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android - 如何在 Kotlin 中将 listView 转换为 RecyclerView

问题描述

我在使用 listView 时遇到问题，因为我在 listview 中显示了许多图像（关于内存）

我需要将 listview 转换为 recyclerview

问题：

当我在手机上显示图像时，使用最后一个视图，你做了很多内存阻塞，这导致应用程序停止，所以我想将 List View 转换为 RecycleView。

主要活动：

    package com.masreta87.hussain

import android.app.Activity
import android.content.pm.PackageManager
import android.graphics.Bitmap
import android.graphics.drawable.BitmapDrawable
import android.os.Build
import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import android.os.Environment
import android.view.View
import android.widget.AdapterView
import android.widget.ImageView
import android.widget.ListView
import android.widget.Toast
import androidx.core.app.ActivityCompat
import androidx.core.content.ContextCompat
import androidx.core.view.get
import java.io.File
import java.io.FileOutputStream
import java.io.OutputStream
import java.lang.Exception
import java.util.jar.Manifest
import androidx.core.content.ContextCompat.getSystemService
import android.icu.lang.UCharacter.GraphemeClusterBreak.T
import androidx.core.app.ComponentActivity.ExtraData
import androidx.core.content.ContextCompat.getSystemService
import android.icu.lang.UCharacter.GraphemeClusterBreak.T
import android.util.Log
import kotlinx.android.synthetic.*


class MainActivity : AppCompatActivity() {
    lateinit var Img:ListView
    lateinit var ImgArr:ArrayList<DataImg>

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

         Img=findViewById(R.id.listviewB)
         ImgArr=ArrayList()

        ImgArr.add(DataImg(R.drawable.h))
        ImgArr.add(DataImg(R.drawable.hh))
        ImgArr.add(DataImg(R.drawable.hhh))
        ImgArr.add(DataImg(R.drawable.v2))
        ImgArr.add(DataImg(R.drawable.v3))
        ImgArr.add(DataImg(R.drawable.v4))
        ImgArr.add(DataImg(R.drawable.v5))
        ImgArr.add(DataImg(R.drawable.v6))
        //ImgArr.add(DataImg(R.drawable.v7))
        ImgArr.add(DataImg(R.drawable.v8))
        ImgArr.add(DataImg(R.drawable.v9))

        Img.adapter=customAdapter(applicationContext,ImgArr)
        Img.setOnItemClickListener{parent:AdapterView<*>, view:View, position:Int, id:Long ->
         var ImgNa=ImgArr.get(position).image.toString()

            Log.d("this",ImgNa)
            if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M){
                if (ContextCompat.checkSelfPermission(this,android.Manifest.permission.WRITE_EXTERNAL_STORAGE )
                    !=PackageManager.PERMISSION_GRANTED){

                    ActivityCompat.requestPermissions(this, arrayOf(android.Manifest.permission.WRITE_EXTERNAL_STORAGE)
                        ,100)

                }else{
                    saveImageToStorage(ImgNa)
                }
            }else{
                saveImageToStorage(ImgNa)
            }

        }


    }

    override fun onRequestPermissionsResult(
        requestCode: Int,
        permissions: Array<out String>,
        grantResults: IntArray
    ) {
        if (requestCode==100){
            if (grantResults.isNotEmpty() && grantResults[0]==PackageManager.PERMISSION_GRANTED){

               // saveImageToStorage(ImgNa)
            }else{
                Toast.makeText(this,"No Permission for save",Toast.LENGTH_SHORT).show()

            }
        }
    }
    public fun saveImageToStorage(ImgNa:String){

        val externalStorageState=Environment.getExternalStorageState()
        if (externalStorageState.equals(Environment.MEDIA_MOUNTED)){
            val storeDirectory=Environment.getExternalStorageDirectory().toString()
            val rnds = (1000..100000000000).random().toString()
            val file=File(storeDirectory,"$rnds.png")//Namephoto
            try {

                Log.d("output",ImgNa)
                val stream:OutputStream =FileOutputStream(file)
                var drawable=ContextCompat.getDrawable(applicationContext,ImgNa.toInt()) //edit
                var bitmap=(drawable as BitmapDrawable).bitmap
                bitmap.compress(Bitmap.CompressFormat.PNG,100,stream)
                stream.flush()
                stream.close()
                Toast.makeText(this,"Image Saved",Toast.LENGTH_LONG).show()
            }catch (e:Exception){
                e.printStackTrace()
            }

        }else{
            Toast.makeText(this,"unable to access the storage",Toast.LENGTH_SHORT).show()
        }
    }
}

和customAdapter

package com.masreta87.hussain

import android.content.Context
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import android.widget.BaseAdapter
import android.widget.ImageView

class customAdapter(var context: Context,var data:ArrayList<DataImg>) :BaseAdapter(){
private class ViewHolder(row:View?){
     var ivImage:ImageView
    init {
        this.ivImage=row?.findViewById(R.id.imageViewN) as ImageView


    }
}
    override fun getView(position: Int, convertView: View?, parent: ViewGroup?): View {
        var view:View?
        var viewHolder:ViewHolder
        if(convertView==null){
            var layout=LayoutInflater.from(context)
            view=layout.inflate(R.layout.listview_item,parent,false)
            viewHolder=ViewHolder(view)
            view.tag=viewHolder

        }else{
            view=convertView
            viewHolder=view.tag as ViewHolder
        }
        var data:DataImg=getItem(position) as DataImg

        viewHolder.ivImage.setImageResource(data.image)
        return view as View
    }

    override fun getItem(position: Int): Any {
        return data.get(position)
    }

    override fun getItemId(position: Int): Long {
        return position.toLong()
    }

    override fun getCount(): Int {
        return data.count()
    }

}

和数据图：

package com.masreta87.hussain

class DataImg(var image:Int) {

}

活动_Main.xml：

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout 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">


    <ListView
        android:id="@+id/listviewB"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        />
</RelativeLayout>

listview_item.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical" android:layout_width="match_parent"
    android:layout_height="match_parent">

    <ImageView
        android:id="@+id/imageViewN"
        android:background="@drawable/image_border"
        android:layout_width="match_parent"
        android:scaleType="fitXY"
        android:layout_height="200dp"

        />
</LinearLayout>

标签： androidlistviewkotlinandroid-recyclerview

解决方案

第一次改变你的activity_Main.xml：

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout 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">


    <RecyclerView
        android:id="@+id/recycler_view"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        />
</RelativeLayout>

然后你必须像这样为 RecyclerView 创建一个适配器：

class CustomAdapter(private val activity: Context?, private val arrData: List<DataImg>) : RecyclerView.Adapter<CustomAdapter.ViewHolder>() {
    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ViewHolder {
        var itemView: View? = null
        itemView = LayoutInflater.from(activity)
                .inflate(R.layout.listview_item, parent, false)
        return ViewHolder(itemView)
    }

    override fun onBindViewHolder(holder: ViewHolder, i: Int) {
        val model = arrData[i]
    }


    override fun getItemCount(): Int {
        return arrData.size
    }

    class ViewHolder(view: View?) : RecyclerView.ViewHolder(view!!) {

    }

}

现在在您的主要活动中，您必须为 RecyclerView 设置布局管理器，并且必须将 Adapter 与它绑定

recyclerViewSearchList = findViewById(R.id.recycler_view)
recyclerView.layoutManager = LinearLayoutManager(context, LinearLayoutManager.VERTICAL, false)
recyclerViewSearchList.adapter = CustomAdapter(MainActivity.this, ImgArr)

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