向下滚动时如何展开AppBarLayout到达RecyclerView的顶部 [英] How to expand AppBarLayout when scrolling down reaches at top of the RecyclerView
本文介绍了向下滚动时如何展开AppBarLayout到达RecyclerView的顶部的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！
问题描述
我正在开发一个Android应用程序，其中使用CoordinatorLayout，AppBarLayout和CollapsingToolbarLayout使用高级折叠栏功能.
I am working on one android app in which I am using CoordinatorLayout,AppBarLayout and CollapsingToolbarLayout to use the advance collapse bar functionality.
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，但是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".
I am using recyclerview to show the number of items in the fragment. When I'm scrolling up recyclerview it smoothly collapse AppBarLayout but when I scroll down and reach at on the first item of the recyclerview it automatically stop scrolling without expanding `AppBarLayout'.
然后再次需要向下滚动以使AppBarLayout可见.因此，我的要求是，当我向下滚动到Recyclerview的顶部时，必须展开"AppBarLayout".
Then again I need to scroll down again to make AppBarLayout visible. So my requirement is that on scrolling down when I reach to top of recyclerview it must expand `AppBarLayout'.
我们如何做到这一点.任何的想法 ?请观看相同
How can we do this. Any idea ? Please see video of same https://www.dropbox.com/s/va5jk27ikytk5ax/app_collapsebar_issue.mp4?dl=0
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>
推荐答案
我刚刚整理了一个示例应用似乎证明了您所追求的行为.每当AppBar下方的RecyclerView滚动到顶部时，它将自动展开，而不是停止并等待再次滑动以打开AppBar.
I've just put together a sample app that seems to demonstrate the behaviour you're after. The AppBar will automatically expand whenever the RecyclerView beneath it is scrolled to the top, rather than stopping and waiting for another swipe to open the AppBar.
最相关的组件位于自定义RecyclerView类中.我添加了一些解释性评论:
The most relevant components reside in a custom RecyclerView class. I've added a few explanatory comments:
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);
}
}
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