I have two activities, one for displaying entries and another for creating them. Here's a standard use case:
User opens app and it displays entries.
User clicks button to create new entry and it opens the new activity.
User finishes creating entry and clicks "Done".
Activity finishes with setResult() and finish().
What I want to add is an AsyncTask that runs after the viewing activity is completely loaded. This AsyncTask shows a dialog while it's running. The problem is, when I put this code into onActivityResult() like this:
#Override
public void onActivityResult(int requestCode, int resultCode, Intent data) {
super.onActivityResult(requestCode, resultCode, data);
switch(resultCode) {
case (Activity.RESULT_OK): {
mEntryListFragment.updateContent();
runAsyncTaskHere();
}
}
}
It runs the AsyncTask before it goes back to the main activity, and no dialog shows. Any ideas what I can do?
Edit: here's the AsyncTask.
public static class LogInTask extends AsyncTask<String, Void, Integer> {
protected String username = "";
protected String password = "";
protected ProgressDialog dialog;
protected boolean showDialogs;
public LogInTask(boolean sd) {
this.showDialogs = sd;
}
#Override
protected void onPreExecute() {
if (this.showDialogs) dialog = ProgressDialog.show(MainActivity.getContext(), null, "Logging in...");
}
#Override
protected Integer doInBackground(String... login) {
if (Config.DEBUG) Log.d(Config.APP_NAME, "in doInBackground() of LogInTask");
HttpResponse response = null;
String username = login[0];
String password = login[1];
try {
HttpPost httpPost = new HttpPost(URL_BASE + URL_LOGIN);
// main (JSON) login method
JSONObject json = new JSONObject().put("user",
new JSONObject()
.put("email", username)
.put("password", password)
.put("remember_me", Config.REMEMBER_LOGIN)
);
this.username = username;
this.password = password;
StringEntity se = new StringEntity(json.toString());
httpPost.setHeader("Accept", "application/json");
httpPost.setHeader("Content-type", "application/json");
httpPost.setEntity(se);
response = httpclient.execute(httpPost);
String responseEntity = EntityUtils.toString(response.getEntity());
JSONObject result = new JSONObject(responseEntity);
return result.getBoolean("success") ? 1 : KEY_ERROR; // Return 1 if successful and -1 if not
} catch (UnknownHostException e) {
e.printStackTrace();
KEY_ERROR;
} catch (Exception e) {
e.printStackTrace();
return KEY_ERROR;
}
}
#Override
protected void onPostExecute(Integer result) {
if (this.showDialogs) {
dialog.dismiss();
String text = result == 1 ? "Login was successful." : "Login failed!";
makeToast(text);
}
}
}
Edit 2: I tried this:
boolean needToUpdate = false;
#Override
public void onActivityResult(int requestCode, int resultCode, Intent data) {
super.onActivityResult(requestCode, resultCode, data);
switch(resultCode) {
case (Activity.RESULT_OK): {
mEntryListFragment.updateContent();
needToUpdate = true;
}
}
}
#Override
public void onResume() {
super.onResume();
if (needToUpdate) {
runAsyncTaskHere();
mEntryListFragment.updateContent();
}
needToUpdate = false;
}
and it did the same thing.
Edit 3: here're the relevant sections of the AndroidManifest:
<activity
android:name=".MainActivity"
android:label="#string/app_name"
android:screenOrientation="portrait">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<activity
android:name=".AddEntryActivity"
android:label="#string/app_name"
android:screenOrientation="portrait"
android:configChanges="orientation" />
AsyncTask is a class for background processing, please, don't try to use it to do something with your UI or Activities, it always leads to a bad and unpredictable behaviour.
Maybe I should elaborate a little. Activities come and go, get killed and restored, destroyed and recreated as a usual way of theirs lives. It's absolutely normal.
Your AsyncTask may easily outlive your Activity, so when you're trying to access UI, it's already gone. Destroyed and recreated again, and all you've got is a dead pointer, which gives you an exception. Load your files in AsyncTask, do networking, access database. Just don't try to access UI/Activities, or your application will eventually crash and burn.
When you click on the Button to create new Entry, launch New Activity. but keep the Activity with entries. do not call finish() after intent.
After creation, and on clicking DONE, just close the Current Activity.(call finish())
mEntryListFragment.updateContent write this method in onStart() of the activity displaying entries.
Use ProgressDialog to achieve this.Start the dialog onPreExecute() and finish it onPostExecute() methods.You have to override those methods in your async task.
i think , you have to use Concept of callbacks ,
like when ever , loading is complete , implement your callback inside which you can deal with AsyncTask and after performing your task inside doInBackGround() , you can use onPostExecute() .
try something like this ,
Callback_interface
{
void async_run_after_some_time() ;
}
main_activity_class extends Activity Implements Callback_interface
{
void async_run_after_some_time()
{
// implement your toast here
}
}
onPostExecute()
{
main_activity_class ob = new main_activity_class ();
ob.async_run_after_some_time();
}
Just a thought.
