BottomSheetBehavior like Google maps
suggest changeThis example depends on Support Library 23.4.0.+.
BottomSheetBehavior is characterized by :
- Two toolbars with animations that respond to the bottom sheet movements.
- A FAB that hides when it is near to the “modal toolbar” (the one that appears when you are sliding up).
- A backdrop image behind bottom sheet with some kind of parallax effect.
- A Title (TextView) in Toolbar that appears when bottom sheet reach it.
- The notification satus bar can turn its background to transparent or full color.
- A custom bottom sheet behavior with an “anchor” state.
Now let’s check them one by one:
ToolBars When you open that view in Google Maps, you can see a toolbar in where you can search, it’s the only one that I’m not doing exactly like Google Maps, because I wanted to do it more generic. Anyway that ToolBar
is inside an AppBarLayout
and it got hidden when you start dragging the BottomSheet and it appears again when the BottomSheet reach the COLLAPSED
state. To achieve it you need to:
- create a
Behavior
and extend it fromAppBarLayout.ScrollingViewBehavior
- override
layoutDependsOn
andonDependentViewChanged
methods. Doing it you will listen for bottomSheet movements. - create some methods to hide and unhide the AppBarLayout/ToolBar with animations.
This is how I did it for first toolbar or ActionBar:
@Override
public boolean layoutDependsOn(CoordinatorLayout parent, View child, View dependency) {
return dependency instanceof NestedScrollView;
}
@Override
public boolean onDependentViewChanged(CoordinatorLayout parent, View child,
View dependency) {
if (mChild == null) {
initValues(child, dependency);
return false;
}
float dVerticalScroll = dependency.getY() - mPreviousY;
mPreviousY = dependency.getY();
//going up
if (dVerticalScroll <= 0 && !hidden) {
dismissAppBar(child);
return true;
}
return false;
}
private void initValues(final View child, View dependency) {
mChild = child;
mInitialY = child.getY();
BottomSheetBehaviorGoogleMapsLike bottomSheetBehavior = BottomSheetBehaviorGoogleMapsLike.from(dependency);
bottomSheetBehavior.addBottomSheetCallback(new BottomSheetBehaviorGoogleMapsLike.BottomSheetCallback() {
@Override
public void onStateChanged(@NonNull View bottomSheet, @BottomSheetBehaviorGoogleMapsLike.State int newState) {
if (newState == BottomSheetBehaviorGoogleMapsLike.STATE_COLLAPSED ||
newState == BottomSheetBehaviorGoogleMapsLike.STATE_HIDDEN)
showAppBar(child);
}
@Override
public void onSlide(@NonNull View bottomSheet, float slideOffset) {
}
});
}
private void dismissAppBar(View child){
hidden = true;
AppBarLayout appBarLayout = (AppBarLayout)child;
mToolbarAnimation = appBarLayout.animate().setDuration(mContext.getResources().getInteger(android.R.integer.config_shortAnimTime));
mToolbarAnimation.y(-(mChild.getHeight()+25)).start();
}
private void showAppBar(View child) {
hidden = false;
AppBarLayout appBarLayout = (AppBarLayout)child;
mToolbarAnimation = appBarLayout.animate().setDuration(mContext.getResources().getInteger(android.R.integer.config_mediumAnimTime));
mToolbarAnimation.y(mInitialY).start();
}
Here is the complete file if you need it
The second Toolbar or “Modal” toolbar: You have to override the same methods, but in this one you have to take care of more behaviors:
- show/hide the ToolBar with animations
- change status bar color/background
- show/hide the BottomSheet title in the ToolBar
- close the bottomSheet or send it to collapsed state
The code for this one is a little extensive, so I will let the link
