在 Android 中四向滑动的 RecyclerView

Question

如何使用四向滑动创建 RecyclerView ？ 我在 java 中使用 MVVM 和 Room。

这是示例：

Answer 1

从你的 gif 中，我实现了一个RaceyclerView Demo版本。 但以同样的方式，您可以从发布的 gif 中实现所有内容。

这个 RecyclerView 在做什么？

• 允许向左或向右滑动并显示新面板
• 点击这个面板可以处理
• Recycler 检测到点击和长按
• 当滑动小于最大尺寸的一半时，面板将折叠
• 向右滑动选择项目，可以选择select最大选择项目数
• 可以观察到选定的项目

它的外观：

这是一个很长的答案，所以首先我尝试制作一个较短的版本来解释一种方法。 首先，您必须为 RecyclerView 项目创建一个布局。 此布局可分为 3 个部分。 MainPanel 其中match_parent宽度和宽度为0dp的左侧和右侧的两个侧面板。 在为这个 RecyclerView 创建一个适配器之后，你已经为视图设置onTouch监听器。 此onTouch function 必须检测您何时向左/向右滑动（以显示侧面板）或顶部/底部（以滚动 Recycler）。 但它还必须检测点击和长按才能正确处理。 当您检测到左右滑动时您可以更改侧面板的宽度。 这是一个包含完整代码的 GitHub 存储库，下面我尝试逐步给出解决方案。 （在 Kotlin 但我认为您可以轻松重构此代码）

---

怎么做：

启动项目：

• 基于Room的数据库。 一个名为DataView的Entity持有id 。 带有标准查询的DAO ，例如insert 、 delete 、 clearAll和getAll
• 带有 ViewModel 和 ViewModelFactory 的 MainActivity。 ViewModel 具有数据库中所有 DataView 的 LiveData。 MainActivity 布局只有一个 Recycler 和用于插入新项目的按钮。
• 3 个图标命名： plus 、 delete 、 selected

0.activity_main.xml：

<layout 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"
    >

    <androidx.constraintlayout.widget.ConstraintLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        tools:context=".ui.MainActivity"
        >

        <androidx.recyclerview.widget.RecyclerView
            android:id="@+id/swipeRecyclerView"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:layout_marginStart="1dp"
            android:layout_marginEnd="1dp"
            android:splitMotionEvents="false"
            app:layoutManager="androidx.recyclerview.widget.LinearLayoutManager"
            />

        <com.google.android.material.floatingactionbutton.FloatingActionButton
            android:id="@+id/butAddCar"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_margin="16dp"
            android:src="@drawable/plus"
            app:layout_constraintBottom_toBottomOf="parent"
            app:layout_constraintEnd_toEndOf="parent"
            />

    </androidx.constraintlayout.widget.ConstraintLayout>
</layout>

文件结构：

1.在RecyclerView和CardView中添加Gradle依赖

// RecyclerView
implementation 'androidx.recyclerview:recyclerview:1.1.0'

// CardView
implementation "androidx.cardview:cardview:1.0.0"

2. Recycler 项目的克里特岛渐变背景。 主视图、删除面板和选定面板。 （当然，它不一定是渐变，但你需要 3 个背景）

colors.xml：

<color name="recycler_left">#FFCDD2</color>
<color name="recycler_right">#C8E6C9</color>
<color name="recycler_delete_left">#E57373</color>
<color name="recycler_select_right">#81C784</color>

gradient_view.xml：

<shape xmlns:android="http://schemas.android.com/apk/res/android"
    android:shape="rectangle">

    <gradient
        android:angle="0"
        android:endColor="@color/recycler_right"
        android:startColor="@color/recycler_left"
        android:type="linear" />

</shape>

gradient_view_delete.xml：

<shape xmlns:android="http://schemas.android.com/apk/res/android"
    android:shape="rectangle">

    <gradient
        android:angle="0"
        android:endColor="@color/recycler_left"
        android:startColor="@color/recycler_delete_left"
        android:type="linear" />

</shape>

gradient_view_select.xml：

<shape xmlns:android="http://schemas.android.com/apk/res/android"
    android:shape="rectangle">

    <gradient
        android:angle="0"
        android:endColor="@color/recycler_select_right"
        android:startColor="@color/recycler_right"
        android:type="linear" />

</shape>

3. 为 Recycler 项目创建一个布局。

swipe_recycler_view.xml：

<?xml version="1.0" encoding="utf-8"?>
<layout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    >

    <data>

        <variable
            name="dataView"
            type="com.myniprojects.swiperecycler.database.DataView"
            />

        <variable
            name="clickListener"
            type="com.myniprojects.swiperecycler.recycler.SwipeListener"
            />

    </data>

    <androidx.cardview.widget.CardView
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        app:cardCornerRadius="6dp"
        app:cardElevation="4dp"
        app:cardPreventCornerOverlap="false"
        >

        <androidx.constraintlayout.widget.ConstraintLayout
            android:id="@+id/rootCL"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:background="@drawable/gradient_view"
            android:onClick="@{()-> clickListener.onClick(dataView)}"
            app:layout_constraintStart_toStartOf="parent"
            app:layout_constraintTop_toTopOf="parent"
            >
            <!-- Delete panel-->
            <FrameLayout
                android:id="@+id/frameDelete"
                android:layout_width="1px"
                android:layout_height="0dp"
                android:layout_gravity="center"
                android:background="@drawable/gradient_view_delete"
                android:onClick="@{()-> clickListener.onDeleteClick(dataView)}"
                app:layout_constraintBottom_toBottomOf="parent"
                app:layout_constraintStart_toStartOf="parent"
                app:layout_constraintTop_toTopOf="parent"
                >

                <ImageView
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content"
                    android:layout_gravity="center"
                    android:adjustViewBounds="true"
                    android:contentDescription="@string/delete"
                    android:padding="10dp"
                    app:srcCompat="@drawable/delete"
                    />

            </FrameLayout>

            <!-- Select panel-->
            <FrameLayout
                android:id="@+id/frameSelect"
                android:layout_width="1px"
                android:layout_height="0dp"
                android:layout_gravity="center"
                android:background="@drawable/gradient_view_select"
                app:layout_constraintBottom_toBottomOf="parent"
                app:layout_constraintEnd_toEndOf="parent"
                app:layout_constraintTop_toTopOf="parent"
                >

                <ImageView
                    android:layout_width="wrap_content"
                    android:layout_height="match_parent"
                    android:layout_gravity="center"
                    android:adjustViewBounds="true"
                    android:contentDescription="@string/select"
                    android:padding="10dp"
                    app:srcCompat="@drawable/selected"
                    />

            </FrameLayout>

            <!-- Main panel-->
            <androidx.constraintlayout.widget.ConstraintLayout
                android:id="@+id/carBackground"
                android:layout_width="0dp"
                android:layout_height="wrap_content"
                app:layout_constraintEnd_toStartOf="@id/frameSelect"
                app:layout_constraintStart_toEndOf="@id/frameDelete"
                app:layout_constraintTop_toTopOf="parent"
                >

                <TextView
                    android:id="@+id/txtContent"
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content"
                    android:layout_marginStart="16dp"
                    android:layout_marginTop="8dp"
                    android:layout_marginBottom="8dp"
                    android:text="@{Integer.toString(dataView.id)}"
                    android:textColor="#1B1919"
                    android:textSize="50sp"
                    app:layout_constraintBottom_toBottomOf="parent"
                    app:layout_constraintStart_toStartOf="parent"
                    app:layout_constraintTop_toTopOf="parent"
                    />

            </androidx.constraintlayout.widget.ConstraintLayout>

        </androidx.constraintlayout.widget.ConstraintLayout>

    </androidx.cardview.widget.CardView>

</layout>

它是如何工作的？ ConstraintLayout 是整个布局的根。 它在左侧和右侧拥有两个 FrameLayout，中间是另一个 ConstrintLayout。 FrameLayouts 宽度设置为 1，因此它们是不可见的。 当有人在此项目上滑动时，我们可以更改 FrameLayouth 宽度以使其可见。

4. 创建 RecyclerViewAdapter。 我将 ListAdapter 与 DiffUtil 一起使用。 适配器还需要 Class 可以处理点击或滑动，因此还需要创建新的 Class SwipeListener。 对代码的很多部分进行了注释更好地理解了代码。

import android.annotation.SuppressLint
import android.os.Handler
import android.view.LayoutInflater
import android.view.MotionEvent
import android.view.View
import android.view.ViewGroup
import androidx.lifecycle.LiveData
import androidx.lifecycle.MutableLiveData
import androidx.recyclerview.widget.DiffUtil
import androidx.recyclerview.widget.ListAdapter
import androidx.recyclerview.widget.RecyclerView
import com.myniprojects.swiperecycler.R
import com.myniprojects.swiperecycler.database.DataView
import com.myniprojects.swiperecycler.databinding.SwipeRecyclerViewBinding
import kotlin.math.abs
import kotlin.math.max
import kotlin.math.min

class SwipeRecyclerAdapter(
    private val swipeListener: SwipeListener, panelSize: Int
) : ListAdapter<DataView, SwipeRecyclerAdapter.ViewHolder>(
    SwipeDiffCallback()
)
{
    companion object
    {
        const val MAX_SELECT_NUMBER: Int = 4 // maximum number of items that user can select

        var PANEL_SIZE = 125 // delete and select panel width, the base is 125 but in the constructor we can pass new value based on DP which override this
            private set
    }

    // LiveData which holds all selected items in Recycler
    private val _selectedValues: MutableLiveData<ArrayList<Int>> = MutableLiveData()
    val selectedValues: LiveData<ArrayList<Int>>
        get() = _selectedValues

    init
    {
        PANEL_SIZE = panelSize //
        _selectedValues.value = ArrayList()
    }

    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ViewHolder
    {
        return ViewHolder.from(
            parent,
            _selectedValues,
            swipeListener
        )
    }


    override fun onBindViewHolder(holder: ViewHolder, position: Int)
    {
        holder.bind(getItem(position)!!, swipeListener)
    }


    class ViewHolder private constructor(
        private val binding: SwipeRecyclerViewBinding,
        private val selectedItems: MutableLiveData<ArrayList<Int>>,
        private val swipeListener: SwipeListener // listener which enables to handle click etc.
    ) :
            RecyclerView.ViewHolder(binding.root), View.OnTouchListener
    {
        private var xStart = 0F // variables which track swiping in onTouch event
        private var lastY = 0F
        private var yStart = 0F
        private val handler: Handler = Handler() // Handler enable to detect long click
        private var isLongClickCanceled = false
        private var wasLongClicked = false
        private var startScrolling = false
        private var status = 0
            set(value)
            {
                field = when
                {
                    value > 0 ->
                    {
                        min(value, PANEL_SIZE)
                    }
                    value < 0 ->
                    {
                        max(value, -PANEL_SIZE)
                    }
                    else ->
                    {
                        value
                    }
                }
                setSizes()
            }

        companion object
        {
            fun from(
                parent: ViewGroup,
                selectedCar: MutableLiveData<ArrayList<Int>>,
                swipeListener: SwipeListener
            ): ViewHolder
            {
                val layoutInflater = LayoutInflater.from(parent.context)
                val binding = SwipeRecyclerViewBinding.inflate(layoutInflater, parent, false)
                return ViewHolder(
                    binding, selectedCar, swipeListener
                )
            }

            private const val LONG_CLICK_TIME = 550L // time in millis to detect long click
            private const val CLICK_DISTANCE = 75 //distance in pixels to disable click/long click and enable scrolling or swiping
        }


        private val isValueSelected: Boolean
            get()
            {
                return selectedItems.value!!.contains(binding.dataView!!.id)
            }

        private val canAdd: Boolean
            get()
            {
                return selectedItems.value!!.size < MAX_SELECT_NUMBER
            }

        private fun addItem()
        {
            if (!isValueSelected)
            {
                selectedItems.value!!.add(binding.dataView!!.id)
                selectedItems.value = selectedItems.value
            }
        }

        private fun removeItem()
        {
            if (isValueSelected)
            {
                selectedItems.value!!.remove(binding.dataView!!.id)
                selectedItems.value = selectedItems.value
            }
        }


