/*
* Copyright 2018 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
@file:RestrictTo(RestrictTo.Scope.LIBRARY)
package androidx.lifecycle
import android.annotation.SuppressLint
import android.app.Application
import android.os.Bundle
import androidx.annotation.RestrictTo
import androidx.lifecycle.ViewModelProvider.AndroidViewModelFactory.Companion.getInstance
import androidx.lifecycle.ViewModelProvider.NewInstanceFactory.Companion.instance
import androidx.lifecycle.viewmodel.CreationExtras
import androidx.savedstate.SavedStateRegistry
import androidx.savedstate.SavedStateRegistryOwner
import java.lang.reflect.Constructor
import java.lang.reflect.InvocationTargetException
/**
* [androidx.lifecycle.ViewModelProvider.Factory] that can create ViewModels accessing and
* contributing to a saved state via [SavedStateHandle] received in a constructor.
* If `defaultArgs` bundle was passed into the constructor, it will provide default
* values in `SavedStateHandle`.
*
* If ViewModel is instance of [androidx.lifecycle.AndroidViewModel], it looks for a
* constructor that receives an [Application] and [SavedStateHandle] (in this order),
* otherwise it looks for a constructor that receives [SavedStateHandle] only.
* [androidx.lifecycle.AndroidViewModel] is only supported if you pass a non-null
* [Application] instance.
*/
class SavedStateViewModelFactory : ViewModelProvider.OnRequeryFactory, ViewModelProvider.Factory {
private var application: Application? = null
private val factory: ViewModelProvider.Factory
private var defaultArgs: Bundle? = null
private var lifecycle: Lifecycle? = null
private var savedStateRegistry: SavedStateRegistry? = null
/**
* Constructs this factory.
*
* When a factory is constructed this way, a component for which [SavedStateHandle] is
* scoped must have called [enableSavedStateHandles].
* @see [createSavedStateHandle] docs for more details.
*/
constructor() {
factory = ViewModelProvider.AndroidViewModelFactory()
}
/**
* Creates [SavedStateViewModelFactory].
*
* [androidx.lifecycle.ViewModel] created with this factory can access to saved state
* scoped to the given `activity`.
*
* @param application an application. If null, [AndroidViewModel] instances will not be
* supported.
* @param owner [SavedStateRegistryOwner] that will provide restored state for created
* [ViewModels][androidx.lifecycle.ViewModel]
*/
constructor(
application: Application?,
owner: SavedStateRegistryOwner
) : this(application, owner, null)
/**
* Creates [SavedStateViewModelFactory].
*
* [androidx.lifecycle.ViewModel] created with this factory can access to saved state
* scoped to the given `activity`.
*
* When a factory is constructed this way, if you add any [CreationExtras] those arguments will
* be used instead of the state passed in here. It is not possible to mix the arguments
* received here with the [CreationExtras].
*
* @param application an application. If null, [AndroidViewModel] instances will not be
* supported.
* @param owner [SavedStateRegistryOwner] that will provide restored state for created
* [ViewModels][androidx.lifecycle.ViewModel]
* @param defaultArgs values from this `Bundle` will be used as defaults by [SavedStateHandle]
* if there is no previously saved state or previously saved state misses a value by such key.
*/
@SuppressLint("LambdaLast")
constructor(application: Application?, owner: SavedStateRegistryOwner, defaultArgs: Bundle?) {
savedStateRegistry = owner.savedStateRegistry
lifecycle = owner.lifecycle
this.defaultArgs = defaultArgs
this.application = application
factory = if (application != null) getInstance(application)
else ViewModelProvider.AndroidViewModelFactory()
}
/**
* {@inheritDoc}
*
* @throws IllegalStateException if the provided extras do not provide a
* [ViewModelProvider.NewInstanceFactory.VIEW_MODEL_KEY]
*/
override fun <T : ViewModel> create(modelClass: Class<T>, extras: CreationExtras): T {
val key = extras[ViewModelProvider.NewInstanceFactory.VIEW_MODEL_KEY]
?: throw IllegalStateException(
"VIEW_MODEL_KEY must always be provided by ViewModelProvider"
)
return if (extras[SAVED_STATE_REGISTRY_OWNER_KEY] != null &&
extras[VIEW_MODEL_STORE_OWNER_KEY] != null) {
val application = extras[ViewModelProvider.AndroidViewModelFactory.APPLICATION_KEY]
val isAndroidViewModel = AndroidViewModel::class.java.isAssignableFrom(modelClass)
val constructor: Constructor<T>? = if (isAndroidViewModel && application != null) {
findMatchingConstructor(modelClass, ANDROID_VIEWMODEL_SIGNATURE)
} else {
findMatchingConstructor(modelClass, VIEWMODEL_SIGNATURE)
}
// doesn't need SavedStateHandle
if (constructor == null) {
return factory.create(modelClass, extras)
}
val viewModel = if (isAndroidViewModel && application != null) {
newInstance(modelClass, constructor, application, extras.createSavedStateHandle())
} else {
newInstance(modelClass, constructor, extras.createSavedStateHandle())
}
viewModel
} else {
val viewModel = if (lifecycle != null) {
create(key, modelClass)
} else {
throw IllegalStateException("SAVED_STATE_REGISTRY_OWNER_KEY and" +
"VIEW_MODEL_STORE_OWNER_KEY must be provided in the creation extras to" +
"successfully create a ViewModel.")
