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BrowseProviderViewModel.kt
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BrowseProviderViewModel.kt
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/*
* Copyright 2018 Google Inc.
*
* 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.google.android.apps.muzei.browse
import android.app.Application
import android.content.ContentUris
import android.content.Context
import android.database.ContentObserver
import android.net.Uri
import android.os.Handler
import androidx.lifecycle.AndroidViewModel
import androidx.lifecycle.LiveData
import androidx.lifecycle.MutableLiveData
import androidx.lifecycle.switchMap
import androidx.lifecycle.viewModelScope
import com.google.android.apps.muzei.room.Artwork
import com.google.android.apps.muzei.util.ContentProviderClientCompat
import kotlinx.coroutines.CoroutineScope
import kotlinx.coroutines.asCoroutineDispatcher
import kotlinx.coroutines.launch
import java.util.concurrent.Executors
class ProviderArtworkLiveData(
val context: Context,
private val coroutineScope: CoroutineScope,
val contentUri: Uri
): MutableLiveData<List<Artwork>>() {
private val authority: String = contentUri.authority
?: throw IllegalArgumentException("Invalid contentUri $contentUri")
private val singleThreadContext by lazy {
Executors.newSingleThreadExecutor { target ->
Thread(target, "ProviderArtworkLiveData")
}.asCoroutineDispatcher()
}
private val contentObserver = object : ContentObserver(Handler()) {
override fun onChange(selfChange: Boolean, uri: Uri?) {
refreshArt()
}
}
private lateinit var contentProviderClient: ContentProviderClientCompat
private var open: Boolean = false
override fun onActive() {
contentProviderClient = ContentProviderClientCompat.getClient(context, contentUri)
?: return
context.contentResolver.registerContentObserver(
contentUri,
true,
contentObserver)
open = true
refreshArt()
}
override fun onInactive() {
if (open) {
context.contentResolver.unregisterContentObserver(contentObserver)
contentProviderClient.close()
open = false
}
}
private fun refreshArt() {
coroutineScope.launch(singleThreadContext) {
val list = mutableListOf<Artwork>()
contentProviderClient.query(contentUri)?.use { data ->
while(data.moveToNext()) {
val providerArtwork =
com.google.android.apps.muzei.api.provider.Artwork.fromCursor(data)
list.add(Artwork(ContentUris.withAppendedId(contentUri,
providerArtwork.id)).apply {
title = providerArtwork.title
byline = providerArtwork.byline
attribution = providerArtwork.attribution
providerAuthority = authority
})
}
}
postValue(list)
}
}
}
class BrowseProviderViewModel(
application: Application
): AndroidViewModel(application) {
private val contentUriLiveData = MutableLiveData<Uri>()
fun setContentUri(contentUri: Uri) {
contentUriLiveData.value = contentUri
}
val artLiveData: LiveData<List<Artwork>> = contentUriLiveData.switchMap { contentUri ->
ProviderArtworkLiveData(application, viewModelScope, contentUri)
}
}