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[英]Android - Display Progress Dialog on button click ONLY if AsyncTask has not completed
[英]Back button only dismissing Progress Dialog and not the AsyncTask
当用户单击“后退”按钮时,我试图取消我的aynctask。 我已经对用于此操作的方法进行了研究,发现很难弄清楚为什么有不止一种方法。 我找到了一种方法并尝试了它,但它只关闭了ProgressDialog,而我的aynctassk仍在执行。 因此,有人可以协助我解决使我的asynctask退出正确方法的问题。
@Override
public void onBackPressed()
{
/** If user Pressed BackButton While Running Asynctask
this will close the ASynctask.
*/
if (mTask != null && mTask.getStatus() != AsyncTask.Status.FINISHED)
{
mTask.cancel(true);
}
super.onBackPressed();
finish();
}
@Override
protected void onDestroy() {
// TODO Auto-generated method stub
/** If Activity is Destroyed While Running Asynctask
this will close the ASynctask. */
if (mTask != null && mTask.getStatus() != AsyncTask.Status.FINISHED)
{
mTask.cancel(true);
}
super.onDestroy();
}
@Override
protected void onPause() {
// TODO Auto-generated method stub
if (pDialog != null)
{
if(pDialog.isShowing())
{
pDialog.dismiss();
}
super.onPause();
}
}
如果需要将我的doInBackGround
方法发布到问题上,请告诉我
protected String doInBackground(String... args) {
try {
Intent in = getIntent();
String searchTerm = in.getStringExtra("TAG_SEARCH");
String query = URLEncoder.encode(searchTerm, "utf-8");
String URL = "http://example.com";
JSONParsser jParser = new JSONParsser();
JSONObject json = jParser.readJSONFeed(URL);
try {
JSONArray questions = json.getJSONObject("all").getJSONArray("questions");
for(int i = 0; i < questions.length(); i++) {
JSONObject question = questions.getJSONObject(i);
String Subject = question.getString(TAG_QUESTION_SUBJECT);
String ChosenAnswer = question.getString(TAG_QUESTION_CHOSENANSWER);
String Content = question.getString(TAG_QUESTION_CONTENT);
HashMap<String, String> map = new HashMap<String, String>();
map.put(TAG_QUESTION_SUBJECT, Subject);
map.put(TAG_QUESTION_CONTENT, Content);
map.put(TAG_QUESTION_CHOSENANSWER, ChosenAnswer);
questionList.add(map);
}
} catch (JSONException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
} catch (UnsupportedEncodingException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return null;
}
我认为问题出在AsyncTask的doInBackground方法中。 当您使用mTask.cancel(true);
取消AsyncTask时mTask.cancel(true);
它不会取消任务,而只是设置一个标志。 您需要检查DoInBackground方法是否已取消任务(标记为取消),如果已取消则返回。
范例:
protected Long doInBackground(URL... urls) {
int count = urls.length;
long totalSize = 0;
for (int i = 0; i < count; i++) {
totalSize += Downloader.downloadFile(urls[i]);
publishProgress((int) ((i / (float) count) * 100));
// Escape early if cancel() is called
if (isCancelled()) break;
}
return totalSize;
}
来源: http : //developer.android.com/reference/android/os/AsyncTask.html
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