问题描述

我有一个 AsyncTask，它在工作时显示一个 progressDialog(它从 doInBackground 中调用 runOnUiThread 来显示进度对话框).

I have an AsyncTask that shows a progressDialog whilst working (it calls runOnUiThread from within doInBackground to show the progress dialog).

在运行时，我想允许使用后退按钮取消操作；其他人遇到了这个问题:返回按钮不起作用，而progressDialog 正在运行

Whilst its running I want to allow the use of the back button to cancel the operation; someone else has had this problem: BACK Button is not working ,while progressDialog is running

由于什么原因我无法回复该主题，因此不得不开始另一个?！(另一天的另一个问题)

For what ever reason I can't reply to that thread, hence having to start another?! (Another question for another day)

我和 Sandy 有同样的想法，但是当 progressDialog 显示时，这段代码从未被调用，这是为什么呢?我已经在我的主要活动类中实现了它，progressDialog 是否暂时将前台焦点从我的类中移开?

I had the same idea as Sandy but this code is never called whilst the progressDialog is showing, why is this? I have implemented it inside my main activity class, does the progressDialog take the foreground focus away from my class temporarily?

推荐答案

首先，您应该从 OnPreExecute 显示您的对话框，将其隐藏在 OnPostExecute 中，并且 - 如有必要- 通过发布进度修改它.(参见这里)

First, you should show your dialog from OnPreExecute, hide it in OnPostExecute, and - if necessary - modify it by publishing progress. (see here)

现在回答您的问题:ProgressDialog.show() 可以将 OnCancelListener 作为参数.您应该提供一个在进度对话框实例上调用 cancel() 的方法.

Now to your question: ProgressDialog.show() can take a OnCancelListener as an argument. You should provide one that calls cancel() on the progress dialog instance.

示例:

    @Override
    protected void onPreExecute(){
        _progressDialog = ProgressDialog.show(
                YourActivity.this,
                "Title",
                "Message",
                true,
                true,
                new DialogInterface.OnCancelListener(){
                    @Override
                    public void onCancel(DialogInterface dialog) {
                        YourTask.this.cancel(true);
                        finish();
                    }
                }
        );
    }

其中 _progressDialog 是 YourTask 的 ProgressDialog 成员.

where _progressDialog is a ProgressDialog member of YourTask.

此类在 API 级别 26 中已弃用.ProgressDialog 是一种模式对话框，它会阻止用户与应用程序交互.反而使用此类，您应该使用进度指示器，例如ProgressBar，可以嵌入到应用程序的 UI 中.或者，您可以使用通知来通知用户任务的进度.链接

This class was deprecated in API level 26. ProgressDialog is a modal dialog, which prevents the user from interacting with the app. Instead of using this class, you should use a progress indicator like ProgressBar, which can be embedded in your app's UI. Alternatively, you can use a notification to inform the user of the task's progress. LINK

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