So erweitern Sie AppBarLayout, wenn das Scrollen am oberen Ende des RecyclerView

Question

Ich arbeite an einer Android-App, in der ich CoordinatorLayout, AppBarLayout und CollapsingToolbarLayout verwenden, um die Fortschrittsbalkenleiste Funktionalität zu verwenden.

Ich verwende Recyclerview, um die Anzahl der Elemente im Fragment anzuzeigen. Wenn ich screwing recyclerview es kollabieren glatt AppBarLayout, aber wenn ich scrollen und erreichen Sie auf das erste Element der recyclerview es automatisch aufhören zu scrollen ohne erweitern "AppBarLayout".

Dann muss ich noch einmal nach unten scrollen, um AppBarLayout sichtbar zu machen. Also meine Anforderung ist, dass beim Herunterscrollen, wenn ich bis zur Spitze der Recycleransicht erreiche, es "AppBarLayout" erweitern muss.

Wie können wir das tun? Irgendeine Idee ? Bitte beachten Sie Video von gleichen https://www.dropbox.com/s/va5jk27ikytk5ax/app_collapsebar_issue.mp4?dl=0

Hier ist mein Layout gleich: -

<?xml version="1.0" encoding="utf-8"?> 

<android.support.v4.widget.DrawerLayout xmlns:android="http://schemas.android.com/apk/res/android" 
    xmlns:app="http://schemas.android.com/apk/res-auto" 
    android:id="@+id/drawerLayout" 
    android:layout_width="match_parent" 
    android:layout_height="match_parent" 

    android:fitsSystemWindows="true"> 

    <FrameLayout 
    android:layout_width="match_parent" 
    android:layout_height="match_parent"> 

    <android.support.design.widget.CoordinatorLayout xmlns:android="http://schemas.android.com/apk/res/android" 
     xmlns:app="http://schemas.android.com/apk/res-auto" 
     xmlns:tools="http://schemas.android.com/tools" 
     android:id="@+id/coordinator" 
     android:layout_width="match_parent" 
     android:layout_height="match_parent" 
     android:adjustViewBounds="true" 
     android:fitsSystemWindows="true" 
     app:layout_scrollFlags="scroll|exitUntilCollapsed" 
     > 

     <android.support.design.widget.AppBarLayout 
     android:id="@+id/app_bar" 
     android:layout_width="match_parent" 
     android:layout_height="220dp" 
     android:background="@drawable/offer_image" 
     android:fitsSystemWindows="true" 
     android:theme="@style/AppTheme.AppBarOverlay" 
     app:layout_scrollFlags="scroll|exitUntilCollapsed"> 

     <!-- <com.flaviofaria.kenburnsview.KenBurnsView 
      android:id="@+id/image" 
      android:layout_width="match_parent" 
      android:layout_height="220dp" 
      android:src="@drawable/offer_image" />--> 
     <android.support.design.widget.CollapsingToolbarLayout 
      android:id="@+id/toolbar_layout" 
      android:layout_width="match_parent" 
      android:layout_height="match_parent" 
      android:fitsSystemWindows="true" 
      app:expandedTitleMarginEnd="64dp" 
      app:expandedTitleMarginStart="48dp" 
      app:layout_scrollFlags="scroll|exitUntilCollapsed"> 


      <com.flaviofaria.kenburnsview.KenBurnsView 
      android:id="@+id/image" 
      android:layout_width="match_parent" 
      android:layout_height="220dp" 

      android:src="@drawable/offer_image" /> 

      <FrameLayout 
      android:id="@+id/collapse_frame" 
      android:layout_width="match_parent" 
      android:layout_height="match_parent" 
      android:background="#B3c85a00"> 

      </FrameLayout> 

      <FrameLayout 
      android:id="@+id/centerCircle" 
      android:layout_width="wrap_content" 
      android:layout_height="wrap_content" 
      android:layout_gravity="center"> 

      <ImageView 
       android:id="@+id/imageViewCenter" 
       android:layout_width="wrap_content" 
       android:layout_height="wrap_content" 
       android:layout_gravity="center" 
       android:src="@drawable/offer" /> 
      </FrameLayout> 

      <include 
      android:id="@+id/toolbar" 
      layout="@layout/toolbar" /> 

      <android.support.design.widget.TabLayout 
      android:id="@+id/tabs" 
      android:layout_width="match_parent" 
      android:layout_height="wrap_content" 
      android:layout_gravity="bottom" 
      android:layout_marginBottom="15dp" 
      app:tabIndicatorColor="#FFFFFF" 
      app:tabMode="scrollable" /> 
      <!--</FrameLayout>--> 
     </android.support.design.widget.CollapsingToolbarLayout> 
     </android.support.design.widget.AppBarLayout> 

