如何避免CollapsingToolbarLayout在滚动时没有被捕捉或"摇摆"？

Question

如何避免CollapsingToolbarLayout在滚动时没有被捕捉或"摇摆"？

and*_*per 27 android android-collapsingtoolbarlayout

背景

假设您创建的应用程序具有与您通过"滚动活动"向导创建的应用程序类似的UI,但您希望滚动标记具有捕捉功能,如下所示:

<android.support.design.widget.CollapsingToolbarLayout ... app:layout_scrollFlags="scroll|exitUntilCollapsed|snap" >

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问题

事实证明,在许多情况下,它存在捕捉问题.有时UI不会捕捉到顶部/底部,使得CollapsingToolbarLayout保持在两者之间.

有时它也会尝试捕捉到一个方向,然后决定捕捉到另一个方向.

您可以在此处查看所附视频的两个问题.

我试过的

我认为这是我在RecyclerView上使用setNestedScrollingEnabled(false)时遇到的问题之一,所以我在这里问了一下,但后来我注意到即使使用解决方案也没有使用此命令,甚至在使用时一个简单的NestedScrollView(由向导创建),我仍然可以注意到这种行为.

这就是为什么我决定这个报告是一个问题,在这里.

可悲的是,我找不到StackOverflow上那些奇怪错误的解决方法.

这个问题

为什么会发生,更重要的是:如何在仍然使用它应该具有的行为的同时避免这些问题？

编辑:这是一个很好的改进Kotlin版本的接受答案:

class RecyclerViewEx @JvmOverloads constructor(context: Context, attrs: AttributeSet? = null, defStyle: Int = 0) : RecyclerView(context, attrs, defStyle) {
    private var mAppBarTracking: AppBarTracking? = null
    private var mView: View? = null
    private var mTopPos: Int = 0
    private var mLayoutManager: LinearLayoutManager? = null

    interface AppBarTracking {
        fun isAppBarIdle(): Boolean
        fun isAppBarExpanded(): Boolean
    }

    override fun dispatchNestedPreScroll(dx: Int, dy: Int, consumed: IntArray?, offsetInWindow: IntArray?, type: Int): Boolean {
        if (mAppBarTracking == null)
            return super.dispatchNestedPreScroll(dx, dy, consumed, offsetInWindow, type)
        if (type == ViewCompat.TYPE_NON_TOUCH && mAppBarTracking!!.isAppBarIdle()
                && isNestedScrollingEnabled) {
            if (dy > 0) {
                if (mAppBarTracking!!.isAppBarExpanded()) {
                    consumed!![1] = dy
                    return true
                }
            } else {
                mTopPos = mLayoutManager!!.findFirstVisibleItemPosition()
                if (mTopPos == 0) {
                    mView = mLayoutManager!!.findViewByPosition(mTopPos)
                    if (-mView!!.top + dy <= 0) {
                        consumed!![1] = dy - mView!!.top
                        return true
                    }
                }
            }
        }
        if (dy < 0 && type == ViewCompat.TYPE_TOUCH && mAppBarTracking!!.isAppBarExpanded()) {
            consumed!![1] = dy
            return true
        }

        val returnValue = super.dispatchNestedPreScroll(dx, dy, consumed, offsetInWindow, type)
        if (offsetInWindow != null && !isNestedScrollingEnabled && offsetInWindow[1] != 0)
            offsetInWindow[1] = 0
        return returnValue
    }

    override fun setLayoutManager(layout: RecyclerView.LayoutManager) {
        super.setLayoutManager(layout)
        mLayoutManager = layoutManager as LinearLayoutManager
    }

    fun setAppBarTracking(appBarTracking: AppBarTracking) {
        mAppBarTracking = appBarTracking
    }

    fun setAppBarTracking(appBarLayout: AppBarLayout) {
        val appBarIdle = AtomicBoolean(true)
        val appBarExpanded = AtomicBoolean()
        appBarLayout.addOnOffsetChangedListener(object : AppBarLayout.OnOffsetChangedListener {
            private var mAppBarOffset = Integer.MIN_VALUE

