RecyclerView的点击事件的两种实现方式

「爱情、让人受尽委屈。」 2021-09-21 15:02 914阅读 0赞

### 文章目录 ###

*  RecyclerView的点击事件
 *   *  (一）在适配器的onBindViewHolder方法中去添加响应事件
     *  (二)写回调方法

# RecyclerView的点击事件 #

RecyclerView中没有提供类似与setOnItemClickListener()这样的注册监听方法，而需要我们自己给子项具体的View去注册点击事件。相比与ListView来说，RecyclerView的功能更加强大，不仅可以实现对点击子项的响应，而且对子项的每一个view都可以轻松的实现点击响应。

下面通过两种方法来实现：

## (一）在适配器的onBindViewHolder方法中去添加响应事件 ##

override fun onBindViewHolder(holder: ViewHolder, position: Int) { 
    		...
            //点击事件(对子项的监听),若想监听子项中的view，将itemView改成对于的Id即可
            holder.itemView.setOnClickListener { 
                val index = holder.layoutPosition
    			...
            }
        	
        }

Demo:这个示例用RecyclerView来显示歌曲列表，点击列表子项后通过Toast弹出具体点击了哪一首歌曲。

1.activity\_main.xml:直接引入一个recyclerView控件即可

<?xml version="1.0" encoding="utf-8"?>
    <androidx.constraintlayout.widget.ConstraintLayout 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" android:layout_width="match_parent" android:layout_height="match_parent" tools:context=".MainActivity">
    
        <androidx.recyclerview.widget.RecyclerView android:id="@+id/recyclerView" android:layout_width="match_parent" android:layout_height="match_parent" />
    
    </androidx.constraintlayout.widget.ConstraintLayout>

2.item子项的布局：这里主要用于显示：图片，歌手以及歌曲名字。用了cardView来形成圆角效果

<?xml version="1.0" encoding="utf-8"?>
    <androidx.cardview.widget.CardView 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="100dp"
        app:cardCornerRadius="10dp"
        app:cardElevation="1dp"
        app:cardUseCompatPadding="true">
    
        <ImageView
            android:id="@+id/songImage"
            android:layout_width="80dp"
            android:layout_height="80dp"
            android:layout_margin="2dp"
            />
    
        <LinearLayout
            android:layout_width="276dp"
            android:layout_height="75dp"
            android:layout_gravity="end"
            android:orientation="vertical">
    
            <TextView
                android:id="@+id/song"
                android:layout_width="266dp"
                android:layout_height="40dp"
                android:textColor="#0800ff"
                android:textSize="20sp" />
    
            <TextView
                android:id="@+id/singer"
                android:layout_width="264dp"
                android:layout_height="29dp" />
        </LinearLayout>
    </androidx.cardview.widget.CardView>

3.res/values下的arrays.xml中存放歌曲信息

<?xml version="1.0" encoding="utf-8"?>
    <resources>
        <string-array name="songName">
            <item>晴天</item>
            <item>我的一个道姑朋友</item>
            <item>城南花已开</item>
        </string-array>
    
        <string-array name="singer">
            <item>周杰伦</item>
            <item>双笙</item>
            <item>三亩地</item>
        </string-array>
    
        <integer-array name="songImage">
            <item>@mipmap/sunny_day</item>
            <item>@mipmap/a_friend_of_mine</item>
            <item>@mipmap/city</item>
        </integer-array>
    </resources>

4.歌曲类

data class Song(var singer:String, val song:String, val imageId:Int)

5.全局Context的设置：因为要Toast是需要Context环境的。而在适配器类中是没有Context环境的。因此可以写一个全局Context的获取类MyApplication。

class MyApplication : Application() { 
    
        companion object{ 
            lateinit var context : Context
        }
    
        override fun onCreate() { 
            super.onCreate()
            context = applicationContext
        }
    }

同时需要在AndroidManfest.xml中添加：Android:name=".MyApplication"  
![在这里插入图片描述][20210110101700160.png]

6.适配器的实现(在OnBindViewHolder中实现了点击事件)

class SongAdapter(val songList:List<Song>):
            RecyclerView.Adapter<SongAdapter.ViewHolder>() { 
        inner class ViewHolder(view: View):RecyclerView.ViewHolder(view){ 
            val songImage : ImageView = view.findViewById(R.id.songImage)
            val song : TextView = view.findViewById(R.id.song)
            val singer : TextView = view.findViewById(R.id.singer)
        }
    
        override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ViewHolder { 
            val view = LayoutInflater.from(parent.context)
                .inflate(R.layout.song_item,parent,false)
            return ViewHolder(view)
        }
    
        override fun getItemCount() = songList.size
    
        override fun onBindViewHolder(holder: ViewHolder, position: Int) { 
            val value = songList[position]
            holder.songImage.setImageResource(value.imageId)
            holder.song.text = value.song
            holder.singer.text = value.singer
    
