Android：ViewPager 卡在视图之间

我有一个在片段之间滑动的 ViewPager。我正在使用 FragmentStatePagerAdapter 将 Fragment 提供给 ViewPager。如果用户以正常速度向左滑动，然后快速向右滑动，他们可能会使 ViewPager 进入一种奇怪的状态，其中显示多个 Fragment。

例如，如果用户在片段 A 上，然后以正常速度向左滑动到片段 B，然后快速向右滑动返回到片段 A，则屏幕上会同时显示片段 A 和 B。

有人知道为什么会发生这种情况，或者有什么好的方法来防止这种情况发生吗？

Here's what it looks like:

这是我在 XML 中的 ViewPager 定义：

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
            android:layout_width="match_parent"
            android:layout_height="match_parent">

<com.company.views.CustomActionBar
    android:id="@+id/customActionBar"
    android:layout_width="match_parent"
    android:layout_height="@dimen/height_actionbar"
    android:layout_alignParentTop="true"/>

<android.support.v4.view.ViewPager
    android:id="@+id/viewPager"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_below="@id/customActionBar"/>

另外，我记录了 onPageChangeListener() 的输出，并注意到当 ViewPager 卡在视图之间时，它报告的 positionOffset 为 0。这是 ViewPager 的值，当它落在这个位置时，它从 STATE_DRAGGING 转换到 STATE_SETTLING 到 STATE_IDLE奇怪的状态：

状态 = 0 前状态：2 位置：1 位置偏移：0.0

状态 = 1 前状态：0 位置：1 位置偏移：0.0

状态 = 2 前状态：1 位置：1 位置偏移：0.4069444

状态 = 0 前状态：2 位置：2 位置偏移：0.0

因此，看起来 ViewPager 正在向我报告错误的positionOffset。

完整的示例代码活动和适配器：

public class ActivityBagelProfileViewer extends CustomAbstractFragmentActivity
    implements CustomActionBarContract, ListenerProgress, ListenerSync
{
public static final String EXTRA_BAGEL_INDEX = "BAGEL";

public static final int REQUEST_CODE_BAGEL_PROFILE_VIEWER = 4000;
public static final int RESULT_GO_TO_PASS_FLOW = 12;
public static final int RESULT_GO_TO_LIKE_FLOW = 14;
public static final int RESULT_GO_TO_SEE_MORE_BAGELS = 16;

private ViewPager mProfilesViewPager;
private CustomActionBar mCustomActionBar;
private int mViewPagerPosition;

private DialogProgress mDialogProgress;

private BagelViewPagerAdapter mAdapterBagelViewPager;
private List<Bagel> mListBagels;

@Override
protected void onCreate(Bundle savedInstanceState)
{
    Logger.d("ENTER");

    super.onCreate(savedInstanceState);

    if (ManagerGive.IS_BRANCH_SESSION_OPEN == false)
    {
        ManagerGive.initializeBranchMetricsSession();
    }

    setContentView(R.layout.activity_with_viewpager);

    mCustomActionBar = (CustomActionBar) findViewById(R.id.customActionBar);
    mCustomActionBar.setMenu(this);

    mProfilesViewPager = (ViewPager) findViewById(R.id.viewPager);

    if (getIntent().getExtras() != null)
    {
        mViewPagerPosition = getIntent().getExtras().getInt(EXTRA_BAGEL_INDEX, 0);
    }
}

@Override
protected void onStop()
{
    super.onStop();
    ManagerGive.closeBranchMetricsSession();
}

public void onIconClick(View view)
{
    Logger.d("ENTER");
    finishWithAnimation();
}

private void finishWithAnimation()
{
    setResult(RESULT_OK);
    finish();
    overridePendingTransition(R.anim.slide_in_from_left, R.anim.slide_out_to_right);
}

@Override
public void onBackPressed()
{
    if (!super.handleBackPressedEvent())
    {
        finishWithAnimation();
    }
}


private void setupNewAdapter()
{
    mListBagels = Bakery.getInstance().getManagerBagel().getCopyOfBagelsWithoutCurrent();
    mAdapterBagelViewPager = new BagelViewPagerAdapter(getSupportFragmentManager(), mListBagels, this);
    mProfilesViewPager.setAdapter(mAdapterBagelViewPager);

    mProfilesViewPager.setOnPageChangeListener(new ViewPager.OnPageChangeListener()
    {
        @Override
        public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels)
        {
        }

        @Override
        public void onPageSelected(int position)
        {
            setActionBar(position);
            mViewPagerPosition = position;
        }