            override fun onOffsetChanged(appBarLayout: AppBarLayout, verticalOffset: Int) {
                if (mAppBarOffset == verticalOffset)
                    return
                mAppBarOffset = verticalOffset
                appBarExpanded.set(verticalOffset == 0)
                appBarIdle.set(mAppBarOffset >= 0 || mAppBarOffset <= -appBarLayout.totalScrollRange)
            }
        })
        setAppBarTracking(object : AppBarTracking {
            override fun isAppBarIdle(): Boolean = appBarIdle.get()
            override fun isAppBarExpanded(): Boolean = appBarExpanded.get()
        })
    }

    override fun fling(velocityX: Int, inputVelocityY: Int): Boolean {
        var velocityY = inputVelocityY
        if (mAppBarTracking != null && !mAppBarTracking!!.isAppBarIdle()) {
            val vc = ViewConfiguration.get(context)
            velocityY = if (velocityY < 0) -vc.scaledMinimumFlingVelocity
            else vc.scaledMinimumFlingVelocity
        }

        return super.fling(velocityX, velocityY)
    }
}

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Answer 1

Che*_*amp 9

更新我稍微更改了代码以解决剩余问题 - 至少是我可以重现的问题.关键更新是dy仅在AppBar展开或折叠时进行处理.在第一次迭代中,dispatchNestedPreScroll()处理滚动而不检查折叠状态的AppBar的状态.

其他变化很小,属于清理类别.代码块在下面更新.

这个答案解决了有关问题的问题RecyclerView.我给出的另一个答案仍然适用于此处.与支持库的26.0.0-beta2中引入的RecyclerView问题相同NestedScrollView.

下面的代码基于对相关问题的这个答案,但包括对AppBar的不稳定行为的修复.我已经删除了修复奇数滚动的代码,因为它似乎不再需要了.

AppBarTracking.java

public interface AppBarTracking {
    boolean isAppBarIdle();
    boolean isAppBarExpanded();
}

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MyRecyclerView.java

public class MyRecyclerView extends RecyclerView {

    public MyRecyclerView(Context context) {
        this(context, null);
    }

    public MyRecyclerView(Context context, AttributeSet attrs) {
        this(context, attrs, 0);
    }

    public MyRecyclerView(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);
    }

    private AppBarTracking mAppBarTracking;
    private View mView;
    private int mTopPos;
    private LinearLayoutManager mLayoutManager;

    @Override
    public boolean dispatchNestedPreScroll(int dx, int dy, int[] consumed, int[] offsetInWindow,
                                           int type) {

        // App bar latching trouble is only with this type of movement when app bar is expanded
        // or collapsed. In touch mode, everything is OK regardless of the open/closed status
        // of the app bar.
        if (type == ViewCompat.TYPE_NON_TOUCH && mAppBarTracking.isAppBarIdle()
                && isNestedScrollingEnabled()) {
            // Make sure the AppBar stays expanded when it should.
            if (dy > 0) { // swiped up
                if (mAppBarTracking.isAppBarExpanded()) {
                    // Appbar can only leave its expanded state under the power of touch...
                    consumed[1] = dy;
                    return true;
                }
            } else { // swiped down (or no change)
                // Make sure the AppBar stays collapsed when it should.
                // Only dy < 0 will open the AppBar. Stop it from opening by consuming dy if needed.
                mTopPos = mLayoutManager.findFirstVisibleItemPosition();
                if (mTopPos == 0) {
                    mView = mLayoutManager.findViewByPosition(mTopPos);
                    if (-mView.getTop() + dy <= 0) {
                        // Scroll until scroll position = 0 and AppBar is still collapsed.
                        consumed[1] = dy - mView.getTop();
                        return true;
                    }
                }
            }
        }

        boolean returnValue = super.dispatchNestedPreScroll(dx, dy, consumed, offsetInWindow, type);
        // Fix the scrolling problems when scrolling is disabled. This issue existed prior
        // to 26.0.0-beta2.
        if (offsetInWindow != null && !isNestedScrollingEnabled() && offsetInWindow[1] != 0) {
            offsetInWindow[1] = 0;
        }
        return returnValue;
    }

    @Override
    public void setLayoutManager(RecyclerView.LayoutManager layout) {
        super.setLayoutManager(layout);
        mLayoutManager = (LinearLayoutManager) getLayoutManager();
    }

    public void setAppBarTracking(AppBarTracking appBarTracking) {
        mAppBarTracking = appBarTracking;
    }

