Unreachablecode是什么意思？package com
.example
.customfactory
import
android.app
.Application
import
android.os
.Bundle
import
androidx
.lifecycle
.*
import
androidx
.savedstate
.SavedStateRegistryOwner
import java
.lang
.reflect
.Constructor
import java
.lang
.reflect
.InvocationTargetException
import kotlin
.reflect
.KClass
/**
* 自定义 SavedStateViewModelFactory
* 功能：
* 1
. 支持 SavedStateHandle
* 2
. 支持
AndroidViewModel
* 3
. 支持传入 Application
和单例 A
* 4
. 保留四种 create 方法
*/
class NewViewModelFactory(
private val application
: Application?,
owner
: SavedStateRegistryOwner,
private val defaultArgs
: Bundle? =
null,
private val singletonA
: Any
)
: ViewModelProvider
.Factory {
private val savedStateRegistry = owner
.savedStateRegistry
private val lifecycle = owner
.lifecycle
private val
androidFactory = if (application !=
null) {
ViewModelProvider
.AndroidViewModelFactory
.getInstance(application)
} else {
ViewModelProvider
.AndroidViewModelFactory()
}
// --- 1
. KClass + extras ---
override fun <T
: ViewModel> create(modelClass
: KClass<T>, extras
: CreationExtras)
: T {
return create(modelClass
.java, extras)
}
// --- 2
. Class + extras ---
fun <T
: ViewModel> create(modelClass
: Class<T>, extras
: CreationExtras)
: T {
val key = extras[ViewModelProvider
.VIEW_MODEL_KEY]
?
: throw IllegalStateException("VIEW_MODEL_KEY
must always
be provided by ViewModelProvider")
return if (extras[SavedStateRegistryOwner
::class
.java] !=
null &&
extras[ViewModelStoreOwner
::class
.java] !=
null
) {
val applicationFromExtras = extras[ViewModelProvider
.AndroidViewModelFactory
.APPLICATION_KEY]
val is
AndroidViewModel =
AndroidViewModel
::class
.java
.isAssignableFrom(modelClass)
val constructor
: Constructor<T>? =
findMatchingConstructor(modelClass, is
AndroidViewModel)
// 如果没有 SavedStateHandle 构造函数，回退原生 Factory
if (constructor ==
null) {
return
androidFactory
.create(modelClass, extras)
}
val handle = extras
.createSavedStateHandle()
val viewModel
: T = if (is
AndroidViewModel && applicationFromExtras !=
null) {
newInstance(modelClass, constructor, applicationFromExtras, handle, singletonA)
} else {
newInstance(modelClass, constructor, handle, singletonA)
}
viewModel
} else {
if (lifecycle !=
null) {
create(key, modelClass)
} else {
throw IllegalStateException(
"SAVED_STATE_REGISTRY_OWNER_KEY and VIEW_MODEL_STORE_OWNER_KEY
must be provided"
)
}
}
}
// --- 3
. Class 单参数 create ---
override fun <T
: ViewModel> create(modelClass
: Class<T>)
: T {
val canonicalName = modelClass
.canonicalName
?
: throw IllegalArgumentException("Local and anonymous classes can
not be ViewModels")
return create(canonicalName, modelClass)
}
// --- 4
. key + Class ---
fun <T
: ViewModel> create(key
: String, modelClass
: Class<T>)
: T {
val is
AndroidViewModel =
AndroidViewModel
::class
.java
.isAssignableFrom(modelClass)
val constructor = findMatchingConstructor(modelClass, is
AndroidViewModel)
// 没有特殊构造函数，回退默认 factory
if (constructor ==
null) {
return if (application !=
null)
androidFactory
.create(modelClass)
else ViewModelProvider
.NewInstanceFactory
.instance
.create(modelClass)
}
val savedStateHandle =
androidx
.lifecycle
.SavedStateHandle(defaultArgs?
.let {
HashMap(it
.keySet()
.associateWith { key -> it
.get(key) })
} ?
: emptyMap())
val params = mutableListOf<Any>()
if (is
AndroidViewModel && application !=
null) params
.add(application)
params
.add(savedStateHandle)
params
.add(singletonA)
return newInstance(modelClass, constructor, *params
.toTypedArray())
}
private fun <T
: ViewModel?> newInstance(modelClass
: Class<T>, constructor
: Constructor<T>, vararg params
: Any)
: T {
return try {
constructor
.newInstance(*params)
} catch (e
: IllegalAccessException) {
throw RuntimeException("Failed to access $modelClass", e)
} catch (e
: InstantiationException) {
throw RuntimeException("A $modelClass can
not be instantiated
.", e)
} catch (e
: InvocationTargetException) {
throw RuntimeException("Exception happened in constructor of $modelClass", e
.cause)
}
}
private fun <T
: ViewModel> findMatchingConstructor(modelClass
: Class<T>, is
AndroidViewModel
: Boolean)
: Constructor<T>? {
val signatures = if (is
AndroidViewModel && application !=
null) {
listOf(Application
::class
.java,
androidx
.lifecycle
.SavedStateHandle
::class
.java, singletonA
::class
.java)
} else {
listOf(
androidx
.lifecycle
.SavedStateHandle
::class
.java, singletonA
::class
.java)
}
for (ctor in modelClass
.constructors) {
if (ctor
.parameterTypes
.toList() == signatures) {
@Suppress("UNCHECKED_CAST")
return ctor as Constructor<T>
}
}
return
null
}
}
当Android Studio升级到3.5及以上版本后，遇到删除module后仍有残留问题，可以尝试关闭AS，删除项目中的.hidden IDEA文件夹和.iml文件，然后重新打开项目，此方法已被验证有效。
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