Kotlin中ListView与RecyclerView的应用讲解
写下来自己以后看:
先是item的布局文件:
里边放了一个图片和一个文本框
<?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="match_parent" android:layout_height="match_parent" android:id="@+id/linearLayout" > <ImageView android:id="@+id/imageView" android:layout_width="40dp" android:layout_height="40dp" android:layout_gravity="center_vertical" /> <TextView android:id="@+id/textView" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_gravity="center_vertical" /> </LinearLayout>
ListView:
布局文件:
<?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=".ListViewActivity"> <ListView android:id="@+id/listView" android:layout_width="0dp" android:layout_height="0dp" app:layout_constraintBottom_toBottomOf="parent" app:layout_constraintEnd_toEndOf="parent" app:layout_constraintStart_toStartOf="parent" app:layout_constraintTop_toTopOf="parent" /> </androidx.constraintlayout.widget.ConstraintLayout>
适配器:
class FruitAdapter(private val context: Context, private val list : List<Fruit>) : BaseAdapter() { override fun getCount(): Int = list.size override fun getItem(position: Int): Any = list[position] override fun getItemId(position: Int): Long = position.toLong() override fun getView(position: Int, convertView: View?, parent: ViewGroup?): View? { var convertView = convertView var holder : ViewHolder? = null if (convertView == null){ holder = ViewHolder() convertView = View.inflate(context,R.layout.item_list_view,null) holder.textView = convertView.findViewById<View>(R.id.textView) as TextView holder.imageView = convertView.findViewById<View>(R.id.imageView) as ImageView holder.linearLayout = convertView.findViewById<View>(R.id.linearLayout) as LinearLayout convertView.tag = holder }else{ holder = convertView.tag as ViewHolder } holder.textView!!.text = list[position].name holder.imageView!!.setImageResource(list[position].image) holder.linearLayout!!.setOnClickListener { Toast.makeText(context,list[position].name,Toast.LENGTH_SHORT).show() } return convertView } internal class ViewHolder{ var textView : TextView? = null var imageView : ImageView? = null var linearLayout : LinearLayout? = null } }
剩下的就是逻辑处理:
class ListViewActivity : AppCompatActivity() { private val bean = ArrayList<Fruit>() override fun onCreate(savedInstanceState: Bundle?) { super.onCreate(savedInstanceState) setContentView(R.layout.activity_list_view) for (i in 1..100){ bean.add(Fruit(i.toString(),R.drawable.ic_launcher_foreground)) } val adapter = FruitAdapter(this,bean) listView.adapter = adapter } }
RecyclerView:
布局文件:
<?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=".RecyclerViewActivity"> <androidx.recyclerview.widget.RecyclerView android:id="@+id/recyclerView" android:layout_width="match_parent" android:layout_height="match_parent"/> </androidx.constraintlayout.widget.ConstraintLayout>
适配器:
class FruitRecyclerViewAdapter(private val context: Context,private val list: List<Fruit>) : RecyclerView.Adapter<FruitRecyclerViewAdapter.ViewHolder>() { override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ViewHolder { val view : View = LayoutInflater.from(context).inflate(R.layout.item_list_view,null) return ViewHolder(view) } override fun onBindViewHolder(holder: ViewHolder, position: Int) { holder.itemView.textView.text = list[position].name holder.itemView.imageView.setImageResource(list[position].image) holder.itemView.linearLayout.setOnClickListener { Toast.makeText(context,list[position].name,Toast.LENGTH_SHORT).show() } } override fun getItemCount(): Int = list.size class ViewHolder(itemView: View) : RecyclerView.ViewHolder(itemView) { private val textView : TextView = itemView.findViewById(R.id.textView) private val imageView : ImageView = itemView.findViewById(R.id.imageView) private val linearLayout : LinearLayout = itemView.findViewById(R.id.linearLayout) } }
逻辑代码:
class RecyclerViewActivity : AppCompatActivity() { private val bean = ArrayList<Fruit>() override fun onCreate(savedInstanceState: Bundle?) { super.onCreate(savedInstanceState) setContentView(R.layout.activity_recycler_view) repeat(3){ for (i in 1..15){ bean.add(Fruit(i.toString(),R.drawable.ic_launcher_foreground)) } } val layoutManger = LinearLayoutManager(this) //layoutManger.orientation = LinearLayoutManager.HORIZONTAL recyclerView.layoutManager = layoutManger val adapter = FruitRecyclerViewAdapter(this,bean) recyclerView.adapter = adapter } }
这里的repeat函数是重复三次,意思就是会有三个1到15,也就是此recyclerView会有45个item.
现在的是纵向滑动的,如果要改成横向的,就把我代码中的注释掉的
//layoutManger.orientation = LinearLayoutManager.HORIZONTAL
取消注释就可以实现横向滑动了,如果不嫌弃难看,布局文件就不用改。
最后是实体类:
class Fruit(val name : String,val image : Int) { }
定义了一个name用来显示名字,定义了一个image,用来显示图片。
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