当您停止在android中滚动listview / recyclerview时，如何隐藏或显示部分隐藏的工具栏/操作栏

Question

So to show and hide the action bar when scrolling I am using this method using coordinator layout and appbarlayout

But when I stop scrolling the list in the middle of toolbar being hidden or shown it stays there and only part of toolbar is visible.

What I want to do is make the toolbar show or hide completely based on the percentage of toolbar visible.

Is there a way I can acheive this using the coordinator layout and appbarlayout?

Answer 1

EDIT - Just get 23.1.0 design library and add "|snap" attribute to your ToolBar layout:

<android.support.design.widget.CoordinatorLayout
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <android.support.design.widget.AppBarLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:theme="@style/ThemeOverlay.AppCompat.Dark.ActionBar">

       <android.support.v7.widget.Toolbar
                android:id="@+id/toolbar"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                app:layout_scrollFlags="scroll|enterAlways|snap />
       -----
       -----

SO YOU DON'T NEED TO USE THE FOLLOWING CODE:

Have you tried to add the layout_behaviour attribute to AppBarLayout?

app:layout_behavior="AppBarLayoutSnapBehavior"

Then you need to create class "AppBarLayoutSnapBehavior":

public class AppBarLayoutSnapBehavior extends AppBarLayout.Behavior {

private ValueAnimator mAnimator;
private boolean mNestedScrollStarted = false;

public AppBarLayoutSnapBehavior(Context context, AttributeSet attrs) {
    super(context, attrs);
}

@Override
public boolean onStartNestedScroll(CoordinatorLayout coordinatorLayout, AppBarLayout child,
                                   View directTargetChild, View target, int nestedScrollAxes) {
    mNestedScrollStarted = super.onStartNestedScroll(coordinatorLayout, child, directTargetChild, target, nestedScrollAxes);
    if (mNestedScrollStarted && mAnimator != null) {
        mAnimator.cancel();
    }
    return mNestedScrollStarted;
}

@Override
public void onStopNestedScroll(CoordinatorLayout coordinatorLayout, AppBarLayout child, View target) {
    super.onStopNestedScroll(coordinatorLayout, child, target);

    if (!mNestedScrollStarted) {
        return;
    }

    mNestedScrollStarted = false;

    int scrollRange = child.getTotalScrollRange();
    int topOffset = getTopAndBottomOffset();

    if (topOffset <= -scrollRange || topOffset >= 0) {
        // Already fully visible or fully invisible
        return;
    }

    if (topOffset < -(scrollRange / 2f)) {
        // Snap up (to fully invisible)
        animateOffsetTo(-scrollRange);
    } else {
        // Snap down (to fully visible)
        animateOffsetTo(0);
    }
}

private void animateOffsetTo(int offset) {
    if (mAnimator == null) {
        mAnimator = new ValueAnimator();
        mAnimator.setInterpolator(new DecelerateInterpolator());
        mAnimator.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {
            @Override
            public void onAnimationUpdate(ValueAnimator animation) {
                setTopAndBottomOffset((int) animation.getAnimatedValue());
            }
        });
    } else {
        mAnimator.cancel();
    }

    mAnimator.setIntValues(getTopAndBottomOffset(), offset);
    mAnimator.start();
}

Should work for you.

Answer 2

I've got partial solution. To your recyclerview add onScrollListener bellow, with AppBarLayout in param

public class ImprovedScrollListener extends RecyclerView.OnScrollListener {

private WeakReference<AppBarLayout> mAppBarLayout;

public ImprovedScrollListener(AppBarLayout appBarLayout) {
    mAppBarLayout = new WeakReference<>(appBarLayout);
}

@Override
public void onScrollStateChanged(RecyclerView recyclerView, int newState) {
    super.onScrollStateChanged(recyclerView, newState);

    if (newState == RecyclerView.SCROLL_STATE_IDLE && mAppBarLayout.get() != null) {

        if (!recyclerView.canScrollVertically(-1) && !recyclerView.canScrollVertically(1)) {
            /// TODO: 21.10.2015  handle this state
        }else if(!recyclerView.canScrollVertically(-1)){
            mAppBarLayout.get().setExpanded(true, true);
        } else {
            mAppBarLayout.get().setExpanded(false, true);
        }
    }
}

}

This will work for recyclerviews that can scroll, this still behaves ugly when recyclerview is not scrollable (see TODO in code). If somebody find solution for this case let me know

Answer 3

Setting Toolbar within AppBarLayout and cordinationLayout will itself take care of hiding and showing the actionBar

<?xml version="1.0" encoding="utf-8"?>
<android.support.design.widget.CoordinatorLayout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:layout_width="match_parent"
android:id="@+id/cordinationLayout"
android:layout_height="match_parent">


<android.support.design.widget.AppBarLayout
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:theme="@style/ThemeOverlay.AppCompat.Dark.ActionBar">


    <android.support.v7.widget.Toolbar
        android:id="@+id/toolbar"
        android:layout_width="match_parent"
        android:layout_height="?attr/actionBarSize"
        android:background="?attr/colorPrimary"
        app:layout_scrollFlags="scroll|enterAlways"
        app:popupTheme="@style/ThemeOverlay.AppCompat.Light" />

</android.support.design.widget.AppBarLayout>

</android.support.design.widget.CoordinatorLayout>