The FAB This is a Custom Behavior too, but extends from FloatingActionButton.Behavior
. In onDependentViewChanged
you have to look when it reach the “offSet” or point in where you want to hide it. In my case I want to hide it when it’s near to the second toolbar, so I dig into FAB parent (a CoordinatorLayout) looking for the AppBarLayout that contains the ToolBar, then I use the ToolBar position like OffSet
:
@Override
public boolean onDependentViewChanged(CoordinatorLayout parent, FloatingActionButton child, View dependency) {
if (offset == 0)
setOffsetValue(parent);
if (dependency.getY() <=0)
return false;
if (child.getY() <= (offset + child.getHeight()) && child.getVisibility() == View.VISIBLE)
child.hide();
else if (child.getY() > offset && child.getVisibility() != View.VISIBLE)
child.show();
return false;
}
Complete Custom FAB Behavior link
The image behind the BottomSheet with parallax effect: Like the others, it’s a custom behavior, the only “complicated” thing in this one is the little algorithm that keeps the image anchored to the BottomSheet and avoid the image collapse like default parallax effect:
@Override
public boolean onDependentViewChanged(CoordinatorLayout parent, View child,
View dependency) {
if (mYmultiplier == 0) {
initValues(child, dependency);
return true;
}
float dVerticalScroll = dependency.getY() - mPreviousY;
mPreviousY = dependency.getY();
//going up
if (dVerticalScroll <= 0 && child.getY() <= 0) {
child.setY(0);
return true;
}
//going down
if (dVerticalScroll >= 0 && dependency.getY() <= mImageHeight)
return false;
child.setY( (int)(child.getY() + (dVerticalScroll * mYmultiplier) ) );
return true;
}
The complete file for backdrop image with parallax effect
Now for the end: The Custom BottomSheet Behavior To achieve the 3 steps, first you need to understand that default BottomSheetBehavior has 5 states: STATE_DRAGGING, STATE_SETTLING, STATE_EXPANDED, STATE_COLLAPSED, STATE_HIDDEN
and for the Google Maps behavior you need to add a middle state between collapsed and expanded: STATE_ANCHOR_POINT
. I tried to extend the default bottomSheetBehavior with no success, so I just copy pasted all the code and modified what I need. To achieve what I’m talking about follow the next steps:
- Create a Java class and extend it from
CoordinatorLayout.Behavior<V>
- Copy paste code from default
BottomSheetBehavior
file to your new one. - Modify the method
clampViewPositionVertical
with the following code:
@Override
public int clampViewPositionVertical(View child, int top, int dy) {
return constrain(top, mMinOffset, mHideable ? mParentHeight : mMaxOffset);
}
int constrain(int amount, int low, int high) {
return amount < low ? low : (amount > high ? high : amount);
}
- Add a new state
public static final int STATE_ANCHOR_POINT = X;
- Modify the next methods:
onLayoutChild
,onStopNestedScroll
,BottomSheetBehavior<V> from(V view)
andsetState
(optional)
public boolean onLayoutChild(CoordinatorLayout parent, V child, int layoutDirection) {
// First let the parent lay it out
if (mState != STATE_DRAGGING && mState != STATE_SETTLING) {
if (ViewCompat.getFitsSystemWindows(parent) &&
!ViewCompat.getFitsSystemWindows(child)) {
ViewCompat.setFitsSystemWindows(child, true);
}
parent.onLayoutChild(child, layoutDirection);
}
// Offset the bottom sheet
mParentHeight = parent.getHeight();
mMinOffset = Math.max(0, mParentHeight - child.getHeight());
mMaxOffset = Math.max(mParentHeight - mPeekHeight, mMinOffset);
//if (mState == STATE_EXPANDED) {
// ViewCompat.offsetTopAndBottom(child, mMinOffset);
//} else if (mHideable && mState == STATE_HIDDEN...
