listeners;
private boolean liftableOverride;
private boolean liftable;
private boolean lifted;
private boolean liftOnScroll;
private int[] tmpStatesArray;
public AppBarLayout(Context context) {
this(context, null);
}
public AppBarLayout(Context context, AttributeSet attrs) {
super(context, attrs);
setOrientation(VERTICAL);
if (Build.VERSION.SDK_INT >= 21) {
// Use the bounds view outline provider so that we cast a shadow, even without a
// background
ViewUtilsLollipop.setBoundsViewOutlineProvider(this);
// If we're running on API 21+, we should reset any state list animator from our
// default style
ViewUtilsLollipop.setStateListAnimatorFromAttrs(
this, attrs, 0, R.style.Widget_Design_AppBarLayout);
}
final TypedArray a =
ThemeEnforcement.obtainStyledAttributes(
context, attrs, R.styleable.AppBarLayout, 0, R.style.Widget_Design_AppBarLayout);
ViewCompat.setBackground(this, a.getDrawable(R.styleable.AppBarLayout_android_background));
if (a.hasValue(R.styleable.AppBarLayout_expanded)) {
setExpanded(
a.getBoolean(R.styleable.AppBarLayout_expanded, false),
false, /* animate */
false /* force */);
}
if (Build.VERSION.SDK_INT >= 21 && a.hasValue(R.styleable.AppBarLayout_elevation)) {
ViewUtilsLollipop.setDefaultAppBarLayoutStateListAnimator(
this, a.getDimensionPixelSize(R.styleable.AppBarLayout_elevation, 0));
}
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
// In O+, we have these values set in the style. Since there is no defStyleAttr for
// AppBarLayout at the AppCompat level, check for these attributes here.
if (a.hasValue(R.styleable.AppBarLayout_android_keyboardNavigationCluster)) {
this.setKeyboardNavigationCluster(
a.getBoolean(R.styleable.AppBarLayout_android_keyboardNavigationCluster, false));
}
if (a.hasValue(R.styleable.AppBarLayout_android_touchscreenBlocksFocus)) {
this.setTouchscreenBlocksFocus(
a.getBoolean(R.styleable.AppBarLayout_android_touchscreenBlocksFocus, false));
}
}
liftOnScroll = a.getBoolean(R.styleable.AppBarLayout_liftOnScroll, false);
a.recycle();
ViewCompat.setOnApplyWindowInsetsListener(
this,
new android.support.v4.view.OnApplyWindowInsetsListener() {
@Override
public WindowInsetsCompat onApplyWindowInsets(View v, WindowInsetsCompat insets) {
return onWindowInsetChanged(insets);
}
});
}
/**
* Add a listener that will be called when the offset of this {@link AppBarLayout} changes.
*
* @param listener The listener that will be called when the offset changes.]
* @see #removeOnOffsetChangedListener(OnOffsetChangedListener)
*/
@SuppressWarnings("FunctionalInterfaceClash")
public void addOnOffsetChangedListener(BaseOnOffsetChangedListener listener) {
if (listeners == null) {
listeners = new ArrayList<>();
}
if (listener != null && !listeners.contains(listener)) {
listeners.add(listener);
}
}
@SuppressWarnings("FunctionalInterfaceClash")
public void addOnOffsetChangedListener(OnOffsetChangedListener listener) {
addOnOffsetChangedListener((BaseOnOffsetChangedListener) listener);
}
/**
* Remove the previously added {@link OnOffsetChangedListener}.
*
* @param listener the listener to remove.
*/
// TODO: change back to removeOnOffsetChangedListener once the widget migration is
// finished since the shim class needs to implement this method.
@SuppressWarnings("FunctionalInterfaceClash")
public void removeOnOffsetChangedListener(BaseOnOffsetChangedListener listener) {
if (listeners != null && listener != null) {
listeners.remove(listener);
}
}
@SuppressWarnings("FunctionalInterfaceClash")
public void removeOnOffsetChangedListener(OnOffsetChangedListener listener) {
removeOnOffsetChangedListener((BaseOnOffsetChangedListener) listener);
}
@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
super.onMeasure(widthMeasureSpec, heightMeasureSpec);
invalidateScrollRanges();
}
@Override
protected void onLayout(boolean changed, int l, int t, int r, int b) {
super.onLayout(changed, l, t, r, b);
invalidateScrollRanges();
haveChildWithInterpolator = false;
for (int i = 0, z = getChildCount(); i < z; i++) {
final View child = getChildAt(i);
final LayoutParams childLp = (LayoutParams) child.getLayoutParams();
final Interpolator interpolator = childLp.getScrollInterpolator();
if (interpolator != null) {
haveChildWithInterpolator = true;
break;
}
}
// If the user has set liftable manually, don't set liftable state automatically.
if (!liftableOverride) {
setLiftableState(liftOnScroll || hasCollapsibleChild());
}
}
private boolean hasCollapsibleChild() {
for (int i = 0, z = getChildCount(); i < z; i++) {
if (((LayoutParams) getChildAt(i).getLayoutParams()).isCollapsible()) {
return true;
}
}
return false;
}
private void invalidateScrollRanges() {
// Invalidate the scroll ranges
totalScrollRange = INVALID_SCROLL_RANGE;
downPreScrollRange = INVALID_SCROLL_RANGE;
downScrollRange = INVALID_SCROLL_RANGE;
}
@Override
public void setOrientation(int orientation) {
if (orientation != VERTICAL) {
throw new IllegalArgumentException(
"AppBarLayout is always vertical and does not support horizontal orientation");
}
super.setOrientation(orientation);
}
/**
* Sets whether this {@link AppBarLayout} is expanded or not, animating if it has already been
* laid out.
*
* As with {@link AppBarLayout}'s scrolling, this method relies on this layout being a direct
* child of a {@link CoordinatorLayout}.
*
* @param expanded true if the layout should be fully expanded, false if it should be fully
* collapsed
* @attr ref com.google.android.material.R.styleable#AppBarLayout_expanded
*/
public void setExpanded(boolean expanded) {
setExpanded(expanded, ViewCompat.isLaidOut(this));
}
/**
* Sets whether this {@link AppBarLayout} is expanded or not.
*
*
As with {@link AppBarLayout}'s scrolling, this method relies on this layout being a direct
* child of a {@link CoordinatorLayout}.
*
* @param expanded true if the layout should be fully expanded, false if it should be fully
* collapsed
* @param animate Whether to animate to the new state
* @attr ref com.google.android.material.R.styleable#AppBarLayout_expanded
*/
public void setExpanded(boolean expanded, boolean animate) {
setExpanded(expanded, animate, true);
}
private void setExpanded(boolean expanded, boolean animate, boolean force) {
pendingAction =
(expanded ? PENDING_ACTION_EXPANDED : PENDING_ACTION_COLLAPSED)
| (animate ? PENDING_ACTION_ANIMATE_ENABLED : 0)
| (force ? PENDING_ACTION_FORCE : 0);
requestLayout();
}
@Override
protected boolean checkLayoutParams(ViewGroup.LayoutParams p) {
return p instanceof LayoutParams;
}
@Override
protected LayoutParams generateDefaultLayoutParams() {
return new LayoutParams(LayoutParams.MATCH_PARENT, LayoutParams.WRAP_CONTENT);
}
@Override
public LayoutParams generateLayoutParams(AttributeSet attrs) {
return new LayoutParams(getContext(), attrs);
}
@Override
protected LayoutParams generateLayoutParams(ViewGroup.LayoutParams p) {
if (Build.VERSION.SDK_INT >= 19 && p instanceof LinearLayout.LayoutParams) {
return new LayoutParams((LinearLayout.LayoutParams) p);
} else if (p instanceof MarginLayoutParams) {
return new LayoutParams((MarginLayoutParams) p);
}
return new LayoutParams(p);
}
boolean hasChildWithInterpolator() {
return haveChildWithInterpolator;
}
/**
* Returns the scroll range of all children.
*
* @return the scroll range in px
*/
public final int getTotalScrollRange() {
if (totalScrollRange != INVALID_SCROLL_RANGE) {
return totalScrollRange;
}
int range = 0;
for (int i = 0, z = getChildCount(); i < z; i++) {
final View child = getChildAt(i);
final LayoutParams lp = (LayoutParams) child.getLayoutParams();
final int childHeight = child.getMeasuredHeight();
final int flags = lp.scrollFlags;
if ((flags & LayoutParams.SCROLL_FLAG_SCROLL) != 0) {
// We're set to scroll so add the child's height
range += childHeight + lp.topMargin + lp.bottomMargin;
if ((flags & LayoutParams.SCROLL_FLAG_EXIT_UNTIL_COLLAPSED) != 0) {
// For a collapsing scroll, we to take the collapsed height into account.
// We also break straight away since later views can't scroll beneath
// us
range -= ViewCompat.getMinimumHeight(child);
break;
}
} else {
// As soon as a view doesn't have the scroll flag, we end the range calculation.
// This is because views below can not scroll under a fixed view.
break;
}
}
return totalScrollRange = Math.max(0, range - getTopInset());
}
boolean hasScrollableChildren() {
return getTotalScrollRange() != 0;
}
/** Return the scroll range when scrolling up from a nested pre-scroll. */
int getUpNestedPreScrollRange() {
return getTotalScrollRange();
}
/** Return the scroll range when scrolling down from a nested pre-scroll. */
int getDownNestedPreScrollRange() {
if (downPreScrollRange != INVALID_SCROLL_RANGE) {
// If we already have a valid value, return it
return downPreScrollRange;
}
int range = 0;
for (int i = getChildCount() - 1; i >= 0; i--) {
final View child = getChildAt(i);
final LayoutParams lp = (LayoutParams) child.getLayoutParams();
final int childHeight = child.getMeasuredHeight();
final int flags = lp.scrollFlags;
if ((flags & LayoutParams.FLAG_QUICK_RETURN) == LayoutParams.FLAG_QUICK_RETURN) {
// First take the margin into account
range += lp.topMargin + lp.bottomMargin;
// The view has the quick return flag combination...
if ((flags & LayoutParams.SCROLL_FLAG_ENTER_ALWAYS_COLLAPSED) != 0) {
// If they're set to enter collapsed, use the minimum height
range += ViewCompat.getMinimumHeight(child);
} else if ((flags & LayoutParams.SCROLL_FLAG_EXIT_UNTIL_COLLAPSED) != 0) {
// Only enter by the amount of the collapsed height
range += childHeight - ViewCompat.getMinimumHeight(child);
} else {
// Else use the full height (minus the top inset)
range += childHeight - getTopInset();
}
} else if (range > 0) {
// If we've hit an non-quick return scrollable view, and we've already hit a
// quick return view, return now
break;
}
}
return downPreScrollRange = Math.max(0, range);
}
/** Return the scroll range when scrolling down from a nested scroll. */
int getDownNestedScrollRange() {
if (downScrollRange != INVALID_SCROLL_RANGE) {
// If we already have a valid value, return it
return downScrollRange;
}
int range = 0;
for (int i = 0, z = getChildCount(); i < z; i++) {
final View child = getChildAt(i);
final LayoutParams lp = (LayoutParams) child.getLayoutParams();
int childHeight = child.getMeasuredHeight();
childHeight += lp.topMargin + lp.bottomMargin;
final int flags = lp.scrollFlags;
if ((flags & LayoutParams.SCROLL_FLAG_SCROLL) != 0) {
// We're set to scroll so add the child's height
range += childHeight;
if ((flags & LayoutParams.SCROLL_FLAG_EXIT_UNTIL_COLLAPSED) != 0) {
// For a collapsing exit scroll, we to take the collapsed height into account.
// We also break the range straight away since later views can't scroll
// beneath us
range -= ViewCompat.getMinimumHeight(child) + getTopInset();
break;
}
} else {
// As soon as a view doesn't have the scroll flag, we end the range calculation.
// This is because views below can not scroll under a fixed view.
break;
}
}
return downScrollRange = Math.max(0, range);
}
void dispatchOffsetUpdates(int offset) {
// Iterate backwards through the list so that most recently added listeners
// get the first chance to decide
if (listeners != null) {
for (int i = 0, z = listeners.size(); i < z; i++) {
final BaseOnOffsetChangedListener listener = listeners.get(i);
if (listener != null) {
listener.onOffsetChanged(this, offset);
}
}
}
}
public final int getMinimumHeightForVisibleOverlappingContent() {
final int topInset = getTopInset();
final int minHeight = ViewCompat.getMinimumHeight(this);
if (minHeight != 0) {
// If this layout has a min height, use it (doubled)
return (minHeight * 2) + topInset;
}
// Otherwise, we'll use twice the min height of our last child
final int childCount = getChildCount();
final int lastChildMinHeight =
childCount >= 1 ? ViewCompat.getMinimumHeight(getChildAt(childCount - 1)) : 0;
if (lastChildMinHeight != 0) {
return (lastChildMinHeight * 2) + topInset;
}
// If we reach here then we don't have a min height explicitly set. Instead we'll take a
// guess at 1/3 of our height being visible
return getHeight() / 3;
}
@Override
protected int[] onCreateDrawableState(int extraSpace) {
if (tmpStatesArray == null) {
// Note that we can't allocate this at the class level (in declaration) since some paths in
// super View constructor are going to call this method before that
tmpStatesArray = new int[4];
}
final int[] extraStates = tmpStatesArray;
final int[] states = super.onCreateDrawableState(extraSpace + extraStates.length);
extraStates[0] = liftable ? R.attr.state_liftable : -R.attr.state_liftable;
extraStates[1] = liftable && lifted ? R.attr.state_lifted : -R.attr.state_lifted;
// Note that state_collapsible and state_collapsed are deprecated. This is to keep compatibility
// with existing state list animators that depend on these states.
extraStates[2] = liftable ? R.attr.state_collapsible : -R.attr.state_collapsible;
extraStates[3] = liftable && lifted ? R.attr.state_collapsed : -R.attr.state_collapsed;
return mergeDrawableStates(states, extraStates);
}
/**
* Sets whether the {@link AppBarLayout} is liftable or not.
*
* @return true if the liftable state changed
*/
public boolean setLiftable(boolean liftable) {
this.liftableOverride = true;
return setLiftableState(liftable);
}
// Internal helper method that updates liftable state without enabling the override.
private boolean setLiftableState(boolean liftable) {
if (this.liftable != liftable) {
this.liftable = liftable;
refreshDrawableState();
return true;
}
return false;
}
/**
* Sets whether the {@link AppBarLayout} is in a lifted state or not.
*
* @return true if the lifted state changed
*/
public boolean setLifted(boolean lifted) {
return setLiftedState(lifted);
}
// Internal helper method that updates lifted state.
boolean setLiftedState(boolean lifted) {
if (this.lifted != lifted) {
this.lifted = lifted;
refreshDrawableState();
return true;
}
return false;
}
/**
* Sets whether the {@link AppBarLayout} lifts on scroll or not.
*
*
If set to true, the {@link AppBarLayout} will animate to the lifted, or elevated, state when
* content is scrolled beneath it. Requires
* `app:layout_behavior="@string/appbar_scrolling_view_behavior` to be set on the scrolling
* sibling (e.g., `NestedScrollView`, `RecyclerView`, etc.).
*/
public void setLiftOnScroll(boolean liftOnScroll) {
this.liftOnScroll = liftOnScroll;
}
/** Returns whether the {@link AppBarLayout} lifts on scroll or not. */
public boolean isLiftOnScroll() {
return liftOnScroll;
}
/**
* @deprecated target elevation is now deprecated. AppBarLayout's elevation is now controlled via
* a {@link android.animation.StateListAnimator}. If a target elevation is set, either by this
* method or the {@code app:elevation} attribute, a new state list animator is created which
* uses the given {@code elevation} value.
* @attr ref com.google.android.material.R.styleable#AppBarLayout_elevation
*/
@Deprecated
public void setTargetElevation(float elevation) {
if (Build.VERSION.SDK_INT >= 21) {
ViewUtilsLollipop.setDefaultAppBarLayoutStateListAnimator(this, elevation);
}
}
/**
* @deprecated target elevation is now deprecated. AppBarLayout's elevation is now controlled via
* a {@link android.animation.StateListAnimator}. This method now always returns 0.
*/
@Deprecated
public float getTargetElevation() {
return 0;
}
int getPendingAction() {
return pendingAction;
}
void resetPendingAction() {
pendingAction = PENDING_ACTION_NONE;
}
@VisibleForTesting
final int getTopInset() {
return lastInsets != null ? lastInsets.getSystemWindowInsetTop() : 0;
}
WindowInsetsCompat onWindowInsetChanged(final WindowInsetsCompat insets) {
WindowInsetsCompat newInsets = null;
if (ViewCompat.getFitsSystemWindows(this)) {
// If we're set to fit system windows, keep the insets
newInsets = insets;
}
// If our insets have changed, keep them and invalidate the scroll ranges...
if (!ObjectsCompat.equals(lastInsets, newInsets)) {
lastInsets = newInsets;
invalidateScrollRanges();
}
return insets;
}
/** A {@link ViewGroup.LayoutParams} implementation for {@link AppBarLayout}. */
public static class LayoutParams extends LinearLayout.LayoutParams {
/** @hide */
@RestrictTo(LIBRARY_GROUP)
@IntDef(
flag = true,
value = {
SCROLL_FLAG_SCROLL,
SCROLL_FLAG_EXIT_UNTIL_COLLAPSED,
SCROLL_FLAG_ENTER_ALWAYS,
SCROLL_FLAG_ENTER_ALWAYS_COLLAPSED,
SCROLL_FLAG_SNAP,
SCROLL_FLAG_SNAP_MARGINS,
})
@Retention(RetentionPolicy.SOURCE)
public @interface ScrollFlags {}
/**
* The view will be scroll in direct relation to scroll events. This flag needs to be set for
* any of the other flags to take effect. If any sibling views before this one do not have this
* flag, then this value has no effect.
*/
public static final int SCROLL_FLAG_SCROLL = 0x1;
/**
* When exiting (scrolling off screen) the view will be scrolled until it is 'collapsed'. The
* collapsed height is defined by the view's minimum height.
*
* @see ViewCompat#getMinimumHeight(View)
* @see View#setMinimumHeight(int)
*/
public static final int SCROLL_FLAG_EXIT_UNTIL_COLLAPSED = 0x2;
/**
* When entering (scrolling on screen) the view will scroll on any downwards scroll event,
* regardless of whether the scrolling view is also scrolling. This is commonly referred to as
* the 'quick return' pattern.
*/
public static final int SCROLL_FLAG_ENTER_ALWAYS = 0x4;
/**
* An additional flag for 'enterAlways' which modifies the returning view to only initially
* scroll back to it's collapsed height. Once the scrolling view has reached the end of it's
* scroll range, the remainder of this view will be scrolled into view. The collapsed height is
* defined by the view's minimum height.
*
* @see ViewCompat#getMinimumHeight(View)
* @see View#setMinimumHeight(int)
*/
public static final int SCROLL_FLAG_ENTER_ALWAYS_COLLAPSED = 0x8;
/**
* Upon a scroll ending, if the view is only partially visible then it will be snapped and
* scrolled to it's closest edge. For example, if the view only has it's bottom 25% displayed,
* it will be scrolled off screen completely. Conversely, if it's bottom 75% is visible then it
* will be scrolled fully into view.
*/
public static final int SCROLL_FLAG_SNAP = 0x10;
/**
* An additional flag to be used with 'snap'. If set, the view will be snapped to its top and
* bottom margins, as opposed to the edges of the view itself.
*/
public static final int SCROLL_FLAG_SNAP_MARGINS = 0x20;
/** Internal flags which allows quick checking features */
static final int FLAG_QUICK_RETURN = SCROLL_FLAG_SCROLL | SCROLL_FLAG_ENTER_ALWAYS;
static final int FLAG_SNAP = SCROLL_FLAG_SCROLL | SCROLL_FLAG_SNAP;
static final int COLLAPSIBLE_FLAGS =
SCROLL_FLAG_EXIT_UNTIL_COLLAPSED | SCROLL_FLAG_ENTER_ALWAYS_COLLAPSED;
int scrollFlags = SCROLL_FLAG_SCROLL;
Interpolator scrollInterpolator;
public LayoutParams(Context c, AttributeSet attrs) {
super(c, attrs);
TypedArray a = c.obtainStyledAttributes(attrs, R.styleable.AppBarLayout_Layout);
scrollFlags = a.getInt(R.styleable.AppBarLayout_Layout_layout_scrollFlags, 0);
if (a.hasValue(R.styleable.AppBarLayout_Layout_layout_scrollInterpolator)) {
int resId = a.getResourceId(R.styleable.AppBarLayout_Layout_layout_scrollInterpolator, 0);
scrollInterpolator = android.view.animation.AnimationUtils.loadInterpolator(c, resId);
}
a.recycle();
}
public LayoutParams(int width, int height) {
super(width, height);
}
public LayoutParams(int width, int height, float weight) {
super(width, height, weight);
}
public LayoutParams(ViewGroup.LayoutParams p) {
super(p);
}
public LayoutParams(MarginLayoutParams source) {
super(source);
}
@RequiresApi(19)
public LayoutParams(LinearLayout.LayoutParams source) {
// The copy constructor called here only exists on API 19+.
super(source);
}
@RequiresApi(19)
public LayoutParams(LayoutParams source) {
// The copy constructor called here only exists on API 19+.
super(source);
scrollFlags = source.scrollFlags;
scrollInterpolator = source.scrollInterpolator;
}
/**
* Set the scrolling flags.
*
* @param flags bitwise int of {@link #SCROLL_FLAG_SCROLL}, {@link
* #SCROLL_FLAG_EXIT_UNTIL_COLLAPSED}, {@link #SCROLL_FLAG_ENTER_ALWAYS}, {@link
* #SCROLL_FLAG_ENTER_ALWAYS_COLLAPSED}, {@link #SCROLL_FLAG_SNAP}, and {@link
* #SCROLL_FLAG_SNAP_MARGINS}.
* @see #getScrollFlags()
* @attr ref com.google.android.material.R.styleable#AppBarLayout_Layout_layout_scrollFlags
*/
public void setScrollFlags(@ScrollFlags int flags) {
scrollFlags = flags;
}
/**
* Returns the scrolling flags.
*
* @see #setScrollFlags(int)
* @attr ref com.google.android.material.R.styleable#AppBarLayout_Layout_layout_scrollFlags
*/
@ScrollFlags
public int getScrollFlags() {
return scrollFlags;
}
/**
* Set the interpolator to when scrolling the view associated with this {@link LayoutParams}.
*
* @param interpolator the interpolator to use, or null to use normal 1-to-1 scrolling.
* @attr ref com.google.android.material.R.styleable#AppBarLayout_Layout_layout_scrollInterpolator
* @see #getScrollInterpolator()
*/
public void setScrollInterpolator(Interpolator interpolator) {
scrollInterpolator = interpolator;
}
/**
* Returns the {@link Interpolator} being used for scrolling the view associated with this
* {@link LayoutParams}. Null indicates 'normal' 1-to-1 scrolling.
*
* @attr ref com.google.android.material.R.styleable#AppBarLayout_Layout_layout_scrollInterpolator
* @see #setScrollInterpolator(Interpolator)
*/
public Interpolator getScrollInterpolator() {
return scrollInterpolator;
}
/** Returns true if the scroll flags are compatible for 'collapsing' */
boolean isCollapsible() {
return (scrollFlags & SCROLL_FLAG_SCROLL) == SCROLL_FLAG_SCROLL
&& (scrollFlags & COLLAPSIBLE_FLAGS) != 0;
}
}
/**
* The default {@link Behavior} for {@link AppBarLayout}. Implements the necessary nested scroll
* handling with offsetting.
*/
// TODO: remove the base class and generic type after the widget migration is done
public static class Behavior extends BaseBehavior {
/** Callback to allow control over any {@link AppBarLayout} dragging. */
public abstract static class DragCallback extends BaseBehavior.BaseDragCallback {}
public Behavior() {
super();
}
public Behavior(Context context, AttributeSet attrs) {
super(context, attrs);
}
}
/**
* The default {@link Behavior} for {@link AppBarLayout}. Implements the necessary nested scroll
* handling with offsetting.
*/
// TODO: remove this base class and generic type after the widget migration is done
protected static class BaseBehavior extends HeaderBehavior {
private static final int MAX_OFFSET_ANIMATION_DURATION = 600; // ms
private static final int INVALID_POSITION = -1;
/** Callback to allow control over any {@link AppBarLayout} dragging. */
// TODO: remove this base class and generic type after the widget migration
public abstract static class BaseDragCallback {
/**
* Allows control over whether the given {@link AppBarLayout} can be dragged or not.
*
* Dragging is defined as a direct touch on the AppBarLayout with movement. This call does
* not affect any nested scrolling.
*
* @return true if we are in a position to scroll the AppBarLayout via a drag, false if not.
