Question

我有以下AsyncTask

public class LoadFromCloudTask extends AsyncTask<Void, String, Boolean> {

    public LoadFromCloudTask(LoadFromCloudTaskFragment loadFromCloudTaskFragment) {
        this.loadFromCloudTaskFragment = loadFromCloudTaskFragment;
    }

    @Override
    protected Boolean doInBackground(Void... params) {
        ...
        ...
        ...
        // How possible I can halt my execution, prompt for user input, and continue execution based on user input.
        // In Swing, I can ...
        //
        /*
           // Hold the execution, and prompt for user input
           final int result = JOptionPane.showConfirmDialog(LoadFromCloudJDialog.this, message, MessagesBundle.getString("question_title_overwrite_your_data_by_cloud_data_at"), JOptionPane.YES_NO_OPTION);
           // Continue execution based on user input.
         */
    }
}

我想知道，是否可以暂停AsyncTask执行，提示用户输入并根据用户输入继续执行？

在Swing中，我可以通过简单地使用JOptionPane.showConfirmDialog来实现这一点。 Android怎么样？

Answer 1

由于doInBackground在不同的线程中执行，您必须在UI线程中显示一些dialog时暂停此线程，一旦对话框解除，您可以恢复AsyncTask并阅读结果。

Answer 2

检查Asynctask 的文档，您可以取消并重新启动异步任务，因为The task can be executed only once

你想要这样的东西ideal-way-to-cancel-an-executing-asynctask

doInBackground不在UI线程中执行，因此您可以执行显示对话框的UI操作

Answer 3

您可以通过publishProgress内部使用doInBackground(Params...)向 UIThread 发送消息来实现此目的，并使用java的 wait / notify 机制来等待untel用户输入他的输入。

psudo代码看起来像这样：

 public Object mLock = new Object();
 protected void doInBackground(Params... params){
  /// do your requests.
  publishProgress(Progress ...progress);
  mLock.wait();

 }
 protected void onProgressUpdate(Progress ....progress) {
    // request user input here
 }

并从您的UIThread中调用mLock.notify()，让代码继续。

此外，您可以通过在多个AsynchTasks之间拆分逻辑来执行更加简洁的行为，因为AsynchTasks由共享（静态）ThreadPoolExecutor和

管理，因此不会非常昂贵

Answer 4

You can create pause and resume method inside asyntask as below, and call it according to your convenience.

        public class LoadFromCloudTask extends AsyncTask<Void, String, Boolean> {

            public LoadFromCloudTask(LoadFromCloudTaskFragment loadFromCloudTaskFragment) {
                this.loadFromCloudTaskFragment = loadFromCloudTaskFragment;
            }

    //call this when you want to halt the task        
                    public void pause() {
                           if (this.getStatus().equals(Status.RUNNING)) {
                                   try {
                                           this.wait();
                                   } catch (InterruptedException e) {
                                           e.printStackTrace();
                                   }
                           }
                   }

    // call this when you need to resume the task
                   public void resume() {
                           if (this.getStatus().equals(Status.PENDING)) {
                                   this.notify();
                           }
                   }

            @Override
            protected Boolean doInBackground(Void... params) {
                ...
                ...
                ...
                // How possible I can halt my execution, prompt for user input, and continue execution based on user input.
                // In Swing, I can ...
                //
                /*
                   // Hold the execution, and prompt for user input
                   final int result = JOptionPane.showConfirmDialog(LoadFromCloudJDialog.this, message, MessagesBundle.getString("question_title_overwrite_your_data_by_cloud_data_at"), JOptionPane.YES_NO_OPTION);
                   // Continue execution based on user input.
                 */
            }
        }

暂停AsyncTask执行，提示用户输入并根据用户输入继续执行

4 个答案: