GestureDetectorWrapper.java
/*
* Copyright 2019 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 androidx.recyclerview.selection;
import static androidx.core.util.Preconditions.checkArgument;
import android.view.GestureDetector;
import android.view.MotionEvent;
import androidx.annotation.NonNull;
import androidx.recyclerview.widget.RecyclerView;
/**
* A wrapper class for GestureDetector allowing it interact with SelectionTracker
* and its dependencies (like RecyclerView) on terms more amenable to SelectionTracker.
*/
final class GestureDetectorWrapper implements RecyclerView.OnItemTouchListener, Resettable {
private final GestureDetector mDetector;
private boolean mDisallowIntercept;
GestureDetectorWrapper(@NonNull GestureDetector detector) {
checkArgument(detector != null);
mDetector = detector;
}
@Override
public boolean onInterceptTouchEvent(@NonNull RecyclerView rv, @NonNull MotionEvent e) {
// Reset disallow when the event is down as advised in http://b/139141511#comment20.
if (mDisallowIntercept && MotionEvents.isActionDown(e)) {
mDisallowIntercept = false;
}
// While the idea of "intercepting" an event stream isn't consistent
// with the world-view of GestureDetector, failure to return true here
// resulted in a bug where a context menu shown on an item view was not
// visible...despite returning reporting that the menu was shown.
// See b/143494310 for further details.
return !mDisallowIntercept && mDetector.onTouchEvent(e);
}
@Override
public void onTouchEvent(@NonNull RecyclerView rv, @NonNull MotionEvent e) {
}
@Override
public void onRequestDisallowInterceptTouchEvent(boolean disallowIntercept) {
if (!disallowIntercept) {
return; // Ignore as advised in http://b/139141511#comment20
}
// Some types of views, such as HorizontalScrollView, may want
// to take over the input stream. In this case they'll call this method
// with disallowIntercept=true. mDisallowIntercept is reset on UP or CANCEL
// events in onInterceptTouchEvent.
mDisallowIntercept = disallowIntercept;
// GestureDetector may have internal state (such as timers) that can
// result in subsequent event handlers being called, even after
// we receive a request to disallow intercept (e.g. LONG_PRESS).
// For that reason we proactively reset GestureDetector.
sendCancelEvent();
}
@Override
public boolean isResetRequired() {
// Always resettable as we don't know the specifics of GD's internal state.
return true;
}
@Override
public void reset() {
mDisallowIntercept = false;
sendCancelEvent();
}
private void sendCancelEvent() {
// GestureDetector does not provide a public affordance for resetting
// it's internal state, so we send it a synthetic ACTION_CANCEL event.
mDetector.onTouchEvent(MotionEvents.createCancelEvent());
}
}