当onDatasetChanged方法包含异步网络调用Android时,Widget ListView不会刷新

Question

我想将互联网上的汽车列表加载到Widget中的ListView中.当我在onDatasetChanged方法中请求汽车时,它不会更新列表.然而,当我手动点击我的刷新按钮时,它会刷新它.可能是什么问题呢？为了提供尽可能多的信息,我将完整的源代码放入ZIP文件中,该文件可以解压缩并在Android Studio中打开.我也将它嵌入下面.注意:我使用RxJava作为异步请求,代码是用Kotlin编写的,尽管这个问题不是每个语言都绑定的.

CarsWidgetProvider

class CarsWidgetProvider : AppWidgetProvider() {
    override fun onUpdate(context: Context, appWidgetManager: AppWidgetManager, appWidgetIds: IntArray) {
        Log.d("CAR_LOG", "Updating")
        val widgets = appWidgetIds.size

        for (i in 0 until widgets) {
            Log.d("CAR_LOG", "Updating number $i")
            val appWidgetId = appWidgetIds[i]

            // Get the layout
            val views = RemoteViews(context.packageName, R.layout.widget_layout)
            val otherIntent = Intent(context, ListViewWidgetService::class.java)
            views.setRemoteAdapter(R.id.cars_list, otherIntent)

            // Set an onclick listener for the action and the refresh button
            views.setPendingIntentTemplate(R.id.cars_list, getPendingSelfIntent(context, "action"))
            views.setOnClickPendingIntent(R.id.refresh, getPendingSelfIntent(context, "refresh"))

            // Tell the AppWidgetManager to perform an update on the current app widget
            appWidgetManager.updateAppWidget(appWidgetId, views)
        }
    }

    private fun onUpdate(context: Context) {
        val appWidgetManager = AppWidgetManager.getInstance(context)
        val thisAppWidgetComponentName = ComponentName(context.packageName, javaClass.name)
        val appWidgetIds = appWidgetManager.getAppWidgetIds(thisAppWidgetComponentName)
        appWidgetManager.notifyAppWidgetViewDataChanged(appWidgetIds, R.id.cars_list)
        onUpdate(context, appWidgetManager, appWidgetIds)
    }

    private fun getPendingSelfIntent(context: Context, action: String): PendingIntent {
        val intent = Intent(context, javaClass)
        intent.action = action
        return PendingIntent.getBroadcast(context, 0, intent, 0)
    }

    @SuppressLint("CheckResult")
    override fun onReceive(context: Context?, intent: Intent?) {
        super.onReceive(context, intent)
        if (context != null) {
            if ("action" == intent!!.action) {
                val car = intent.getSerializableExtra("car") as Car

                // Toggle car state
                Api.toggleCar(car)
                        .subscribeOn(Schedulers.io())
                        .observeOn(AndroidSchedulers.mainThread())
                        .subscribe {
                            Log.d("CAR_LOG", "We've got a new state: $it")
                            car.state = it
                            onUpdate(context)
                        }

            } else if ("refresh" == intent.action) {
                onUpdate(context)
            }
        }
    }
}

ListViewWidgetService

class ListViewWidgetService : RemoteViewsService() {
    override fun onGetViewFactory(intent: Intent): RemoteViewsService.RemoteViewsFactory {
        return ListViewRemoteViewsFactory(this.applicationContext, intent)
    }
}

internal class ListViewRemoteViewsFactory(private val context: Context, intent: Intent) : RemoteViewsService.RemoteViewsFactory {
    private var cars: ArrayList<Car> = ArrayList()

    override fun onCreate() {
        Log.d("CAR_LOG", "Oncreate")
        cars = ArrayList()
    }

    override fun getViewAt(position: Int): RemoteViews {
        val remoteViews = RemoteViews(context.packageName, R.layout.widget_list_item_car)

        // Get the current car
        val car = cars[position]
        Log.d("CAR_LOG", "Get view at $position")
        Log.d("CAR_LOG", "Car: $car")

        // Fill the list item with data
        remoteViews.setTextViewText(R.id.title, car.title)
        remoteViews.setTextViewText(R.id.description, car.model)
        remoteViews.setTextViewText(R.id.action, "${car.state}")
        remoteViews.setInt(R.id.action, "setBackgroundColor",
                if (car.state == 1) context.getColor(R.color.colorGreen) else context.getColor(R.color.colorRed))

        val extras = Bundle()
        extras.putSerializable("car", car)

        val fillInIntent = Intent()
        fillInIntent.putExtras(extras)

        remoteViews.setOnClickFillInIntent(R.id.activity_chooser_view_content, fillInIntent)
        return remoteViews
    }

    override fun getCount(): Int {
        Log.d("CAR_LOG", "Counting")
        return cars.size
    }