    @SuppressWarnings("unused")
    private static final String TAG = "MyRecyclerView";
}

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ScrollingActivity.java

public class ScrollingActivity extends AppCompatActivity
        implements AppBarTracking {

    private MyRecyclerView mNestedView;
    private int mAppBarOffset;
    private boolean mAppBarIdle = false;
    private int mAppBarMaxOffset;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_scrolling);
        Toolbar toolbar = findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);

        mNestedView = findViewById(R.id.nestedView);

        final AppBarLayout appBar = findViewById(R.id.app_bar);

        appBar.addOnOffsetChangedListener(new AppBarLayout.OnOffsetChangedListener() {
            @Override
            public final void onOffsetChanged(AppBarLayout appBarLayout, int verticalOffset) {
                mAppBarOffset = verticalOffset;
                // mAppBarOffset = 0 if app bar is expanded; If app bar is collapsed then
                // mAppBarOffset = mAppBarMaxOffset
                // mAppBarMaxOffset is always <=0 (-AppBarLayout.getTotalScrollRange())
                // mAppBarOffset should never be > zero or less than mAppBarMaxOffset
                mAppBarIdle = (mAppBarOffset >= 0) || (mAppBarOffset <= mAppBarMaxOffset);
            }
        });

        appBar.post(new Runnable() {
            @Override
            public void run() {
                mAppBarMaxOffset = -appBar.getTotalScrollRange();
            }
        });

        findViewById(R.id.disableNestedScrollingButton).setOnClickListener(new OnClickListener() {
            @Override
            public void onClick(final View v) {
                // If the AppBar is fully expanded or fully collapsed (idle), then disable
                // expansion and apply the patch; otherwise, set a flag to disable the expansion
                // and apply the patch when the AppBar is idle.
                setExpandEnabled(false);
            }
        });

        findViewById(R.id.enableNestedScrollingButton).setOnClickListener(new OnClickListener() {
            @Override
            public void onClick(final View v) {
                setExpandEnabled(true);
            }
        });

        mNestedView.setAppBarTracking(this);
        mNestedView.setLayoutManager(new LinearLayoutManager(this));
        mNestedView.setAdapter(new Adapter() {
            @Override
            public ViewHolder onCreateViewHolder(final ViewGroup parent, final int viewType) {
                return new ViewHolder(LayoutInflater.from(parent.getContext()).inflate(
                        android.R.layout.simple_list_item_1,
                        parent,
                        false)) {
                };
            }

            @SuppressLint("SetTextI18n")
            @Override
            public void onBindViewHolder(final ViewHolder holder, final int position) {
                ((TextView) holder.itemView.findViewById(android.R.id.text1)).setText("item " + position);
            }

            @Override
            public int getItemCount() {
                return 100;
            }
        });
    }

    private void setExpandEnabled(boolean enabled) {
        mNestedView.setNestedScrollingEnabled(enabled);
    }

    @Override
    public boolean isAppBarExpanded() {
        return mAppBarOffset == 0;
    }

    @Override
    public boolean isAppBarIdle() {
        return mAppBarIdle;
    }

    @SuppressWarnings("unused")
    private static final String TAG = "ScrollingActivity";
}

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这里发生了什么？

从问题来看,很明显,当用户的手指不在屏幕上时,布局无法将应用栏关闭或打开.拖动时,应用栏的行为应该如此.

在版本26.0.0-beta2中,引入了一些新方法 - 特别是带有新参数的dispatchNestedPreScroll()type.所述type,如果所指定的运动参数指定dx和dy是由于用户触摸屏幕ViewCompat.TYPE_TOUCH 或不ViewCompat.TYPE_NON_TOUCH.

尽管没有确定导致问题的特定代码,但修复的方法是在不需要垂直移动传播的情况下在需要时消除dispatchNestedPreScroll()(处置dy)垂直移动.实际上,应用栏在展开时将被锁定到位,并且在通过触摸手势关闭之前不允许开始关闭.应用栏也将在关闭时锁定,直到RecyclerView位于其最顶部,并且dy在执行触摸手势时足以打开应用栏.

所以,这不是一个解决问题,而是对有问题的条件的劝阻.