            //点击事件
            holder.itemView.setOnClickListener { 
                val id = holder.layoutPosition
                val name = songList[id]
                Toast.makeText(MyApplication.context,"点击了歌曲${ name}",Toast.LENGTH_SHORT).show()
    
            }
        }
    }

7.MainActivity

class MainActivity : AppCompatActivity() { 
        override fun onCreate(savedInstanceState: Bundle?) { 
            super.onCreate(savedInstanceState)
            setContentView(R.layout.activity_main)
            val layoutManager = LinearLayoutManager(this)
            recyclerView.layoutManager = layoutManager
            val adapter = SongAdapter(getSongs())
            recyclerView.adapter = adapter
        }
    
    
        //加载数据
        private fun getSongs():List<Song>{ 
            val songList = ArrayList<Song>()
            val songName = resources.getStringArray(R.array.songName)
            val singer = resources.getStringArray(R.array.singer)
            val songImage = resources.obtainTypedArray(R.array.songImage)
    
            for( i in 0..songName.size-1){ 
                val temp = Song(singer[i],
                    songName[i],
                    songImage.getResourceId(i,R.mipmap.sunny_day))
                songList.add(temp)
            }
            return songList
        }
    }

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2ljemZ5NTg1_size_16_color_FFFFFF_t_70]

## (二)写回调方法 ##

若想在点击后实现AlertDialog，但是AlertDialog是需要依附于Activity的。全局的Context是不能用的。这时候就可以写一个回调方法，在MainActivity中来实现事件的监听。

修改适配器类的代码（修改处写了注释）

package com.example.recyclerviewtest
    
    import android.view.LayoutInflater
    import android.view.View
    import android.view.ViewGroup
    import android.widget.ImageView
    import android.widget.TextView
    import android.widget.Toast
    import androidx.recyclerview.widget.RecyclerView
    
    class SongAdapter(val songList:List<Song>):
            RecyclerView.Adapter<SongAdapter.ViewHolder>() { 
    
        //1.定义接口类型的成员数据
        private var myItemClickListener : OnItemClickListener ?= null
    
        //2.定义接口
        interface OnItemClickListener{ 
            fun onItemClick(position:Int)
        }
        //3.set方法
        fun setOnItemClickListener(onItemClickListener : OnItemClickListener?){ 
            myItemClickListener = onItemClickListener
        }
    
    
        inner class ViewHolder(view: View):RecyclerView.ViewHolder(view){ 
            val songImage : ImageView = view.findViewById(R.id.songImage)
            val song : TextView = view.findViewById(R.id.song)
            val singer : TextView = view.findViewById(R.id.singer)
        }
    
        override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ViewHolder { 
            val view = LayoutInflater.from(parent.context)
                .inflate(R.layout.song_item,parent,false)
            return ViewHolder(view)
        }
    
        override fun getItemCount() = songList.size
    
        override fun onBindViewHolder(holder: ViewHolder, position: Int) { 
            val value = songList[position]
            holder.songImage.setImageResource(value.imageId)
            holder.song.text = value.song
            holder.singer.text = value.singer
    
            //4.传入position
            holder.itemView.setOnClickListener { 
                myItemClickListener!!.onItemClick(position)
            }
        }
    }

在MainActivity中

override fun onCreate(savedInstanceState: Bundle?) { 
            super.onCreate(savedInstanceState)
            setContentView(R.layout.activity_main)
            val layoutManager = LinearLayoutManager(this)
            recyclerView.layoutManager = layoutManager
            val songList = getSongs()
            val adapter = SongAdapter(songList)
            recyclerView.adapter = adapter
    
            adapter.setOnItemClickListener(object:SongAdapter.OnItemClickListener{ 
                override fun onItemClick(position: Int) { 
                    AlertDialog.Builder(this@MainActivity).apply { 
                        setTitle("test")
                        setMessage("点击了${ songList[position]}")
                        setCancelable(false)
                        setPositiveButton("OK"){ dialog, which ->  }
                        setNegativeButton("Cancel"){ dialog, which ->  }
                        show()
                    }
                }
            })
        }

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2ljemZ5NTg1_size_16_color_FFFFFF_t_70 1]

[20210110101700160.png]: /images/20210920/05642495ff62428a897a189c6147212a.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2ljemZ5NTg1_size_16_color_FFFFFF_t_70]: /images/20210920/fb218ec6e26e441e8a5f84f13045f226.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2ljemZ5NTg1_size_16_color_FFFFFF_t_70 1]: /images/20210920/8a40cc9aecd0412db945fb005d12c5f8.png