LiveData with timeout

LiveDataWithTimeout.kt

/*
 * Copyright (C) 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.
 */

package io.github.yaraki.timeout

import android.arch.lifecycle.LiveData
import android.arch.lifecycle.MediatorLiveData
import android.arch.lifecycle.MutableLiveData
import android.os.Handler
import android.os.Message
import java.lang.ref.WeakReference


private class ClearLiveDataHandler(liveData: MutableLiveData<*>) : Handler() {
    companion object {
        const val CLEAR_LIVE_DATA = 1
    }

    private val liveDataRef = WeakReference<MutableLiveData<*>>(liveData)
    override fun handleMessage(msg: Message?) {
        if (msg?.what == CLEAR_LIVE_DATA) {
            liveDataRef.get()?.value = null
        }
    }
}

fun <T> LiveData<T>.withTimeout(timeout: Long): LiveData<T> {
    val result = MediatorLiveData<T>()
    val handler = ClearLiveDataHandler(result)
    result.addSource(this) { v ->
        result.value = v
        handler.removeMessages(ClearLiveDataHandler.CLEAR_LIVE_DATA)
        handler.sendMessageDelayed(Message.obtain(handler, ClearLiveDataHandler.CLEAR_LIVE_DATA),
                timeout)
    }
    return result
}

MainViewModel.kt

package io.github.yaraki.timeout

import android.arch.lifecycle.LiveData
import android.arch.lifecycle.MutableLiveData
import android.arch.lifecycle.ViewModel

class MainViewModel : ViewModel() {

    private val _message = MutableLiveData<String>().apply { value = "Hello, world!" }

    val message: LiveData<String> = _message.withTimeout(3000)

    fun updateMessage(message: String) {
        _message.value = message
    }

}