Android 中 RecyclerView 中的自动隐藏或自动扩展浮动操作按钮

在 Android 中的 NestedScrollView 的自动隐藏或自动扩展浮动操作按钮一文中，讨论并演示了如何在嵌套滚动视图中自动扩展或隐藏浮动操作按钮。在本文中，讨论了如何在 Android 中隐藏或扩展浮动操作按钮。查看下图以了解讨论的概况。

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创建一个空的活动项目

要在 Android Studio 中创建新项目，请参阅如何在 Android Studio 中创建/启动新项目。

添加所需的依赖

在build.gradle文件中包含 google material design components 依赖项。添加依赖项后，不要忘记单击右上角的“立即同步”按钮。

implementation “androidx.recyclerview:recyclerview:1.2.1”

请注意，在同步项目时，您需要连接到网络，并确保将依赖项添加到应用级 Gradle文件中，如下所示。

在 RecyclerView 中滚动时隐藏或扩展 FAB 的步骤

步骤 1：使用 activity_main.xml 文件

项目的主要布局包含一个 RecyclerView 和一个 Normal Floating Action Button。要实现相同的布局，请调用 activity_main.xml 文件中的以下代码。

在进入输出之前，我们需要用数据填充 RecyclerView。所以我们现在需要使用 RecyclerView Adapter 和 RecyclerView 的自定义视图。

第 2 步：为 RecyclerView 创建自定义视图

RecyclerView 的自定义视图在左侧包含一个简单的图标和两个 TextView。要实现相同的功能，请在布局文件夹中创建一个名为recycler_data_view.xml的文件并调用以下代码。

上面的自定义视图为列表中的每个项目生成以下输出：

第 3 步：为 RecyclerView 创建数据类

现在通过使用以下代码创建数据类来为上述自定义视图创建数据。

科特林

data class RecyclerViewData(
    val text1: String,
    val text2: String
)

第 4 步：创建 RecyclerView 适配器

以下代码需要通过创建名为 MyRecyclerAdapter 的类在单独的类中调用。

科特林

import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import android.widget.TextView
import androidx.recyclerview.widget.RecyclerView
  
class MyRecyclerViewAdapter(private val items: List) :
    RecyclerView.Adapter() {
  
    inner class MyRecyclerViewDataHolder(itemView: View) : RecyclerView.ViewHolder(itemView)
  
    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): MyRecyclerViewDataHolder {
        val view: View =
            LayoutInflater.from(parent.context).inflate(R.layout.recycler_data_view, parent, false)
        return MyRecyclerViewDataHolder(view)
    }
  
    override fun onBindViewHolder(holder: MyRecyclerViewDataHolder, position: Int) {
        val currentItem: RecyclerViewData = items[position]
  
        val tvNumber: TextView = holder.itemView.findViewById(R.id.tvNumber)
        tvNumber.text = currentItem.text1
  
        val tvNumbersInText: TextView = holder.itemView.findViewById(R.id.tvNumbersInText)
        tvNumbersInText.text = currentItem.text2
    }
  
    override fun getItemCount(): Int {
        return items.size
    }
}

步骤 5：使用 MainActivity.kt 文件

在这个类中，我们必须以列表的形式为 RecyclervView 创建一些示例数据，并在向上和向下滚动时处理回收器视图的滚动侦听器。当它向上滚动时，我们必须隐藏 FAB 并在向下滚动时显示 FAB。要实现相同的调用，请在 MainActivity.kt 文件中调用以下代码（添加注释以便更好地理解）。

科特林

import android.os.Bundle
import androidx.appcompat.app.AppCompatActivity
import androidx.recyclerview.widget.LinearLayoutManager
import androidx.recyclerview.widget.RecyclerView
import com.google.android.material.floatingactionbutton.FloatingActionButton
  
class MainActivity : AppCompatActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
  
        // create an instance of the Normal Floating Action Button
        // and register with the appropriate ID
        val fab: FloatingActionButton = findViewById(R.id.normalFAB)
  
        // create instance of RecyclerView and 
        // register with the appropriate ID
        val recyclerView: RecyclerView = findViewById(R.id.recyclerView)
  
        // create list of RecyclerViewData
        var recyclerViewData = listOf()
        recyclerViewData = recyclerViewData + RecyclerViewData("1", "One")
        recyclerViewData = recyclerViewData + RecyclerViewData("2", "Two")
        recyclerViewData = recyclerViewData + RecyclerViewData("3", "Three")
        recyclerViewData = recyclerViewData + RecyclerViewData("4", "Four")
        recyclerViewData = recyclerViewData + RecyclerViewData("5", "Five")
        recyclerViewData = recyclerViewData + RecyclerViewData("6", "Six")
        recyclerViewData = recyclerViewData + RecyclerViewData("7", "Seven")
        recyclerViewData = recyclerViewData + RecyclerViewData("8", "Eight")
        recyclerViewData = recyclerViewData + RecyclerViewData("9", "Nine")
        recyclerViewData = recyclerViewData + RecyclerViewData("10", "Ten")
        recyclerViewData = recyclerViewData + RecyclerViewData("11", "Eleven")
        recyclerViewData = recyclerViewData + RecyclerViewData("12", "Twelve")
        recyclerViewData = recyclerViewData + RecyclerViewData("13", "Thirteen")
        recyclerViewData = recyclerViewData + RecyclerViewData("14", "Fourteen")
        recyclerViewData = recyclerViewData + RecyclerViewData("15", "Fifteen")
  