*/
public abstract boolean canDrag(@NonNull T appBarLayout);
}
private int offsetDelta;
@NestedScrollType private int lastStartedType;
private ValueAnimator offsetAnimator;
private int offsetToChildIndexOnLayout = INVALID_POSITION;
private boolean offsetToChildIndexOnLayoutIsMinHeight;
private float offsetToChildIndexOnLayoutPerc;
private WeakReference lastNestedScrollingChildRef;
private BaseDragCallback onDragCallback;
public BaseBehavior() {}
public BaseBehavior(Context context, AttributeSet attrs) {
super(context, attrs);
}
@Override
public boolean onStartNestedScroll(
CoordinatorLayout parent,
T child,
View directTargetChild,
View target,
int nestedScrollAxes,
int type) {
// Return true if we're nested scrolling vertically, and we either have lift on scroll enabled
// or we can scroll the children.
final boolean started =
(nestedScrollAxes & ViewCompat.SCROLL_AXIS_VERTICAL) != 0
&& (child.isLiftOnScroll() || canScrollChildren(parent, child, directTargetChild));
if (started && offsetAnimator != null) {
// Cancel any offset animation
offsetAnimator.cancel();
}
// A new nested scroll has started so clear out the previous ref
lastNestedScrollingChildRef = null;
// Track the last started type so we know if a fling is about to happen once scrolling ends
lastStartedType = type;
return started;
}
// Return true if there are scrollable children and the scrolling view is big enough to scroll.
private boolean canScrollChildren(CoordinatorLayout parent, T child, View directTargetChild) {
return child.hasScrollableChildren()
&& parent.getHeight() - directTargetChild.getHeight() <= child.getHeight();
}
@Override
public void onNestedPreScroll(
CoordinatorLayout coordinatorLayout,
T child,
View target,
int dx,
int dy,
int[] consumed,
int type) {
if (dy != 0) {
int min;
int max;
if (dy < 0) {
// We're scrolling down
min = -child.getTotalScrollRange();
max = min + child.getDownNestedPreScrollRange();
} else {
// We're scrolling up
min = -child.getUpNestedPreScrollRange();
max = 0;
}
if (min != max) {
consumed[1] = scroll(coordinatorLayout, child, dy, min, max);
stopNestedScrollIfNeeded(dy, child, target, type);
}
}
}
@Override
public void onNestedScroll(
CoordinatorLayout coordinatorLayout,
T child,
View target,
int dxConsumed,
int dyConsumed,
int dxUnconsumed,
int dyUnconsumed,
int type) {
if (dyUnconsumed < 0) {
// If the scrolling view is scrolling down but not consuming, it's probably be at
// the top of it's content
scroll(coordinatorLayout, child, dyUnconsumed, -child.getDownNestedScrollRange(), 0);
stopNestedScrollIfNeeded(dyUnconsumed, child, target, type);
}
if (child.isLiftOnScroll()) {
child.setLiftedState(target.getScrollY() > 0);
}
}
private void stopNestedScrollIfNeeded(int dy, T child, View target, int type) {
if (type == ViewCompat.TYPE_NON_TOUCH) {
final int curOffset = getTopBottomOffsetForScrollingSibling();
if ((dy < 0 && curOffset == 0)
|| (dy > 0 && curOffset == -child.getDownNestedScrollRange())) {
ViewCompat.stopNestedScroll(target, ViewCompat.TYPE_NON_TOUCH);
}
}
}
@Override
public void onStopNestedScroll(
CoordinatorLayout coordinatorLayout, T abl, View target, int type) {
// onStartNestedScroll for a fling will happen before onStopNestedScroll for the scroll. This
// isn't necessarily guaranteed yet, but it should be in the future. We use this to our
// advantage to check if a fling (ViewCompat.TYPE_NON_TOUCH) will start after the touch scroll
// (ViewCompat.TYPE_TOUCH) ends
if (lastStartedType == ViewCompat.TYPE_TOUCH || type == ViewCompat.TYPE_NON_TOUCH) {
// If we haven't been flung, or a fling is ending
snapToChildIfNeeded(coordinatorLayout, abl);
}
// Keep a reference to the previous nested scrolling child
lastNestedScrollingChildRef = new WeakReference<>(target);
}
/**
* Set a callback to control any {@link AppBarLayout} dragging.
*
* @param callback the callback to use, or {@code null} to use the default behavior.
*/
public void setDragCallback(@Nullable BaseDragCallback callback) {
onDragCallback = callback;
}
private void animateOffsetTo(
final CoordinatorLayout coordinatorLayout,
final T child,
final int offset,
float velocity) {
final int distance = Math.abs(getTopBottomOffsetForScrollingSibling() - offset);
final int duration;
velocity = Math.abs(velocity);
if (velocity > 0) {
duration = 3 * Math.round(1000 * (distance / velocity));
} else {
final float distanceRatio = (float) distance / child.getHeight();
duration = (int) ((distanceRatio + 1) * 150);
}
animateOffsetWithDuration(coordinatorLayout, child, offset, duration);
}
private void animateOffsetWithDuration(
final CoordinatorLayout coordinatorLayout,
final T child,
final int offset,
final int duration) {
final int currentOffset = getTopBottomOffsetForScrollingSibling();
if (currentOffset == offset) {
if (offsetAnimator != null && offsetAnimator.isRunning()) {
offsetAnimator.cancel();
}
return;
}
if (offsetAnimator == null) {
offsetAnimator = new ValueAnimator();
offsetAnimator.setInterpolator(AnimationUtils.DECELERATE_INTERPOLATOR);
offsetAnimator.addUpdateListener(
new ValueAnimator.AnimatorUpdateListener() {
@Override
public void onAnimationUpdate(ValueAnimator animator) {
setHeaderTopBottomOffset(
coordinatorLayout, child, (int) animator.getAnimatedValue());
}
});
} else {
offsetAnimator.cancel();
}
offsetAnimator.setDuration(Math.min(duration, MAX_OFFSET_ANIMATION_DURATION));
offsetAnimator.setIntValues(currentOffset, offset);
offsetAnimator.start();
}
private int getChildIndexOnOffset(T abl, final int offset) {
for (int i = 0, count = abl.getChildCount(); i < count; i++) {
View child = abl.getChildAt(i);
int top = child.getTop();
int bottom = child.getBottom();
final LayoutParams lp = (LayoutParams) child.getLayoutParams();
if (checkFlag(lp.getScrollFlags(), LayoutParams.SCROLL_FLAG_SNAP_MARGINS)) {
// Update top and bottom to include margins
top -= lp.topMargin;
bottom += lp.bottomMargin;
}
if (top <= -offset && bottom >= -offset) {
return i;
}
}
return -1;
}
private void snapToChildIfNeeded(CoordinatorLayout coordinatorLayout, T abl) {
final int offset = getTopBottomOffsetForScrollingSibling();
final int offsetChildIndex = getChildIndexOnOffset(abl, offset);
if (offsetChildIndex >= 0) {
final View offsetChild = abl.getChildAt(offsetChildIndex);
final LayoutParams lp = (LayoutParams) offsetChild.getLayoutParams();
final int flags = lp.getScrollFlags();
if ((flags & LayoutParams.FLAG_SNAP) == LayoutParams.FLAG_SNAP) {
// We're set the snap, so animate the offset to the nearest edge
