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原文地址
先看看官网对于AppBarLayout.OnOffsetChangedListener的解释：
Interface definition for a callback to be invoked when an AppBarLayout's vertical offset changes.
当AppBarLayout垂直方向上的偏移量发生改变时，为触发一个回调方法定义的接口。
触发的回调方法是：
onOffsetChanged(AppBarLayout appBarLayout, int verticalOffset)
再来看看对于onOffsetChanged的解释：
Called when the AppBarLayout's layout offset has been changed. This allows child views to implement custom behavior based on the offset (for instance pinning a view at a certain y value).
在AppBarLayout的布局偏移量发生改变时被调用。这个方法允许子view根据偏移量实现自定义的行为（比如在特定Y值的时候固定住一个View）。
解释的非常清楚了，不过我们需要点例子才好理解。
就以stackoverflow上的一个问题为例吧。
http://stackoverflow.com/questions/30779667/android-collapsingtoolbarlayout-and-swiperefreshlayout/30785823#30785823
问题描述
当我把CollapsingToolbarLayout，CollapsingToolbarLayout以及SwipeRefreshLayout用在一起的时候：
<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/drawer_layout"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:fitsSystemWindows="true"><android.support.design.widget.CoordinatorLayout
android:id="@+id/coordinator_layout"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:fitsSystemWindows="true"><android.support.design.widget.AppBarLayout
android:id="@+id/appbar"
android:layout_width="match_parent"
android:layout_height="@dimen/collapse_toolbar_height"
android:fitsSystemWindows="true"
android:theme="@style/ThemeOverlay.AppCompat.Dark.ActionBar">
<android.support.design.widget.CollapsingToolbarLayout
android:id="@+id/collapsing_toolbar"
android:layout_width="match_parent"
android:layout_height="match_parent"
app:contentScrim="?attr/colorPrimary"
android:fitsSystemWindows="true"
app:expandedTitleMarginStart="48dp"
app:expandedTitleMarginEnd="64dp"
app:layout_scrollFlags="scroll|exitUntilCollapsed">
<ImageView
android:id="@+id/toolbar_image"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:scaleType="centerCrop"
android:fitsSystemWindows="true"
app:layout_collapseMode="parallax" />
<include
layout="@layout/activity_main_toolbar"/>
</android.support.design.widget.CollapsingToolbarLayout></android.support.design.widget.AppBarLayout>
<android.support.v4.widget.SwipeRefreshLayout
android:id="@+id/swipe_container"
android:layout_width="match_parent"
android:layout_height="match_parent"
app:layout_behavior="@string/appbar_scrolling_view_behavior">
<cz.yetanotherview.webcamviewer.app.helper.EmptyRecyclerView
android:id="@+id/mainList"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:scrollbars="vertical" />
</android.support.v4.widget.SwipeRefreshLayout>
<android.support.design.widget.FloatingActionButton
android:id="@+id/floating_action_button"
android:layout_height="wrap_content"
android:layout_width="wrap_content"
app:layout_anchor="@id/appbar"
app:layout_anchorGravity="bottom|right|end"
android:layout_margin="16dp"
app:fabSize="mini"
android:src="@drawable/ic_action_edit"
android:onClick="assignSelectedWebCamsToCategory"/>
<com.github.clans.fab.FloatingActionMenu
android:id="@+id/floating_action_menu"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_gravity="bottom|end"
android:paddingRight="10dp"
android:paddingBottom="8dp"
android:paddingLeft="10dp"
fab:menu_shadowColor="#37000000"
fab:menu_colorNormal="#DA4336"
fab:menu_colorPressed="#E75043"
fab:menu_colorRipple="#99FFFFFF"
fab:menu_icon="@drawable/fab_add"
fab:menu_buttonSpacing="10dp"
fab:menu_labels_textColor="@color/very_dark_grey"
fab:menu_labels_textSize="14sp"
fab:menu_labels_colorNormal="@color/white"
fab:menu_labels_colorPressed="@color/next_grey"
fab:menu_labels_colorRipple="#99FFFFFF"
fab:menu_labels_margin="8dp"
fab:menu_backgroundColor="@color/black_transparent">
<com.github.clans.fab.FloatingActionButton
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:src="@drawable/ic_action_content_import"
fab:fab_size="mini"
fab:fab_label="@string/pref_import_from_server"
fab:fab_colorNormal="@color/white"
app:fab_colorPressed="@color/next_grey"
app:fab_colorRipple="#99FFFFFF"
android:onClick="showSelectionDialog"/>
<com.github.clans.fab.FloatingActionButton
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:src="@drawable/ic_action_content_manually"
fab:fab_size="mini"
fab:fab_label="@string/create_manually"
fab:fab_colorNormal="@color/white"
app:fab_colorPressed="@color/next_grey"
app:fab_colorRipple="#99FFFFFF"
android:onClick="showAddDialog"/>
<com.github.clans.fab.FloatingActionButton
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:src="@drawable/ic_action_content_suggestion"
fab:fab_size="mini"
fab:fab_label="@string/submit_suggestion"
fab:fab_colorNormal="@color/white"
app:fab_colorPressed="@color/next_grey"
app:fab_colorRipple="#99FFFFFF"
android:onClick="showSuggestionDialog"/>
</com.github.clans.fab.FloatingActionMenu></android.support.design.widget.CoordinatorLayout><include
layout="@layout/activity_main_drawer"/></android.support.v4.widget.DrawerLayout>
java代码：
swipeRefreshLayout = (SwipeRefreshLayout) findViewById(R.id.swipe_container);
swipeRefreshLayout.setOnRefreshListener(this);
如何才能让滑动刷新只发生在collapsing toolbar完全展开并且 scrollview (或者recyclerview)在顶部 的时候呢？类似于g＋和Inbox中的效果。
错误的效果:
正确的效果：
回答：
可以尝试为AppBarLayout添加 offset change listener同时根据情况启用或者关闭滑动刷新，需要增加的代码在这里：
https://gist.github.com/blackcj/001a90c7775765ad5212
关键改动：
public class MainActivity extends AppCompatActivity implements AppBarLayout.OnOffsetChangedListener {
...
private AppBarLayout appBarLayout;
private SwipeRefreshLayout mSwipeRefreshLayout;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
...
mSwipeRefreshLayout = (SwipeRefreshLayout) findViewById(R.id.contentView);
appBarLayout = (AppBarLayout) findViewById(R.id.appBarLayout);
}
@Override
public void onOffsetChanged(AppBarLayout appBarLayout, int i) {
if (i == 0) {
mSwipeRefreshLayout.setEnabled(true);
} else {
mSwipeRefreshLayout.setEnabled(false);
}
}
@Override
protected void onResume() {
super.onResume();
appBarLayout.addOnOffsetChangedListener(this);
}
@Override
protected void onPause() {
super.onPause();
appBarLayout.removeOnOffsetChangedListener(this);
}}
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