我正在开发一个Android应用，我在其中使用CoordinatorLayout，AppBarLayout和CollapsingToolbarLayout来使用高级折叠栏功能。
我正在使用recyclerview来显示片段中的项目数。当我向上滚动recyclerview时，它会平滑地折叠AppBarLayout，但当我向下滚动并到达recyclerview的第一项时，它会自动停止滚动而不会扩展`AppBarLayout＆＃39;。
然后，我需要再次向下滚动以使AppBarLayout可见。所以我的要求是当我到达recyclerview的顶部时向下滚动它必须扩展`AppBarLayout＆＃39;。
我们怎么做到这一点。任何的想法 ？请参阅同一https://www.dropbox.com/s/va5jk27ikytk5ax/app_collapsebar_issue.mp4?dl=0
的视频这是我的布局： -
<?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>
答案 0 :(得分：9)
我只是把sample app放在一起，似乎证明了你之后的行为。每当AppBar下方的RecyclerView滚动到顶部时，AppBar都会自动展开，而不是停止并等待另一次滑动以打开RecyclerView。
最相关的组件位于自定义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);
}
}
类中。我添加了一些解释性评论：
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);
}
}
-Dmaven.javadoc.skip=true