Question

我使用 Android设计库创建了一个应用，其中包含工具栏和TabLayout。
实际上有两个标签，都有2个RecyclerView，滚动时会自动折叠工具栏。

我的问题是：当RecyclerView包含少量项目且完全适合屏幕时（如TAB 2中），我可以禁用工具栏折叠吗？

我已经看到很多像CheeseSquare这样的例子，由Google员工提出问题仍然存在：即使RecyclerView只有1个项目，工具栏仍会隐藏在滚动状态。

我想我可以找出是否在屏幕上显示RecyclerView的第一项，如果是，则禁用工具栏折叠。前者易于实现，后者又如何呢？

这是我的布局：

<android.support.design.widget.CoordinatorLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:id="@+id/coordinator_layout"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

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

        <android.support.v7.widget.Toolbar
            android:id="@+id/toolbar"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            app:layout_scrollFlags="scroll|enterAlwaysCollapsed"
            android:background="?attr/colorPrimary"
            app:theme="@style/ThemeOverlay.AppCompat.Dark.ActionBar"
            app:popupTheme="@style/ThemeOverlay.AppCompat.Light"/>

        <android.support.design.widget.TabLayout
            android:id="@+id/tab_layout"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:background="@color/glucosio_pink"
            app:tabSelectedTextColor="@android:color/white"
            app:tabIndicatorColor="@color/glucosio_accent"
            app:tabTextColor="#80ffffff"/>
        </android.support.design.widget.AppBarLayout>

        <android.support.v4.view.ViewPager
            android:id="@+id/pager"
            app:layout_behavior="@string/appbar_scrolling_view_behavior"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"/>

    <android.support.design.widget.FloatingActionButton
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:id="@+id/main_fab"
        android:layout_margin="16dp"
        android:onClick="onFabClicked"
        app:backgroundTint="@color/glucosio_accent"
        android:src="@drawable/ic_add_black_24dp"
        android:layout_gravity="bottom|right"
        />
    </android.support.design.widget.CoordinatorLayout>

Answer 1

最终解决方案（感谢MichałZ。）

关闭/打开工具栏滚动的方法：

public void turnOffToolbarScrolling() {
    Toolbar mToolbar = (Toolbar) findViewById(R.id.toolbar);
    AppBarLayout appBarLayout = (AppBarLayout) findViewById(R.id.appbar_layout);

    //turn off scrolling
    AppBarLayout.LayoutParams toolbarLayoutParams = (AppBarLayout.LayoutParams) mToolbar.getLayoutParams();
    toolbarLayoutParams.setScrollFlags(0);
    mToolbar.setLayoutParams(toolbarLayoutParams);

    CoordinatorLayout.LayoutParams appBarLayoutParams = (CoordinatorLayout.LayoutParams) appBarLayout.getLayoutParams();
    appBarLayoutParams.setBehavior(null);
    appBarLayout.setLayoutParams(appBarLayoutParams);
}

public void turnOnToolbarScrolling() {
    Toolbar mToolbar = (Toolbar) findViewById(R.id.toolbar);
    AppBarLayout appBarLayout = (AppBarLayout) findViewById(R.id.appbar_layout);

    //turn on scrolling
    AppBarLayout.LayoutParams toolbarLayoutParams = (AppBarLayout.LayoutParams) mToolbar.getLayoutParams();
    toolbarLayoutParams.setScrollFlags(AppBarLayout.LayoutParams.SCROLL_FLAG_SCROLL | AppBarLayout.LayoutParams.SCROLL_FLAG_ENTER_ALWAYS);
    mToolbar.setLayoutParams(toolbarLayoutParams);

    CoordinatorLayout.LayoutParams appBarLayoutParams = (CoordinatorLayout.LayoutParams) appBarLayout.getLayoutParams();
    appBarLayoutParams.setBehavior(new AppBarLayout.Behavior());
    appBarLayout.setLayoutParams(appBarLayoutParams);
}

找出我的片段中是否可以看到RecyclerView的最后一项如果是，请禁用滚动：

public void updateToolbarBehaviour(){
    if (mLayoutManager.findLastCompletelyVisibleItemPosition() == items.size()-1) {
        ((MainActivity) getActivity()).turnOffToolbarScrolling();
    } else {
        ((MainActivity)getActivity()).turnOnToolbarScrolling();
    }
}

