Question

我AsyncTask正在运行Activity。在AsyncTask doInBackground(Object[])方法中，我执行网络操作，使用HTTP POST方法将一些数据发送到服务器，接收响应，然后在其onPostExecute(Object)中它将响应发送到Service，然后所有作业都从Service执行。问题是：在Activity完成之前，我无法关闭AsyncTask。 Activity只会冻结，直到AsyncTask完成。有时，如果AsyncTask需要更多时间来完成，屏幕会变为黑色，并保持这样状态直到AsyncTask完成。这是为什么？怎么避免这个？我尝试在AsyncTask cancel(boolean)方法中呼叫Activity onStop()，但它仍然执行相同的操作。

编辑：我的AsyncTask代码：

private static class PostCommentTask extends AsyncTask<String, Void, String> {
    Activity activity;
    int status;
    Toast indicationMsg;

    public PostCommentTask(Context context) {
        activity = (Activity) context;
    }

    private boolean isNetworkAvailable() {
        Log.i("ilog", "isNetworkAvailable() called");
        ConnectivityManager connManager = (ConnectivityManager) activity.getSystemService(Context.CONNECTIVITY_SERVICE);
        NetworkInfo activeNetworkInfo = connManager.getActiveNetworkInfo();

        return activeNetworkInfo != null && activeNetworkInfo.isConnected() && activeNetworkInfo.isAvailable();
    }

    protected String doInBackground(String... param) {
        if (!isNetworkAvailable()) {
            return "";
        }

        HttpClient httpClient = new DefaultHttpClient();
        HttpPost httpPost = new HttpPost(param[7]);
        String responseBody = "error in PostComment.doInBackground()";

        try {
            List<NameValuePair> params = new ArrayList<NameValuePair>(7);
            params.add(new BasicNameValuePair("somevar", param[0]));
            params.add(new BasicNameValuePair("somevar", param[1]));
            params.add(new BasicNameValuePair("somevar", param[2]));
            params.add(new BasicNameValuePair("somevar", param[3]));
            params.add(new BasicNameValuePair("somevar", param[4]));
            params.add(new BasicNameValuePair("somevar", param[5]));
            params.add(new BasicNameValuePair("somevar", param[6]));

            httpPost.setEntity(new UrlEncodedFormEntity(params));

            HttpResponse response = httpClient.execute(httpPost);

            status = response.getStatusLine().getStatusCode();
            Log.i("ilog", "response status: " + status);

            HttpEntity responseEntity = response.getEntity();
            if (responseEntity != null) {
                responseBody = EntityUtils.toString(responseEntity);
            }

        } catch (ClientProtocolException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }

        Log.i("ilog", "Response: " + responseBody);

        return responseBody;
    }

    public void onPostExecute(String responseBody) {
        String success = "{\"status\":\"OK\"}";
        if (responseBody.equals(success) && status == 200){
            indicationMsg = Toast.makeText(activity, "Success!!!", Toast.LENGTH_LONG);

            CommentsFragment.CommentsHandler commentsHandler = new CommentsFragment.CommentsHandler();

            Messenger messenger = new Messenger(commentsHandler);

            Intent serviceIntent = new Intent(activity, WindowService.class);
            serviceIntent.putExtra("messenger", messenger);
            serviceIntent.putExtra("somevar", somevar);
            serviceIntent.putExtra("somevar", activity.getIntent().getStringExtra("somevar"));
            activity.startService(serviceIntent);
            //
        }
        else
            indicationMsg = Toast.makeText(activity, "Failed...", Toast.LENGTH_LONG);
        indicationMsg.show();
    }
}

CommentsHandler class是一个处理Service响应的类。这就是我在Activity和Service之间进行沟通的方式。

我使用以下代码启动AsyncTask：

public static class CommentsFragment extends Fragment {
    /** ... **/
    @Override
    public void onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        /** ... **/
        Button queryButton = (Button) rootView.findViewById(R.id.query_button);
        queryButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                /** ... **/
                new PostCommentTask(activity).execute(somevar, somevar, somevar, somevar, somevar, somevar, somevar, somevar);
                /** ... **/
            }
        });
        /** ...  **/
    }
    /** ... **/
}

Answer 1

我已经解决了这个问题。 Activity冻结是因为Activity我将从AsyncTask方法中使用onResume()，因此它必须等到第一个任务来自关闭Activity在执行自己的任务之前完成，这导致了UI的冻结。现在我使用executeOnExecutor(AsyncTask.THREAD_POOL_EXECUTOR, Object[]能够并行运行多个任务，而不是逐个运行（逐个）。

AsyncTask未完成时无法关闭活动

1 个答案: