| /* |
| * Copyright 2018 Google LLC All Rights Reserved. |
| * |
| * 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.google.skar.examples.helloskar.helpers; |
| |
| import android.content.Context; |
| import android.view.GestureDetector; |
| import android.view.MotionEvent; |
| import android.view.View; |
| import android.view.View.OnTouchListener; |
| import java.util.concurrent.ArrayBlockingQueue; |
| import java.util.concurrent.BlockingQueue; |
| |
| /** |
| * Helper to detect gestures using Android GestureDetector, and pass the taps between UI thread and |
| * render thread. |
| */ |
| |
| public final class GestureHelper implements OnTouchListener { |
| private final GestureDetector gestureDetector; |
| private final BlockingQueue<MotionEvent> queuedSingleTaps = new ArrayBlockingQueue<>(16); |
| private final BlockingQueue<ScrollEvent> queuedFingerHold = new ArrayBlockingQueue<>(16); |
| private boolean isScrolling = false; |
| private boolean previousScroll = true; |
| |
| // Struct holding a MotionEvent obtained from onScroll() callbacks, and a boolean evaluating to |
| // true if the MotionEven was the start of the scrolling motion |
| public static class ScrollEvent { |
| public MotionEvent event; |
| public boolean isStartOfScroll; |
| |
| public ScrollEvent(MotionEvent e, boolean isStartOfScroll) { |
| this.event = e; |
| this.isStartOfScroll = isStartOfScroll; |
| } |
| } |
| |
| /** |
| * Creates the gesture helper. |
| * |
| * @param context the application's context. |
| */ |
| public GestureHelper(Context context) { |
| gestureDetector = |
| new GestureDetector( |
| context, |
| new GestureDetector.SimpleOnGestureListener() { |
| @Override |
| public boolean onSingleTapUp(MotionEvent e) { |
| // Queue tap if there is space. Tap is lost if queue is full. |
| queuedSingleTaps.offer(e); |
| return true; |
| } |
| |
| @Override |
| public boolean onScroll (MotionEvent e1, MotionEvent e2, |
| float distanceX, float distanceY) { |
| // Queue motion events when scrolling |
| if (e2.getPointerCount() == 1 && e1.getPointerCount() == 1) { |
| previousScroll = isScrolling; |
| isScrolling = true; |
| |
| queuedFingerHold.offer(new ScrollEvent(e2, |
| isStartedScrolling())); |
| |
| return true; |
| } |
| return false; |
| } |
| |
| |
| @Override |
| public boolean onDown(MotionEvent e) { |
| return true; |
| } |
| }); |
| } |
| |
| /** |
| * Polls for a tap. |
| * |
| * @return if a tap was queued, a MotionEvent for the tap. Otherwise null if no taps are queued. |
| */ |
| public MotionEvent poll() { |
| return queuedSingleTaps.poll(); |
| } |
| |
| /** |
| * Polls for a scrolling motion. |
| * |
| * @return if a scrolling event was queued, a ScrollEvent for the gesture. Otherwise null |
| */ |
| public ScrollEvent holdPoll() { return queuedFingerHold.poll(); } |
| |
| @Override |
| public boolean onTouch(View view, MotionEvent motionEvent) { |
| boolean val = gestureDetector.onTouchEvent(motionEvent); |
| |
| // If finger is up + is scrolling: don't scroll anymore, and empty touch hold queue |
| if (motionEvent.getAction() == MotionEvent.ACTION_UP && isScrolling) { |
| previousScroll = true; |
| isScrolling = false; |
| queuedFingerHold.clear(); |
| } |
| return val; |
| } |
| private boolean isStartedScrolling() { return isScrolling && !previousScroll; } |
| } |