}
viewModel
}
}
/**
* Creates a new instance of the given `Class`.
*
* @param key a key associated with the requested ViewModel
* @param modelClass a `Class` whose instance is requested
* @return a newly created ViewModel
*
* @throws UnsupportedOperationException if the there is no lifecycle
*/
fun <T : ViewModel> create(key: String, modelClass: Class<T>): T {
// empty constructor was called.
val lifecycle = lifecycle
?: throw UnsupportedOperationException(
"SavedStateViewModelFactory constructed with empty constructor supports only " +
"calls to create(modelClass: Class<T>, extras: CreationExtras)."
)
val isAndroidViewModel = AndroidViewModel::class.java.isAssignableFrom(modelClass)
val constructor: Constructor<T>? = if (isAndroidViewModel && application != null) {
findMatchingConstructor(modelClass, ANDROID_VIEWMODEL_SIGNATURE)
} else {
findMatchingConstructor(modelClass, VIEWMODEL_SIGNATURE)
}
// doesn't need SavedStateHandle
constructor
?: // If you are using a stateful constructor and no application is available, we
// use an instance factory instead.
return if (application != null) factory.create(modelClass)
else instance.create(modelClass)
val controller = LegacySavedStateHandleController.create(
savedStateRegistry!!, lifecycle, key, defaultArgs
)
val viewModel: T = if (isAndroidViewModel && application != null) {
newInstance(modelClass, constructor, application!!, controller.handle)
} else {
newInstance(modelClass, constructor, controller.handle)
}
viewModel.setTagIfAbsent(
AbstractSavedStateViewModelFactory.TAG_SAVED_STATE_HANDLE_CONTROLLER, controller
)
return viewModel
}
/**
* {@inheritDoc}
*
* @throws IllegalArgumentException if the given modelClass does not have a classname
*/
override fun <T : ViewModel> create(modelClass: Class<T>): T {
// ViewModelProvider calls correct create that support same modelClass with different keys
// If a developer manually calls this method, there is no "key" in picture, so factory
// simply uses classname internally as as key.
val canonicalName = modelClass.canonicalName
?: throw IllegalArgumentException("Local and anonymous classes can not be ViewModels")
return create(canonicalName, modelClass)
}
/**
* @hide
*/
@RestrictTo(RestrictTo.Scope.LIBRARY_GROUP)
override fun onRequery(viewModel: ViewModel) {
// needed only for legacy path
if (lifecycle != null) {
LegacySavedStateHandleController.attachHandleIfNeeded(
viewModel,
savedStateRegistry!!,
lifecycle!!
)
}
}
}
internal 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 cannot be instantiated.", e)
} catch (e: InvocationTargetException) {
throw RuntimeException(
"An exception happened in constructor of $modelClass", e.cause
)
}
}
private val ANDROID_VIEWMODEL_SIGNATURE = listOf<Class<*>>(
Application::class.java,
SavedStateHandle::class.java
)
private val VIEWMODEL_SIGNATURE = listOf<Class<*>>(SavedStateHandle::class.java)
// it is done instead of getConstructor(), because getConstructor() throws an exception
// if there is no such constructor, which is expensive
internal fun <T> findMatchingConstructor(
modelClass: Class<T>,
signature: List<Class<*>>
): Constructor<T>? {
for (constructor in modelClass.constructors) {
val parameterTypes = constructor.parameterTypes.toList()
if (signature == parameterTypes) {
@Suppress("UNCHECKED_CAST")
return constructor as Constructor<T>
}
if (signature.size == parameterTypes.size && parameterTypes.containsAll(signature)) {
throw UnsupportedOperationException(
"Class ${modelClass.simpleName} must have parameters in the proper " +
"order: $signature"
)
}
}
return null
}
帮我分析这部分代码
本文详细阐述了在使用Blazeds与后台Java交互时，访问FlexSession中值时遇到TargetException的问题。文章指出，问题源于在写入和取出session值时使用了看似相同的类实则为不同类的情况。通过深入分析，作者分享了如何避免此类错误的方法，以及在实际开发中如何提高代码质量与细心的重要性。
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