Android: Custom bottom sheet dialog - dialog

Question

How can I implement following design functionality with android standard component bottom sheet:
Image when Bottom sheet dialog fragment will appear:
Image when user scrolled to up to view bottom of content:
I will use ViewPager to scrolling header images and RecyclerView to showing descriptions and other informations. And parallax effect to ImageView(which are placed in ViewPager) when scrolling content vertically. Have a minimum height of the ImageView(and ViewPager), user can't collapse fully it (Look to second screenshot, which is user scrolled until the end of content).
I want stop scrolling ImageView when it will reach to minimum height(look to second one Screenshot), but the content of below ImageView should be continue scrolling

Answer 1

This can be done with an if statement in an on scroll view such as shown below:
ScrollView scrollView = findViewById(R.id.scrollView); //Adjust for your code
ImageView imageView = findViewById(R.id.imageView); //Adjust for your code
boolean imageIsHidden = false;
int threshold = 250;
scrollView.getViewTreeObserver().addOnScrollChangedListener(new OnScrollChangedListener() {
#Override
public void onScrollChanged() {
int scrollY = rootScrollView.getScrollY();
if(scrollY >= threshold){
imageIsHidden = true;
//Move image outside of scroll view so it doesn't scroll
}
else if(scrollY < threshold && imageIsHidden){
imageIsHidden = false;
//Move image inside of scroll view so it does scroll
}
}
});
What this does is has a boolean called imageIsHidden and an integer called threshold. Threshold is where you want it to make it disappear. You will need to play around with this value to find a sweet spot.
You will also need to implement moving the image inside and outside of the scroll view as well in the if and if else statement.