package me.ccrama.redditslide.Views;
import android.content.Context;
import android.support.v4.view.MotionEventCompat;
import android.support.v4.view.NestedScrollingChild;
import android.support.v4.view.NestedScrollingChildHelper;
import android.support.v4.view.NestedScrollingParent;
import android.support.v4.view.VelocityTrackerCompat;
import android.support.v4.view.ViewCompat;
import android.support.v4.widget.ScrollerCompat;
import android.util.AttributeSet;
import android.util.Log;
import android.view.MotionEvent;
import android.view.VelocityTracker;
import android.view.ViewConfiguration;
import android.view.ViewParent;
import android.webkit.WebView;
/**
* Copyright (c) Tuenti Technologies. All rights reserved.
*
* WebView compatible with CoordinatorLayout.
* The implementation based on NestedScrollView of design library
*/
public class NestedWebView extends WebView implements NestedScrollingChild, NestedScrollingParent {
private static final int INVALID_POINTER = -1;
private static final String TAG = "NestedWebView";
private final int[] mScrollOffset = new int[2];
private final int[] mScrollConsumed = new int[2];
private int mLastMotionY;
private NestedScrollingChildHelper mChildHelper;
private boolean mIsBeingDragged = false;
private VelocityTracker mVelocityTracker;
private int mTouchSlop;
private int mActivePointerId = INVALID_POINTER;
private int mNestedYOffset;
private ScrollerCompat mScroller;
private int mMinimumVelocity;
private int mMaximumVelocity;
public NestedWebView(Context context) {
this(context, null);
}
public NestedWebView(Context context, AttributeSet attrs) {
this(context, attrs, android.R.attr.webViewStyle);
}
public NestedWebView(Context context, AttributeSet attrs, int defStyleAttr) {
super(context, attrs, defStyleAttr);
setOverScrollMode(WebView.OVER_SCROLL_NEVER);
initScrollView();
mChildHelper = new NestedScrollingChildHelper(this);
setNestedScrollingEnabled(true);
}
private void initScrollView() {
mScroller = ScrollerCompat.create(getContext(), null);
final ViewConfiguration configuration = ViewConfiguration.get(getContext());
mTouchSlop = configuration.getScaledTouchSlop();
mMinimumVelocity = configuration.getScaledMinimumFlingVelocity();
mMaximumVelocity = configuration.getScaledMaximumFlingVelocity();
}
@Override
public boolean onInterceptTouchEvent(MotionEvent ev) {
final int action = ev.getAction();
if ((action == MotionEvent.ACTION_MOVE) && (mIsBeingDragged)) {
return true;
}
switch (action & MotionEventCompat.ACTION_MASK) {
case MotionEvent.ACTION_MOVE: {
final int activePointerId = mActivePointerId;
if (activePointerId == INVALID_POINTER) {
break;
}
final int pointerIndex = ev.findPointerIndex(activePointerId);
if (pointerIndex == -1) {
Log.e(TAG, "Invalid pointerId=" + activePointerId
+ " in onInterceptTouchEvent");
break;
}
final int y = (int) ev.getY(pointerIndex);
final int yDiff = Math.abs(y - mLastMotionY);
if (yDiff > mTouchSlop
&& (getNestedScrollAxes() & ViewCompat.SCROLL_AXIS_VERTICAL) == 0) {
mIsBeingDragged = true;
mLastMotionY = y;
initVelocityTrackerIfNotExists();
mVelocityTracker.addMovement(ev);
mNestedYOffset = 0;
final ViewParent parent = getParent();
if (parent != null) {
parent.requestDisallowInterceptTouchEvent(true);
}
}
break;
}
case MotionEvent.ACTION_DOWN: {
final int y = (int) ev.getY();
mLastMotionY = y;
mActivePointerId = ev.getPointerId(0);
initOrResetVelocityTracker();
mVelocityTracker.addMovement(ev);
mScroller.computeScrollOffset();
mIsBeingDragged = !mScroller.isFinished();
startNestedScroll(ViewCompat.SCROLL_AXIS_VERTICAL);
break;
}
case MotionEvent.ACTION_CANCEL:
