Android FAB behaviour with listview for custom layout

问题

I would like to achieve behaviour similar to this example

but without toolbar move and for custom view not for a FAB. So, firstly i would like to see layout similar to https://www.google.com/design/spec/components/bottom-sheets.html (it can be simple LinearLayout placed on bottom of the screen with some child views) which hides when i start scroll down listview and appears when i scroll up a little. Have digged deep in web but found nothing what really works. Thanks in advance.

回答1:

First you need to extend default FAB behavior, in order to keep FAB behavior when Snackbar is shown. Otherwise you will see it not translating upwards when Snackbar pops up.

React on vertical scrolling only:

@Override
public boolean onStartNestedScroll(CoordinatorLayout parent,
        View child, View target, View target,int scrollAxes) {
    return (scrollAxes & ViewCompat.SCROLL_AXIS_VERTICAL) != 0;
}

Once you have vertical nested scrolling accumulate how much has been scrolled. Start translating the FAB when you have scrolled as much as FAB height:

    Override
    public void onNestedPreScroll(CoordinatorLayout coordinatorLayout, FloatingActionButton child, View target, int dx, int dy, int[] consumed) {
         if (dy > 0 && mTotalDy < 0 || dy < 0 && mTotalDy > 0) {
             mTotalDy = 0;
         }

         mTotalDy += dy;
         if ( mTotalDy > child.getHeight() 
                && child.getVisibility() == View.VISIBLE) {
             //translate to it's height, offscreen, set visbility to gone at end of translation animation
        } else if (mTotalDy < 0 
                && child.getVisibility() == View.GONE) {
            //translate to 0 set visbility to visible at end of translation animation
        }

}

When mTotalDy is greater than FAB height we have scrolling down, when the mTotalDy we are scrolling up.

You should also take care of nested flinging in onNestedPreFling() method. Hide the FAB when the velocityY < 0 and show it when velocityY > 0, all these conditions only when Math.abs(velocityY) > Math.abs(velocityX). In other words, only when there is vertical flinging.

来源：https://stackoverflow.com/questions/34027192/android-fab-behaviour-with-listview-for-custom-layout

标签

android

listview

material-design