如何正确地从PostExecute开始在Android的活动？ [英] How to correctly start activity from PostExecute in Android?

问题描述

我有一个AsyncTask的，填充来自互联网的解析数据的自定义列表。

I have an AsyncTask, that fills a custom List with parsed data from Internet.

在PostExecute我填补这一名单，并得到它准备将其转移到一个新的活动。

In PostExecute I fill that List and get it ready to transfer it to a new Activity.

我做这种方式：

@Override
protected void onPostExecute(List<VideoDataDescription> result) 
{
    super.onPostExecute(result);
    MainActivity.progressDialog.dismiss();

    context.startActivity(new Intent(context, ResultsQueryActivity.class));


}

在这里的上下文

where context

    private Context context;

在LogCat中执行此code，我收到了显示java.lang.NullPointerException之后。 这是可能的，正确的启动活动，因为我做到这一点？

In LogCat after executing this code I get a Java.lang.NullPointerException. Is this possible and correct to start an Activity as I do it?

UPD 我已经加入

    private Context mContext;


public YoutubeAndYahooParser(Context context) 
{
    super();
    this.mContext = context;
}

要初始化上下文，并调用

to initialize context and call

YoutubeAndYahooParser youtubeAndYahooParser = new YoutubeAndYahooParser(ResultsQueryActivity.this);
                    youtubeAndYahooParser.execute("my string to pass in asynctak");

在这PostExecute

After this in PostExecute

Intent intent = new Intent(mContext, ResultsQueryActivity.class);
 intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
 mContext.startActivity(intent);    

我添加了新的标志，因为我有在LogCat中的下一个：

I added new flag because of I have got in LogCat the next:

*从活动背景以外调用startActivity（）需要FLAG_ACTIVITY_NEW_TASK标志。这真的是你想要的吗？*

*Calling startActivity() from outside of an Activity context requires the FLAG_ACTIVITY_NEW_TASK flag. Is this really what you want?*

我说得对不对？

推荐答案

您应该通过在应用程序上下文，而不是从本地活动上下文。即使用context.getApplicationContext（）并保存在你的AsyncTask subsclass的局部变量。

You should pass in the application context rather than a context from the local activity. I.e. use context.getApplicationContext() and save that in a local variable in your AsyncTask subsclass.

在code力量看起来是这样的：

The code might looks something like this:

public class MyAsyncTask extends AsyncTask {

    Context context;
    private MyAsyncTask(Context context) {
        this.context = context.getApplicationContext();
    }

    @Override
    protected Object doInBackground(Object... params) {
        ...
    }

    @Override
    protected void onPostExecute(List<VideoDataDescription> result) {
        super.onPostExecute(result);
        MainActivity.progressDialog.dismiss();

        context.startActivity(new Intent(context, ResultsQueryActivity.class));
    }
}

你会这样称呼它：

you'd call it like this:

   new MyAsyncTask(context).execute();

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