Answer 2

RecyclerView现在（自版本23.2起）支持wrap_content。只需使用wrap_content作为高度。

Answer 3

我采用了一种稍微不同的方法来解决这个问题。

我创建了一个自定义AppBarBehavior，根据单元格禁用其自我。

public class CustomAppBarBehavior extends AppBarLayout.Behavior {

    private RecyclerView recyclerView;
    private boolean enabled;

    public CustomAppBarBehavior() {
    }

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

    @Override
    public boolean onInterceptTouchEvent(CoordinatorLayout parent, AppBarLayout child, MotionEvent ev) {
        updatedEnabled();
        return enabled && super.onInterceptTouchEvent(parent, child, ev);
    }

    @Override
    public boolean onStartNestedScroll(CoordinatorLayout parent, AppBarLayout child, View directTargetChild, View target, int nestedScrollAxes) {
        return enabled && super.onStartNestedScroll(parent, child, directTargetChild, target, nestedScrollAxes);
    }

    @Override
    public boolean onNestedFling(CoordinatorLayout coordinatorLayout, AppBarLayout child, View target, float velocityX, float velocityY, boolean consumed) {
        return enabled && super.onNestedFling(coordinatorLayout, child, target, velocityX, velocityY, consumed);
    }

    private void updatedEnabled() {
        enabled = false;
        if(recyclerView != null) {
            RecyclerView.Adapter adapter = recyclerView.getAdapter();
            if (adapter != null) {
                int count = adapter.getItemCount();
                RecyclerView.LayoutManager layoutManager = recyclerView.getLayoutManager();
                if (layoutManager != null) {
                    int lastItem = 0;
                    if (layoutManager instanceof LinearLayoutManager) {
                        LinearLayoutManager linearLayoutManager = (LinearLayoutManager) layoutManager;
                        lastItem = Math.abs(linearLayoutManager.findLastCompletelyVisibleItemPosition());
                    } else if (layoutManager instanceof StaggeredGridLayoutManager) {
                        StaggeredGridLayoutManager staggeredGridLayoutManager = (StaggeredGridLayoutManager) layoutManager;
                        int[] lastItems = staggeredGridLayoutManager.findLastCompletelyVisibleItemPositions(new int[staggeredGridLayoutManager.getSpanCount()]);
                        lastItem = Math.abs(lastItems[lastItems.length - 1]);
                    }
                    enabled = lastItem < count - 1;
                }
            }
        }
    }

    public void setRecyclerView(RecyclerView recyclerView) {
        this.recyclerView = recyclerView;
    }
}

然后在应用栏布局

上设置自定义行为

appBarBehavior = new CustomAppBarBehavior();
CoordinatorLayout.LayoutParams appBarLayoutParams = (CoordinatorLayout.LayoutParams) appBarLayout.getLayoutParams();
appBarLayoutParams.setBehavior(appBarBehavior);
appBarLayout.setLayoutParams(appBarLayoutParams);

最后页面更改视图寻呼机更新了RecyclerView的行为

private ViewPager.OnPageChangeListener pageChangeListener = new ViewPager.OnPageChangeListener() {
        @Override
        public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) { }

        @Override
        public void onPageSelected(final int position) {             
            appBarLayout.setExpanded(true, true);
            appBarLayout.post(new Runnable() {
                @Override
                public void run() {
                    appBarBehavior.setRecyclerView(childFragments.get(position).getRecyclerView());
                }
            });
        }

        @Override
        public void onPageScrollStateChanged(int state) { }
    };

这应该适用于更改数据集。

Answer 4

在适配器中更改数据后添加以下代码：

recyclerView.afterMeasured {
    val isTurnedOff = recyclerView.turnOffNestedScrollingIfEnoughItems()
    if (isTurnedOff) appBarLayout.setExpanded(true)
}

这是功能：

inline fun <T: View> T.afterMeasured(crossinline action: T.() -> Unit) {
    viewTreeObserver.addOnGlobalLayoutListener(object : ViewTreeObserver.OnGlobalLayoutListener {
        override fun onGlobalLayout() {             
            viewTreeObserver.removeOnGlobalLayoutListener(this)
            action()
        }
    })
}


fun RecyclerView.turnOffNestedScrollingIfEnoughItems(): Boolean {
    val lm = (layoutManager as LinearLayoutManager)
    val count = if (lm.itemCount <= 0) 0 else lm.itemCount - 1
    val isFirstVisible = lm.findFirstCompletelyVisibleItemPosition() == 0
    val isLastItemVisible = lm.findLastCompletelyVisibleItemPosition() == count

    isNestedScrollingEnabled = !(isLastItemVisible && isFirstVisible)
    return isNestedScrollingEnabled.not()
}

