Kotlin - IllegalArgumentException：指定為非null的參數為null

Question

我將數據傳遞給bundle中的某個片段，並在接收它時拋出異常。 恢復Fragment的狀態時會發生此錯誤。

調用createFromParcel時， Intrinsics.checkParameterIsNotNull中發生錯誤。 這發生在Model中所有不可為空的字段中。

Caused by java.lang.IllegalArgumentException: Parameter specified as non-null is null: method kotlin.jvm.b.h.b, parameter realtorImageUrl
   at com.android.app.ui.common.model.Property.(Unknown Source:16)
   at com.android.app.ui.common.model.Property$Creator.createFromParcel(Unknown Source:637)
   at android.os.Parcel.readParcelable(Parcel.java:2797)
   at android.os.Parcel.readValue(Parcel.java:2691)
   at android.os.Parcel.readArrayMapInternal(Parcel.java:3058)
   at android.os.BaseBundle.unparcel(BaseBundle.java:257)
   at android.os.BaseBundle.getInt(BaseBundle.java:961)
   at me.yokeyword.fragmentation.SupportFragmentDelegate.onCreate(SourceFile:93)
   at me.yokeyword.fragmentation.SupportFragment.onCreate(SourceFile:48)
   at android.support.v4.app.Fragment.performCreate(SourceFile:2331)
   at android.support.v4.app.FragmentManagerImpl.moveToState(SourceFile:1386)
   at android.support.v4.app.FragmentManagerImpl.moveFragmentToExpectedState(SourceFile:1759)
   at android.support.v4.app.FragmentManagerImpl.moveToState(SourceFile:1827)
   at android.support.v4.app.FragmentManagerImpl.dispatchStateChange(SourceFile:3244)
   at android.support.v4.app.FragmentManagerImpl.dispatchCreate(SourceFile:3194)
   at android.support.v4.app.Fragment.restoreChildFragmentState(SourceFile:1444)
   at android.support.v4.app.Fragment.onCreate(SourceFile:1415)
   at me.yokeyword.fragmentation.SupportFragment.onCreate(SourceFile:47)
   at android.support.v4.app.Fragment.performCreate(SourceFile:2331)
   at android.support.v4.app.FragmentManagerImpl.moveToState(SourceFile:1386)
   at android.support.v4.app.FragmentManagerImpl.moveFragmentToExpectedState(SourceFile:1759)
   at android.support.v4.app.FragmentManagerImpl.moveToState(SourceFile:1827)
   at android.support.v4.app.FragmentManagerImpl.dispatchStateChange(SourceFile:3244)
   at android.support.v4.app.FragmentManagerImpl.dispatchCreate(SourceFile:3194)
   at android.support.v4.app.FragmentController.dispatchCreate(SourceFile:184)
   at android.support.v4.app.FragmentActivity.onCreate(SourceFile:355)
   at android.support.v7.app.AppCompatActivity.onCreate(SourceFile:84)
   at me.yokeyword.fragmentation.SupportActivity.onCreate(SourceFile:38)
   at com.android.app.ui.home.HomeActivity.onCreate(SourceFile:47)
   at android.app.Activity.performCreate(Activity.java:7174)
   at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1220)
   at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2908)
   at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3030)
   at android.app.ActivityThread.-wrap11(Unknown Source)
   at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1696)
   at android.os.Handler.dispatchMessage(Handler.java:105)
   at android.os.Looper.loop(Looper.java:164)
   at android.app.ActivityThread.main(ActivityThread.java:6938)
   at java.lang.reflect.Method.invoke(Method.java)
   at com.android.internal.os.Zygote$MethodAndArgsCaller.run(Zygote.java:327)
   at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1374)

Property.kt

@Parcelize
data class Property(
    ...
    @Json(name = "RealtorImageUrl")
    val realtorImageUrl: String
    ...
) : Parcelable

Kotlin 1.1.4，Android Extensions插件使用@Parcelize提供Parcelable實現生成器。

PropertyListFragment.kt

override fun showPropertyDetails(property: Property) {
    (parentFragment as PropertySearchResultFragment).start(
        PropertyDetailsFragment.newInstance(property)
    )
}

PropertyDetailsFragment.kt

class PropertyDetailsFragment{
    ...
    companion object {
        fun newInstance(property: Property) = PropertyDetailsFragment().withArgs {
            putParcelable(INT_EXTRA_PROPERTY, property)
        }
    }
    ...
}

我該怎么做才能解決這個問題？

Answer 1

由於realtorImageUrl的定義不為null，因此kotlin不允許將其設置為null。 因此，唯一可行的方法是通過反射設置空值。 Json幫助程序庫基於注釋處理並使用反射將值設置為字段，因此問題肯定來自它們。

• 首先，我強烈建議您使用谷歌Gson 。
• 其次，確保配置更改后json字符串不為null或為空。
• 第三，確保你在依賴項中使用moshi-kotlin （不是簡單的moshi ）並向moshi builder添加一個KotlinJsonAdapterFactory實例。

的build.gradle：

implementation 'com.squareup.moshi:moshi-kotlin:1.8.0'

測試：

val json = "{\"RealtorImageUrl\": \"http://www.gstatic.com/tv/thumb/persons/667736/667736_v9_ba.jpg\"}"

val moshi = Moshi.Builder()
        .add(KotlinJsonAdapterFactory()) // com.squareup.moshi.kotlin.reflect.KotlinJsonAdapterFactory
        .build()

val jsonAdapter = moshi.adapter(Property::class.java) as JsonAdapter<Property>
val property = jsonAdapter.fromJson(json) as Property

supportFragmentManager.beginTransaction()
        .replace(R.id.container, PropertyDetailsFragment.newInstance(property))
        .commit()

這是更好地使用withArguments從ANKO把論點的片段：

PropertyDetailsFragment.kt：

class PropertyDetailsFragment : Fragment() {

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

        val property = arguments?.getParcelable(KEY_EXTRA_PROPERTY) as Property
        val realtorImageUrl = property.realtorImageUrl
    }

    companion object {
        private const val KEY_EXTRA_PROPERTY = "KEY_EXTRA_PROPERTY"

        fun newInstance(property: Property) = PropertyDetailsFragment().withArguments(
                KEY_EXTRA_PROPERTY to property
        )
    }
}

Answer 2

嗯，這可能不是完美的解決方案，但它可以解決您的問題。 您可以使您的屬性可以為空，只需在訪問它們時添加空檢查即可。

只需像這樣初始化變量

Property.kt

@Parcelize
data class Property(
    ...
    @Json(name = "RealtorImageUrl")
    val realtorImageUrl: String
    ...
) : Parcelable

PropertyListFragment.kt

override fun showPropertyDetails(property: Property?) {
    (parentFragment as PropertySearchResultFragment).start(
        PropertyDetailsFragment.newInstance(property)
    )
}

並在PropertyDetailsFragment.kt中

class PropertyDetailsFragment{
    ...
    companion object {
        fun newInstance(property: Property?) = PropertyDetailsFragment().withArgs {
            property?.let{
                putParcelable(INT_EXTRA_PROPERTY, property)
            }
        }
    }
    ...
}

Answer 3

您可以嘗試使用@field：Json（name =“RealtorImageUrl”）並檢查它是否有效嗎？

另外，檢查是否添加了正確的工廠KotlinJsonAdapterFactory（）

 val moshi = Moshi.Builder()
    .add(KotlinJsonAdapterFactory())
    .build()