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

    mProfilesViewPager.setCurrentItem(mViewPagerPosition, false);
}

@Override
protected void onResume()
{
    Logger.d("ENTER");
    super.onResume();

    Bakery.getInstance().getManagerSyncData().addListener(this);

    if (mProfilesViewPager.getAdapter() == null)
    {
        Logger.d("Adapter null. Setting new adapter");
        setupNewAdapter();
    }
    else
    {
        if (mProfilesViewPager.getAdapter().getCount() !=
                Bakery.getInstance().getManagerBagel().getCopyOfBagelsWithoutCurrent().size())
        {
            Logger.d("Bagel list in Bakery changed size. Setting new adapter");
            setupNewAdapter();
        }
    }

    if (mListBagels.size() > 0)
    {
        setActionBar(mViewPagerPosition);
        mDialogProgress = new DialogProgress(this);
    }
    else
    {
        //kv Something has gone terribly wrong if we don't have any Bagels, just finish
        finish();
    }
}

private void setActionBar(int bagelIndex)
{
    Logger.d("bagelIndex=" + bagelIndex);

    Bagel bagel = mListBagels.get(bagelIndex);

    //kv If this is our current bagel and we haven't taken action yet, then show timer
    if (Bakery.getInstance().getManagerBagel().getCurrentBagel() == bagel
            && bagel.getAction() != Bagel.ACTION_LIKED && bagel.getAction() != Bagel.ACTION_PASSED)
    {
        Logger.d("Setting up #timer in action bar");
        mCustomActionBar.startTimeLeftTimer(DateUtils.getMillisFromUtc(bagel.getEndDate()),
                this, new ListenerTimer()
                {
                    @Override
                    public void onTimerExpired()
                    {
                        Logger.d("ENTER");
                        Bakery.getInstance().getManagerSyncData().performSync(null, false);
                    }
                }, mCustomActionBar.getTextViewTimeLeft(), R.string.timer_blank);
        mCustomActionBar.setLabel(R.string.time_left);
        mCustomActionBar.hideTitle();
    }
    //kv Otherwise show date
    else
    {
        mCustomActionBar.setTitle(DateUtils.getLocalizedDateFromStringDate(bagel.getStartDate(), DateUtils.DATE_WITH_TIME_PATTERN));
        mCustomActionBar.stopTimeLeftTimer();
        mCustomActionBar.hideTimeLeft();
    }
}

@Override
protected void onSaveInstanceState(Bundle outState)
{
    super.onSaveInstanceState(outState);
    outState.putInt(EXTRA_BAGEL_INDEX, mViewPagerPosition);
}

@Override
protected void onRestoreInstanceState(Bundle savedInstanceState)
{
    Logger.d("ENTER");

    super.onRestoreInstanceState(savedInstanceState);
    if (savedInstanceState.containsKey(EXTRA_BAGEL_INDEX))
    {
        mViewPagerPosition = savedInstanceState.getInt(EXTRA_BAGEL_INDEX);
    }
}

@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data)
{
    super.onActivityResult(requestCode, resultCode, data);
    Logger.d("requestCode=" + requestCode + ", resultCode=" + resultCode + ", data=" + data);

    switch (requestCode)
    {
        case ActivityBeanShop.REQUEST_CODE:
            if (resultCode == Activity.RESULT_OK && data != null)
            {
                //fp user purchased sufficient beans to resume their transaction
                PurchaseType interruptedPurchaseType = (PurchaseType) data.getSerializableExtra(ActivityBeanShop.EXTRA_PURCHASE_TYPE);

                switch (interruptedPurchaseType)
                {
                    case BONUS_BAGEL:
                    case OPEN_SESAME:
                    case REMATCH:
                        Bundle bundle = new Bundle();
                        bundle.putSerializable(ManagerPurchase.EXTRA_PURCHASE_TYPE, interruptedPurchaseType);
                        ManagerEvents.notifyListeners(EventType.BEAN_TRANSACTION_FOR_FEATURE_UNLOCK_COMPLETE, bundle);
                        Logger.d("Notified listeners about #purchase bean transaction, can now resume feature #purchase");
                        break;

                    default:
                        Logger.w("Unrecognized purchase type: " + interruptedPurchaseType.getItemName());
                }
            }

            break;
        default:
            Logger.w("Could not recognize code: " + requestCode);
    }
}

