如何使用Kotlin在Android Studio中拖放ListView行

Question

我正在与Kotlin一起使用Android Studio。我希望能够在listView中拖放项目以重新排序它们。我也想向左滑动以删除。这在iOS的Xcode/Swift中非常简单，但是我很难找到Android/Kotlin的示例。我已经看到了与Java和Recyclerview的一些相当古老的讨论，但是能够在Kotlin中使用ListView做到这一点，真是太好了。我应该补充说，ListView可以完成我到目前为止所需的一切 - 我意识到有关ListView与RecyClerview的讨论很多。

我并不是要人们为我解决这个问题，但是如果您能指出可能会让我前进的任何事情，那就太好了。

通过背景，这是我的代码。它只是一个列表视图，其数字为“零”至“十”，并且突出显示了选定的行。我应该补充说，我在这里和YouTube上的许多讨论中编写了此代码，我非常感谢。

我也有一个列表视图，其中有需要这些选项的部分，但是我没有将代码放在这里（如果需要，很高兴这样做）。

activity_main.xml

<?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">
<ListView
    android:id="@+id/list_view"
    android:layout_width="0dp"
    android:layout_height="0dp"
    app:layout_constraintTop_toTopOf="parent"
    app:layout_constraintBottom_toBottomOf="parent"
    app:layout_constraintLeft_toLeftOf="parent"
    app:layout_constraintRight_toRightOf="parent"
    android:layout_margin="16dp" />
</androidx.constraintlayout.widget.ConstraintLayout>

listview_row.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">
    <TextView
        android:id="@+id/rowText"
        android:layout_width="match_parent"
        android:layout_height="48dp"
        android:textColor="@color/black"
        android:paddingLeft="0dp"
        android:paddingTop="8dp"
        android:paddingRight="0dp"
        android:paddingBottom="8dp"
        android:autoSizeTextType="uniform"
        android:autoSizeMaxTextSize="40sp"
        android:autoSizeMinTextSize="8sp"
        android:autoSizeStepGranularity="2sp"
        android:lines="1" />
</LinearLayout>

listview_selected_row.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">
    <TextView
        android:id="@+id/selectedRowText"
        android:layout_width="match_parent"
        android:layout_height="48dp"
        android:paddingLeft="0dp"
        android:paddingRight="0dp"
        android:paddingTop="8dp"
        android:paddingBottom="8dp"
        android:background="@color/teal_200"
        android:textColor="@color/black"
        android:autoSizeTextType="uniform"
        android:autoSizeMaxTextSize="40sp"
        android:autoSizeMinTextSize="8sp"
        android:autoSizeStepGranularity="2sp"
        android:lines="1" />
</LinearLayout>

listviewadapter.kt

package com.ijmusic.listviewrearrange

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

val TYPE_LISTVIEW_ITEM = 0
val TYPE_LISTVIEW_SELECTED_ITEM = 1

class ListViewAdapter(private val context: Context): BaseAdapter() {

    private val mData: ArrayList<String> = ArrayList()
    private var mIndex: ArrayList<Int> = ArrayList()
    private var mSelectedItem = -1

    private lateinit var textView: TextView

    fun addItem(item: String, index: Int) {
        mData.add(item)
        mIndex.add(index)
        notifyDataSetChanged()
    }

    fun addSelectedItem(item: String, index: Int) {
        mData.add(item)
        mIndex.add(index)
        mSelectedItem = mData.size - 1
        notifyDataSetChanged()
    }

    fun highlightSelection(int: Int) {
        mSelectedItem = int
        notifyDataSetChanged()
    }

    override fun getItemViewType(position: Int): Int {
        return if (position == mSelectedItem) TYPE_LISTVIEW_SELECTED_ITEM
        else TYPE_LISTVIEW_ITEM
    }

    override fun getCount(): Int {
        return mData.size
    }

    override fun getItem(position: Int): Any {
        return mData[position]
    }

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

    override fun getView(position: Int, view: View?, parent: ViewGroup?): View? {
        var view = view
        var type = getItemViewType(position)
        if (position == mSelectedItem) type = TYPE_LISTVIEW_SELECTED_ITEM
        when (type) {
            TYPE_LISTVIEW_ITEM -> {
                view = LayoutInflater.from(context).inflate(R.layout.listview_row, parent, false)
                textView = view.findViewById(R.id.rowText)
            }
            TYPE_LISTVIEW_SELECTED_ITEM -> {
                view = LayoutInflater.from(context).inflate(R.layout.listview_selected_row, parent, false)
                textView = view.findViewById(R.id.selectedRowText)
            }
        }
        textView.text = mData[position]
        return view
    }
}

mainactivity.kt

package com.ijmusic.listviewrearrange

import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import android.view.View
import android.widget.AdapterView
import com.ijmusic.listviewrearrange.databinding.ActivityMainBinding

val list = listOf("zero", "one", "two", "three", "four", "five", "six", "seven", "eight", "nine", "ten")
class MainActivity : AppCompatActivity() {

    private lateinit var binding: ActivityMainBinding
    private lateinit var mAdapter: ListViewAdapter

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        binding = ActivityMainBinding.inflate(layoutInflater)
        setContentView(binding.root)
        mAdapter = ListViewAdapter(this)
        setListView()
        binding.listView.onItemClickListener = object: AdapterView.OnItemClickListener {
            override fun onItemClick(parent: AdapterView<*>?, view: View?, position: Int, id: Long) {
                binding.listView.setSelection(position)
                mAdapter.highlightSelection(position)
            }
        }
    }

    fun setListView() {
        for ( i in 0 until list.count() ) {
            if ( i == 0 )
                mAdapter.addSelectedItem(list[i], i)
            else
                mAdapter!!.addItem(list[i], i)
        }
        binding.listView.adapter = mAdapter
    }
}

Answer 1

您可以研究Android Kotlin中称为手势的概念。它将有所帮助。