     <!--<FrameLayout--> 

     <!--android:layout_width="match_parent"--> 
     <!--android:layout_height="match_parent"--> 
     <!-- --> 
     <!--android:visibility="visible">--> 

     <android.support.design.widget.FloatingActionButton 
     android:id="@+id/fab" 
     style="@style/floating_action_button" 
     android:layout_width="wrap_content" 
     android:layout_height="wrap_content" 
     android:layout_gravity="bottom|end" 
     android:src="@drawable/ic_share_white_24dp" 
     android:visibility="gone" 
     app:backgroundTint="#FF9800" 
     app:elevation="6dp" 
     app:pressedTranslationZ="12dp" /> 

     <android.support.v4.view.ViewPager xmlns:android="http://schemas.android.com/apk/res/android" 
     android:id="@+id/pager" 
     android:layout_width="match_parent" 
     android:layout_height="wrap_content" 
     android:layout_gravity="left|bottom|fill_vertical" 
     android:layout_marginTop="0dp" 
     app:layout_behavior="@string/appbar_scrolling_view_behavior"></android.support.v4.view.ViewPager> 
     <!--</FrameLayout>--> 

     <!--<include layout="@layout/content_scrolling" />--> 

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

    <RelativeLayout 
     android:id="@+id/bannerView" 
     android:layout_width="match_parent" 
     android:layout_height="58dp" 
     android:layout_gravity="bottom|center" 
     android:background="@drawable/curved_white_with_blue_border" 
     android:visibility="gone"> 

     <TextView 
     android:id="@+id/bannerText" 
     android:layout_width="wrap_content" 
     android:layout_height="wrap_content" 
     android:layout_centerHorizontal="true" 
     android:layout_centerInParent="true" 
     android:layout_centerVertical="true" 
     android:gravity="center" 
     android:padding="3dp" 
     android:text="Banner" 
     android:visibility="gone" /> 

     <ImageView 
     android:id="@+id/bannerImage" 
     android:layout_width="match_parent" 
     android:layout_height="match_parent" 
     android:layout_alignParentLeft="true" 
     android:layout_centerHorizontal="true" 
     android:layout_centerVertical="true" 
     android:gravity="center" 
     android:padding="3dp" 
     android:scaleType="fitXY" 
     android:visibility="gone" /> 

     <ImageView 
     android:id="@+id/bannerClose" 
     android:layout_width="wrap_content" 
     android:layout_height="wrap_content" 
     android:layout_alignParentRight="true" 
     android:layout_alignParentTop="true" 
     android:layout_centerVertical="true" 
     android:src="@drawable/cross_icon" /> 
    </RelativeLayout> 


    <LinearLayout 
     android:id="@+id/socialTabs" 
     android:layout_width="match_parent" 
     android:layout_height="46dp" 
     android:layout_gravity="bottom|center" 
     android:layout_marginBottom="5dp" 
     android:background="@color/White" 
     android:orientation="horizontal" 
     android:visibility="gone"> 

     <ImageView 
     android:layout_width="wrap_content" 
     android:layout_height="match_parent" 
     android:adjustViewBounds="true" 
     android:src="@drawable/follow" /> 

     <FrameLayout 
     android:layout_width="match_parent" 
     android:layout_height="match_parent" 
     android:layout_gravity="center" 
     android:background="@color/White"> 

     <LinearLayout 
      android:layout_width="match_parent" 
      android:layout_height="46dp" 
      android:layout_gravity="center" 
      android:gravity="center" 
      android:paddingLeft="10dp" 
      android:paddingRight="10dp" 
      android:weightSum="3"> 

      <ImageView 
      android:id="@+id/facebookImageView" 
      android:layout_width="30dp" 
      android:layout_height="30dp" 
      android:layout_weight="1" 
      android:src="@drawable/fb_follow" /> 

      <ImageView 
      android:id="@+id/googlePlusImageView" 
      android:layout_width="30dp" 
      android:layout_height="30dp" 
      android:layout_marginLeft="5dp" 
      android:layout_marginRight="5dp" 
      android:layout_weight="1" 
      android:adjustViewBounds="true" 
      android:src="@drawable/google_follow" /> 

      <ImageView 
      android:id="@+id/twitterImageView" 
      android:layout_width="30dp" 
      android:layout_height="30dp" 
      android:layout_weight="1" 
      android:adjustViewBounds="true" 
      android:src="@drawable/twitter_follow" /> 
     </LinearLayout> 
     </FrameLayout> 
    </LinearLayout> 
    </FrameLayout> 

