NavArgsLazy.kt
/*
* Copyright 2019 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.
*/
package androidx.navigation
import android.annotation.SuppressLint
import android.os.Bundle
import androidx.collection.ArrayMap
import java.lang.reflect.Method
import kotlin.reflect.KClass
internal val methodSignature = arrayOf(Bundle::class.java)
internal val methodMap = ArrayMap<KClass<out NavArgs>, Method>()
/**
* An implementation of [Lazy] used by [android.app.Activity.navArgs] and
* [androidx.fragment.app.Fragment.navArgs].
*
* [argumentProducer] is a lambda that will be called during initialization to provide
* arguments to construct an [Args] instance via reflection.
*/
public class NavArgsLazy<Args : NavArgs>(
private val navArgsClass: KClass<Args>,
private val argumentProducer: () -> Bundle
) : Lazy<Args> {
private var cached: Args? = null
override val value: Args
get() {
var args = cached
if (args == null) {
val arguments = argumentProducer()
val method: Method = methodMap[navArgsClass]
?: navArgsClass.java.getMethod("fromBundle", *methodSignature).also { method ->
// Save a reference to the method
methodMap[navArgsClass] = method
}
@SuppressLint("BanUncheckedReflection") // needed for method.invoke
@Suppress("UNCHECKED_CAST")
args = method.invoke(null, arguments) as Args
cached = args
}
return args
}
override fun isInitialized(): Boolean = cached != null
}