        @SuppressLint("ClickableViewAccessibility")
        fun bind(
            dataView: DataView,
            swipeListener: SwipeListener
        )
        {
            binding.dataView = dataView
            binding.clickListener = swipeListener

            binding.rootCL.setOnLongClickListener {
                swipeListener.clickLongListener(dataView.id)
                true
            }

            binding.rootCL.setOnTouchListener(this)

            status = if (isValueSelected) //value was selected, show right panel
            {
                -PANEL_SIZE
            }
            else
            {
                0
            }

            binding.executePendingBindings()
        }

        private val leftPanel = binding.rootCL.getChildAt(0)
        private val rightPanel = binding.rootCL.getChildAt(1)
        private val centerPanel = binding.rootCL.getChildAt(2)

        private fun setSizes()
        {
            when
            {
                status == 0 -> // center
                {
                    leftPanel.layoutParams.width = 1
                    rightPanel.layoutParams.width = 1
                }
                status > 0 -> //right
                {
                    leftPanel.layoutParams.width = status
                    rightPanel.layoutParams.width = 1
                }
                else -> //left
                {
                    leftPanel.layoutParams.width = 1
                    rightPanel.layoutParams.width = -status
                }
            }

            leftPanel.requestLayout()
            rightPanel.requestLayout()

            centerPanel.setBackgroundResource(R.drawable.gradient_view)
            leftPanel.setBackgroundResource(R.drawable.gradient_view_delete)
            rightPanel.setBackgroundResource(R.drawable.gradient_view_select)
        }

        // here swiping, clicking and scrolling is detected. MotionEvent is tracked and function recognize what to do
        override fun onTouch(v: View?, event: MotionEvent?): Boolean
        {
            if (v != null && event != null)
            {
                v.parent.requestDisallowInterceptTouchEvent(true)
                when (event.action)
                {
                    MotionEvent.ACTION_DOWN ->
                    {
                        xStart = event.x
                        yStart = event.y
                        isLongClickCanceled = false
                        wasLongClicked = false
                        startScrolling = false
                        handler.postDelayed({ //long click
                            wasLongClicked = true
                            v.performLongClick()
                                            }, LONG_CLICK_TIME)
                    }
                    MotionEvent.ACTION_UP ->
                    {
                        handler.removeCallbacksAndMessages(null)
                        if (!startScrolling && !isLongClickCanceled && !wasLongClicked)
                        {
                            if ((event.eventTime - event.downTime) < LONG_CLICK_TIME) //click
                            {
                                if (status == 0)
                                {
                                    v.performClick()
                                }
                                else
                                {
                                    status = 0
                                    removeItem()
                                }
                            }
                        }
                        else if (!startScrolling)
                        {
                            when
                            {
                                status > (PANEL_SIZE / 2) -> //show left
                                {
                                    status = PANEL_SIZE
                                    removeItem()
                                }
                                status < -(PANEL_SIZE / 2) -> //show right
                                {

                                    if (canAdd)//car can be added
                                    {
                                        status = -PANEL_SIZE
                                        addItem()
                                    }
                                    else
                                    {
                                        status = 0
                                        swipeListener.cannotSelectValue()
                                    }
                                }
                                else ->
                                {
                                    status = 0
                                    removeItem()
                                }
                            }
                        }
                    }
                    MotionEvent.ACTION_MOVE ->
                    {
                        if (startScrolling)
                        {
                            swipeListener.scroll((lastY - event.rawY).toInt())
                            lastY = event.rawY
                        }
                        else
                        {
                            if (!wasLongClicked)
                            {

                                if (isLongClickCanceled)
                                {
                                    val deltaX = (event.x - xStart).toInt()

                                    if (abs(deltaX) > 75)
                                    {

                                        if (deltaX > 0)
                                        {
                                            status = (deltaX - CLICK_DISTANCE)
                                        }
                                        else if (deltaX < 0)
                                        {
                                            status = (deltaX + CLICK_DISTANCE)
                                        }

                                    }
                                }
                                else if (abs(yStart - event.y) > CLICK_DISTANCE)
                                {
                                    lastY = event.rawY
                                    startScrolling = true
                                    handler.removeCallbacksAndMessages(null)
                                }
                                else if (!isLongClickCanceled && abs(xStart - event.x) >= CLICK_DISTANCE)
                                {
                                    isLongClickCanceled = true
                                    handler.removeCallbacksAndMessages(null)
                                }
                            }
                        }

