Android的，异步和进度对话框 [英] Android, async and progress dialogs

问题描述

我有下面这段code：

 公共类SomeActivity延伸活动{
    上下文语境;
    名单＆LT;菜单项＆GT;菜单项;

    公共无效importList（视图v）{
        菜单项=新的ArrayList＆LT;菜单项＆GT;（）;
        ProgressDialog对话框= ProgressDialog.show（this.context，标题，味精）;

        MyAsyncTask任务=新MyAsyncTask（上下文）; // Context是在这里，因为我试图创建ProgressDialog内pre / postExecute，但它也不管用
        task.execute（）;
        尝试 {
            //菜单项= task.get（）;
        }赶上（例外五）{
            //：（
        }
    }

    @覆盖
    保护无效的onCreate（包savedInstanceState）{
        // ...
        this.context =这一点;
    }
}
 

在我注释行，在那里我得到的AsyncTask值（菜单项= task.get（））万物工作正常。但是，当我取消它，ProgressDialog后出现的任务完成，并返回值。这是为什么呢？

我认为它有某事做这些环境（这就是为什么我包括onCreate方法），但我没有任何想法如何解决它。很显然，我希望ProgressDialog显示前任务完成，而不是之后。

不知道是否有关 - MyAsyncTask做HTTP请求和一些JSON解析

解决方案

  

我认为它有某事做这些上下文

不尽然。此外，发送时上下文从活动您不必创建一个变量。只需使用这或 ActivityName.this 。

  MyAsyncTask任务=新MyAsyncTask（本）;
 

  

但是，当我取消它，ProgressDialog后出现的任务完成，并返回值。这是为什么呢？

调用的get（）块中的 UI ，这就是为什么你没有看到的进展，直到它完成。你不需要调用此。 onProgressUpdate的点（）是这样后台线程（ doInBackground（））可以调用它来更新 UI ，因为 doInBackground（）不上的 UI 运行。

从code删除了这一行，从不看它了。如果你认为你需要它，那么请解释一下，我们可以帮你找到更好的方法有原因的。

修改

<一个href="http://stackoverflow.com/questions/18517400/inner-class-can-access-but-not-update-values-asynctask/18517648#18517648">See这太回答在更新时，任务完成

I have following piece of code:

public class SomeActivity extends Activity {
    Context context;
    List<MenuItem> menuItems;

    public void importList(View v) {
        menuItems = new ArrayList<MenuItem>();
        ProgressDialog dialog = ProgressDialog.show(this.context, "TITLE", "MSG");

        MyAsyncTask task = new MyAsyncTask(context); // Context is here because I tried to create ProgressDialog inside pre/postExecute, but it doesn't work either
        task.execute();
        try {
            // menuItems = task.get();
        } catch(Exception e) {
            // : (
        }
    }

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        // ...
        this.context = this;
    }
}

When I comment the line, where i get values from AsyncTask ("menuItems = task.get()") everythings work ok. But when I uncomment it, ProgressDialog appears AFTER the task is finished, and value returned. Why is that?

I think that it has sth to do with these contexts (that's why I included onCreate method) but I don't have any idea how to fix it. Obviously, I want ProgressDialog to display BEFORE task is finished, not after.

Not sure if relevant - MyAsyncTask is doing http request and some json parsing.

解决方案

I think that it has sth to do with these contexts

Not at all. Also, when sending Context from an Activity you don't need to create a variable. Simply use this or ActivityName.this.

 MyAsyncTask task = new MyAsyncTask(this);

But when I uncomment it, ProgressDialog appears AFTER the task is finished, and value returned. Why is that?

Calling get() blocks the UI, this is why you don't see the progress until it is done. You don't need to call this. The point of onProgressUpdate() is so the background thread (doInBackground()) can call it to update the UI since doInBackground() doesn't run on the UI.

Remove that line from your code and never look at it again. If there is a reason that you think you need it then please explain and we can help you find a better way.

Edit

See this SO answer on updating when the task is finished

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