package com.luorrak.ouroboros.thread;
import android.content.Context;
import android.graphics.PointF;
import android.hardware.SensorManager;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.LinearSmoothScroller;
import android.support.v7.widget.RecyclerView;
import android.view.View;
import android.view.ViewGroup;
/**
* Ouroboros - An 8chan browser
* Copyright (C) 2015 Luorrak
* <p/>
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
* <p/>
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
* <p/>
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
public class SnappyLinearLayoutManager extends LinearLayoutManager implements SnappyRecyclerView.ISnappyLayoutManager {
// These variables are from android.widget.Scroller, which is used, via ScrollerCompat, by
// Recycler View. The scrolling distance calculation logic originates from the same place. Want
// to use their variables so as to approximate the look of normal Android scrolling.
// Find the Scroller fling implementation in android.widget.Scroller.fling().
private static final float INFLEXION = 0.35f; // Tension lines cross at (INFLEXION, 1)
private static float DECELERATION_RATE = (float) (Math.log(0.78) / Math.log(0.9));
private static double FRICTION = 0.84;
private double deceleration;
public SnappyLinearLayoutManager(Context context) {
super(context);
calculateDeceleration(context);
}
public SnappyLinearLayoutManager(Context context, int orientation, boolean reverseLayout) {
super(context, orientation, reverseLayout);
calculateDeceleration(context);
setAutoMeasureEnabled(false);
}
private void calculateDeceleration(Context context) {
deceleration = SensorManager.GRAVITY_EARTH // g (m/s^2)
* 39.3700787 // inches per meter
// pixels per inch. 160 is the "default" dpi, i.e. one dip is one pixel on a 160 dpi
// screen
* context.getResources().getDisplayMetrics().density * 160.0f * FRICTION;
}
@Override
public int getPositionForVelocity(int velocityX, int velocityY) {
if (getChildCount() == 0) {
return 0;
}
if (getOrientation() == HORIZONTAL) {
return calcPosForVelocity(velocityX, getPosition(getChildAt(0)));
} else {
return calcPosForVelocity(velocityY, getPosition(getChildAt(0)));
}
}
private int calcPosForVelocity(int velocity, int currPos) {
if (velocity < 0) {
return Math.max(currPos, 0);
} else {
return currPos + 1;
}
}
@Override
public void smoothScrollToPosition(RecyclerView recyclerView, RecyclerView.State state, int position) {
final LinearSmoothScroller linearSmoothScroller =
new LinearSmoothScroller(recyclerView.getContext()) {
// I want a behavior where the scrolling always snaps to the beginning of
// the list. Snapping to end is also trivial given the default implementation.
// If you need a different behavior, you may need to override more
// of the LinearSmoothScrolling methods.
protected int getHorizontalSnapPreference() {
return SNAP_TO_START;
}
protected int getVerticalSnapPreference() {
return SNAP_TO_START;
}
@Override
public PointF computeScrollVectorForPosition(int targetPosition) {
return SnappyLinearLayoutManager.this
.computeScrollVectorForPosition(targetPosition);
}
};
linearSmoothScroller.setTargetPosition(position);
startSmoothScroll(linearSmoothScroller);
}
/**
* This implementation obviously doesn't take into account the direction of the
* that preceded it, but there is no easy way to get that information without more
* hacking than I was willing to put into it.
*/
@Override
public int getFixScrollPos() {
if (this.getChildCount() == 0) {
return 0;
}
final View child = getChildAt(0);
final int childPos = getPosition(child);
if (getOrientation() == HORIZONTAL
&& Math.abs(child.getLeft()) > child.getMeasuredWidth() / 2) {
// Scrolled first view more than halfway offscreen
return childPos + 1;
} else if (getOrientation() == VERTICAL
&& Math.abs(child.getTop()) > child.getMeasuredWidth() / 2) {
// Scrolled first view more than halfway offscreen
return childPos + 1;
}
return childPos;
}
//http://stackoverflow.com/questions/26649406/nested-recycler-view-height-doesnt-wrap-its-content
private int[] mMeasuredDimension = new int[2];
@Override
public void onMeasure(RecyclerView.Recycler recycler, RecyclerView.State state,
int widthSpec, int heightSpec) {
final int widthMode = View.MeasureSpec.getMode(widthSpec);
final int heightMode = View.MeasureSpec.getMode(heightSpec);
final int widthSize = View.MeasureSpec.getSize(widthSpec);
final int heightSize = View.MeasureSpec.getSize(heightSpec);
int width = 0;
int height = 0;
for (int i = 0; i < getItemCount(); i++) {
measureScrapChild(recycler, i,
View.MeasureSpec.makeMeasureSpec(i, View.MeasureSpec.UNSPECIFIED),
View.MeasureSpec.makeMeasureSpec(i, View.MeasureSpec.UNSPECIFIED),
mMeasuredDimension);
if (getOrientation() == HORIZONTAL) {
width = width + mMeasuredDimension[0];
if (i == 0) {
height = mMeasuredDimension[1];
}
} else {
height = height + mMeasuredDimension[1];
if (i == 0) {
width = mMeasuredDimension[0];
}
}
}
switch (widthMode) {
case View.MeasureSpec.EXACTLY:
width = widthSize;
case View.MeasureSpec.AT_MOST:
case View.MeasureSpec.UNSPECIFIED:
}
switch (heightMode) {
case View.MeasureSpec.EXACTLY:
height = heightSize;
case View.MeasureSpec.AT_MOST:
case View.MeasureSpec.UNSPECIFIED:
}
setMeasuredDimension(width, height);
}
private void measureScrapChild(RecyclerView.Recycler recycler, int position, int widthSpec,
int heightSpec, int[] measuredDimension) {
View view = recycler.getViewForPosition(position);
if (view != null) {
RecyclerView.LayoutParams p = (RecyclerView.LayoutParams) view.getLayoutParams();
int childWidthSpec = ViewGroup.getChildMeasureSpec(widthSpec,
getPaddingLeft() + getPaddingRight(), p.width);
int childHeightSpec = ViewGroup.getChildMeasureSpec(heightSpec,
getPaddingTop() + getPaddingBottom(), p.height);
view.measure(childWidthSpec, childHeightSpec);
measuredDimension[0] = view.getMeasuredWidth() + p.leftMargin + p.rightMargin;
measuredDimension[1] = view.getMeasuredHeight() + p.bottomMargin + p.topMargin;
recycler.recycleView(view);
}
}
}