方向从横向更改为纵向后，RecyclerView位于中间而不是顶部

Question

I have used recyclerview in a fragment. If activity's configChanges includes orientation, recycler view appears in the middle of the screen after phone orientation changes from landscape to portrait. However it should be on top always. If configChanges does not include orientation, it always appear on top on orientation changes.

Do you have any idea what it is the reason?

This is the activity layout

 <android.support.design.widget.CoordinatorLayout 
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    tools:context="com.butterfly.LoginActivity">

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

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

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


    <FrameLayout
        app:layout_behavior="@string/appbar_scrolling_view_behavior"
        android:id="@+id/butterflypi_fragment"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_gravity="top|start" />


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

This is the fragment layout replaces framelayout above.

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:padding="8dp"
    xmlns:card_view="http://schemas.android.com/apk/res-auto"
    tools:context="com.butterfly.fragment.ButterflyPIsFragment">

    <android.support.v7.widget.RecyclerView
        android:id="@+id/my_pi_recycler_view"
        android:scrollbars="vertical"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_alignParentTop="true"

        />
</RelativeLayout>

Answer 1

I found solution here .

Basically you are creating your own behavior class:

public class PatchedScrollingViewBehavior extends AppBarLayout.ScrollingViewBehavior {

    public PatchedScrollingViewBehavior() {
        super();
    }

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

    @Override
    public boolean onMeasureChild(CoordinatorLayout parent, View child, int parentWidthMeasureSpec, int widthUsed, int parentHeightMeasureSpec, int heightUsed) {
        if (child.getLayoutParams().height == -1) {
            List dependencies = parent.getDependencies(child);
            if (dependencies.isEmpty()) {
                return false;
            }

            AppBarLayout appBar = findFirstAppBarLayout(dependencies);
            if (appBar != null && ViewCompat.isLaidOut(appBar)) {
                if (ViewCompat.getFitsSystemWindows(appBar)) {
                    ViewCompat.setFitsSystemWindows(child, true);
                }

                int scrollRange = appBar.getTotalScrollRange();
//                int height = parent.getHeight() - appBar.getMeasuredHeight() + scrollRange;
                int parentHeight = View.MeasureSpec.getSize(parentHeightMeasureSpec);
                int height = parentHeight - appBar.getMeasuredHeight() + scrollRange;
                int heightMeasureSpec = View.MeasureSpec.makeMeasureSpec(height, View.MeasureSpec.AT_MOST);
                parent.onMeasureChild(child, parentWidthMeasureSpec, widthUsed, heightMeasureSpec, heightUsed);
                return true;
            }
        }

        return false;
    }


    private static AppBarLayout findFirstAppBarLayout(List<View> views) {
        int i = 0;

        for (int z = views.size(); i < z; ++i) {
            View view = (View) views.get(i);
            if (view instanceof AppBarLayout) {
                return (AppBarLayout) view;
            }
        }

        return null;
    }
}

and changing app:layout_behavior in your FrameLayout:

<FrameLayout
        app:layout_behavior="your_package.PatchedScrollingViewBehavior"
        android:id="@+id/butterflypi_fragment"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_gravity="top|start" />

UPDATE: As I just checked - this issue was fixed in 22.2.1 library, so please update library, if you are still using 22.2.0

Answer 2

You may be able to achieve the desired effect by creating PORTRAIT and LANDSCAPE layout much like in the demo here . Take a look at attached clip if this is the behavior you desire.