int snapTop = -offsetChild.getTop();
int snapBottom = -offsetChild.getBottom();
if (offsetChildIndex == abl.getChildCount() - 1) {
// If this is the last child, we need to take the top inset into account
snapBottom += abl.getTopInset();
}
if (checkFlag(flags, LayoutParams.SCROLL_FLAG_EXIT_UNTIL_COLLAPSED)) {
// If the view is set only exit until it is collapsed, we'll abide by that
snapBottom += ViewCompat.getMinimumHeight(offsetChild);
} else if (checkFlag(
flags, LayoutParams.FLAG_QUICK_RETURN | LayoutParams.SCROLL_FLAG_ENTER_ALWAYS)) {
// If it's set to always enter collapsed, it actually has two states. We
// select the state and then snap within the state
final int seam = snapBottom + ViewCompat.getMinimumHeight(offsetChild);
if (offset < seam) {
snapTop = seam;
} else {
snapBottom = seam;
}
}
if (checkFlag(flags, LayoutParams.SCROLL_FLAG_SNAP_MARGINS)) {
// Update snap destinations to include margins
snapTop += lp.topMargin;
snapBottom -= lp.bottomMargin;
}
final int newOffset = offset < (snapBottom + snapTop) / 2 ? snapBottom : snapTop;
animateOffsetTo(
coordinatorLayout, abl, MathUtils.clamp(newOffset, -abl.getTotalScrollRange(), 0), 0);
}
}
}
private static boolean checkFlag(final int flags, final int check) {
return (flags & check) == check;
}
@Override
public boolean onMeasureChild(
CoordinatorLayout parent,
T child,
int parentWidthMeasureSpec,
int widthUsed,
int parentHeightMeasureSpec,
int heightUsed) {
final CoordinatorLayout.LayoutParams lp =
(CoordinatorLayout.LayoutParams) child.getLayoutParams();
if (lp.height == CoordinatorLayout.LayoutParams.WRAP_CONTENT) {
// If the view is set to wrap on it's height, CoordinatorLayout by default will
// cap the view at the CoL's height. Since the AppBarLayout can scroll, this isn't
// what we actually want, so we measure it ourselves with an unspecified spec to
// allow the child to be larger than it's parent
parent.onMeasureChild(
child,
parentWidthMeasureSpec,
widthUsed,
MeasureSpec.makeMeasureSpec(0, MeasureSpec.UNSPECIFIED),
heightUsed);
return true;
}
// Let the parent handle it as normal
return super.onMeasureChild(
parent, child, parentWidthMeasureSpec, widthUsed, parentHeightMeasureSpec, heightUsed);
}
@Override
public boolean onLayoutChild(CoordinatorLayout parent, T abl, int layoutDirection) {
boolean handled = super.onLayoutChild(parent, abl, layoutDirection);
// The priority for actions here is (first which is true wins):
// 1. forced pending actions
// 2. offsets for restorations
// 3. non-forced pending actions
final int pendingAction = abl.getPendingAction();
if (offsetToChildIndexOnLayout >= 0 && (pendingAction & PENDING_ACTION_FORCE) == 0) {
View child = abl.getChildAt(offsetToChildIndexOnLayout);
int offset = -child.getBottom();
if (offsetToChildIndexOnLayoutIsMinHeight) {
offset += ViewCompat.getMinimumHeight(child) + abl.getTopInset();
} else {
offset += Math.round(child.getHeight() * offsetToChildIndexOnLayoutPerc);
}
setHeaderTopBottomOffset(parent, abl, offset);
} else if (pendingAction != PENDING_ACTION_NONE) {
final boolean animate = (pendingAction & PENDING_ACTION_ANIMATE_ENABLED) != 0;
if ((pendingAction & PENDING_ACTION_COLLAPSED) != 0) {
final int offset = -abl.getUpNestedPreScrollRange();
if (animate) {
animateOffsetTo(parent, abl, offset, 0);
} else {
setHeaderTopBottomOffset(parent, abl, offset);
}
} else if ((pendingAction & PENDING_ACTION_EXPANDED) != 0) {
if (animate) {
animateOffsetTo(parent, abl, 0, 0);
} else {
setHeaderTopBottomOffset(parent, abl, 0);
}
}
}
// Finally reset any pending states
abl.resetPendingAction();
offsetToChildIndexOnLayout = INVALID_POSITION;
// We may have changed size, so let's constrain the top and bottom offset correctly,
// just in case we're out of the bounds
setTopAndBottomOffset(
MathUtils.clamp(getTopAndBottomOffset(), -abl.getTotalScrollRange(), 0));
// Update the AppBarLayout's drawable state for any elevation changes. This is needed so that
// the elevation is set in the first layout, so that we don't get a visual jump pre-N (due to
// the draw dispatch skip)
updateAppBarLayoutDrawableState(
parent, abl, getTopAndBottomOffset(), 0 /* direction */, true /* forceJump */);
// Make sure we dispatch the offset update
abl.dispatchOffsetUpdates(getTopAndBottomOffset());
return handled;
}
@Override
boolean canDragView(T view) {
if (onDragCallback != null) {
// If there is a drag callback set, it's in control
return onDragCallback.canDrag(view);
}
// Else we'll use the default behaviour of seeing if it can scroll down
if (lastNestedScrollingChildRef != null) {
// If we have a reference to a scrolling view, check it
final View scrollingView = lastNestedScrollingChildRef.get();
return scrollingView != null
&& scrollingView.isShown()
&& !scrollingView.canScrollVertically(-1);
} else {
// Otherwise we assume that the scrolling view hasn't been scrolled and can drag.
return true;
}
}
@Override
void onFlingFinished(CoordinatorLayout parent, T layout) {
// At the end of a manual fling, check to see if we need to snap to the edge-child
snapToChildIfNeeded(parent, layout);
}
@Override
int getMaxDragOffset(T view) {
return -view.getDownNestedScrollRange();
}
@Override
int getScrollRangeForDragFling(T view) {
return view.getTotalScrollRange();
}
@Override
int setHeaderTopBottomOffset(
CoordinatorLayout coordinatorLayout,
T appBarLayout,
int newOffset,
int minOffset,
int maxOffset) {
final int curOffset = getTopBottomOffsetForScrollingSibling();
int consumed = 0;
if (minOffset != 0 && curOffset >= minOffset && curOffset <= maxOffset) {
// If we have some scrolling range, and we're currently within the min and max
// offsets, calculate a new offset
newOffset = MathUtils.clamp(newOffset, minOffset, maxOffset);
if (curOffset != newOffset) {
final int interpolatedOffset =
appBarLayout.hasChildWithInterpolator()
? interpolateOffset(appBarLayout, newOffset)
: newOffset;
final boolean offsetChanged = setTopAndBottomOffset(interpolatedOffset);
// Update how much dy we have consumed
consumed = curOffset - newOffset;
// Update the stored sibling offset
offsetDelta = newOffset - interpolatedOffset;
if (!offsetChanged && appBarLayout.hasChildWithInterpolator()) {
// If the offset hasn't changed and we're using an interpolated scroll
// then we need to keep any dependent views updated. CoL will do this for
// us when we move, but we need to do it manually when we don't (as an
// interpolated scroll may finish early).
