Question

我正在与Kotlin一起使用android应用。我在AddDebtFragment中设置了3个微调器，在资源文件中设置了3个String数组。但是当我尝试从HomeFragment导航到该片段时，该应用程序终止，并且在Logcat的片段中显示了问题

这是我在fragment_add_debt.xml中的微调器

<Spinner
    android:id="@+id/debtCategorySpinner"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    style="@style/SpinnerStyle"
    android:spinnerMode="dialog" 
    android:entries="@array/debtCategoryList"/>

<Spinner
    android:id="@+id/financialNameSpinner"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:spinnerMode="dialog"
    style="@style/SpinnerStyle"
    android:entries="@array/financialNameList"/>
<Spinner
        android:id="@+id/rateTypeSpinner"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        style="@style/SpinnerStyle"
        android:spinnerMode="dialog"
        android:entries="@array/rateTypeList"/>

资源文件中的字符串数组

<string-array name="financialNameList">
        <item>Bangkok Bank</item>
        <item>Kasikorn Bank</item>
        <item>Krung Thai Bank</item>
        <item>The Siam Commercial Bank</item>
        <item>TMB Bank</item>
        <item>Bank of Ayudhya</item>
    </string-array>

    <string-array name="debtCategoryList">
        <item>Personal Loan</item>
        <item>Vehicle Loan</item>
        <item>Indonesia</item>
        <item>Mortgage</item>
        <item>Student Loan</item>
        <item>Credit Card</item>
    </string-array>

    <string-array name="rateTypeList">
        <item>Effective Rate</item>
        <item>Flat Rate</item>
        <item>Fixed Rate</item>
        <item>MRR</item>
        <item>MOR</item>
        <item>MLR</item>
        <item>Student Rate</item>
        <item>Credit Card</item>
        <item>Ceiling</item>
        <item>Default</item>
    </string-array>

AddDebtFragment

import android.os.Bundle
import android.util.Log
import androidx.fragment.app.Fragment
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import android.widget.AdapterView
import android.widget.ArrayAdapter
import com.example.debtrearragement.R
import kotlinx.android.synthetic.main.fragment_add_debt.*
class AddDebtFragment : Fragment(), AdapterView.OnItemSelectedListener {

    private val financialSpinner = financialNameSpinner
    private val debtSpinner = debtCategorySpinner
    private val rateSpinner = rateTypeSpinner

    override fun onCreateView(
        inflater: LayoutInflater, container: ViewGroup?,
        savedInstanceState: Bundle?
    ): View? {
        return inflater.inflate(R.layout.fragment_add_debt, container, false)
    }

    override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
        super.onViewCreated(view, savedInstanceState)

        ArrayAdapter.createFromResource(context, R.array.financialNameList, android.R.layout.simple_spinner_item)
            .also { adapter ->
            adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item)
            financialSpinner.adapter
            financialSpinner.onItemSelectedListener
        }

        ArrayAdapter.createFromResource(this.context, R.array.debtCategoryList, android.R.layout.simple_spinner_dropdown_item)
            .also { adapter ->
            adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item)
            debtSpinner.adapter
            debtSpinner.onItemSelectedListener
        }

        ArrayAdapter.createFromResource(this.context, R.array.rateTypeList, android.R.layout.simple_spinner_dropdown_item)
            .also { adapter ->
            adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item)
            rateSpinner.adapter
            rateSpinner.onItemSelectedListener
        }

    }

    override fun onNothingSelected(parent: AdapterView<*>) {

    }
    override fun onItemSelected(parent: AdapterView<*>, view: View,position: Int, id: Long) {

    }
}

编辑：1-这是Logcat

E/AndroidRuntime: FATAL EXCEPTION: main
    Process: com.example.debtrearragement, PID: 29305
    java.lang.IllegalStateException: financialSpinner must not be null
        at com.example.debtrearragement.view.ui.debt.AddDebtFragment.onViewCreated(AddDebtFragment.kt:34)
        at androidx.fragment.app.FragmentManagerImpl.moveToState(FragmentManagerImpl.java:892)
        at androidx.fragment.app.FragmentManagerImpl.addAddedFragments(FragmentManagerImpl.java:2097)
        at androidx.fragment.app.FragmentManagerImpl.executeOpsTogether(FragmentManagerImpl.java:1871)
        at androidx.fragment.app.FragmentManagerImpl.removeRedundantOperationsAndExecute(FragmentManagerImpl.java:1827)
        at androidx.fragment.app.FragmentManagerImpl.execPendingActions(FragmentManagerImpl.java:1727)
        at androidx.fragment.app.FragmentManagerImpl$2.run(FragmentManagerImpl.java:150)
        at android.os.Handler.handleCallback(Handler.java:873)
        at android.os.Handler.dispatchMessage(Handler.java:99)
        at android.os.Looper.loop(Looper.java:193)
        at android.app.ActivityThread.main(ActivityThread.java:6669)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:493)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:858)
I/Process: Sending signal. PID: 29305 SIG: 9
Application terminated.

编辑：2-我也看到它也显示在编译器上。

Answer 1

使用kotlin合成属性时，无需为Spinners声明新变量。只需删除

private val financialSpinner = financialNameSpinner
private val debtSpinner = debtCategorySpinner
private val rateSpinner = rateTypeSpinner

并在代码中将financialSpinner替换为financialNameSpinner，将debtSpinner替换为debtCategorySpinner，将rateSpinner替换为rateTypeSpinner。

您可以从docs

中找到有关Kotlin Android扩展的更多信息

修正警告

之所以收到此警告，是因为ArrayAdapter.createFromResource需要一个Context对象，而context（来自getContext）返回一个可为空的Context对象。您可以使用!!

将可空对象转换为非空对象

ArrayAdapter.createFromResource(context!!, R.array.financialNameList, android.R.layout.simple_spinner_item)

阅读doc，以了解有关科特林的零安全的更多信息

我在片段中使用spinneradapter有问题

1 个答案: