如何获得列表的应用程序图标和名称在kotlin回收视图

Question

所以我是kotlin的新手，我正在尝试让设备上所有安装的应用程序到回收器查看我的问题是回收器适配器中的所有活动返回空值，即使我传递了上下文

这是我的代码：

class Games_listx  : RecyclerView.Adapter<Games_listx.viewxlist>() {

    var appsx = Gamesff()
    var listofapps  = ArrayList<String>()
    var  all_apps : MutableList<ApplicationInfo>? = null
    var icons  : Drawable? = null

    class viewxlist(itemView: View) : RecyclerView.ViewHolder(itemView) {
        val txt_game = itemView.findViewById<View>(R.id.txtgames) as TextView
        val im_game = itemView.findViewById<View>(R.id.imgames) as ImageView
    }

    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): Games_listx.viewxlist {




        val layoutInflater = LayoutInflater.from(parent.context)

        val view = layoutInflater.inflate(R.layout.lay_allgames,parent,false)


        all_apps = appsx.activity?.packageManager?.getInstalledApplications(0)
        Log.w("apps" , "app " + all_apps?.size)

        for (app in all_apps?.indices!!) {
            val name = all_apps?.get(app)?.loadLabel(appsx.activity?.packageManager!!)

            if  (!(name?.startsWith("com.")!!)) {
                listofapps.add(name?.toString())
            }

        }
        return viewxlist(view)
    }

    override fun getItemCount(): Int {

       return listofapps.size
    }

    override fun onBindViewHolder(holder: Games_listx.viewxlist, position: Int) {


        holder.txt_game.text = listofapps.get(position).toString()




    }

}

listofapps的大小为0，包管理器为空

我使用相同的代码在onstart中获取应用程序，并且它可以工作

我做错了什么

如何在适配器中不为空的情况下获取活动或上下文

片段中的回收视图

class Gamesff : Fragment() {





override fun onStart() {
    super.onStart()



}

override fun onCreateView(
    inflater: LayoutInflater,
    container: ViewGroup?,
    savedInstanceState: Bundle?
): View? {

    val viewx = inflater.inflate(R.layout.fragment_gamesff,container,false)

    val all_games_list = viewx.findViewById<View>(R.id.gamelistfounds) as RecyclerView
    val add_game_folder = viewx.findViewById(R.id.txtaddgamefolder) as TextView









    add_game_folder.setOnClickListener {

        Toast.makeText(activity,"Make your own gaming folder",Toast.LENGTH_SHORT).show()

        val i = Intent(activity,GamingFolder::class.java)
        i.action = "add"

        startActivity(i)

    }


    val gridlay = GridLayoutManager(activity,4,GridLayoutManager.VERTICAL,false)

    all_games_list.layoutManager = gridlay
    all_games_list.fitsSystemWindows = true
    all_games_list.hasFixedSize()
    all_games_list.adapter = Games_listx()


    return viewx
}

Answer 1

如果我理解正确，您需要一种在适配器中初始化数据的方法。您所做的错误是试图初始化onCreateViewHolder（）中的列表。在调用onCreateViewHolder（）之前，将调用getItemCount（）。它将返回0，因为它返回了0，所以永远不会调用onCreateViewHolder（）。您应该做的是初始化构造函数（）中的列表应用程序

class AppsAdapter() : RecyclerView.Adapter<AppsAdapter.AppsViewHolder>() {

private var list: MutableList<App> = ArrayList()

constructor(packageManager: PackageManager): this() {
    val packageInfos = packageManager.getInstalledPackages(0)
    for (packageInfo in packageInfos) {
        val appName = packageInfo.applicationInfo.loadLabel(packageManager) as String
        if (appName.startsWith("com.", true)) {
            continue
        }
        val appDrawable = packageInfo.applicationInfo.loadIcon(packageManager)
        list.add(App(appDrawable, appName))
    }
}



override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): AppsViewHolder {
    val inflater = LayoutInflater.from(parent.context)
    val view: View = inflater.inflate(R.layout.item_app, parent, false)
    return AppsViewHolder(view)
}

override fun onBindViewHolder(holder: AppsViewHolder, position: Int) {
    holder.onBind(list[position])
}

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

class AppsViewHolder(itemView: View) : RecyclerView.ViewHolder(itemView) {
    fun onBind(app: App) {
        val appIcon = itemView.findViewById<ImageView>(R.id.appIconImageView)
        val textView = itemView.findViewById<TextView>(R.id.appNameTextView)
        appIcon.setImageDrawable(app.appIcon)
        textView.text = app.appName
    }
}}

