如何使用 java.util.concurrent 包實現后台線程？

Question

這是我首先使用的代碼，但在最新的 Android 版本中不推薦使用AsyncTask類，因此它沒有響應，然后我使用了Thread類，但該類也不起作用。 我想要與使用AsyncTask類獲得的結果相同的結果。 我知道我必須使用 java.util.concurrent 包的一些執行程序類，但不知道哪個以及如何使用它。 請幫我解決這個問題。

private static final String USGS_REQUEST_URL =
            "https://earthquake.usgs.gov/fdsnws/event/1/query?format=geojson&starttime=2016-01-01&endtime=2016-05-02&minfelt=50&minmagnitude=5";

EarthquakeAsyncTask task = new EarthquakeAsyncTask();
        task.execute(USGS_REQUEST_URL);
private class EarthquakeAsyncTask extends AsyncTask<String, Void, Event> {

        @Override
        protected Event doInBackground(String... urls) {

            // Perform the HTTP request for earthquake data and process the response.
            Event result = Utils.fetchEarthquakeData(urls[0]);
            return result;
        }

        @Override
        protected void onPostExecute(Event result) {
            // Update the information displayed to the user.
            updateUi(result);
        }
    }

private static final String USGS_REQUEST_URL =
            "https://earthquake.usgs.gov/fdsnws/event/1/query?format=geojson&starttime=2016-01-01&endtime=2016-05-02&minfelt=50&minmagnitude=5";

earthquakeRunnable runnable = new earthquakeRunnable(USGS_REQUEST_URL);
        runnable.start();

private class earthquakeRunnable extends Thread{

            String urls;
            earthquakeRunnable(String url){
                this.urls = url;
            }
            @Override
            public void run() {
                // Perform the HTTP request for earthquake data and process the response.
                Event result = Utils.fetchEarthquakeData(urls);
                // Update the information displayed to the user
                updateUi(result);
            }
        }

Answer 1

以下是如何在 Activity/Fragment 中使用 ExecutorService 的示例：

// Create some member variables for the ExecutorService 
// and for the Handler that will update the UI from the main thread
ExecutorService mExecutor = Executors.newSingleThreadExecutor();
Handler mHandler = new Handler(Looper.getMainLooper());

// Create an interface to respond with the result after processing
public interface OnProcessedListener {
    public void onProcessed(Event result);
}

private void processInBg(final String url, final boolean finished){
    
    final OnProcessedListener listener = new OnProcessedListener(){
        @Override
        public void onProcessed(Event result){
            // Use the handler so we're not trying to update the UI from the bg thread
            mHandler.post(new Runnable(){
                @Override
                public void run(){
                    // Update the UI here
                    updateUi(result);
                    
                    // ...
                    
                    // If we're done with the ExecutorService, shut it down.
                    // (If you want to re-use the ExecutorService,
                    // make sure to shut it down whenever everything's completed
                    // and you don't need it any more.)
                    if(finished){
                        mExecutor.shutdown();
                    }
                }
            });
        }
    };
    
    Runnable backgroundRunnable = new Runnable(){
        @Override
        public void run(){
            // Perform your background operation(s) and set the result(s)
            Event result = Utils.fetchEarthquakeData(url);
            
            // ...
            
            // Use the interface to pass along the result
            listener.onProcessed(result);
        }
    };
    
    mExecutor.execute(backgroundRunnable);
}

然后，無論您需要在何處觸發后台處理：

processInBg("some_url", true);

根據您的情況，您需要自定義 ExecutorService 的實現以更好地滿足您的需求。