@Override
public int getTitleId()
{
    return R.string.bagel_action_checked;
}

@Override
public int getIconId()
{
    return R.drawable.selector_icon_up;
}

@Override
public void showProgress(int stringId)
{
    mDialogProgress.setText(stringId);
    mDialogProgress.show();
}

@Override
public void dismissProgress()
{
    ViewUtils.safelyDismissDialog(mDialogProgress);
}

public void setActionBar()
{
    setActionBar(mViewPagerPosition);
}

@Override
public void onSyncComplete()
{
    Logger.d("ENTER");
    mListBagels = Bakery.getInstance().getManagerBagel().getCopyOfBagelsWithoutCurrent();
    mAdapterBagelViewPager.setBagels(mListBagels);
}

public boolean isShowingThisBagel(Bagel bagel)
{
    Bagel currentlyShownBagel = mListBagels.get(mViewPagerPosition);
    return bagel == currentlyShownBagel;
}

private static class BagelViewPagerAdapter extends FragmentStatePagerAdapter
{
    private List<Bagel> mBagels;
    private ListenerProgress mListenerProgress;

    public BagelViewPagerAdapter(FragmentManager fragmentManager, List<Bagel> bagels,
                                 ListenerProgress listenerProgress)
    {
        super(fragmentManager);
        Logger.d("bagels=" + bagels);
        this.mBagels = bagels;
        mListenerProgress = listenerProgress;
    }

    @Override
    public Fragment getItem(int i)
    {
        Logger.d("i=" + i);
        UserProfile myProfile = Bakery.getInstance().getManagerUserProfile().getMyOwnProfile();
        FragmentProfile fragment = FragmentProfile.newInstance(mBagels.get(i), false, myProfile);
        fragment.setListenerProgress(mListenerProgress);
        return fragment;
    }

    @Override
    public int getCount()
    {
        return mBagels.size();
    }

    public void setBagels(List<Bagel> bagels)
    {
        mBagels = bagels;
        notifyDataSetChanged();
    }
}
}

下面是每个片段布局的 XML 布局代码（必须删除 SO 字符限制的一些 b/c）：

<?xml version="1.0" encoding="utf-8"?>
<ScrollView xmlns:android="http://schemas.android.com/apk/res/android"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:id="@+id/scrollView">

<LinearLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_marginTop="-0.5dp"
    android:orientation="vertical"
    android:animateLayoutChanges="true"
    android:id="@+id/profile_top_container">

    <!-- Photos section with pager/carousel -->
    <FrameLayout
        android:id="@+id/photoViewpagerContainer"
        android:layout_width="match_parent"
        android:layout_height="wrap_content">

        <com.coffeemeetsbagel.views.CustomAsShitViewPager
            android:id="@+id/pager_profile_images"
            xmlns:android="http://schemas.android.com/apk/res/android"
            app:aspectRatio="@integer/photo_ratio_height_over_width"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"/>

        <LinearLayout
            android:id="@+id/linearLayout_bulletsAndFriendsContainer"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:orientation="vertical"
            android:gravity="bottom">

            <com.coffeemeetsbagel.views.CustomTextView
                android:id="@+id/textView_stamp"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:visibility="invisible"
                app:customFont="Raleway-Bold.ttf"
                android:layout_gravity="end"
                android:textSize="@dimen/text_stamp"
                android:paddingTop="@dimen/margin_large"
                android:layout_marginEnd="@dimen/margin_xxxxxsmall"
                android:layout_marginRight="@dimen/profile_margin_smaller"/>

            <!-- photo circle indicators -->
            <com.viewpagerindicator.CirclePageIndicator
                android:id="@+id/bullet_indicators"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:layout_marginBottom="@dimen/circle_indicator_margin_bottom"
                android:clickable="false"
                app:fillColor="@color/blue_cmb"
                app:pageColor="@color/gray_background"
                app:radius="@dimen/circle_indicator_radius"
                app:strokeWidth="0dp"/>

            <!-- container for mutual friends strip -->
            <RelativeLayout
                android:id="@+id/relativeLayout_mutual_friends_container"
                android:layout_width="match_parent"
                android:layout_height="@dimen/baseline_grid_component_touchable"
                android:background="@color/white_transparent"
                android:visibility="gone">

                <com.coffeemeetsbagel.views.CustomTextView
                    android:id="@+id/textView_mutual_friends_label"
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content"
                    android:layout_alignParentStart="true"
                    android:layout_alignParentLeft="true"
                    style="@style/profile_mutual_friends_text"/>

