Java tutorial
/* * Copyright 2013 Google Inc. * Modified by Jonas Kalderstam 2015. * * 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.nononsenseapps.feeder.ui; import android.animation.Animator; import android.animation.AnimatorListenerAdapter; import android.support.v4.view.animation.FastOutLinearInInterpolator; import android.view.MotionEvent; import android.view.VelocityTracker; import android.view.View; import android.view.ViewConfiguration; import com.nononsenseapps.feeder.R; /** * A {@link View.OnTouchListener} that makes any {@link View} dismissable when the * user swipes (drags her finger) horizontally across the view. * * <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> * */ public class SwipeDismissTouchListener implements View.OnTouchListener { private final View mSwipingView; // 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; private final FastOutLinearInInterpolator mInterpolator; private boolean notNotifiedSwipeStart = true; /** * 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); /** * Called when a swipe is started. * @param goingRight true if swiping to the right, false if left */ void onSwipeStarted(boolean goingRight); /** * Called when user doesn't swipe all the way. */ void onSwipeCancelled(); /** * * @return the subview which should move */ View getSwipingView(); } /** * 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; mSwipingView = callbacks.getSwipingView(); mToken = token; mCallbacks = callbacks; mInterpolator = new FastOutLinearInInterpolator(); } @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); } return false; } 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 && 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 mSwipingView.animate().translationX(dismissRight ? mViewWidth : -mViewWidth) //.alpha(0) .setDuration(mAnimationTime).setListener(new AnimatorListenerAdapter() { @Override public void onAnimationEnd(Animator animation) { performDismiss(); } }); } else if (mSwiping) { // cancel mSwipingView.animate().translationX(0) //.alpha(1) .setDuration(mAnimationTime).setListener(new AnimatorListenerAdapter() { @Override public void onAnimationEnd(Animator animation) { mCallbacks.onSwipeCancelled(); } }); } mVelocityTracker.recycle(); mVelocityTracker = null; mTranslationX = 0; mDownX = 0; mDownY = 0; mSwiping = false; notNotifiedSwipeStart = true; break; } case MotionEvent.ACTION_CANCEL: { if (mVelocityTracker == null) { break; } mSwipingView.animate().translationX(0) //.alpha(1) .setDuration(mAnimationTime).setListener(new AnimatorListenerAdapter() { @Override public void onAnimationEnd(Animator animation) { mCallbacks.onSwipeCancelled(); } }); mVelocityTracker.recycle(); mVelocityTracker = null; mTranslationX = 0; mDownX = 0; mDownY = 0; mSwiping = false; notNotifiedSwipeStart = true; 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) { if (notNotifiedSwipeStart) { notNotifiedSwipeStart = false; mCallbacks.onSwipeStarted(deltaX > 0); } mTranslationX = deltaX; mSwipingView.setTranslationX(deltaX - mSwipingSlop); //mView.setAlpha(mInterpolator.getInterpolation(1f - 1f * Math.abs(deltaX) / mViewWidth)); // mView.setAlpha(Math.max(0f, Math.min(1f, // 1f - 2f * Math.abs(deltaX) / mViewWidth))); return true; } break; } } return false; } private void performDismiss() { // Let recyclerview handle dismissal mCallbacks.onDismiss(mView, mToken); } }