package com.steven.babyiyo.navigationbar; import android.content.Context; import android.os.Parcelable; import android.support.annotation.IntDef; import android.support.design.widget.CoordinatorLayout; import android.support.v4.view.WindowInsetsCompat; import android.util.AttributeSet; import android.view.View; import java.lang.annotation.Retention; import java.lang.annotation.RetentionPolicy; public abstract class VerticalScrollingBehavior<V extends View> extends CoordinatorLayout.Behavior<V> { private int mTotalDyUnconsumed = 0; private int mTotalDy = 0; @ScrollDirection private int mOverScrollDirection = ScrollDirection.SCROLL_NONE; @ScrollDirection private int mScrollDirection = ScrollDirection.SCROLL_NONE; @Retention(RetentionPolicy.SOURCE) @IntDef({ScrollDirection.SCROLL_DIRECTION_UP, ScrollDirection.SCROLL_DIRECTION_DOWN}) public @interface ScrollDirection { int SCROLL_DIRECTION_UP = 1; int SCROLL_DIRECTION_DOWN = -1; int SCROLL_NONE = 0; } public VerticalScrollingBehavior() { super(); } public VerticalScrollingBehavior(final Context context, final AttributeSet attrs) { super(context, attrs); } @ScrollDirection public int getOverScrollDirection() { return mOverScrollDirection; } @ScrollDirection public int getScrollDirection() { return mScrollDirection; } // Direction of the overscroll: SCROLL_DIRECTION_UP, SCROLL_DIRECTION_DOWN // Unconsumed value, negative or positive based on the direction // Cumulative value for current direction public abstract void onNestedVerticalOverScroll(CoordinatorLayout coordinatorLayout, V child, @ScrollDirection int direction, int currentOverScroll, int totalOverScroll); // Direction of the overscroll: SCROLL_DIRECTION_UP, SCROLL_DIRECTION_DOWN public abstract void onDirectionNestedPreScroll(CoordinatorLayout coordinatorLayout, V child, View target, int dx, int dy, int[] consumed, @ScrollDirection int scrollDirection); @Override public boolean onStartNestedScroll(CoordinatorLayout coordinatorLayout, V child, View directTargetChild, View target, int nestedScrollAxes) { return (nestedScrollAxes & View.SCROLL_AXIS_VERTICAL) != 0; } @Override public void onNestedScrollAccepted(CoordinatorLayout coordinatorLayout, V child, View directTargetChild, View target, int nestedScrollAxes) { super.onNestedScrollAccepted(coordinatorLayout, child, directTargetChild, target, nestedScrollAxes); } @Override public void onStopNestedScroll(CoordinatorLayout coordinatorLayout, V child, View target) { super.onStopNestedScroll(coordinatorLayout, child, target); } @Override public void onNestedScroll(CoordinatorLayout coordinatorLayout, V child, View target, int dxConsumed, int dyConsumed, int dxUnconsumed, int dyUnconsumed) { super.onNestedScroll(coordinatorLayout, child, target, dxConsumed, dyConsumed, dxUnconsumed, dyUnconsumed); if (dyUnconsumed > 0 && mTotalDyUnconsumed < 0) { mTotalDyUnconsumed = 0; mOverScrollDirection = ScrollDirection.SCROLL_DIRECTION_UP; } else if (dyUnconsumed < 0 && mTotalDyUnconsumed > 0) { mTotalDyUnconsumed = 0; mOverScrollDirection = ScrollDirection.SCROLL_DIRECTION_DOWN; } mTotalDyUnconsumed += dyUnconsumed; onNestedVerticalOverScroll(coordinatorLayout, child, mOverScrollDirection, dyConsumed, mTotalDyUnconsumed); } @Override public void onNestedPreScroll(CoordinatorLayout coordinatorLayout, V child, View target, int dx, int dy, int[] consumed) { super.onNestedPreScroll(coordinatorLayout, child, target, dx, dy, consumed); if (dy > 0 && mTotalDy < 0) { mTotalDy = 0; mScrollDirection = ScrollDirection.SCROLL_DIRECTION_UP; } else if (dy < 0 && mTotalDy > 0) { mTotalDy = 0; mScrollDirection = ScrollDirection.SCROLL_DIRECTION_DOWN; } mTotalDy += dy; onDirectionNestedPreScroll(coordinatorLayout, child, target, dx, dy, consumed, mScrollDirection); } @Override public boolean onNestedFling(CoordinatorLayout coordinatorLayout, V child, View target, float velocityX, float velocityY, boolean consumed) { super.onNestedFling(coordinatorLayout, child, target, velocityX, velocityY, consumed); mScrollDirection = velocityY > 0 ? ScrollDirection.SCROLL_DIRECTION_UP : ScrollDirection.SCROLL_DIRECTION_DOWN; return onNestedDirectionFling(coordinatorLayout, child, target, velocityX, velocityY, mScrollDirection); } protected abstract boolean onNestedDirectionFling(CoordinatorLayout coordinatorLayout, V child, View target, float velocityX, float velocityY, @ScrollDirection int scrollDirection); @Override public boolean onNestedPreFling(CoordinatorLayout coordinatorLayout, V child, View target, float velocityX, float velocityY) { return super.onNestedPreFling(coordinatorLayout, child, target, velocityX, velocityY); } @Override public WindowInsetsCompat onApplyWindowInsets(CoordinatorLayout coordinatorLayout, V child, WindowInsetsCompat insets) { return super.onApplyWindowInsets(coordinatorLayout, child, insets); } @Override public Parcelable onSaveInstanceState(CoordinatorLayout parent, V child) { return super.onSaveInstanceState(parent, child); } }