Android: 等待多个任务完成

Question

我有 4 个从 Internet 加载数据的异步任务。同时我用动画显示 activity ，当任务完成时我需要用加载的数据开始另一个活动。

我在 Kotlin 上的异步方法（与在 java 上编写的异步任务相同）

private fun getArtistData(name: String) {
    val getArtistDataAsync = object : AsyncTask<String, Void, Artist>() {

        override fun doInBackground(vararg args: String?): Artist? {
            Log.i(TAG, "Получаем данные в AsyncTask для $mArtistName")
            Caller.getInstance().cache = null
            return Artist.getInfo(args[0], "26cc2ebf6da38bc646733f661bfc6268");
        }

        override fun onPostExecute(result: Artist?) {
            super.onPostExecute(result)
            Log.i(TAG, "Возвращаем данные из AsyncTask для $mArtistName")
            CommonUtilities.artistInstance = result as Artist;
        }
    }

    val getTopTracksAsync = object : AsyncTask<String,Void,ArrayList<Track>>(){
        override fun doInBackground(vararg args: String?): ArrayList<Track>? {
            Log.i(TAG, "Получаем список песен в AsyncTask для $mArtistName")
            Caller.getInstance().cache = null
            return Artist.getTopTracks(args[0], "26cc2ebf6da38bc646733f661bfc6268") as ArrayList<Track>;
        }

        override fun onPostExecute(result: ArrayList<Track>?) {
            super.onPostExecute(result)
            Log.i(TAG, "Возвращаем список песен из AsyncTask для $mArtistName")
            CommonUtilities.trackListInstance = result;
        }
    }

    val getSimilarBandsAsync = object : AsyncTask<String,Void,ArrayList<Artist>>(){
        override fun doInBackground(vararg args: String?): ArrayList<Artist>? {
            Log.i(TAG, "Получаем список похожих групп в AsyncTask для $mArtistName")
            Caller.getInstance().cache = null
            return Artist.getSimilar(args[0], "26cc2ebf6da38bc646733f661bfc6268") as ArrayList<Artist>?
        }

        override fun onPostExecute(result: ArrayList<Artist>?) {
            super.onPostExecute(result)
            Log.i(TAG, "Возвращаем список похожих групп из AsyncTask для $mArtistName")
            CommonUtilities.artistListInstance = result;
        }
    }

    val getTopAlbumsAsync = object : AsyncTask<String,Void, ArrayList<Album>>(){
        override fun doInBackground(vararg p0: String?): ArrayList<Album>? {
            Log.i(TAG, "Получаем список альбомов в AsyncTask для $mArtistName")
            Caller.getInstance().cache = null
            return Artist.getTopAlbums(p0[0],"26cc2ebf6da38bc646733f661bfc6268") as ArrayList<Album>?;
        }

        override fun onPostExecute(result: ArrayList<Album>?) {
            super.onPostExecute(result)
            Log.i(TAG, "Возвращаем список альбомов из AsyncTask для $mArtistName")
            CommonUtilities.albumListInstance = result;
        }
    }

我试图在这里调用我的方法：

val runAllTasks = object : AsyncTask<Void,Void,Void>(){
        override fun doInBackground(vararg p0: Void?): Void? {
            getArtistDataAsync.executeOnExecutor(AsyncTask.SERIAL_EXECUTOR, name)
            getSimilarBandsAsync.executeOnExecutor(AsyncTask.SERIAL_EXECUTOR, name)
            getTopTracksAsync.executeOnExecutor(AsyncTask.SERIAL_EXECUTOR, name)
            getTopAlbumsAsync.executeOnExecutor(AsyncTask.SERIAL_EXECUTOR, name)
            return null
        }

        override fun onPostExecute(result: Void?) {
            super.onPostExecute(result)

            startActivity(Intent(applicationContext, DetailsActivity::class.java))
        }
    }

    runAllTasks.executeOnExecutor(AsyncTask.THREAD_POOL_EXECUTOR)

Answer 1

您可以调用一个 synchronized 通用方法来计算已经完成的 asyncTask 的数量。像这样：

private static final int NUMBER_ASYNCTASK = 4;
private static int counter = 0;

public static synchronized void asyncTaskCompleted() {
   counter++; 
    if(counter == NUMBER_ASYNCTASK)
       //start new activity
}

Answer 2

我会使用 Kovenant library instead, it has support on Android, is tiny, and makes this type of thing very easy using all(), combine() or and()。

Kovenant 是 Kotlin 的 Promise 库。如果你要搬到 Kotlin，这是一个很好的机会来检查让生活更轻松的东西。对于 UI 线程上的回调，您可以使用 UI Module。

然后无论是 Android 还是后端 JVM 编程，您都可以使用相同的库、相同的语义，并且拥有更简单的编程模型。

Android: 等待多个任务完成

Android: Wait for multiple tasks complete

android

android-asynctask

kotlin