        // create a vertical layout manager
        val layoutManager = LinearLayoutManager(this, LinearLayoutManager.VERTICAL, false)
  
        // create instance of MyRecyclerViewAdapter
        val myRecyclerViewAdapter = MyRecyclerViewAdapter(recyclerViewData)
  
        // attach the adapter to the recycler view
        recyclerView.adapter = myRecyclerViewAdapter
  
        // also attach the layout manager
        recyclerView.layoutManager = layoutManager
  
        // make the adapter the data set changed for the recycler view
        myRecyclerViewAdapter.notifyDataSetChanged()
  
        // now creating the scroll listener for the recycler view
        recyclerView.addOnScrollListener(object : RecyclerView.OnScrollListener() {
            override fun onScrolled(recyclerView: RecyclerView, dx: Int, dy: Int) {
                super.onScrolled(recyclerView, dx, dy)
  
                // if the recycler view is scrolled
                // above hide the FAB
                if (dy > 10 && fab.isShown) {
                    fab.hide()
                }
  
                // if the recycler view is 
                // scrolled above show the FAB
                if (dy < -10 && !fab.isShown) {
                    fab.show()
                }
  
                // of the recycler view is at the first
                // item always show the FAB
                if (!recyclerView.canScrollVertically(-1)) {
                    fab.show()
                }
            }
        })
    }
}

输出：

对于扩展浮动操作按钮

通过调用以下代码对activity_main.xml文件进行更改。

通过调用以下代码在MainActivity.kt文件中进行更改。

科特林

import android.os.Bundle
import androidx.appcompat.app.AppCompatActivity
import androidx.recyclerview.widget.LinearLayoutManager
import androidx.recyclerview.widget.RecyclerView
import com.google.android.material.floatingactionbutton.ExtendedFloatingActionButton
import com.google.android.material.floatingactionbutton.FloatingActionButton
  
class MainActivity : AppCompatActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
  
        // create an instance of the Normal Floating Action Button
        // and register with the appropriate ID
        val fab: ExtendedFloatingActionButton = findViewById(R.id.extendedFAB)
  
        // create instance of RecyclerView and register with the appropriate ID
        val recyclerView: RecyclerView = findViewById(R.id.recyclerView)
  
        // create list of RecyclerViewData
        var recyclerViewData = listOf()
        recyclerViewData = recyclerViewData + RecyclerViewData("1", "One")
        recyclerViewData = recyclerViewData + RecyclerViewData("2", "Two")
        recyclerViewData = recyclerViewData + RecyclerViewData("3", "Three")
        recyclerViewData = recyclerViewData + RecyclerViewData("4", "Four")
        recyclerViewData = recyclerViewData + RecyclerViewData("5", "Five")
        recyclerViewData = recyclerViewData + RecyclerViewData("6", "Six")
        recyclerViewData = recyclerViewData + RecyclerViewData("7", "Seven")
        recyclerViewData = recyclerViewData + RecyclerViewData("8", "Eight")
        recyclerViewData = recyclerViewData + RecyclerViewData("9", "Nine")
        recyclerViewData = recyclerViewData + RecyclerViewData("10", "Ten")
        recyclerViewData = recyclerViewData + RecyclerViewData("11", "Eleven")
        recyclerViewData = recyclerViewData + RecyclerViewData("12", "Twelve")
        recyclerViewData = recyclerViewData + RecyclerViewData("13", "Thirteen")
        recyclerViewData = recyclerViewData + RecyclerViewData("14", "Fourteen")
        recyclerViewData = recyclerViewData + RecyclerViewData("15", "Fifteen")
  
        // create a vertical layout manager
        val layoutManager = LinearLayoutManager(this, LinearLayoutManager.VERTICAL, false)
  
        // create instance of MyRecyclerViewAdapter
        val myRecyclerViewAdapter = MyRecyclerViewAdapter(recyclerViewData)
  
        // attach the adapter to the recycler view
        recyclerView.adapter = myRecyclerViewAdapter
  
        // also attach the layout manager
        recyclerView.layoutManager = layoutManager
  
        // make the adapter the data set
        // changed for the recycler view
        myRecyclerViewAdapter.notifyDataSetChanged()
  
        // now creating the scroll listener
        // for the recycler view
        recyclerView.addOnScrollListener(object : RecyclerView.OnScrollListener() {
            override fun onScrolled(recyclerView: RecyclerView, dx: Int, dy: Int) {
                super.onScrolled(recyclerView, dx, dy)
  
                // if the recycler view is scrolled 
                // above shrink the FAB
                if (dy > 10 && fab.isExtended) {
                    fab.shrink()
                }
  
                // if the recycler view is scrolled
                // above extend the FAB
                if (dy < -10 && !fab.isExtended) {
                    fab.extend()
                }
  
                // of the recycler view is at the first
                // item always extend the FAB
                if (!recyclerView.canScrollVertically(-1)) {
                    fab.extend()
                }
            }
        })
    }
}

输出：