Android2:构建交互式应用

一。创建项目

项目名Beer Adviser

二。更新布局

activity_main.xml

三。增加资源
strings.xml

    Beer Adviser
    Find Beer
    No beer selected
    
        Light
        Amber
        Brown
        Dark
    

四。响应点击

MainActivity.kt

package com.demo.beeradviser

import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import android.widget.Button
import android.widget.Spinner
import android.widget.TextView

class MainActivity : AppCompatActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        val findBeer = findViewById(R.id.find_beer)
        findBeer.setOnClickListener {
            val beerColor = findViewById(R.id.beer_color)
            val color = beerColor.selectedItem
            val beerList = getBeers(color.toString())
            val beers = beerList.reduce { str, item -> str + '\n' + item }
            val brands = findViewById(R.id.brands)
            brands.text = beers
        }
    }

    fun getBeers(color: String): List {
        return when (color) {
            "Light" -> listOf("Jail Pale Ale", "Lager Lite")
            "Amber" -> listOf("Jack Amber", "Red Moose")
            "Brown" -> listOf("Brown Bear Beer", "Bock Brownie")
            else -> listOf("Gout Stout", "Dark Daniel")
        }
    }
}

知识点：