case MotionEvent.ACTION_UP:
mIsBeingDragged = false;
mActivePointerId = INVALID_POINTER;
recycleVelocityTracker();
if (mScroller.springBack(getScrollX(), getScrollY(), 0, 0, 0, getScrollRange())) {
ViewCompat.postInvalidateOnAnimation(this);
}
stopNestedScroll();
break;
case MotionEventCompat.ACTION_POINTER_UP:
onSecondaryPointerUp(ev);
break;
}
return mIsBeingDragged;
}
@Override
public boolean onTouchEvent(MotionEvent ev) {
initVelocityTrackerIfNotExists();
MotionEvent vtev = MotionEvent.obtain(ev);
final int actionMasked = MotionEventCompat.getActionMasked(ev);
if (actionMasked == MotionEvent.ACTION_DOWN) {
mNestedYOffset = 0;
}
vtev.offsetLocation(0, mNestedYOffset);
switch (actionMasked) {
case MotionEvent.ACTION_DOWN: {
if (mIsBeingDragged = !mScroller.isFinished()) {
final ViewParent parent = getParent();
if (parent != null) {
parent.requestDisallowInterceptTouchEvent(true);
}
}
if (!mScroller.isFinished()) {
mScroller.abortAnimation();
}
mLastMotionY = (int) ev.getY();
mActivePointerId = ev.getPointerId(0);
startNestedScroll(ViewCompat.SCROLL_AXIS_VERTICAL);
break;
}
case MotionEvent.ACTION_MOVE:
final int activePointerIndex = ev.findPointerIndex(mActivePointerId);
if (activePointerIndex == -1) {
Log.e(TAG, "Invalid pointerId=" + mActivePointerId + " in onTouchEvent");
break;
}
final int y = (int) ev.getY(activePointerIndex);
int deltaY = mLastMotionY - y;
if (dispatchNestedPreScroll(0, deltaY, mScrollConsumed, mScrollOffset)) {
deltaY -= mScrollConsumed[1];
vtev.offsetLocation(0, mScrollOffset[1]);
mNestedYOffset += mScrollOffset[1];
}
if (!mIsBeingDragged && Math.abs(deltaY) > mTouchSlop) {
final ViewParent parent = getParent();
if (parent != null) {
parent.requestDisallowInterceptTouchEvent(true);
}
mIsBeingDragged = true;
if (deltaY > 0) {
deltaY -= mTouchSlop;
} else {
deltaY += mTouchSlop;
}
}
if (mIsBeingDragged) {
mLastMotionY = y - mScrollOffset[1];
final int oldY = getScrollY();
final int scrolledDeltaY = getScrollY() - oldY;
final int unconsumedY = deltaY - scrolledDeltaY;
if (dispatchNestedScroll(0, scrolledDeltaY, 0, unconsumedY, mScrollOffset)) {
mLastMotionY -= mScrollOffset[1];
vtev.offsetLocation(0, mScrollOffset[1]);
mNestedYOffset += mScrollOffset[1];
}
}
break;
case MotionEvent.ACTION_UP:
if (mIsBeingDragged) {
final VelocityTracker velocityTracker = mVelocityTracker;
velocityTracker.computeCurrentVelocity(1000, mMaximumVelocity);
int initialVelocity = (int) VelocityTrackerCompat.getYVelocity(velocityTracker,
mActivePointerId);
if (Math.abs(initialVelocity) > mMinimumVelocity) {
flingWithNestedDispatch(-initialVelocity);
} else if (mScroller.springBack(getScrollX(), getScrollY(), 0, 0, 0,
getScrollRange())) {
ViewCompat.postInvalidateOnAnimation(this);
}
}
mActivePointerId = INVALID_POINTER;
endDrag();
break;
case MotionEvent.ACTION_CANCEL:
if (mIsBeingDragged && getChildCount() > 0) {
if (mScroller.springBack(getScrollX(), getScrollY(), 0, 0, 0,
getScrollRange())) {
ViewCompat.postInvalidateOnAnimation(this);
}
}
mActivePointerId = INVALID_POINTER;
endDrag();
break;
case MotionEventCompat.ACTION_POINTER_DOWN: {
final int index = MotionEventCompat.getActionIndex(ev);
mLastMotionY = (int) ev.getY(index);
mActivePointerId = ev.getPointerId(index);
break;
}
case MotionEventCompat.ACTION_POINTER_UP:
onSecondaryPointerUp(ev);
mLastMotionY = (int) ev.getY(ev.findPointerIndex(mActivePointerId));
break;
}
if (mVelocityTracker != null) {
mVelocityTracker.addMovement(vtev);
}
vtev.recycle();
return super.onTouchEvent(ev);
}
int getScrollRange() {
//Using scroll range of webview instead of childs as NestedScrollView does.