    @SuppressLint("CheckResult")
    override fun onDataSetChanged() {
        Log.d("CAR_LOG", "Data set changed")

        // Get a token
        Api.getToken()
                .subscribeOn(Schedulers.io())
                .observeOn(AndroidSchedulers.mainThread())
                .subscribe { token ->
                    if (token.isNotEmpty()) {
                        Log.d("CAR_LOG", "Retrieved token")
                        DataModel.token = token

                        // Get the cars
                        Api.getCars()
                                .subscribeOn(Schedulers.io())
                                .observeOn(AndroidSchedulers.mainThread())
                                .subscribe {
                                    cars = it as ArrayList<Car>

                                    Log.d("CAR_LOG", "Found cars: $cars")
                                }
                    } else {
                        Api.getCars()
                                .subscribeOn(Schedulers.io())
                                .observeOn(AndroidSchedulers.mainThread())
                                .subscribe {
                                    cars = it as ArrayList<Car>

                                    Log.d("CAR_LOG", "Found cars: $cars")
                                }
                    }
                }
    }

    override fun getViewTypeCount(): Int {
        Log.d("CAR_LOG", "Get view type count")
        return 1
    }

    override fun getItemId(position: Int): Long {
        Log.d("CAR_LOG", "Get item ID")
        return position.toLong()
    }

    override fun onDestroy() {
        Log.d("CAR_LOG", "On Destroy")
        cars.clear()
    }

    override fun hasStableIds(): Boolean {
        Log.d("CAR_LOG", "Has stable IDs")
        return true
    }

    override fun getLoadingView(): RemoteViews? {
        Log.d("CAR_LOG", "Get loading view")
        return null
    }
}

的DataModel

object DataModel {
    var token: String = ""
    var currentCar: Car = Car()
    var cars: ArrayList<Car> = ArrayList()

    init {
        Log.d("CAR_LOG", "Creating data model")
    }

    override fun toString(): String {
        return "Token : $token \n currentCar: $currentCar \n Cars: $cars"
    }
}

汽车

class Car : Serializable {
    var id : String = ""
    var title: String = ""
    var model: String = ""
    var state: Int = 0
}

编辑

在我收到一些答案之后,我开始找出一个临时修复,它在AsyncTask上调用.get(),这使它同步

@SuppressLint("CheckResult")
override fun onDataSetChanged() {
    cars = GetCars().execute().get() as ArrayList<Car>
}

class GetCars : AsyncTask<String, Void, List<Car>>() {
    override fun doInBackground(vararg params: String?): List<Device> {
        return Api.getCars().blockingFirst();
    }
}

Answer 1

正如@ferini 所说，你的 rx 链是一个异步调用，所以当你调用时实际发生了什么appWidgetManager.notifyAppWidgetViewDataChanged(appWidgetIds, R.id.cars_list)：

如您所见，在将调用notifyAppWidgetViewDataChanged() onDataSetChange() 之后，但您的调用是异步的，这就是 RemoteViewFactory 进一步访问 FetchMetaData（检查图像）的原因。因此，在第一次启动小部件时，您将汽车初始化为 ArrayList()，这就是您的 ListView 为空的原因。当您发送刷新操作时，您的汽车不为空，因为您在 onDataSetChange() 中启动的异步调用已经获取数据并填充您的汽车，这就是为什么在刷新操作时您通过上次异步调用填充 ListView。

如您所见， onDataSetChanged() 旨在从数据库或类似内容中填充一些数据。您有一些如何更新小部件的选项：

1. 通过调用IntentService中的 notifyAppWidgetViewDataChanged() 保存在数据库中并在 onDataSetChange()中获取。处理完整更新并为带有可分割数据的列表视图适配器和 RemoteView 上的 setRemoteAdapter() 制定新的意图，因此在onCreate RemoteViewsService 中，将意图传递给 RemoteViewsFactory，您可以从意图获取汽车数组列表 并将其设置为 RemoteViewsFactory，在这种情况下，您不需要根本不需要 onDataSetChange() 回调。

2. 只需在 onDataSetChange() 中进行所有同步（阻塞）调用，因为它不是 UI 线程。

您可以通过在onDataSetChanged() 中进行阻塞 rx 调用来轻松检查这一点，并且您的小部件将按您的需要工作。

override fun onDataSetChanged() {
    Log.d("CAR_LOG", "Data set changed")
    cars = Api.getCars().blockingFirst() as ArrayList<Car>
}

更新： 实际上，如果您将在 RemoteViewFactory 回调中记录当前线程，您将看到只有 onCreate() 在主线程上，其他回调在绑定线程池的线程上工作。所以可以在 onDataSetChanged() 中进行同步调用，因为它不在 UI 线程上，所以进行阻塞调用是可以的，你不会得到 ANR