如何访问片段中 Recycler View 中每个项目的共享首选项

Question

我想将 Button 的共享首选项存储在 Fragment 使用的 Recycler View Adapter 中。

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

private val name = arrayOf("Android Dev W1",
    "Android Dev W2", "Web Dev W1", "Learn Kotlin B1",
    "Android Dev W3", "Android Dev W4", "Web Dev W2",
    "Learn DSA")

private val date = arrayOf("20:00 18th May, 2021", "04:00 18th May, 2021",
    "07:00 19th May, 2021", "04:00 20th May, 2021",
    "01:00 21th May, 2021", "10:00 21th May, 2021",
    "20:00 27th May, 2021", "10:00 30th May, 2021")

private val btn = arrayOf(false, false, false, false, false, false, false, false)

inner class ViewHolder(itemView: View) : RecyclerView.ViewHolder(itemView) {

    var itemName: TextView = itemView.findViewById(R.id.workshopName)
    var itemDate: TextView = itemView.findViewById(R.id.workshopDate)
    var button: Button = itemView.findViewById(R.id.applyBtn)

    val prefs = itemView.context.getSharedPreferences("prefs", MODE_PRIVATE)

    init {

        for(i in 0 .. 7) {
            //checking via sharedPreferences if this app is being run first time or not
            btn[i] = prefs.getBoolean("registered$i", false)
            if (btn[i]) {
                hideButton()
            } else {
                showButton()
            }
        }

    }

     fun hideButton() {
         button.text = "Applied"
         button.isClickable = false
         button.setBackgroundColor(Color.parseColor("#FF3700E9"))
    }

    private fun showButton() {
        button.text = "Apply"
        button.isClickable = true
        button.setBackgroundColor(Color.parseColor("#FF6200EE"))
    }
}

override fun onCreateViewHolder(viewGroup: ViewGroup, i: Int): ViewHolder {
    val v = LayoutInflater.from(viewGroup.context)
        .inflate(R.layout.frame_textview, viewGroup, false)
    return ViewHolder(v)
}

override fun onBindViewHolder(viewHolder: ViewHolder, i: Int) {
    viewHolder.itemName.text = name[i]
    viewHolder.itemDate.text = date[i]
    viewHolder.button.setOnClickListener {
        viewHolder.prefs.edit().putBoolean("registered$i", true).apply()
        btn[i] = true
        viewHolder.hideButton()
    }

}

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

正在使用此适配器的片段

class AvailableWorkshops : Fragment() {

override fun onCreateView(
    inflater: LayoutInflater, container: ViewGroup?,
    savedInstanceState: Bundle?
): View? {
    // Inflate the layout for this fragment
    return inflater.inflate(R.layout.fragment_available_workshops, container, false)
}

override fun onViewCreated(itemView: View, savedInstanceState: Bundle?) {
    super.onViewCreated(itemView, savedInstanceState)
    val recyclerView = itemView.findViewById<RecyclerView>(R.id.recycler_view)
    recyclerView.apply {
        // set a LinearLayoutManager to handle Android
        // RecyclerView behavior
        layoutManager = LinearLayoutManager(activity)
        // set the custom adapter to the RecyclerView
        adapter = RecyclerViewAdapter()
        }
    }
}

例如，此适配器中有 8 个项目，我单击第 5 个项目，它将调用 onClickListener() 并更改按钮属性，这完全没问题。

但是，当我们重新启动应用程序时，它会变回默认按钮属性（共享首选项不起作用）

同样，如果我单击每个项目并重新启动应用程序，它现在将显示每个项目的新更改（共享首选项在这里起作用）。

我想存储如果我点击第 5 个项目，然后在应用程序重新启动时它应该只更改第 5 个项目的显示，而不是每个项目。

Answer 1

I want to store that if I click on 5th Item, then on app restart it should change display of only 5th item, not for every item.

你的问题

一个ViewHolder表示RecyclerView中的一项。当您初始化 ViewHolder 时，您将首选项应用了 7 次 到同一个按钮 。

inner class ViewHolder(itemView: View) : RecyclerView.ViewHolder(itemView) {
  
 //...

 init {
        // ** THIS IS NOT HIDING OR SHOWING SEVEN DIFFERENT BUTTONS - THIS IS HIDING OR
        // SHOWING THIS VIEWHOLDER'S ONE BUTTON SEVEN TIMES **

        for(i in 0 .. 7) {
            //checking via sharedPreferences if this app is being run first time or not
            btn[i] = prefs.getBoolean("registered$i", false)
            if (btn[i]) {
                hideButton()
            } else {
                showButton()
            }
        }

    }

一个解决方案

删除 ViewHolder 中的 init 块，并将隐藏/显示逻辑移动到 onBindViewHolder 方法，在该方法中设置 每个实例.

override fun onBindViewHolder(viewHolder: ViewHolder, i: Int) {
    viewHolder.itemName.text = name[i]
    viewHolder.itemDate.text = date[i]

    // ** SHOW OR HIDE THIS INSTANCE'S BUTTON - AND ONLY THIS INSTANCE'S BUTTON **
    if (viewHolder.prefs.getBoolean("registered$i", false)) {
        viewHolder.hideButton()
    } else {
        viewHolder.showButton()
    }

    viewHolder.button.setOnClickListener {
        viewHolder.prefs.edit().putBoolean("registered$i", true).apply()
        btn[i] = true
        viewHolder.hideButton()
    }
}

如何访问片段中 Recycler View 中每个项目的共享首选项

How to access Shared Preferences for each item in Recycler View in Fragment

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sharedpreferences

android-listfragment

android-recyclerview