MyRecyclerView代码的最后一部分处理了此问题中确定的问题,该问题涉及禁用嵌套滚动时的不正确滚动移动.这是调用super之后的部分,dispatchNestedPreScroll()它改变了值offsetInWindow[1].此代码背后的想法与问题的已接受答案中提供的内容相同.唯一的区别是,由于底层嵌套滚动代码已更改,因此参数offsetInWindow有时为null.幸运的是,它在重要时似乎是非空的,所以最后一部分继续工作.

需要注意的是,这个"修复"对于提出的问题非常具体,并不是一般解决方案.这个修复可能会有很短的保质期,因为我预计这个明显的问题很快就会得到解决.

Answer 2

vyn*_*dor 9

看起来onStartNestedScroll和onStopNestedScroll调用可以重新排序,它导致"摇摇欲坠".我在AppBarLayout.Behavior中做了一个小黑客.不要真的想搞砸其他答案提出的活动中的所有东西.

@SuppressWarnings("unused")
public class ExtAppBarLayoutBehavior extends AppBarLayout.Behavior {

    private int mStartedScrollType = -1;
    private boolean mSkipNextStop;

    public ExtAppBarLayoutBehavior() {
        super();
    }

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

    @Override
    public boolean onStartNestedScroll(CoordinatorLayout parent, AppBarLayout child, View directTargetChild, View target, int nestedScrollAxes, int type) {
        if (mStartedScrollType != -1) {
            onStopNestedScroll(parent, child, target, mStartedScrollType);
            mSkipNextStop = true;
        }
        mStartedScrollType = type;
        return super.onStartNestedScroll(parent, child, directTargetChild, target, nestedScrollAxes, type);
    }

    @Override
    public void onStopNestedScroll(CoordinatorLayout coordinatorLayout, AppBarLayout abl, View target, int type) {
        if (mSkipNextStop) {
            mSkipNextStop = false;
            return;
        }
        if (mStartedScrollType == -1) {
            return;
        }
        mStartedScrollType = -1;
        // Always pass TYPE_TOUCH, because want to snap even after fling
        super.onStopNestedScroll(coordinatorLayout, abl, target, ViewCompat.TYPE_TOUCH);
    }
}

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XML布局中的用法:

<android.support.design.widget.CoordinatorLayout>

    <android.support.design.widget.AppBarLayout
        app:layout_behavior="com.example.ExtAppBarLayoutBehavior">

        <!-- Put here everything you usually add to AppBarLayout: CollapsingToolbarLayout, etc... -->

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

    <!-- Content: recycler for example -->
    <android.support.v7.widget.RecyclerView
        app:layout_behavior="@string/appbar_scrolling_view_behavior" />

    ...

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

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它很可能是问题的根本原因RecyclerView.现在没有机会深入挖掘.

Answer 3

Che*_*amp 5

编辑代码已更新,使其更符合接受答案的代码.这个答案关注的NestedScrollView是接受的答案RecyclerView.

这是API 26.0.0-beta2版本中引入的问题.它不会发生在beta 1版本或API 25上.正如您所指出的,API 26.0.0也会发生这种情况.通常,问题似乎与beta2中如何处理flings和嵌套滚动有关.嵌套滚动有一个重大改写(参见"继续滚动"),因此出现这种类型的问题就不足为奇了.

我的想法是,多余的卷轴没有在某处妥善处理NestedScrollView.解决方法是type == ViewCompat.TYPE_NON_TOUCH在AppBar展开或折叠时静静地使用某些"非触摸"卷轴().这会停止弹跳,允许捕捉,通常会使AppBar表现更好.

ScrollingActivity已被修改以跟踪AppBar的状态以报告它是否被扩展.一个新的类调用"MyNestedScrollView"覆盖dispatchNestedPreScroll()(新的,请参见此处)来操纵多余滚动的消耗.

以下代码应足以阻止AppBarLayout摆动和拒绝捕捉.(XML也必须更改以适应MyNestedSrollView.以下仅适用于支持lib 26.0.0-beta2及更高版本.)