Answer 5

我想这是最好的解决方案。您需要定义自定义AppBarLayout行为：

class CustomScrollingViewBehavior : AppBarLayout.Behavior {

    constructor() : super()
    constructor(context: Context, attrs: AttributeSet?) : super(context, attrs)

    var shouldScroll = true

    override fun onStartNestedScroll(coordinatorLayout: CoordinatorLayout, child: AppBarLayout, directTargetChild: View, target: View, axes: Int, type: Int): Boolean {
        return shouldScroll && when (target) {
            is NestedScrollView, is ScrollView, is RecyclerView -> {
                return target.canScrollVertically(1) || target.canScrollVertically(-1)
            }
            else -> super.onStartNestedScroll(coordinatorLayout, child, directTargetChild, target, axes, type)
        }
    }
}

然后您只需要在布局中将其用作AppBarLayout的属性即可

...

 <com.google.android.material.appbar.AppBarLayout
            android:id="@+id/appbar"
            android:layout_width="match_parent"
            android:layout_height="56dp"
            app:layout_behavior=".CustomScrollingViewBehavior">

...

就是这样。

注意：自定义行为还支持完全禁用滚动-您只需要将shouldScroll标志设置为false

customScrollingViewBehavior.shouldScroll = false

Answer 6

如果根据正确答案帮助Kotlin中的任何人，我都会为Kotlin做到这一点：

fun changeToolbarScroll(isToScrolling: Boolean){

    val params = toolbar.layoutParams as AppBarLayout.LayoutParams
    val appBarLayoutParams = appBarLayout.layoutParams as 
                             CoordinatorLayout.LayoutParams
    params.scrollFlags = 0
    toolbar.layoutParams = params
    appBarLayoutParams.behavior = null
    appBarLayout.layoutParams = appBarLayoutParams

    if(isToScrolling){
        params.scrollFlags =
            AppBarLayout.LayoutParams.SCROLL_FLAG_SCROLL or 
            AppBarLayout.LayoutParams.SCROLL_FLAG_ENTER_ALWAYS
        toolbar.layoutParams = params

        appBarLayoutParams.behavior = AppBarLayout.Behavior()
        appBarLayout.layoutParams = appBarLayoutParams
    }
}

就我而言，我遇到了一个MainActivity问题，该问题按2个片段管理导航，工具栏和其他共享的东西，第一个Framgent使用RecyclerView，第二个用于显示数据。问题是当我设置菜单并从MainAcitivity更改MenuItem时

听起来听起来很愚蠢而且完全合乎逻辑，但是请记住在更改片段不起作用或无法正确更新的情况下，始终在致电supportFragmentManager.beginTransaction（）之前对Menu或MenuItem进行更改.add，.replace（），show（）...

fun showDetailImageFragment(searchImage: SearchImage) {
    val searchFragment = 
    supportFragmentManager.findFragmentByTag(SEARCH_IMAGES)

    changeToolbarScroll(false)

    if (supportActionBar != null) {
        supportActionBar!!.collapseActionView()
        supportActionBar!!.setDisplayHomeAsUpEnabled(true)
        supportActionBar!!.title = getString(R.string.detail_image_title)
    }

    actionSearch.isVisible = false
    actionNighMOde.isVisible = false
    actionAppSetings.isVisible = false
    actionAbout.isVisible = false

    supportFragmentManager.beginTransaction()
        .setCustomAnimations(
            R.animator.fade_in,
            R.animator.fade_out,
            R.animator.fade_in,
            R.animator.fade_out
        )
        .hide(searchFragment!!)
        .add(
            R.id.frameLayout,
            DetailImageFragment().newInstance(searchImage)
        ).addToBackStack(null)
        .commit()
}

Answer 7

您可以通过以下方式在XML中添加值为layout_behaviour的属性@string/appbar_scrolling_view_behavior：

app:layout_behavior="@string/appbar_scrolling_view_behavior"

Answer 8

//turn off scrolling
AppBarLayout.LayoutParams toolbarLayoutParams = (AppBarLayout.LayoutParams) mToolbar.getLayoutParams();
toolbarLayoutParams.setScrollFlags(0);
mToolbar.setLayoutParams(toolbarLayoutParams);

Answer 9

只需从

中删除滚动条

app:layout_scrollFlags="scroll|enterAlways"

所以它应该是

app:layout_scrollFlags="enterAlways"

当RecyclerView适合屏幕时，不要折叠工具栏

9 个答案: