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/*
* Copyright (C) 2020 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.systemui.accessibility;
import android.annotation.DisplayContext;
import android.annotation.NonNull;
import android.content.Context;
import android.graphics.PointF;
import android.os.Handler;
import android.view.Display;
import android.view.MotionEvent;
import android.view.ViewConfiguration;
/**
* Detects single tap and drag gestures using the supplied {@link MotionEvent}s. The {@link
* OnGestureListener} callback will notify users when a particular motion event has occurred. This
* class should only be used with {@link MotionEvent}s reported via touch (don't use for trackball
* events).
*/
class MagnificationGestureDetector {
interface OnGestureListener {
/**
* Called when a tap is completed within {@link ViewConfiguration#getLongPressTimeout()} and
* the offset between {@link MotionEvent}s and the down event doesn't exceed {@link
* ViewConfiguration#getScaledTouchSlop()}.
*
* @return {@code true} if this gesture is handled.
*/
boolean onSingleTap();
/**
* Called when the user is performing dragging gesture. It is started after the offset
* between the down location and the move event location exceed
* {@link ViewConfiguration#getScaledTouchSlop()}.
*
* @param offsetX The X offset in screen coordinate.
* @param offsetY The Y offset in screen coordinate.
* @return {@code true} if this gesture is handled.
*/
boolean onDrag(float offsetX, float offsetY);
/**
* Notified when a tap occurs with the down {@link MotionEvent} that triggered it. This will
* be triggered immediately for every down event. All other events should be preceded by
* this.
*
* @param x The X coordinate of the down event.
* @param y The Y coordinate of the down event.
* @return {@code true} if the down event is handled, otherwise the events won't be sent to
* the view.
*/
boolean onStart(float x, float y);
/**
* Called when the detection is finished. In other words, it is called when up/cancel {@link
* MotionEvent} is received. It will be triggered after single-tap
*
* @param x The X coordinate on the screen of the up event or the cancel event.
* @param y The Y coordinate on the screen of the up event or the cancel event.
* @return {@code true} if the event is handled.
*/
boolean onFinish(float x, float y);
}
private final PointF mPointerDown = new PointF();
private final PointF mPointerLocation = new PointF(Float.NaN, Float.NaN);
private final Handler mHandler;
private final Runnable mCancelTapGestureRunnable;
private final OnGestureListener mOnGestureListener;
private int mTouchSlopSquare;
// Assume the gesture default is a single-tap. Set it to false if the gesture couldn't be a
// single-tap anymore.
private boolean mDetectSingleTap = true;
private boolean mDraggingDetected = false;
/**
* @param context {@link Context} that is from {@link Context#createDisplayContext(Display)}.
* @param handler The handler to post the runnable.
* @param listener The listener invoked for all the callbacks.
*/
MagnificationGestureDetector(@DisplayContext Context context, @NonNull Handler handler,
@NonNull OnGestureListener listener) {
final int touchSlop = ViewConfiguration.get(context).getScaledTouchSlop();
mTouchSlopSquare = touchSlop * touchSlop;
mHandler = handler;
mOnGestureListener = listener;
mCancelTapGestureRunnable = () -> mDetectSingleTap = false;
}
/**
* Analyzes the given motion event and if applicable to trigger the appropriate callbacks on the
* {@link OnGestureListener} supplied.
*
* @param event The current motion event.
* @return {@code True} if the {@link OnGestureListener} consumes the event, else false.
*/
boolean onTouch(MotionEvent event) {
final float rawX = event.getRawX();
final float rawY = event.getRawY();
boolean handled = false;
switch (event.getActionMasked()) {
case MotionEvent.ACTION_DOWN:
mPointerDown.set(rawX, rawY);
mHandler.postAtTime(mCancelTapGestureRunnable,
event.getDownTime() + ViewConfiguration.getLongPressTimeout());
handled |= mOnGestureListener.onStart(rawX, rawY);
break;
case MotionEvent.ACTION_POINTER_DOWN:
stopSingleTapDetection();
break;
case MotionEvent.ACTION_MOVE:
stopSingleTapDetectionIfNeeded(rawX, rawY);
handled |= notifyDraggingGestureIfNeeded(rawX, rawY);
break;
case MotionEvent.ACTION_UP:
stopSingleTapDetectionIfNeeded(rawX, rawY);
if (mDetectSingleTap) {
handled |= mOnGestureListener.onSingleTap();
}
// Fall through
case MotionEvent.ACTION_CANCEL:
handled |= mOnGestureListener.onFinish(rawX, rawY);
reset();
break;
}
return handled;
}
private void stopSingleTapDetectionIfNeeded(float x, float y) {
if (mDraggingDetected) {
return;
}
if (!isLocationValid(mPointerDown)) {
return;
}
final int deltaX = (int) (mPointerDown.x - x);
final int deltaY = (int) (mPointerDown.y - y);
final int distanceSquare = (deltaX * deltaX) + (deltaY * deltaY);
if (distanceSquare > mTouchSlopSquare) {
mDraggingDetected = true;
stopSingleTapDetection();
}
}
private void stopSingleTapDetection() {
mHandler.removeCallbacks(mCancelTapGestureRunnable);
mDetectSingleTap = false;
}
private boolean notifyDraggingGestureIfNeeded(float x, float y) {
if (!mDraggingDetected) {
return false;
}
if (!isLocationValid(mPointerLocation)) {
mPointerLocation.set(mPointerDown);
}
final float offsetX = x - mPointerLocation.x;
final float offsetY = y - mPointerLocation.y;
mPointerLocation.set(x, y);
return mOnGestureListener.onDrag(offsetX, offsetY);
}
private void reset() {
resetPointF(mPointerDown);
resetPointF(mPointerLocation);
mHandler.removeCallbacks(mCancelTapGestureRunnable);
mDetectSingleTap = true;
mDraggingDetected = false;
}
private static void resetPointF(PointF pointF) {
pointF.x = Float.NaN;
pointF.y = Float.NaN;
}
private static boolean isLocationValid(PointF location) {
return !Float.isNaN(location.x) && !Float.isNaN(location.y);
}
}
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