AsyncTask 通知父 Activity 完成的最佳方式是什么? [英] What is the best way for AsyncTask to notify parent Activity about completion?

问题描述

public class ListingFoundBeaconService 
                    extends AsyncTask<String, String, String> {

    public ListingFoundBeaconService(Context contextGiven, 
                                     JSONObject jsonParams) {
        this.contextGiven = contextGiven;
        this.jsonParams = jsonParams;
    }

    protected void onPreExecute() {
        super.onPreExecute();
        pDialog = new ProgressDialog(contextGiven);
        pDialog.setMessage("Loading list of active Beacons..");
        pDialog.setIndeterminate(false);
        pDialog.setCancelable(true);
        pDialog.show();
        Log.d("onPreExecute","onPreExecute worked" );
    }

    protected String doInBackground(String... args) {}

    protected void onPostExecute(String file_url) {   
        // Two activities will need this thread so I have 
        // kept this as a separate class. Here I want to send a
        // boolean value to the parent activity to show that 
        // the task has completed or not.
    }

我能否在onPostExecute() 函数中触发一个通知或完成事件监听器，以便通知启动这个类(ListingFoundBeaconService) 的父类?这样做的标准方法是什么?

Can I trigger a notification or complete event listener in onPostExecute() function so that the parent class which started this class(ListingFoundBeaconService) is notified? What is the standard way of doing it?

推荐答案

最好的方法是调用delegate.在你的 AsyncTask 类中创建一个构造函数并有一个委托

Best way is to call delegate. In your AsyncTask class make a constructor and have a delegate

委托接口:

public interface TaskDelegate {
    public void taskCompletionResult(String result);
}

现在在 AsyncTask 中:

private TaskDelegate delegate;

public ListingFoundBeaconService(Context contextGiven, 
                                 JSONObject jsonParams,
                                 TaskDelegate delegate) {
    this.contextGiven = contextGiven;
    this.jsonParams = jsonParams;
    this.delegate = delegate;
}

在 postExecute 上:

delegate.taskCompletionResult(result/msg/json);

在你的主类中实现 TaskDelegate 并实现一个在任务完成时调用的方法.

In your main class implement TaskDelegate and implemented a method which is called when the task completed.

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