在回收站Kotlin中添加和删除项目

Question

我在Kotlin的回收视图中有关于添加和删除项目的问题。第一个任务是添加“添加”按钮，单击它之后，必须一遍又一遍地添加一个特定的图像。当我在主xml中实现该按钮时，该按钮将永远不会显示。第二项任务是单击时删除项目。这是我到目前为止所做的。

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

<LinearLayout
android:layout_height="match_parent"
xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:orientation="vertical">

<androidx.recyclerview.widget.RecyclerView
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:orientation="vertical"
    android:id="@+id/recycleview"/>
<Button
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="Add an item"
    android:layout_marginStart="280dp"/>

</LinearLayout>

package com.example.lecture11
import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import androidx.recyclerview.widget.LinearLayoutManager
import kotlinx.android.synthetic.main.activity_main.*

class MainActivity : AppCompatActivity() {



private var ItemsList= mutableListOf<ModelItem>()
private lateinit var adapter:MyAdapter


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

private  fun init(){

    adapter= MyAdapter(ItemsList)
    recycleview.layoutManager=LinearLayoutManager(this)
    recycleview.adapter=adapter



    setData()
}



private  fun setData(){
        ItemsList.add(ModelItem(R.mipmap.messi,"Messi"))
        ItemsList.add(ModelItem(R.mipmap.iniesta, "Iniesta"))
        ItemsList.add(ModelItem(R.mipmap.henry,"Henry"))
        ItemsList.add(ModelItem(R.mipmap.buffon,"Buffon"))
        ItemsList.add(ModelItem(R.mipmap.messi,"Messi"))
        ItemsList.add(ModelItem(R.mipmap.iniesta, "Iniesta" ))
        ItemsList.add(ModelItem(R.mipmap.henry,"Henry"))
        ItemsList.add(ModelItem(R.mipmap.buffon,"Buffon"))

  }
}


package com.example.lecture11

class ModelItem(var image:Int, var title:String)

package com.example.lecture11

import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import androidx.recyclerview.widget.RecyclerView
import kotlinx.android.synthetic.main.items_layout.view.*

class MyAdapter(val ItemsList:MutableList<ModelItem>) : RecyclerView.Adapter<MyAdapter.ViewHolder>() {


override fun getItemCount(): Int {
    return ItemsList.size
}
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ViewHolder {

    return  
ViewHolder(LayoutInflater.from(parent.context).inflate(R.layout.items_layout,parent,false))
}



override fun onBindViewHolder(holder: ViewHolder, position: Int) {



    holder.onBound()

}

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

    private lateinit var model:ModelItem

    fun onBound(){
        model=ItemsList[adapterPosition]
        itemView.imageview.setImageResource(model.image)
        itemView.title.text=model.title


      }

  }

}

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

<ImageView
    android:scaleType="centerCrop"
    android:src="@mipmap/messi"
    android:id="@+id/imageview"
    android:layout_width="match_parent"
    android:layout_height="200dp"/>
<TextView
    android:layout_marginTop="10dp"
    android:id="@+id/title"
    android:textColor="#fff"
    android:textStyle="bold"
    android:textAlignment="center"
    android:text="@string/messi"
    android:textSize="25sp"
    android:layout_width="match_parent"
    android:layout_height="40dp"/>





</LinearLayout>

Answer 1

如果要在屏幕底部显示按钮，并让recyclerview填充其余部分，则必须使用布局权重-

<LinearLayout
    android:layout_height="match_parent"
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:orientation="vertical">

    <androidx.recyclerview.widget.RecyclerView
        android:layout_width="match_parent"
        android:layout_height="0dp"
        android:layout_weight="1"
        android:orientation="vertical"
        android:id="@+id/recycleview"/>
    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Add an item"
        android:layout_marginStart="280dp"/>

</LinearLayout>