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package com.segmentfault.app.view;
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.ViewCompat;
import android.support.v4.widget.SwipeRefreshLayout;
import android.util.AttributeSet;
import android.view.MotionEvent;
import android.view.ViewConfiguration;
/**
* Created by geminiwen on 15/6/2.
*/
public class NestedScrollSwipeRefreshLayout extends SwipeRefreshLayout implements NestedScrollingChild{
private static final int INVALID_POINTER = -1;
private int mTouchSlop;
private int mActivePointerId = INVALID_POINTER;
private NestedScrollingChildHelper mChildHelper;
public NestedScrollSwipeRefreshLayout(Context context) {
this(context, null);
}
public NestedScrollSwipeRefreshLayout(Context context, AttributeSet attrs) {
super(context, attrs);
mChildHelper = new NestedScrollingChildHelper(this);
setNestedScrollingEnabled(true);
mTouchSlop = ViewConfiguration.get(context).getScaledTouchSlop();
}
@Override
public void setNestedScrollingEnabled(boolean enabled) {
mChildHelper.setNestedScrollingEnabled(enabled);
}
@Override
public boolean isNestedScrollingEnabled() {
return mChildHelper.isNestedScrollingEnabled();
}
@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);
}
private float mLastMotionY;
private final int[] mScrollOffset = new int[2];
private final int[] mScrollConsumed = new int[2];
private boolean mIsBeginDrag = false;
@Override
public boolean onInterceptTouchEvent(MotionEvent ev) {
final int action = MotionEventCompat.getActionMasked(ev);
switch (action) {
case MotionEvent.ACTION_DOWN: {
mActivePointerId = MotionEventCompat.getPointerId(ev, 0);
final float initialDownY = getMotionEventY(ev, mActivePointerId);
if (initialDownY == -1) {
return false;
}
mLastMotionY = initialDownY;
startNestedScroll(ViewCompat.SCROLL_AXIS_VERTICAL);
super.onInterceptTouchEvent(ev);
mIsBeginDrag = false;
break;
}
case MotionEvent.ACTION_MOVE: {
if (mActivePointerId == INVALID_POINTER) {
return false;
}
final float y = getMotionEventY(ev, mActivePointerId);
if (y == -1) {
return false;
}
int deltaY = (int)(mLastMotionY - y);
mLastMotionY = y;
if (Math.abs(deltaY) >= mTouchSlop) {
mIsBeginDrag = true;
}
if (mIsBeginDrag && dispatchNestedPreScroll(0, deltaY, mScrollConsumed, mScrollOffset)) {
mLastMotionY -= mScrollOffset[1];
deltaY -= mScrollConsumed[1];
ev.offsetLocation(0, mScrollConsumed[1]);
if (dispatchNestedScroll(0, 0, 0, deltaY, mScrollOffset)) {
mLastMotionY -= mScrollOffset[1];
ev.offsetLocation(0, mScrollOffset[1]);
}
return false;
} else {
return super.onInterceptTouchEvent(ev);
}
}
case MotionEvent.ACTION_CANCEL:
case MotionEvent.ACTION_UP: {
stopNestedScroll();
mActivePointerId = INVALID_POINTER;
mIsBeginDrag = false;
return super.onInterceptTouchEvent(ev);
}
}
return super.onInterceptTouchEvent(ev);
}
private float getMotionEventY(MotionEvent ev, int activePointerId) {
final int index = MotionEventCompat.findPointerIndex(ev, activePointerId);
if (index < 0) {
return -1;
}
return MotionEventCompat.getY(ev, index);
}
}

SwipeRefreshLayout本身就已经实现了NestedScrollingChild接口的

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