coordinatorLayout.dispatchDependentViewsChanged(appBarLayout);
}
// Dispatch the updates to any listeners
appBarLayout.dispatchOffsetUpdates(getTopAndBottomOffset());
// Update the AppBarLayout's drawable state (for any elevation changes)
updateAppBarLayoutDrawableState(
coordinatorLayout,
appBarLayout,
newOffset,
newOffset < curOffset ? -1 : 1,
false /* forceJump */);
}
} else {
// Reset the offset delta
offsetDelta = 0;
}
return consumed;
}
@VisibleForTesting
boolean isOffsetAnimatorRunning() {
return offsetAnimator != null && offsetAnimator.isRunning();
}
private int interpolateOffset(T layout, final int offset) {
final int absOffset = Math.abs(offset);
for (int i = 0, z = layout.getChildCount(); i < z; i++) {
final View child = layout.getChildAt(i);
final AppBarLayout.LayoutParams childLp = (LayoutParams) child.getLayoutParams();
final Interpolator interpolator = childLp.getScrollInterpolator();
if (absOffset >= child.getTop() && absOffset <= child.getBottom()) {
if (interpolator != null) {
int childScrollableHeight = 0;
final int flags = childLp.getScrollFlags();
if ((flags & LayoutParams.SCROLL_FLAG_SCROLL) != 0) {
// We're set to scroll so add the child's height plus margin
childScrollableHeight += child.getHeight() + childLp.topMargin + childLp.bottomMargin;
if ((flags & LayoutParams.SCROLL_FLAG_EXIT_UNTIL_COLLAPSED) != 0) {
// For a collapsing scroll, we to take the collapsed height
// into account.
childScrollableHeight -= ViewCompat.getMinimumHeight(child);
}
}
if (ViewCompat.getFitsSystemWindows(child)) {
childScrollableHeight -= layout.getTopInset();
}
if (childScrollableHeight > 0) {
final int offsetForView = absOffset - child.getTop();
final int interpolatedDiff =
Math.round(
childScrollableHeight
* interpolator.getInterpolation(
offsetForView / (float) childScrollableHeight));
return Integer.signum(offset) * (child.getTop() + interpolatedDiff);
}
}
// If we get to here then the view on the offset isn't suitable for interpolated
// scrolling. So break out of the loop
break;
}
}
return offset;
}
private void updateAppBarLayoutDrawableState(
final CoordinatorLayout parent,
final T layout,
final int offset,
final int direction,
final boolean forceJump) {
final View child = getAppBarChildOnOffset(layout, offset);
if (child != null) {
final AppBarLayout.LayoutParams childLp = (LayoutParams) child.getLayoutParams();
final int flags = childLp.getScrollFlags();
boolean lifted = false;
if ((flags & LayoutParams.SCROLL_FLAG_SCROLL) != 0) {
final int minHeight = ViewCompat.getMinimumHeight(child);
if (direction > 0
&& (flags
& (LayoutParams.SCROLL_FLAG_ENTER_ALWAYS
| LayoutParams.SCROLL_FLAG_ENTER_ALWAYS_COLLAPSED))
!= 0) {
// We're set to enter always collapsed so we are only collapsed when
// being scrolled down, and in a collapsed offset
lifted = -offset >= child.getBottom() - minHeight - layout.getTopInset();
} else if ((flags & LayoutParams.SCROLL_FLAG_EXIT_UNTIL_COLLAPSED) != 0) {
// We're set to exit until collapsed, so any offset which results in
// the minimum height (or less) being shown is collapsed
lifted = -offset >= child.getBottom() - minHeight - layout.getTopInset();
}
}
if (layout.isLiftOnScroll()) {
// Only update lifted state based on first scrolling child because it represents the
// content that would be scrolled beneath the app bar.
View scrollingChild = findFirstScrollingChild(parent);
if (scrollingChild != null) {
lifted = scrollingChild.getScrollY() > 0;
}
}
final boolean changed = layout.setLiftedState(lifted);
if (Build.VERSION.SDK_INT >= 11
&& (forceJump || (changed && shouldJumpElevationState(parent, layout)))) {
// If the collapsed state changed, we may need to
// jump to the current state if we have an overlapping view
layout.jumpDrawablesToCurrentState();
}
}
}
private boolean shouldJumpElevationState(CoordinatorLayout parent, T layout) {
// We should jump the elevated state if we have a dependent scrolling view which has
// an overlapping top (i.e. overlaps us)
final List dependencies = parent.getDependents(layout);
for (int i = 0, size = dependencies.size(); i < size; i++) {
final View dependency = dependencies.get(i);
final CoordinatorLayout.LayoutParams lp =
(CoordinatorLayout.LayoutParams) dependency.getLayoutParams();
final CoordinatorLayout.Behavior behavior = lp.getBehavior();
if (behavior instanceof ScrollingViewBehavior) {
return ((ScrollingViewBehavior) behavior).getOverlayTop() != 0;
}
}
return false;
}
private static View getAppBarChildOnOffset(final AppBarLayout layout, final int offset) {
final int absOffset = Math.abs(offset);
for (int i = 0, z = layout.getChildCount(); i < z; i++) {
final View child = layout.getChildAt(i);
if (absOffset >= child.getTop() && absOffset <= child.getBottom()) {
return child;
}
}
return null;
}
@Nullable
private View findFirstScrollingChild(CoordinatorLayout parent) {
for (int i = 0, z = parent.getChildCount(); i < z; i++) {
final View child = parent.getChildAt(i);
if (child instanceof NestedScrollingChild) {
return child;
}
}
return null;
}
@Override
int getTopBottomOffsetForScrollingSibling() {
return getTopAndBottomOffset() + offsetDelta;
}
@Override
public Parcelable onSaveInstanceState(CoordinatorLayout parent, T abl) {
final Parcelable superState = super.onSaveInstanceState(parent, abl);
final int offset = getTopAndBottomOffset();
// Try and find the first visible child...