    <ExpandableListView 
    android:id="@+id/left_drawer" 
    android:layout_width="265dp" 
    android:layout_height="match_parent" 
    android:layout_gravity="start" 
    android:background="#fff" 
    android:choiceMode="singleChoice" 
    android:divider="@null" 
    android:dividerHeight="0dp" 
    android:drawSelectorOnTop="true" 
    android:groupIndicator="@null" 
    android:scrollbars="@null" /> 

</android.support.v4.widget.DrawerLayout> 

Answer 1

ich gerade habe ein sample app zusammengestellt, die das Verhalten Sie nach zu demonstrieren scheint. Die AppBar wird automatisch erweitert, wenn die RecyclerView darunter nach oben gescrollt wird, anstatt zu stoppen und warten auf einen weiteren Swipe, um die AppBar zu öffnen.

Die relevantesten Komponenten befinden sich in einer benutzerdefinierten RecyclerView-Klasse. Ich habe ein paar erklärenden Kommentare hinzugefügt:

public class ScrollFeedbackRecyclerView extends RecyclerView { 

    private WeakReference<Callbacks> mCallbacks; 

    public ScrollFeedbackRecyclerView(Context context) { 
     super(context); 
     attachCallbacks(context); 
    } 

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

    /*If the first completely visible item in the RecyclerView is at 
    index 0, then we're at the top of the list, so we want the AppBar to expand 
    **if the AppBar is also collapsed** (otherwise the AppBar will constantly 
    attempt to expand). 
    */ 
    @Override 
    public void onScrolled(int dx, int dy) { 
     if(((LinearLayoutManager)getLayoutManager()).findFirstCompletelyVisibleItemPosition() == 0) { 
      Log.e(getClass().getSimpleName(), "index 0 visible"); 
      if(mCallbacks.get().isAppBarCollapsed()) { 
       mCallbacks.get().setExpanded(true); 
      } 
     } 
     super.onScrolled(dx, dy); 
    } 

    /* the findFirstCompletelyVisibleItem() method is only available with 
    LinearLayoutManager and its subclasses, so test for it when setting the 
    LayoutManager 
    */ 
    @Override 
    public void setLayoutManager(LayoutManager layout) { 
     if(!(layout instanceof LinearLayoutManager)) { 
      throw new IllegalArgumentException(layout.toString() + " must be of type LinearLayoutManager"); 
     } 
     super.setLayoutManager(layout); 
    } 

    private void attachCallbacks(Context context) { 

     try { 
      mCallbacks = new WeakReference<>((Callbacks)context); 
     } catch (ClassCastException e) { 
      throw new ClassCastException(context.toString() + " must implement " + 
        "ScrollFeedbackRecyclerView.Callbacks"); 
     } 

    } 

    /* Necessary to interact with the AppBarLayout in the hosting Activity 
    */ 
    interface Callbacks { 

     boolean isAppBarCollapsed(); 
     void setExpanded(boolean expanded); 

    } 
} 

MainActivity.java

public class MainActivity extends AppCompatActivity implements ScrollFeedbackRecyclerView.Callbacks{ 

    private AppBarLayout mAppBarLayout; 
    private Toolbar mToolbar; 

    @Override 
    protected void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
     setContentView(R.layout.activity_main); 

     ScrollFeedbackRecyclerView mRecyclerView = (ScrollFeedbackRecyclerView) findViewById(R.id.rv_container); 
     RecyclerViewAdapter mAdapter = new RecyclerViewAdapter(); 

     mRecyclerView.setAdapter(mAdapter); 
     mRecyclerView.setLayoutManager(new LinearLayoutManager(this)); 

     mAppBarLayout = (AppBarLayout) findViewById(R.id.app_bar); 
     mToolbar = (Toolbar) findViewById(R.id.toolbar); 

    } 

    /* When collapsed, calling getY() on the AppBar will return a negative number. 
    Adding this number to getHeight() will return the same value as the toolbar's 
    height if the AppBar is fully collapsed. 
    */ 
    @Override 
    public boolean isAppBarCollapsed() { 
     final int appBarVisibleHeight = (int) (mAppBarLayout.getY() + mAppBarLayout.getHeight()); 
     final int toolbarHeight = mToolbar.getHeight(); 
     return (appBarVisibleHeight == toolbarHeight); 
    } 

    @Override 
    public void setExpanded(boolean expanded) { 
     mAppBarLayout.setExpanded(expanded, true); 
    } 
}