RecycleView基本使用及常见问题汇总

RecycleView属于android基础组件，比较常用，下面总结下其使用的基础流程及常见问题解决办法（常见问题会定期更新）

基础使用

首先在xml里引入RecycleView

<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=".RecycleTestActivity">
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```
  <androidx.recyclerview.widget.RecyclerView
      android:id="@+id/recyclerView"
      android:layout_marginTop="50dp"
      android:layout_width="match_parent"
      android:layout_height="match_parent"
      android:scrollbars="vertical"
      app:layoutManager="androidx.recyclerview.widget.LinearLayoutManager"/>
```
</androidx.constraintlayout.widget.ConstraintLayout>
编写adapter，分以下几步

1.创建自定义adapter类,创建内部类MyViewHolder,并实现RecycleView的ViewHolder,参数传递view

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class MyAdapter(val data:List<Int>) {
    class MyHolder(view:View):ViewHolder(view){
        
    }
}

创建item layout，里面根据需要创建对应的布局，这里假如里面仅有一个progressbar,注意根布局高度改为wrap content，否则的话实际效果每个item占用了一屏

<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="wrap_content"
xmlns:app="http://schemas.android.com/apk/res-auto">

</androidx.constraintlayout.widget.ConstraintLayout>

3.在MyHolder里获取到progressBar

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class MyAdapter(val data:List<Int>) {
    class MyHolder(view:View):ViewHolder(view){
        val progressBar:ProgressBar = view.findViewById(R.id.progress)
    }
}

4.MyAdapter继承Recycleview.Adapter,并实现对应的三个方法

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class MyAdapter(val data:List<Int>):Adapter<MyAdapter.MyHolder>() {
    class MyHolder(view:View):ViewHolder(view){
        val progressBar:ProgressBar = view.findViewById(R.id.progress)
    }

    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): MyHolder {
        TODO("Not yet implemented")
    }

    override fun getItemCount(): Int {
        TODO("Not yet implemented")
    }

    override fun onBindViewHolder(holder: MyHolder, position: Int) {
        TODO("Not yet implemented")
    }
}

在onCreateViewHolder里创建MyHolder并返回，在getItemCount里返回 data.size,在onBindViewHolder里绑定组件

override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): MyHolder {
val view = LayoutInflater.from(parent.context).inflate(R.layout.my_item, parent, false)
return MyHolder(view)
}
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```
 override fun getItemCount(): Int {
    return data.size
 }

 override fun onBindViewHolder(holder: MyHolder, position: Int) {
     holder.progressBar.progress = data[position]
 }
```
在activity里获取recycleView，设置adapter 设置manager，adapter创建时把数据传入

recyclerView = findViewById(R.id.recyclerView)
myAdapter = MyAdapter(list)
recyclerView.adapter = myAdapter
recyclerView.layoutManager = LinearLayoutManager(this)

遇到的问题

1.当item里有progress bar时，数据变化让progress bar进度条变化，此时没什么问题，但如果progress bar设置了自定义的progressDrawable，那么其中一个item的进度条变化就会导致别的item显示的progress进度出现异常

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android:progressDrawable="@drawable/progress_bg"

progress_bg文件内容

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<?xml version="1.0" encoding="utf-8"?>
<layer-list xmlns:android="http://schemas.android.com/apk/res/android">
    <!--背景色-->
    <item android:id="@+id/background">
        <shape>
            <corners android:radius="100px" />
            <solid android:color="@color/progress_track" />
        </shape>
    </item>

    <!--进度条色-->
    <item android:id="@+id/progress">
        <clip android:clipOrientation="horizontal">
            <shape>
                <corners android:radius="100px" />
                <solid android:color="@color/progress_indicator" />
            </shape>
        </clip>
    </item>
</layer-list>

解决办法：

在onBindViewHolder时调用 holder.ProgressBar.progressDrawable.mutate()

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  override fun onBindViewHolder(holder: MyViewHolder, position: Int) {
        holder.ProgressBar.progressDrawable.mutate()