                <LinearLayout
                    android:id="@+id/linearLayout_mutual_friends_icons"
                    android:layout_width="wrap_content"
                    android:layout_height="match_parent"
                    android:orientation="horizontal"
                    android:layout_alignParentEnd="true"
                    android:layout_alignParentRight="true"
                    android:layout_marginEnd="@dimen/baseline_grid_small"
                    android:layout_marginRight="@dimen/baseline_grid_small"
                    android:layout_centerVertical="true">

                    <ImageView
                        android:id="@+id/imageView_icon0"
                        android:layout_width="@dimen/baseline_grid_component_touchable"
                        android:layout_height="@dimen/baseline_grid_component_touchable"
                        android:padding="@dimen/typography_smallest"
                        android:background="@color/transparent"
                        android:visibility="gone"/>

                    <ImageView
                        android:id="@+id/imageView_icon1"
                        android:layout_width="@dimen/baseline_grid_component_touchable"
                        android:layout_height="@dimen/baseline_grid_component_touchable"
                        android:background="@color/transparent"
                        android:padding="@dimen/typography_smallest"
                        android:visibility="gone"/>

                    <ImageView
                        android:id="@+id/imageView_icon2"
                        android:layout_width="@dimen/baseline_grid_component_touchable"
                        android:layout_height="@dimen/baseline_grid_component_touchable"
                        android:background="@color/transparent"
                        android:padding="@dimen/typography_smallest"
                        android:visibility="gone"/>
                </LinearLayout>
            </RelativeLayout>
        </LinearLayout>
    </FrameLayout>

    <!-- Buttons section with User Actions for pass / like-->
    <LinearLayout
        android:id="@+id/linearLayout_buttons_pass_like"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_marginBottom="@dimen/baseline_grid_smaller"
        android:layout_marginLeft="@dimen/baseline_grid_small"
        android:layout_marginRight="@dimen/baseline_grid_small"
        android:layout_marginTop="@dimen/baseline_grid_medium"
        android:orientation="horizontal"
        android:visibility="gone">

        <ImageView
            android:id="@+id/button_pass"
            android:layout_width="0dp"
            android:layout_height="@dimen/profile_action_button_height"
            android:layout_weight="1"
            android:background="@drawable/ripple_button_pass"
            android:clickable="true"
            android:src="@drawable/icon_pass_pressed"
            android:scaleType="center"
            android:layout_marginRight="@dimen/margin_small"/>

        <ImageView
            android:id="@+id/button_like"
            android:layout_width="0dp"
            android:layout_height="@dimen/profile_action_button_height"
            android:layout_weight="1"
            android:background="@drawable/ripple_button_like"
            android:clickable="true"
            android:src="@drawable/icon_like_pressed"
            android:scaleType="center"
            android:layout_marginLeft="@dimen/margin_small"/>
    </LinearLayout>

    <!-- Buttons section with User Actions for rematch / give-->
    <LinearLayout
        android:id="@+id/linearLayout_buttons_rematch_give"
        android:layout_width="match_parent"
        android:layout_height="@dimen/give_ten_button_height"
        android:layout_marginBottom="@dimen/baseline_grid_smaller"
        android:layout_marginLeft="@dimen/baseline_grid_small"
        android:layout_marginRight="@dimen/baseline_grid_small"
        android:layout_marginTop="@dimen/baseline_grid_medium"
        android:orientation="horizontal"
        android:gravity="center"
        android:visibility="gone">

        <com.coffeemeetsbagel.views.CustomTextView
            android:id="@+id/textView_rematch"
            android:layout_width="@dimen/zero_dip"
            android:layout_height="match_parent"
            android:layout_marginRight="@dimen/give_take_button_margin_side"
            android:layout_weight="1"
            style="@style/button_give_take_rematch"
            android:text="@string/rematch"/>

        <com.coffeemeetsbagel.views.CustomTextView
            android:id="@+id/text_view_give_with_rematch"
            android:layout_width="@dimen/zero_dip"
            android:layout_weight="1"
            android:layout_height="match_parent"
            style="@style/button_give_take_rematch"
            android:text="@string/give"/>
    </LinearLayout>

    <com.coffeemeetsbagel.views.CustomTextView
        android:id="@+id/textView_they_like_you"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:drawableLeft="@drawable/icon_like_alert"
        android:drawablePadding="@dimen/margin_xxsmall"
        style="@style/profile_info_item_value"
        android:layout_marginLeft="@dimen/margin_med"
        android:paddingTop="@dimen/baseline_grid_smaller"/>