Where应用。kt是：

class App (val appIcon: Drawable, val appName: String)

而在Main活动中，您应该：

class MainActivity : AppCompatActivity() {

private lateinit var adapter: AppsAdapter

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

    adapter = AppsAdapter(packageManager)
    val recyclerView = findViewById<RecyclerView>(R.id.recyclerView)
    recyclerView.layoutManager = GridLayoutManager(
        this,
        4,
        GridLayoutManager.VERTICAL,
        false
    )
    recyclerView.adapter = adapter
}}

Answer 2

由于关注点的分离，适配器不应该负责搜索要显示的数据。

首先，为每个应用程序的信息创建一个数据类，这些信息与您的RecyclerView显示或操作相关，例如：

data class AppInfo (
    val appName: String,
    val packageName: String,
    val icon: Drawable
)

您的适配器应该为数据列表公开一个公共属性。这是任何适配器应该如何工作。您可以在onCreateViewHolder中创建视图和ViewHolder，并在onBindViewHolder中绑定您的值。我喜欢设置ViewHolder来在内部处理这个问题，所以我的onBind和onCreate函数非常简单。我还为项目单击侦听器公开了一个单一的属性，因此单击功能也在外部处理。除了将数据和逻辑连接到视图之外，适配器不做任何事情。

class AppsListAdapter: RecyclerView.Adapter<AppsListAdapter.ViewHolder>() {

    inner class ViewHolder(val rootView: ViewGroup): RecyclerView.ViewHolder(rootView), View.OnClickListener {

        init { rootView.onClickListener = this }

        val titleView = rootView.findViewById<TextView>(android.R.id.title)
        val iconView = rootView.findViewById<ImageView>(android.R.id.icon)

        var data: AppInfo? = null
            set(value) {
                field = value
                value ?: return
                titleView.text = value.appName
                iconView.setImageDrawable(value.icon)
            }

        override fun onClick(v: View) {
            data?.let {
                onListItemClick(it)
            }
        }
    }

    fun interface OnItemClickListener {
        fun onItemClick(appInfo: AppInfo)
    }

    var dataList: List<AppInfo> = emptyList()
        set(value) {
            field = value
            notifyDataSetChanged()
        }

    private var onItemClickListener: OnItemClickListener? = null
    
    fun setOnItemClickListener(listener: OnItemClickListener) 
        this.onItemClickListener = listener
    }

    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int) =
        ViewHolder(
            LayoutInflater.from(parent.context)
                .inflate(R.layout.app_list_item, parent, false)
        )

    override fun onBindViewHolder(holder: ViewHolder, position: Int) {
        holder.data = dataList[position]
    }
}

然后，在Activity、Fragment或ViewModel中，您可以使用一个协同程序获取所有数据，这样就不会在主线程上加载drawables。在我的例子中，我在ViewModel中执行此操作，并填充UI订阅的SharedFlow，但为了简单起见，既然您提到了活动，下面是如何在活动中执行此操作：

val adapter = AppsListAdapter()
adapter.setOnItemClickListener { // Set what to do when item is clicked
    Log.d("item click", "Clicked package ${it.packageName}")
    
}
myRecyclerView.adapter = adapter

lifecycleScope.launch {
    val packageManager = context.packageManager
    val appsData = withContext(Dispatchers.IO) { // do all loading in background thread
        packageManager.getInstalledPackages(0)
            .filterNot { it.packageName.startsWith("com.") } // any filtering you want before loading
            .map {
                AppInfo(
                    it.applicationInfo.loadLabel(packageManager).toString(),
                    it.packageName,
                    it.applicationInfo.loadIcon(packageManager)
                )
            }
    }
    adapter.dataList = appsData
}

实际上，由于用户可能安装了许多应用程序，我也支持在获得初始列表和每五个图标后提前取消协同程序，如下所示：

lifecycleScope.launch {
    val packageManager = context.packageManager
    val appsData = withContext(Dispatchers.IO) { 
        packageManager.getInstalledPackages(0)
            .filterNot { it.packageName.startsWith("com.") }
            .mapIndexed { idx, it ->
                if (idx % 5 == 0) yield()
                AppsInfo(
                    it.applicationInfo.loadLabel(packageManager).toString(),
                    it.packageName,
                    it.applicationInfo.loadIcon(packageManager)
                )
            }
    }
    adapter.dataList = appsData
}