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/*
* Copyright (C) 2015 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.launcher3;
import android.content.Context;
import android.support.v7.widget.RecyclerView;
import android.util.AttributeSet;
import android.view.MotionEvent;
import com.android.launcher3.util.Thunk;
/**
* A base {@link RecyclerView}, which will NOT intercept a touch sequence unless the scrolling
* velocity is below a predefined threshold.
*/
public class BaseRecyclerView extends RecyclerView
implements RecyclerView.OnItemTouchListener {
private static final int SCROLL_DELTA_THRESHOLD_DP = 4;
/** Keeps the last known scrolling delta/velocity along y-axis. */
@Thunk int mDy = 0;
private float mDeltaThreshold;
public BaseRecyclerView(Context context) {
this(context, null);
}
public BaseRecyclerView(Context context, AttributeSet attrs) {
this(context, attrs, 0);
}
public BaseRecyclerView(Context context, AttributeSet attrs, int defStyleAttr) {
super(context, attrs, defStyleAttr);
mDeltaThreshold = getResources().getDisplayMetrics().density * SCROLL_DELTA_THRESHOLD_DP;
ScrollListener listener = new ScrollListener();
setOnScrollListener(listener);
}
private class ScrollListener extends OnScrollListener {
public ScrollListener() {
// Do nothing
}
@Override
public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
mDy = dy;
}
}
@Override
protected void onFinishInflate() {
super.onFinishInflate();
addOnItemTouchListener(this);
}
@Override
public boolean onInterceptTouchEvent(RecyclerView rv, MotionEvent ev) {
if (shouldStopScroll(ev)) {
stopScroll();
}
return false;
}
@Override
public void onTouchEvent(RecyclerView rv, MotionEvent ev) {
// Do nothing.
}
public void onRequestDisallowInterceptTouchEvent(boolean disallowIntercept) {
// DO NOT REMOVE, NEEDED IMPLEMENTATION FOR M BUILDS
}
/**
* Returns whether this {@link MotionEvent} should trigger the scroll to be stopped.
*/
protected boolean shouldStopScroll(MotionEvent ev) {
if (ev.getAction() == MotionEvent.ACTION_DOWN) {
if ((Math.abs(mDy) < mDeltaThreshold &&
getScrollState() != RecyclerView.SCROLL_STATE_IDLE)) {
// now the touch events are being passed to the {@link WidgetCell} until the
// touch sequence goes over the touch slop.
return true;
}
}
return false;
}
}
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