if (mState == STATE_ANCHOR_POINT) {
ViewCompat.offsetTopAndBottom(child, mAnchorPoint);
} else if (mState == STATE_EXPANDED) {
ViewCompat.offsetTopAndBottom(child, mMinOffset);
} else if (mHideable && mState == STATE_HIDDEN) {
ViewCompat.offsetTopAndBottom(child, mParentHeight);
} else if (mState == STATE_COLLAPSED) {
ViewCompat.offsetTopAndBottom(child, mMaxOffset);
}
if (mViewDragHelper == null) {
mViewDragHelper = ViewDragHelper.create(parent, mDragCallback);
}
mViewRef = new WeakReference<>(child);
mNestedScrollingChildRef = new WeakReference<>(findScrollingChild(child));
return true;
}
public void onStopNestedScroll(CoordinatorLayout coordinatorLayout, V child, View target) {
if (child.getTop() == mMinOffset) {
setStateInternal(STATE_EXPANDED);
return;
}
if (target != mNestedScrollingChildRef.get() || !mNestedScrolled) {
return;
}
int top;
int targetState;
if (mLastNestedScrollDy > 0) {
//top = mMinOffset;
//targetState = STATE_EXPANDED;
int currentTop = child.getTop();
if (currentTop > mAnchorPoint) {
top = mAnchorPoint;
targetState = STATE_ANCHOR_POINT;
}
else {
top = mMinOffset;
targetState = STATE_EXPANDED;
}
} else if (mHideable && shouldHide(child, getYVelocity())) {
top = mParentHeight;
targetState = STATE_HIDDEN;
} else if (mLastNestedScrollDy == 0) {
int currentTop = child.getTop();
if (Math.abs(currentTop - mMinOffset) < Math.abs(currentTop - mMaxOffset)) {
top = mMinOffset;
targetState = STATE_EXPANDED;
} else {
top = mMaxOffset;
targetState = STATE_COLLAPSED;
}
} else {
//top = mMaxOffset;
//targetState = STATE_COLLAPSED;
int currentTop = child.getTop();
if (currentTop > mAnchorPoint) {
top = mMaxOffset;
targetState = STATE_COLLAPSED;
}
else {
top = mAnchorPoint;
targetState = STATE_ANCHOR_POINT;
}
}
if (mViewDragHelper.smoothSlideViewTo(child, child.getLeft(), top)) {
setStateInternal(STATE_SETTLING);
ViewCompat.postOnAnimation(child, new SettleRunnable(child, targetState));
} else {
setStateInternal(targetState);
}
mNestedScrolled = false;
}
public final void setState(@State int state) {
if (state == mState) {
return;
}
if (mViewRef == null) {
// The view is not laid out yet; modify mState and let onLayoutChild handle it later
/**
* New behavior (added: state == STATE_ANCHOR_POINT ||)
*/
if (state == STATE_COLLAPSED || state == STATE_EXPANDED ||
state == STATE_ANCHOR_POINT ||
(mHideable && state == STATE_HIDDEN)) {
mState = state;
}
return;
}
V child = mViewRef.get();
if (child == null) {
return;
}
int top;
if (state == STATE_COLLAPSED) {
top = mMaxOffset;
} else if (state == STATE_ANCHOR_POINT) {
top = mAnchorPoint;
} else if (state == STATE_EXPANDED) {
top = mMinOffset;
} else if (mHideable && state == STATE_HIDDEN) {
top = mParentHeight;
} else {
throw new IllegalArgumentException("Illegal state argument: " + state);
}
setStateInternal(STATE_SETTLING);
if (mViewDragHelper.smoothSlideViewTo(child, child.getLeft(), top)) {
ViewCompat.postOnAnimation(child, new SettleRunnable(child, state));
}
}
public static <V extends View> BottomSheetBehaviorGoogleMapsLike<V> from(V view) {
ViewGroup.LayoutParams params = view.getLayoutParams();
if (!(params instanceof CoordinatorLayout.LayoutParams)) {
throw new IllegalArgumentException("The view is not a child of CoordinatorLayout");
}
CoordinatorLayout.Behavior behavior = ((CoordinatorLayout.LayoutParams) params)
.getBehavior();
if (!(behavior instanceof BottomSheetBehaviorGoogleMapsLike)) {
throw new IllegalArgumentException(
"The view is not associated with BottomSheetBehaviorGoogleMapsLike");
}
return (BottomSheetBehaviorGoogleMapsLike<V>) behavior;
}
Link to the whole project where you can see all the Custom Behaviors
And here it is how it looks like:
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