If you want to achieve it using Support Library 23.4.0.+ I will tell you how I got it and how its works.
As far I can see that activity/fragment has the followings behaviors:
- 2 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 the bottom sheet with some kind of parallax effect.
- A Title (TextView) in Toolbar that appears when the bottom sheet reaches it.
- The notification status bar can turn its background to transparent or full color.
- A custom bottom sheet behavior with an "anchor" state.
note2: This answer talk about 6 things not about 1 or 2 like other question, can you see the difference now?
Ok, now let's check one bye one:
ToolBars
When you open that view in google maps u can see a toolbar where you can search, it's the only one that I'm not doing equals 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 reaches the COLLAPSED state.
To achieve it you need:
- create a
Behavior and extend it from AppBarLayout.ScrollingViewBehavior
- override
layoutDependsOn and onDependentViewChanged 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 the 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();
}
the complete file if you need it
The second Toolbar or "Modal" toolbar:
You have to override some 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 a 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 reaches 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 CoordiantorLayout) 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 its a custom behavior, the only "complicated" thing in this one is the little algorithm that keeps the Image anchored to the BottomSheet and avoids the image collapse like the 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;
}
[complete file for backdrop Image with parallax effect][4]
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 extends the default bottomSheetBehavior with no success, so I just copy-paste all code and modified what I need.
To achieve what I'm talking about following the next steps:
Create a Java class and extend it from CoordinatorLayout.Behavior<V>
Copy paste code from the 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) and setState (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;
targ
