Kotlin Android扩展访问文本视图

所以我在自学android开发，我只是想用截击get调用的结果更新一个文本视图。我看过其他stackoverflow线程和kotlin教程，但似乎没有任何效果

我有三个主要的文件，我正在处理

带有这些视图的activity_main.xml

<TextView
    android:id="@+id/message"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_marginLeft="@dimen/activity_horizontal_margin"
    android:layout_marginStart="@dimen/activity_horizontal_margin"
    android:layout_marginTop="@dimen/activity_vertical_margin"
    android:text="Title"
    app:layout_constraintLeft_toLeftOf="parent"
    app:layout_constraintTop_toTopOf="parent" />

<android.support.design.widget.BottomNavigationView
    android:id="@+id/navigation"
    android:layout_width="0dp"
    android:layout_height="wrap_content"
    android:layout_marginEnd="0dp"
    android:layout_marginStart="0dp"
    android:background="?android:attr/windowBackground"
    app:layout_constraintBottom_toBottomOf="parent"
    app:layout_constraintLeft_toLeftOf="parent"
    app:layout_constraintRight_toRightOf="parent"
    app:menu="@menu/navigation" />

<TextView
    android:id="@+id/story"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_marginStart="16dp"
    android:layout_marginLeft="16dp"
    android:layout_marginTop="32dp"
    android:text="Story Contents"
    app:layout_constraintStart_toStartOf="parent"
    app:layout_constraintTop_toBottomOf="@+id/message" />

文本视图未更新，因此我不确定是否正确访问了activity_main.xml上的文本视图

---

有人能帮我看看我做错了什么吗？< /p> 你可以把每一个活动视为一个屏幕，因为你已经附上了代码> r.Frase.AccviyyOnMy/<代码> XML文件，带有<代码>主活动< /代码>，所以你不应该把它附加到其他任何地方（除非你想用同一个布局创建另一个屏幕）。code>GetRequestUtils是一个用于获取数据的类，因此它不应扩展

活动

。要在从API获取数据后返回值，可以使用接口回调

    class GetRequestUtils {

        interface Callback {
            fun onDone(book: Book)
        }

        val parseResponseUtil = ParseResponseUtil()

        fun makeGetRequest(context: Context, callback: Callback) {
            val queue = Volley.newRequestQueue(context)
            val stringRequest = StringRequest(Request.Method.GET, <Get Request URL>, Response.Listener<String> { response ->
                val book = parseResponseUtil.getBookComponents(response)
                callback.onDone(book)
            }, Response.ErrorListener { 
                val book = Book("Something went wrong", "Something went wrong", "Something went wrong")
                callback.onDone(book)
            })
            queue.add(stringRequest)
        }
    }

---

我可以知道这是什么吗？message.setText（“HERE”）story.setText（“HERE2”）@Ticherhaz

.kt

是Kotlin文件的扩展名，它来自MainActivity.kt？这很有效！我很感激你简单易懂的解释你为什么要做出改变。非常感谢。

import android.app.Activity
import android.content.Context
import android.os.Bundle
import com.android.volley.Request
import com.android.volley.Response
import com.android.volley.toolbox.StringRequest
import com.android.volley.toolbox.Volley
import kotlinx.android.synthetic.main.activity_main.*
import <Book>
import <R>

class GetRequestUtils : Activity(){
    val parseResponseUtil = ParseResponseUtil()

    fun makeGetRequest(context: Context) {
        val queue = Volley.newRequestQueue(context)
        val stringRequest = StringRequest(Request.Method.GET, <Get Request URL>, Response.Listener<String> { response ->
            val book = parseResponseUtil.getBookComponents(response)
            message?.text = book.title
            story?.text = book.story
        }, Response.ErrorListener { Book("Something went wrong", "Something went wrong", "Something went wrong")})
        queue.add(stringRequest)
    }

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

override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)
    setContentView(R.layout.activity_main)
    message.setText("HERE")
    story.setText("HERE2")
}

    class GetRequestUtils {

        interface Callback {
            fun onDone(book: Book)
        }

        val parseResponseUtil = ParseResponseUtil()

        fun makeGetRequest(context: Context, callback: Callback) {
            val queue = Volley.newRequestQueue(context)
            val stringRequest = StringRequest(Request.Method.GET, <Get Request URL>, Response.Listener<String> { response ->
                val book = parseResponseUtil.getBookComponents(response)
                callback.onDone(book)
            }, Response.ErrorListener { 
                val book = Book("Something went wrong", "Something went wrong", "Something went wrong")
                callback.onDone(book)
            })
            queue.add(stringRequest)
        }
    }

R.id.navigation_home -> {
    val getRequestUtils = GetRequestUtils()
    getRequestUtils.makeGetRequest(this, object : GetRequestUtils.Callback {
        override fun onDone(book: Book) {
            message?.text = book.title
            story?.text = book.story
        })
    return@OnNavigationItemSelectedListener true
}