    <ViewStub
        android:id="@+id/viewStub_profile_feedback"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout="@layout/profile_feedback"/>

    <!-- Profile information table -->
    <!-- Name -->
    <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
                  android:layout_width="match_parent"
                  android:layout_height="wrap_content"
                  style="@style/profile_info_item_layout_margins"
                  android:paddingTop="@dimen/baseline_grid_smaller"
                  android:orientation="horizontal">

        <com.coffeemeetsbagel.views.CustomTextView
            android:text="@string/profile_info_label_name"
            style="@style/profile_info_item_label"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_weight="1"/>

        <com.coffeemeetsbagel.views.CustomTextView
            android:id="@+id/profile_info_value_name"
            style="@style/profile_info_item_value"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_weight="2"/>
    </LinearLayout>

    <!-- Age -->
    <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
                  android:layout_width="match_parent"
                  android:layout_height="wrap_content"
                  style="@style/profile_info_item_layout_margins"
                  android:orientation="horizontal">

        <com.coffeemeetsbagel.views.CustomTextView
            android:text="@string/profile_info_label_age"
            style="@style/profile_info_item_label"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            />

        <com.coffeemeetsbagel.views.CustomTextView
            android:id="@+id/profile_info_value_age"
            style="@style/profile_info_item_value"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_weight="2"/>
    </LinearLayout>

    <!-- Location -->
    <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
                  android:layout_width="match_parent"
                  android:layout_height="wrap_content"
                  style="@style/profile_info_item_layout_margins"
                  android:orientation="horizontal">

        <com.coffeemeetsbagel.views.CustomTextView
            android:text="@string/location"
            style="@style/profile_info_item_label"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            />

        <com.coffeemeetsbagel.views.CustomTextView
            android:id="@+id/profile_info_value_location"
            style="@style/profile_info_item_value"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_weight="2"/>
    </LinearLayout>

    <!-- Ethnicity -->
    <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
                  android:layout_width="match_parent"
                  android:layout_height="wrap_content"
                  style="@style/profile_info_item_layout_margins"
                  android:orientation="horizontal">

        <com.coffeemeetsbagel.views.CustomTextView
            android:text="@string/profile_info_label_ethnicity"
            style="@style/profile_info_item_label"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            />

        <com.coffeemeetsbagel.views.CustomTextView
            android:id="@+id/profile_info_value_ethnicity"
            style="@style/profile_info_item_value"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_weight="2"/>
    </LinearLayout>

    <!-- Height -->
    <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
                  android:layout_width="match_parent"
                  android:layout_height="wrap_content"
                  style="@style/profile_info_item_layout_margins"
                  android:orientation="horizontal">

        <com.coffeemeetsbagel.views.CustomTextView
            android:text="@string/profile_info_label_height"
            style="@style/profile_info_item_label"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            />

        <com.coffeemeetsbagel.views.CustomTextView
            android:id="@+id/profile_info_value_height"
            style="@style/profile_info_item_value"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_weight="2"/>
    </LinearLayout>

    <!-- Religion -->
    <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
                  android:layout_width="match_parent"
                  android:layout_height="wrap_content"
                  style="@style/profile_info_item_layout_margins"
                  android:orientation="horizontal">

        <com.coffeemeetsbagel.views.CustomTextView
            android:text="@string/profile_info_label_religion"
            style="@style/profile_info_item_label"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            />

        <com.coffeemeetsbagel.views.CustomTextView
            android:id="@+id/profile_info_value_religion"
            style="@style/profile_info_item_value"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_weight="2"/>
    </LinearLayout>

    <!-- Occupation -->
    <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
                  android:layout_width="match_parent"
                  android:layout_height="wrap_content"
                  style="@style/profile_info_item_layout_margins"
                  android:orientation="horizontal">

        <com.coffeemeetsbagel.views.CustomTextView
            android:text="@string/profile_info_label_occupation"
            style="@style/profile_info_item_label"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            />

        <com.coffeemeetsbagel.views.CustomTextView
            android:id="@+id/profile_info_value_occupation"
            style="@style/profile_info_item_value"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_weight="2"/>
    </LinearLayout>

    <!-- Employer -->
    <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
                  android:layout_width="match_parent"
                  android:layout_height="wrap_content"
                  style="@style/profile_info_item_layout_margins"
                  android:orientation="horizontal">

...

我注意到，如果我有一些动画，我会看到这个问题动画布局更改。只需在 xml 文件中停用它，即可防止页面卡在中间。