                    }
                }
            }
            return true
        }
    }


}

// DiffUtil class, it helps to better calculate when to refresh Recycler
class SwipeDiffCallback : DiffUtil.ItemCallback<DataView>()
{
    override fun areItemsTheSame(oldItem: DataView, newItem: DataView): Boolean
    {
        return oldItem.id == newItem.id
    }

    override fun areContentsTheSame(oldItem: DataView, newItem: DataView): Boolean
    {
        return oldItem == newItem
    }
}

// listener which can handle clicking, swiping, scrolling and selecting too many items
class SwipeListener(
    val clickListener: (dataViewId: Int) -> Unit,
    val clickLongListener: (dataViewId: Int) -> Unit,
    val clickDeleteListener: (dataViewId: Int) -> Unit,
    val scroll: (dy: Int) -> Unit,
    val cannotSelectValue: () -> Unit
)
{
    fun onClick(dataView: DataView) = clickListener(dataView.id)
    fun onDeleteClick(dataView: DataView) = clickDeleteListener(dataView.id)
}

5. 创建Item装饰器，在Recycler中的item之间添加空格

import android.graphics.Rect
import android.view.View
import androidx.recyclerview.widget.RecyclerView

class TopSpacingItemDecoration(private val padding: Int) : RecyclerView.ItemDecoration()
{
    override fun getItemOffsets(
        outRect: Rect,
        view: View,
        parent: RecyclerView,
        state: RecyclerView.State
    )
    {
        super.getItemOffsets(outRect, view, parent, state)
        outRect.top = padding
        outRect.bottom = padding
    }
}

6.最后一部分，在MainActivity中设置好一切

import android.os.Bundle
import android.widget.Toast
import androidx.appcompat.app.AppCompatActivity
import androidx.databinding.DataBindingUtil
import androidx.lifecycle.ViewModelProvider
import com.myniprojects.swiperecycler.R
import com.myniprojects.swiperecycler.database.AppDatabase
import com.myniprojects.swiperecycler.databinding.ActivityMainBinding
import com.myniprojects.swiperecycler.recycler.SwipeListener
import com.myniprojects.swiperecycler.recycler.SwipeRecyclerAdapter
import com.myniprojects.swiperecycler.recycler.TopSpacingItemDecoration
import kotlinx.android.synthetic.main.activity_main.*


class MainActivity : AppCompatActivity()
{
    private lateinit var viewModel: MainActivityViewModel
    private lateinit var toast: Toast
    private lateinit var binding: ActivityMainBinding

    // simple function which only show one toast without accumulation
    private fun showToast(text: Any)
    {
        if (this::toast.isInitialized)
            toast.cancel()
        toast = Toast.makeText(this, text.toString(), Toast.LENGTH_SHORT)
        toast.show()
    }

    override fun onCreate(savedInstanceState: Bundle?)
    {
        super.onCreate(savedInstanceState)
        binding = DataBindingUtil.setContentView(this, R.layout.activity_main)

        // Init view model
        val database = AppDatabase.getInstance(application).dataViewDAO
        val viewModelFactory = MainActivityViewModelFactory(database)
        viewModel = ViewModelProvider(this, viewModelFactory).get(MainActivityViewModel::class.java)

        // set listener to handle events like click, long click, swipe left/right, selecting too many items and scrolling
        val swipeListener = SwipeListener(
            { id -> showToast("Click $id") }, // click
            { id -> showToast("Long click $id") }, // long click
            { id ->
                viewModel.delete(id)
            }, // delete
            { dy -> swipeRecyclerView.scrollBy(0, dy) }, // scroll
            {
                showToast("You can select up to  ${SwipeRecyclerAdapter.MAX_SELECT_NUMBER}")
            }
        )

        val adapter = SwipeRecyclerAdapter(
            swipeListener,
            resources.displayMetrics.widthPixels / 8 //maximum size of left/right panel
        )

        // observe items in database and update RecyclerView
        viewModel.dataViewItems.observe(this, {
            adapter.submitList(it)
        })

        // observe selected items in RecyclerView
        adapter.selectedValues.observe(this, {
            showToast("Selected id: $it")
        })

        binding.swipeRecyclerView.adapter = adapter
        binding.swipeRecyclerView.addItemDecoration(TopSpacingItemDecoration(10)) //setting space between items in RecyclerView

        // add new value to RecyclerView
        binding.butAddCar.setOnClickListener {
            viewModel.insertNextValueToDB()
        }
    }
}