for (int i = 0, count = abl.getChildCount(); i < count; i++) {
View child = abl.getChildAt(i);
final int visBottom = child.getBottom() + offset;
if (child.getTop() + offset <= 0 && visBottom >= 0) {
final SavedState ss = new SavedState(superState);
ss.firstVisibleChildIndex = i;
ss.firstVisibleChildAtMinimumHeight =
visBottom == (ViewCompat.getMinimumHeight(child) + abl.getTopInset());
ss.firstVisibleChildPercentageShown = visBottom / (float) child.getHeight();
return ss;
}
}
// Else we'll just return the super state
return superState;
}
@Override
public void onRestoreInstanceState(CoordinatorLayout parent, T appBarLayout, Parcelable state) {
if (state instanceof SavedState) {
final SavedState ss = (SavedState) state;
super.onRestoreInstanceState(parent, appBarLayout, ss.getSuperState());
offsetToChildIndexOnLayout = ss.firstVisibleChildIndex;
offsetToChildIndexOnLayoutPerc = ss.firstVisibleChildPercentageShown;
offsetToChildIndexOnLayoutIsMinHeight = ss.firstVisibleChildAtMinimumHeight;
} else {
super.onRestoreInstanceState(parent, appBarLayout, state);
offsetToChildIndexOnLayout = INVALID_POSITION;
}
}
/** A {@link Parcelable} implementation for {@link AppBarLayout}. */
protected static class SavedState extends AbsSavedState {
int firstVisibleChildIndex;
float firstVisibleChildPercentageShown;
boolean firstVisibleChildAtMinimumHeight;
public SavedState(Parcel source, ClassLoader loader) {
super(source, loader);
firstVisibleChildIndex = source.readInt();
firstVisibleChildPercentageShown = source.readFloat();
firstVisibleChildAtMinimumHeight = source.readByte() != 0;
}
public SavedState(Parcelable superState) {
super(superState);
}
@Override
public void writeToParcel(Parcel dest, int flags) {
super.writeToParcel(dest, flags);
dest.writeInt(firstVisibleChildIndex);
dest.writeFloat(firstVisibleChildPercentageShown);
dest.writeByte((byte) (firstVisibleChildAtMinimumHeight ? 1 : 0));
}
public static final Creator CREATOR =
new ClassLoaderCreator() {
@Override
public SavedState createFromParcel(Parcel source, ClassLoader loader) {
return new SavedState(source, loader);
}
@Override
public SavedState createFromParcel(Parcel source) {
return new SavedState(source, null);
}
@Override
public SavedState[] newArray(int size) {
return new SavedState[size];
}
};
}
}
/**
* Behavior which should be used by {@link View}s which can scroll vertically and support nested
* scrolling to automatically scroll any {@link AppBarLayout} siblings.
*/
public static class ScrollingViewBehavior extends HeaderScrollingViewBehavior {
public ScrollingViewBehavior() {}
public ScrollingViewBehavior(Context context, AttributeSet attrs) {
super(context, attrs);
final TypedArray a =
context.obtainStyledAttributes(attrs, R.styleable.ScrollingViewBehavior_Layout);
setOverlayTop(
a.getDimensionPixelSize(R.styleable.ScrollingViewBehavior_Layout_behavior_overlapTop, 0));
a.recycle();
}
@Override
public boolean layoutDependsOn(CoordinatorLayout parent, View child, View dependency) {
// We depend on any AppBarLayouts
return dependency instanceof AppBarLayout;
}
@Override
public boolean onDependentViewChanged(CoordinatorLayout parent, View child, View dependency) {
offsetChildAsNeeded(child, dependency);
updateLiftedStateIfNeeded(child, dependency);
return false;
}
@Override
public boolean onRequestChildRectangleOnScreen(
CoordinatorLayout parent, View child, Rect rectangle, boolean immediate) {
final AppBarLayout header = findFirstDependency(parent.getDependencies(child));
if (header != null) {
// Offset the rect by the child's left/top
rectangle.offset(child.getLeft(), child.getTop());
final Rect parentRect = tempRect1;
parentRect.set(0, 0, parent.getWidth(), parent.getHeight());
if (!parentRect.contains(rectangle)) {
// If the rectangle can not be fully seen the visible bounds, collapse
// the AppBarLayout
header.setExpanded(false, !immediate);
return true;
}
}
return false;
}
private void offsetChildAsNeeded(View child, View dependency) {
final CoordinatorLayout.Behavior behavior =
((CoordinatorLayout.LayoutParams) dependency.getLayoutParams()).getBehavior();
if (behavior instanceof BaseBehavior) {
// Offset the child, pinning it to the bottom the header-dependency, maintaining
// any vertical gap and overlap
final BaseBehavior ablBehavior = (BaseBehavior) behavior;
ViewCompat.offsetTopAndBottom(
child,
(dependency.getBottom() - child.getTop())
+ ablBehavior.offsetDelta
+ getVerticalLayoutGap()
- getOverlapPixelsForOffset(dependency));
}
}
@Override
float getOverlapRatioForOffset(final View header) {
if (header instanceof AppBarLayout) {
final AppBarLayout abl = (AppBarLayout) header;
final int totalScrollRange = abl.getTotalScrollRange();
final int preScrollDown = abl.getDownNestedPreScrollRange();
final int offset = getAppBarLayoutOffset(abl);
if (preScrollDown != 0 && (totalScrollRange + offset) <= preScrollDown) {
// If we're in a pre-scroll down. Don't use the offset at all.
return 0;
} else {
final int availScrollRange = totalScrollRange - preScrollDown;
if (availScrollRange != 0) {
// Else we'll use a interpolated ratio of the overlap, depending on offset
return 1f + (offset / (float) availScrollRange);
}
}
}
return 0f;
}
private static int getAppBarLayoutOffset(AppBarLayout abl) {
final CoordinatorLayout.Behavior behavior =
((CoordinatorLayout.LayoutParams) abl.getLayoutParams()).getBehavior();
if (behavior instanceof BaseBehavior) {
return ((BaseBehavior) behavior).getTopBottomOffsetForScrollingSibling();
}
return 0;
}
@Override
AppBarLayout findFirstDependency(List views) {
for (int i = 0, z = views.size(); i < z; i++) {
View view = views.get(i);
if (view instanceof AppBarLayout) {
return (AppBarLayout) view;
}
}
return null;
}
@Override
int getScrollRange(View v) {
if (v instanceof AppBarLayout) {
return ((AppBarLayout) v).getTotalScrollRange();
} else {
return super.getScrollRange(v);
}
}
private void updateLiftedStateIfNeeded(View child, View dependency) {
if (dependency instanceof AppBarLayout) {
AppBarLayout appBarLayout = (AppBarLayout) dependency;
if (appBarLayout.isLiftOnScroll()) {
appBarLayout.setLiftedState(child.getScrollY() > 0);
}
}
}
}
}