return computeVerticalScrollRange();
}
private void endDrag() {
mIsBeingDragged = false;
recycleVelocityTracker();
stopNestedScroll();
}
private void onSecondaryPointerUp(MotionEvent ev) {
final int pointerIndex = (ev.getAction() & MotionEventCompat.ACTION_POINTER_INDEX_MASK)
>> MotionEventCompat.ACTION_POINTER_INDEX_SHIFT;
final int pointerId = ev.getPointerId(pointerIndex);
if (pointerId == mActivePointerId) {
final int newPointerIndex = pointerIndex == 0 ? 1 : 0;
mLastMotionY = (int) ev.getY(newPointerIndex);
mActivePointerId = ev.getPointerId(newPointerIndex);
if (mVelocityTracker != null) {
mVelocityTracker.clear();
}
}
}
private void initOrResetVelocityTracker() {
if (mVelocityTracker == null) {
mVelocityTracker = VelocityTracker.obtain();
} else {
mVelocityTracker.clear();
}
}
private void initVelocityTrackerIfNotExists() {
if (mVelocityTracker == null) {
mVelocityTracker = VelocityTracker.obtain();
}
}
private void recycleVelocityTracker() {
if (mVelocityTracker != null) {
mVelocityTracker.recycle();
mVelocityTracker = null;
}
}
private void flingWithNestedDispatch(int velocityY) {
final int scrollY = getScrollY();
final boolean canFling = (scrollY > 0 || velocityY > 0)
&& (scrollY < getScrollRange() || velocityY < 0);
if (!dispatchNestedPreFling(0, velocityY)) {
dispatchNestedFling(0, velocityY, canFling);
if (canFling) {
fling(velocityY);
}
}
}
public void fling(int velocityY) {
if (getChildCount() > 0) {
int height = getHeight() - getPaddingBottom() - getPaddingTop();
int bottom = getChildAt(0).getHeight();
mScroller.fling(getScrollX(), getScrollY(), 0, velocityY, 0, 0, 0,
Math.max(0, bottom - height), 0, height / 2);
ViewCompat.postInvalidateOnAnimation(this);
}
}
@Override
public boolean isNestedScrollingEnabled() {
return mChildHelper.isNestedScrollingEnabled();
}
@Override
public void setNestedScrollingEnabled(boolean enabled) {
mChildHelper.setNestedScrollingEnabled(enabled);
}
@Override
public boolean startNestedScroll(int axes) {
return mChildHelper.startNestedScroll(axes);
}
@Override
public void stopNestedScroll() {
mChildHelper.stopNestedScroll();
}
@Override
public boolean hasNestedScrollingParent() {
return mChildHelper.hasNestedScrollingParent();
}
@Override
public boolean dispatchNestedScroll(int dxConsumed, int dyConsumed, int dxUnconsumed, int dyUnconsumed,
int[] offsetInWindow) {
return mChildHelper.dispatchNestedScroll(dxConsumed, dyConsumed, dxUnconsumed, dyUnconsumed, offsetInWindow);
}
@Override
public boolean dispatchNestedPreScroll(int dx, int dy, int[] consumed, int[] offsetInWindow) {
return mChildHelper.dispatchNestedPreScroll(dx, dy, consumed, offsetInWindow);
}
@Override
public boolean dispatchNestedFling(float velocityX, float velocityY, boolean consumed) {
return mChildHelper.dispatchNestedFling(velocityX, velocityY, consumed);
}
@Override
public boolean dispatchNestedPreFling(float velocityX, float velocityY) {
return mChildHelper.dispatchNestedPreFling(velocityX, velocityY);
}
@Override
public int getNestedScrollAxes() {
return ViewCompat.SCROLL_AXIS_NONE;
}
}