kotlin - 类型不匹配Kotlin和getStringArrayListExtra

Question

我尝试在Kotlin中建立语音识别。
我的大部分代码都是从互联网上粘贴下来的。但是我失败了。
我有一个简单的android.xml，带有1个textview，1个editview和1个按钮，其中“onclick” = mybuttondo。

我的Kotlin代码:

package com.example.mytestspeech
import android.app.Activity
import android.content.Intent
import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import android.speech.RecognizerIntent
import android.view.ActionMode
import android.view.View
import kotlinx.android.synthetic.main.activity_main.*
import java.util.*
import kotlin.collections.ArrayList
class MainActivity : AppCompatActivity() {
    val SPEECHINTENTRQ = 0
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
        textView.text = "newworld"
    }
    fun mybuttondo(view: View) {
        // only my test for ListOf<String>
        var mytext = "mystring"
        var myarr = listOf<String>("one","two")
        editText.setText(myarr[1])
        // the speechrecognition
        val speechRecognitionIntent = Intent(RecognizerIntent.ACTION_RECOGNIZE_SPEECH)
        speechRecognitionIntent.putExtra(RecognizerIntent.EXTRA_LANGUAGE, Locale.getDefault().toString())
        startActivityForResult(speechRecognitionIntent, SPEECHINTENTRQ)
    }
    override fun onActivityResult(requestCode: Int, resultCode: Int, data: Intent?) {
        super.onActivityResult(requestCode, resultCode, data)
        //var speechresult2: kotlin.collections.ArrayList<String>
        var speechresult2 : kotlin.collections.ArrayList<String> = kotlin.collections.ArrayList()
        //var speechresult2: ArrayList<String> = arrayListOf()
        //var speechresult2: kotlin.collections.List<String> = kotlin.collections.ArrayList() // compiled successfully
        //var speechresult2 = java.util.ArrayList(String)
        //var spokenText: java.util.ArrayList<String>         //ArrayList<String>
        var speechresult: String? = String()
        if (requestCode == SPEECHINTENTRQ  &&  resultCode == Activity.RESULT_OK) {
            // this works with String
            speechresult = data?.getStringExtra(RecognizerIntent.EXTRA_RESULTS)
            editText.setText(speechresult)
            //this does not work
            //no matter, which var definition from above i use
            speechresult2 = data?.getStringArrayListExtra(RecognizerIntent.EXTRA_RESULTS)
            // here I get compiler message:
            //Type mismatch: inferred type is java.util.ArrayList<String!>? but kotlin.collections.ArrayList<String> /* = java.util.ArrayList<String> */ was expected

            //spokenText  = speechresult2[0]
            //textView.text = spokenText
        }
        else
            editText.setText("Keine Eingabe"+requestCode)
    }
}

我将问题写到代码中
在编译

speechresult2 = data?.getStringArrayListExtra(RecognizerIntent.EXTRA_RESULTS) 

不适用于类型不匹配......
我尝试了几个数组列表定义(在代码中带有//的注释)
他们都不起作用

当我尝试

var speechresult2 = data?.getStringArrayListExtra(RecognizerIntent.EXTRA_RESULTS) 

没有预定义的数组列表，编译器可以工作。但后来我有了问题
例如

var spokenText = speechresult2[0] 

不起作用。相同的编译器消息。

我对array-list的定义有什么问题？

Answer 1

好了data?.getStringArrayListExtra(RecognizerIntent.EXTRA_RESULTS)返回ArrayList吗？即ArrayList可以为空。

您可以创建一个可为空的ArrayList变量，或者如果新的ArrayList返回null，则可以将其初始化。

示例

// to populate speech result with empty arraylist if the call returns null
val speechresult2: ArrayList<String> =
    data?.getStringArrayListExtra(RecognizerIntent.EXTRA_RESULTS) ?: ArrayList()

// or just take nullable array list
val speechresult2: ArrayList<String>? =
    data?.getStringArrayListExtra(RecognizerIntent.EXTRA_RESULTS)