AppBarTracking.java

public interface AppBarTracking {
    boolean isAppBarIdle();
    boolean isAppBarExpanded();
}

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ScrollingActivity.java

public class ScrollingActivity extends AppCompatActivity implements AppBarTracking {

    private int mAppBarOffset;
    private int mAppBarMaxOffset;
    private MyNestedScrollView mNestedView;
    private boolean mAppBarIdle = true;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        AppBarLayout appBar;

        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_scrolling);
        final Toolbar toolbar = findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);
        appBar = findViewById(R.id.app_bar);
        mNestedView = findViewById(R.id.nestedScrollView);
        mNestedView.setAppBarTracking(this);
        appBar.addOnOffsetChangedListener(new AppBarLayout.OnOffsetChangedListener() {
            @Override
            public void onOffsetChanged(AppBarLayout appBarLayout, int verticalOffset) {
                mAppBarOffset = verticalOffset;
            }
        });

        appBar.addOnOffsetChangedListener(new AppBarLayout.OnOffsetChangedListener() {
            @Override
            public final void onOffsetChanged(AppBarLayout appBarLayout, int verticalOffset) {
                mAppBarOffset = verticalOffset;
                // mAppBarOffset = 0 if app bar is expanded; If app bar is collapsed then
                // mAppBarOffset = mAppBarMaxOffset
                // mAppBarMaxOffset is always <=0 (-AppBarLayout.getTotalScrollRange())
                // mAppBarOffset should never be > zero or less than mAppBarMaxOffset
                mAppBarIdle = (mAppBarOffset >= 0) || (mAppBarOffset <= mAppBarMaxOffset);
            }
        });

        mNestedView.post(new Runnable() {
            @Override
            public void run() {
                mAppBarMaxOffset = mNestedView.getMaxScrollAmount();
            }
        });
    }

    @Override
    public boolean isAppBarIdle() {
        return mAppBarIdle;
    }

    @Override
    public boolean isAppBarExpanded() {
        return mAppBarOffset == 0;
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.menu_scrolling, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();

        //noinspection SimplifiableIfStatement
        if (id == R.id.action_settings) {
            return true;
        }
        return super.onOptionsItemSelected(item);
    }

    @SuppressWarnings("unused")
    private static final String TAG = "ScrollingActivity";
}

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MyNestedScrollView.java

public class MyNestedScrollView extends NestedScrollView {

    public MyNestedScrollView(Context context) {
        this(context, null);
    }

    public MyNestedScrollView(Context context, AttributeSet attrs) {
        this(context, attrs, 0);
    }

    public MyNestedScrollView(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);

        setOnScrollChangeListener(new View.OnScrollChangeListener() {
            @Override
            public void onScrollChange(View view, int x, int y, int oldx, int oldy) {
                mScrollPosition = y;
            }
        });
    }

    private AppBarTracking mAppBarTracking;
    private int mScrollPosition;

    @Override
    public boolean dispatchNestedPreScroll(int dx, int dy, int[] consumed, int[] offsetInWindow,
                                           int type) {

        // App bar latching trouble is only with this type of movement when app bar is expanded
        // or collapsed. In touch mode, everything is OK regardless of the open/closed status
        // of the app bar.
        if (type == ViewCompat.TYPE_NON_TOUCH && mAppBarTracking.isAppBarIdle()
                && isNestedScrollingEnabled()) {
            // Make sure the AppBar stays expanded when it should.
            if (dy > 0) { // swiped up
                if (mAppBarTracking.isAppBarExpanded()) {
                    // Appbar can only leave its expanded state under the power of touch...
                    consumed[1] = dy;
                    return true;
                }
            } else { // swiped down (or no change)
                // Make sure the AppBar stays collapsed when it should.
                if (mScrollPosition + dy < 0) {
                    // Scroll until scroll position = 0 and AppBar is still collapsed.
                    consumed[1] = dy + mScrollPosition;
                    return true;
                }
            }
        }

        boolean returnValue = super.dispatchNestedPreScroll(dx, dy, consumed, offsetInWindow, type);
        // Fix the scrolling problems when scrolling is disabled. This issue existed prior
        // to 26.0.0-beta2. (Not sure that this is a problem for 26.0.0-beta2 and later.)
        if (offsetInWindow != null && !isNestedScrollingEnabled() && offsetInWindow[1] != 0) {
            Log.d(TAG, "<<<<offsetInWindow[1] forced to zero");
            offsetInWindow[1] = 0;
        }
        return returnValue;
    }

    public void setAppBarTracking(AppBarTracking appBarTracking) {
        mAppBarTracking = appBarTracking;
    }

    @SuppressWarnings("unused")
    private static final String TAG = "MyNestedScrollView";
}

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