Kotlin 第一个 app

我会带着你远行 2022-05-27 09:27 255阅读 0赞

使用 RecycleView 显示测试数据 显示结果

![70][]

在activity\_main.xml 添加对应控件布局 （TextView RecycleView）

<?xml version="1.0" encoding="utf-8"?>
    <android.support.constraint.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="com.example.administrator.kotlintapplication.MainActivity">
        <TextView
            android:id="@+id/content"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            app:layout_constraintRight_toRightOf="parent"
            app:layout_constraintLeft_toLeftOf="parent"
            android:text="test"/>
        <android.support.v7.widget.RecyclerView
            android:id="@+id/recycler"
            app:layout_constraintTop_toBottomOf="@+id/content"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"/>
    </android.support.constraint.ConstraintLayout>

item\_text.xml (TextView)

<?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="wrap_content"
        android:gravity="center_horizontal">
        <TextView
            android:id="@+id/item_content"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:textSize="25sp"/>
    </LinearLayout>

MainActivity 相关代码

setContentView(R.layout.activity_main)
    content.text = "Hello_Kotlin"
    val list : MutableList<Test> = ArrayList()//创建一个可添加内容的List
    for (i in 1..30){//添加数据
        list.add(Test("ff_" + i, "ff_hh_" + i))
    }
    recycler.layoutManager = LinearLayoutManager(this)//设置RecycleView 的 LayoutManager
    val adapter = Adapter(this, list, { p, t ->
        Toast.makeText(this@MainActivity, "position= " + p +
                "\nname = " + t.n, Toast.LENGTH_SHORT).show()
    })
    recycler.adapter = adapter

Adapter 相关代码

class Adapter(context: Context, list: List<Test>, val itemListener: (Int, Test) -> Unit) : RecyclerView.Adapter<Adapter.ViewHolder>() {
        private var context: Context? = context
        private var list: List<Test>? = list
        override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ViewHolder {
            val convertView = LayoutInflater.from(context).inflate(R.layout.item_text, parent, false)
            return ViewHolder(convertView)
        }
        override fun onBindViewHolder(holder: ViewHolder, position: Int) {
            val t = list!![position]
            holder.textView.text = t.n
            holder.textView.setOnClickListener { itemListener(position, t) }
        }
        override fun getItemCount(): Int {
            return list!!.size
        }
    
        class ViewHolder(v: View) : RecyclerView.ViewHolder(v) {
            var textView: TextView = v.findViewById(R.id.item_content)
        }
    }

OnItemClickListener 接口

interface OnItemClickListener {
        fun onItemClick(position: Int, test: Test)
    }

Kotlin 创建类时会自动生成 对应的 get/set方法

如果只有一个构造函数数时书写方法如下：

Test 类

class Test (name: String, surName: String){
        val n = name
        val sur = surName;
    }

附带githup 链接地址  [demo githup 地址][demo githup]

https://github.com/androidkf93/Kotlin.git

[70]: /images/20220527/9f63ec42880949fcbe68ba4100ed2016.png
[demo githup]: https://github.com/androidkf93/Kotlin