = view;
        mToken = token;
        mCallbacks = callbacks;
    }

    @Override
    public boolean onTouch(View view, MotionEvent motionEvent) {
        // offset because the view is translated during swipe
        motionEvent.offsetLocation(mTranslationX, 0);

        if (mViewWidth < 2) {
            mViewWidth = mView.getWidth();
        }

        switch (motionEvent.getActionMasked()) {
            case MotionEvent.ACTION_DOWN: {
                // TODO: ensure this is a finger, and set a flag
                mDownX = motionEvent.getRawX();
                mDownY = motionEvent.getRawY();
                if (mCallbacks.canDismiss(mToken)) {
                    mVelocityTracker = VelocityTracker.obtain();
                    mVelocityTracker.addMovement(motionEvent);
                }
                view.onTouchEvent(motionEvent);
                return true;
            }

            case MotionEvent.ACTION_UP: {
                if (mVelocityTracker == null) {
                    break;
                }

                float deltaX = motionEvent.getRawX() - mDownX;
                mVelocityTracker.addMovement(motionEvent);
                mVelocityTracker.computeCurrentVelocity(1000);
                float velocityX = mVelocityTracker.getXVelocity();
                float absVelocityX = Math.abs(velocityX);
                float absVelocityY = Math.abs(mVelocityTracker.getYVelocity());
                boolean dismiss = false;
                boolean dismissRight = false;
                if (Math.abs(deltaX) > mViewWidth / 2 && mSwiping) {
                    dismiss = true;
                    dismissRight = deltaX > 0;
                } else if (mMinFlingVelocity <= absVelocityX && absVelocityX <= mMaxFlingVelocity
                        && absVelocityY < absVelocityX
                        && mSwiping) {
                    // dismiss only if flinging in the same direction as dragging
                    dismiss = (velocityX < 0) == (deltaX < 0);
                    dismissRight = mVelocityTracker.getXVelocity() > 0;
                }
                if (dismiss) {
                    // dismiss
                    mView.animate()
                            .translationX(dismissRight ? mViewWidth : -mViewWidth)
                            .alpha(0)
                            .setDuration(mAnimationTime)
                            .setListener(new AnimatorListenerAdapter() {
                                @Override
                                public void onAnimationEnd(Animator animation) {
                                    performDismiss();
                                }
                            });
                } else if (mSwiping) {
                    // cancel
                    mView.animate()
                            .translationX(0)
                            .alpha(1)
                            .setDuration(mAnimationTime)
                            .setListener(null);
                }
                mVelocityTracker.recycle();
                mVelocityTracker = null;
                mTranslationX = 0;
                mDownX = 0;
                mDownY = 0;
                mSwiping = false;
                break;
            }

            case MotionEvent.ACTION_CANCEL: {
                if (mVelocityTracker == null) {
                    break;
                }

                mView.animate()
                        .translationX(0)
                        .alpha(1)
                        .setDuration(mAnimationTime)
                        .setListener(null);
                mVelocityTracker.recycle();
                mVelocityTracker = null;
                mTranslationX = 0;
                mDownX = 0;
                mDownY = 0;
                mSwiping = false;
                break;
            }

            case MotionEvent.ACTION_MOVE: {
                if (mVelocityTracker == null) {
                    break;
                }

                mVelocityTracker.addMovement(motionEvent);
                float deltaX = motionEvent.getRawX() - mDownX;
                float deltaY = motionEvent.getRawY() - mDownY;
                if (Math.abs(deltaX) > mSlop && Math.abs(deltaY) < Math.abs(deltaX) / 2) {
                    mSwiping = true;
                    mSwipingSlop = (deltaX > 0 ? mSlop : -mSlop);
                    mView.getParent().requestDisallowInterceptTouchEvent(true);

                    // Cancel listview's touch
                    MotionEvent cancelEvent = MotionEvent.obtain(motionEvent);
                    cancelEvent.setAction(MotionEvent.ACTION_CANCEL |
                            (motionEvent.getActionIndex() <<
                                    MotionEvent.ACTION_POINTER_INDEX_SHIFT));
                    mView.onTouchEvent(cancelEvent);
                    cancelEvent.recycle();
                }

                if (mSwiping) {
                    mTranslationX = deltaX;
                    mView.setTranslationX(deltaX - mSwipingSlop);
                    // TODO: use an ease-out interpolator or such
                    mView.setAlpha(Math.max(0f, Math.min(1f,
                            1f - 2f * Math.abs(deltaX) / mViewWidth)));
                    return true;
                }
                break;
            }
        }
        return false;
    }

    private void performDismiss() {
        // Animate the dismissed view to zero-height and then fire the dismiss callback.
        // This triggers layout on each animation frame; in the future we may want to do something
        // smarter and more performant.

        final ViewGroup.LayoutParams lp = mView.getLayoutParams();
        final int originalHeight = mView.getHeight();

        ValueAnimator animator = ValueAnimator.ofInt(originalHeight, 1).setDuration(mAnimationTime);

        animator.addListener(new AnimatorListenerAdapter() {
            @Override
            public void onAnimationEnd(Animator animation) {
                mCallbacks.onDismiss(mView, mToken);
                // Reset view presentation
                mView.setAlpha(1f);
                mView.setTranslationX(0);
                lp.height = originalHeight;
                mView.setLayoutParams(lp);
            }
        });

        animator.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {
            @Override
            public void onAnimationUpdate(ValueAnimator valueAnimator) {
                lp.height = (Integer) valueAnimator.getAnimatedValue();
                mView.setLayoutParams(lp);
            }
        });

        animator.start();
    }
}

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