android - 所有异步任务完成后如何做某事？

Question

我正在使用 AsyncTask 下载一些文件，并希望在所有任务完成后执行某些操作。

有什么简单的方法可以做到这一点吗？

Answer 1

跟踪您正在运行的异步任务数量，并在总数为 0 时执行某些操作。

import android.os.AsyncTask;
import android.os.Bundle;
import android.app.Activity;
import android.view.Menu;

public class MainActivity extends Activity {

    public int numOfTasks = 0;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        getMenuInflater().inflate(R.menu.activity_main, menu);
        return true;
    }
    public void addTask(){
        numOfTasks++;
    }

    public void removeTask(){
        numOfTasks--;
    }

    public void allTasksComplete(){

        if(numOfTasks ==0){
            //do what you want to do if all tasks are finished
        }

    }

    class RequestTask extends AsyncTask<String, String, String>{

        @Override
        protected String doInBackground(String... uri) {

            String responseString = "";
            return responseString;
        }

         @Override
            protected void onPreExecute() 
            {
                    addTask(); // adds one to task count.
                    super.onPreExecute();

            }

        @Override
        protected void onPostExecute(String result) {
            super.onPostExecute(result);
            removeTask(); // subtracts one from task count.
            allTasksComplete(); // checks to see if all tasks are done...  task count is 0
            }
        }
    }