ObservableViewModel.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 com.jephtecolin.kwii.util

import androidx.lifecycle.ViewModel
import androidx.databinding.Bindable
import androidx.databinding.Observable
import androidx.databinding.PropertyChangeRegistry

/**
 * An [Observable] [ViewModel] for Data Binding.
 */
open class ObservableViewModel : ViewModel(), Observable {

    private val callbacks: PropertyChangeRegistry by lazy { PropertyChangeRegistry() }

    override fun addOnPropertyChangedCallback(callback: Observable.OnPropertyChangedCallback) {
        callbacks.add(callback)
    }

    override fun removeOnPropertyChangedCallback(callback: Observable.OnPropertyChangedCallback) {
        callbacks.remove(callback)
    }

    /**
     * Notifies listeners that all properties of this instance have changed.
     */
    @Suppress("unused")
    fun notifyChange() {
            callbacks.notifyCallbacks(this, 0, null)
    }

    /**
     * Notifies listeners that a specific property has changed. The getter for the property
     * that changes should be marked with [Bindable] to generate a field in
     * `BR` to be used as `fieldId`.
     *
     * @param fieldId The generated BR id for the Bindable field.
     */
    fun notifyPropertyChanged(fieldId: Int) {
        callbacks.notifyCallbacks(this, fieldId, null)
    }
}