需要说明：如何使用AsyncTask的？ [英] Need an explanation : how to use AsyncTask?

问题描述

我有一个包含一些数据的XML文件，所以我创建了一个类重presenting是：

I have a XML file containing some data, so I created a class representing it :

public class MyData
{
    ArrayList<SpecialData> list;
    int currentPage, totalPages;
}

正如您可以猜到我有 SpecialData 的项目，每一个都包含许多领域，列表和当前页 / 总页数是XML文件中的两个独特的价值。我需要和异步解析XML文件，所以我创建了这个类：

As you can guess I have a list of SpecialData items, each one containing many fields, and currentPage/totalPages are two unique values in the XML file. I need to get and parse the XML file asynchronously, so I created this class :

class GetXMLTask extends AsyncTask<String, Void, MyData>
{
    @Override
    protected MyData doInBackground(String... params)
    {
        MyData md = null;
        // Getting/parsing data
        return md;
    }
}

我给它一个尝试，这个问题并非来自这里，因为我正确地分析我的XML文件和我的迈德特对象是完美的。但后来我用这个任务，这样在我的主活动类：

I gave it a try and the problem doesn't come from here because I correctly parse my XML file and my MyData object is perfect. But then I use this task like this in my main Activity class :

MyData md = null;
GetXMLTask task = new GetXMLTask(this);
task.execute(new String[]{url});
// How can this change my md object?

这可能是非常愚蠢的，但我根本不知道怎么我的迈德特实例从我的主类链接到一个我与的AsyncTask 。我该怎么办？谢谢你。

This may be very silly but I simply don't know how to link my MyData instance from my main class to the one that I get with AsyncTask. What should I do? Thanks.

推荐答案

覆盖的AsyncTask 的 onPostExecute 方法：

protected void onPostExecute(MyData result) {
     md = result;
 }

请注意，这里假设你的AsyncTask是一个内部类中的活动。如果不是的话，你可以在构造函数中的AsyncTask的参考，你的活动通过。在这种情况下，你应该小心使用的WeakReference 你的活动，以prevent资源泄漏：

Note that this assumes your AsyncTask is an inner class to your activity. If that isn't the case, you can pass in a reference to your Activity in the constructor to your AsyncTask. In those cases, you should be careful to use a WeakReference to your Activity to prevent resource leaks:

GetXMLTask(MyActivity activity)
{
    this.mActivity = new WeakReference<MyActivity>(activity);
}

protected void onPostExecute(MyData result)
{
     MyActivity activity = this.mActivity.get();
     if (activity == null) // Activity was destroyed due to orientation change, etc.
         return;
     activity.updateUiFromXml(result);
 }

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