fragment便捷传参

Ext.kt

import android.os.Bundle
import androidx.fragment.app.Fragment
import kotlin.properties.ReadWriteProperty

class FragmentBundleDataDelegate<T : Any>(private val clazz: Class<T>, private val defaultValue: T? = null) :
        ReadWriteProperty<Fragment, T?> {

    @Suppress("UNCHECKED_CAST")
    override fun getValue(
        thisRef: Fragment,
        property: KProperty<*>
    ): T? {
        val key = property.name
        return thisRef.arguments
            ?.get(key, clazz) ?: defaultValue
    }

    override fun setValue(
        thisRef: Fragment,
        property: KProperty<*>, value: T?
    ) {
        val args = thisRef.arguments
            ?: Bundle().also(thisRef::setArguments)
        val key = property.name
        args.put(key, value)
    }
}

fun <T> Bundle.put(key: String, value: T) {
    when (value) {
        is Boolean -> putBoolean(key, value)
        is String -> putString(key, value)
        is Int -> putInt(key, value)
        is Short -> putShort(key, value)
        is Long -> putLong(key, value)
        is Byte -> putByte(key, value)
        is ByteArray -> putByteArray(key, value)
        is Char -> putChar(key, value)
        is CharArray -> putCharArray(key, value)
        is CharSequence -> putCharSequence(key, value)
        is Float -> putFloat(key, value)
        else -> throw IllegalStateException("Type of property $key is not supported")
    }
}

@Suppress("IMPLICIT_CAST_TO_ANY")
private fun <T> Bundle.get(key: String, clazz: Class<T>): T? {
    return when (clazz) {
        Boolean::class.java -> getBoolean(key)
        String::class.java -> getString(key)
        Int::class.java -> getInt(key)
        Short::class.java -> getShort(key)
        Long::class.java -> getLong(key)
        Byte::class.java -> getByte(key)
        ByteArray::class.java -> getByteArray(key) ?: ByteArray(0)
        Char::class.java -> getChar(key)
        CharArray::class.java -> getCharArray(key) ?: CharArray(0)
        CharSequence::class.java -> getCharSequence(key)
        Float::class.java -> getFloat(key)
        else -> throw IllegalStateException("Type of property $key is not supported")
    } as? T?
}

inline fun <reified T : Any> Fragment.argument() = FragmentBundleDataDelegate(T::class.java)


// usage 

class SomeFragment() {
  companion object {
    fun newInstance(arg1: Int?) = SomeFragment().also {
        it.arg1 = arg1
    }
  }
  
  private val arg1: Int? by argument()
}