嵌套的AsyncTask和onPostExecute

Question

我AsyncTask在另一个AsyncTask(2)中使用(1 ).AsyncTask 1获取在线用户数据,计算响应中的条目数以及每个条目,onPostExecute显示用户名并运行新的AsyncTask(2)以从服务器获取图像并将其加载到ImageView.这一切都发生在onPostExecute.这完美地工作,获取并显示用户数据,并且每个条目逐个显示图像.

然而,通过阵列的itteration和的更新TextView中AsyncTask1的onPostExecute情况发生得这么快,它基本上只显示数组中的最后一个用户名,其他的人被加载,但无法与人眼检测:)

同时,AsyncTask2仍在从网上获取图像,并显示错误用户的个人资料图像.我在这里遇到的问题显然是这两个需要同步.所以我以为我只是等待方法中的输出AsyncTask2 get(),但现在根本没有任何更新,不TextView...这对我来说是意想不到的行为.

那么,问题是如何同步2 AsyncTasks？

如果仍然需要,可以澄清一些代码

    //instantiate first AsyncTask
    new AsyncRequest().execute(bundle);

    private class AsyncRequest extends AsyncTask<Bundle, Void, String> {
    protected String doInBackground(Bundle... bundle) {
        String data = null;
        try {
            data = request(null, bundle[0]); //request the data
            return data;
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (MalformedURLException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
        return data;
    }// end method

    protected void onPostExecute(String response) {
        JSONArray data = null;
        try {
            JSONObject response2 = Util.parseJson(response);
            data        = response2.optJSONArray("data");
            int amount  = data.length();
            TextView s1 = (TextView) findViewById(R.id.some_id);
            s1.setText("" + amount); //displays number of items

            //display the data
            for(int i=0; i<amount; i++){
                String email        = "";
                String id           = "";
                JSONObject json_obj = data.getJSONObject(i);
                Log.d("JSONObject ", ""+json_obj);
                String name         = json_obj.getString("name");
                if (json_obj.has("email")){
                    email           = json_obj.getString("email");
                }
                if (json_obj.has("id")){
                    id          = json_obj.getString("id");
                }
                String picture  = "http://www.domain.com/"+id+"/picture";
                TextView s2     = (TextView) findViewById(R.id.name_placeholder);
                s2.setText(name);
                //here we do a new AsynTask for each entry and wait until the data is fetched
                new DownloadProfileImageTask().execute(picture, name).get(); 
            }
        } catch (JSONException e) {
            e.printStackTrace();
        } catch (InterruptedException e) {
            e.printStackTrace();
        } catch (ExecutionException e) {
            e.printStackTrace();
        }
    }// end method

Answer 1

为什么要调用具有多个名称setText的单个单词并不十分清楚TextView.正如您所提到的,尽管您拥有setText所有名称,但您只能看到一个名称.也许你需要使用ListView或类似的东西.

现在关于你的问题:可能你不需要两个AsyncTask.你可以做到一切AsyncTask.代码如下所示:

//Create a Holder class as a data holder. 
//For simplicity, public attributes are used
class Holder{
  public String name;
  public String email;
  public String id;
  public BitmapDrawable imageDrawable;
}

//instantiate the AsyncTask
new AsyncRequest().execute(bundle);

private class AsyncRequest extends AsyncTask<Bundle, Holder, Integer> {
protected Integer doInBackground(Bundle... bundle) {
    int amount = 0;
    try {
        data = request(null, bundle[0]); //request the data

        JSONArray data = null;
        JSONObject response2 = Util.parseJson(response);
        data        = response2.optJSONArray("data");
        amount  = data.length();

        //display the data
        for(int i=0; i<amount; i++){
            Holder holder = new Holder();
            holder.email        = "";
            holder.id           = "";
            JSONObject json_obj = data.getJSONObject(i);
            Log.d("JSONObject ", ""+json_obj);
            holder.name         = json_obj.getString("name");
            if (json_obj.has("email")){
                holder.email           = json_obj.getString("email");
            }
            if (json_obj.has("id")){
                holder.id          = json_obj.getString("id");
            }
            String picture  = "http://www.domain.com/"+id+"/picture";

            //Fetch the image and create a Drawable from it - Synchronously
            holder.imageDrawable = getImageDrawable(picture, name);

            publishProgress(holder);

        }
    } catch (Exception e) {
        e.printStackTrace();
    } 
    return amount;
}// end method

protected void onProgressUpdate(Holder... holder) {
    //Update the user name and image
    TextView s2     = (TextView) findViewById(R.id.name_placeholder);
    s2.setText(holder[0].name);

    ImageView imgView = (ImageView) findViewById(R.id.imageViewId);
    imgView.setImageDrawable(holder[0].imageDrawable);

}

protected void onPostExecute(Integer amount) {
    TextView s1 = (TextView) findViewById(R.id.some_id);
    s1.setText(amount.toString()); //displays number of items
}// end method