Are you sure you are retrieving the proper context.
Is the boolean set correctly?
Plus, I do believe you are using HttpCore. From what I remember it requires some more attention networking and dis/connection wise due to it's granularity (compared to the HttpConnection class available by default). As such I don't think it is the best to use it with AsyncTask classes since they have little connection with the UI thread. Thus don't give much control for the user and may live beyond application's lifespan.
Related
I have an activity (let us call "ResultActivity") which receives some results from another activity ("AuditTest"), and there will be two buttons for user:
First button: let user to send the above-mentioned results to the server via connecting to a PHP webpage, and then go back to the main menu (so called "MainActivity")
Second button: let user to send the results to the server by ASyncTask, then ASyncTask will finish
For going back to the main menu, I have tried to use Intent, setClass, startactivity and finish. It could manage to go back to main menu, but this ResultActivity won't finish. Once you press back button on the phone, startActivity will close and that ResultActivity comes out again.
And for quitting the app, I also tried to use simply finish() method to achieve this, but still have no luck.
So here is the code for ResultActivity, and I also included comments to briefly illustrate operations in the app
public class ResultActivity extends AppCompatActivity
{
TextView result_showResultLbl;
Button result_retry,result_leaveBtn;
TextView result_noticeLbl;
boolean fail = false;
char PF = ' ';
final int BUTTON_RETRY=1;
final int BUTTON_LEAVE=2;
#Override
protected void onCreate(Bundle savedInstanceState)
{
//Summary: Just initializing all widgets, get back all elements
//from previous activity and show result to user.
........
........
//setting up onClickListeners for two buttons (result_retry and
result_leavebtn. So the ASyncTask is called SendData.
result_retry.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
//send result to server
SendData s = new
SendData(PF,FArecord,questionAnswers,BUTTON_RETRY);
s.execute();
}
});
result_leaveBtn.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
SendData s = new
SendData(PF,FArecord,questionAnswers,BUTTON_LEAVE);
s.execute();
}
});
}
//ASyncTask class SendData
private class SendData extends AsyncTask<String, String ,String>
{
.......//variables, not mentioned here
//parameters are data from previous activity and which button that user clicked.
SendData(..........)
{
.........
}
#Override
protected String doInBackground(String... strings)
{
//doInBackground of SendData will get all data sent from
//previous activity, then use HttpURLConnection to send out the data and get back the result.
...............//get all data from previous activity
//send php request
URL dbServerURL = new URL(URLAddr);
HttpURLConnection conn = (HttpURLConnection) dbServerURL.openConnection();
Log.v("ResultActivity","URL = "+URLAddr);//for debug
conn.setDoInput(true);
conn.setDoOutput(true);
conn.setUseCaches(false);
conn.setRequestMethod("POST");
OutputStream out = conn.getOutputStream();
//concat the information fields and then send out the data
parameters = ....;// parameters is a concatenated string to carry the data.
out.write(parameters.getBytes());
Log.v("ResultActivity","Trying to send parameter: "+parameters);
out.flush();
out.close();//finish sending out
//data request is successful
InputStream is = conn.getInputStream();
String response = FacilityAuditTest.convertStreamToString(is);
if (response.contentEquals("Error"))
{
//error occurred
Log.v("ResultActivity","Received String: "+response);
} else
{
//get JSON object if no error
JSONObject json = new JSONObject(response);
success = json.getInt("success");
Log.v("ResultActivity","Success= "+success);
Log.v("ResultActivity","Record sent successfully");
}
is.close();
conn.disconnect();
} catch (Exception e)
{
e.printStackTrace();
}
return null;
}
#Override
protected void onPostExecute(String s)
{
super.onPostExecute(s);
if (success == 1)
{
//I use runOnUiThread() to detect which button the user has clicked, then swap activity or close the app.
runOnUiThread(new Runnable() {
#Override
public void run() {
if (clickedButtonType == BUTTON_RETRY)
{
//if user clicked retry button before, show a success message and then go back to information entry page
Toast.makeText(ResultActivity.this,R.string.result_sendSuccess,Toast.LENGTH_SHORT).show();
Intent i = new Intent();
i.setClass(ResultActivity.this,AuditorInf.class);
startActivity(i);
finish();
}
if (clickedButtonType == BUTTON_LEAVE)
{
Toast.makeText(ResultActivity.this,R.string.result_sendSuccess,Toast.LENGTH_SHORT).show();
//I tried to use android.os.Process.killProcess to kill app, but the app still restart and show this ResultActivity after running killProcess. android.os.Process.killProcess(android.os.Process.myPid());
System.exit(1);
//finish();
}
}
});
} else
{
//just show fail to transmit message, but the action is similar to (success == 1)
}
}
}
}
As what I have added in the comments of the code, the app won't switch to main menu and close current activity. It also cannot close the app by calling finish. I can give more detail code if you need. Thank you.
i have i problem that i don't know the cause, so when running my application after an asynctask call in POST i change activity and when the new Activity is setting the main content to the screen the app crashes with any log.
The activty chages code is written in onPostExecute method of asynctask and i've tried to do this in another thread calling the runOnUIThread method from activity but isn't working.
the only log that I see:
03-10 12:03:20.312: I/MyHttpClient(3160): HTTPResponse received in [1210ms]
03-10 12:03:20.367: I/my.app.package.ActivationActivity(3160): SendActivation onPostExecute: ActivationResponse [my.app.result.json.with.SUCCESS:result.code]
03-10 12:03:25.398: D/OpenGLRenderer(3160): Flushing caches (mode 0)
EDIT: now i have changed some names of classes and objects but is the code that don't work for me
class MyAsincTask extends AsyncTask<String, Void, String>
{
private Exception exception;
private Gson gson;
protected void onPostExecute(String response) {
hideProgressDialog();
if (exception != null) {
//deleted log code here
} else if (response != null) {
// I manage the json response from the server
try {
// I manage the json response
// determining if the server call was SUCCESS or ERROR
if (resultCode.equals(Constants.RESULT_ERROR)) {
//deleted log code here
}else if (resultCode.equals(Constants.RESULT_SUCCESS)) {
launchRegistration(); // I enter Here and then crashes
}
} catch (Exception e) {
//deleted log code here
}
//deleted log code here
} else {
//deleted log code here
}
}
}
protected void launchRegistration(){
runOnUiThread(new Runnable() {
#Override
public void run() {
Intent mIntent = new Intent(mContext, ActivityToOpen.class);
mIntent.setAction(Constants.ACTION_TO_OPEN_ACTIVITY);
mIntent.putExtra(Constants.SOME_EXTRA, extras);
startActivity(mIntent);
finish();
}
});
}
is inside other activity, and the asynctask class is inner in other activity class. this code for me work on many recent device, with recdent hardware and recent version like 4.4 and 5 and 4.3, but the problem is happening in other devicewith 4.0 and 4.1 with less hardware resource.
`<activity android:name="com.example.Activity"
android:excludeFromRecents="true"
android:icon="#drawable/app_icon"
android:label="#string/wizard.welcome.title"
android:theme="#style/Theme.NoDisplay" /> `
the error that I did, is in the manifest declaration, some activity has the theme "NoDisplay" that don't work in recent version of android, but works in previous versions. And for this I had an issue.
Thank
Ever get those moments where you stare at a piece of code for an hour and still can't come up with an answer? Yeah that's me now.
I'm working on a final project for class and I can't get this one piece of code to work. It is absolutely crucial that it works, or else it defeats the purpose of the program. I even asked my professor for help... and he doesn't know how to help me solve the issue. I posted a similar problem a day ago but I want to re-ask in a different way to see if it helps (Sorry if its a re-post, I have no other source for help :/).
My problem is that I need to access array elements on my MainActivity after its populated inside an AsyncTask class. The array is defined globally but as soon as I try to access it's element or size, it crashes. I need to be able to call this array outside of AsyncTask.
I've searched for hours and tried "returning" the array from AsyncTask but it crashes as well.
Here is my code (I've included comments as to where it crashes):
public class PostsActivity extends Activity {
public static GlobalRates[] gr;
TextView view;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_posts);
view = (TextView) findViewById(R.id.textView1);
BitRateFetcher br = new BitRateFetcher();
br.execute();
// !!! Line below crashes !!!
Log.i("BitRateFetcher", "Size from onCreate: " + gr.length);
}
private class BitRateFetcher extends AsyncTask<Void, Void, GlobalRates[]> {
private static final String TAG = "BitRateFetcher";
public String BIT_PAY_SERVER = "https://bitpay.com/api/rates";
private ProgressDialog dialog;
GlobalRates[] test;
#Override
protected void onPreExecute() {
super.onPreExecute();
dialog = new ProgressDialog(PostsActivity.this);
dialog.setMessage("Please Wait... Downloading Information");
dialog.show();
}
#Override
protected GlobalRates[] doInBackground(Void... params) {
try {
// Create an HTTP client
HttpClient client = new DefaultHttpClient();
HttpGet getBitRates = new HttpGet(BIT_PAY_SERVER);
// Perform the request and check the status code
HttpResponse bitRatesResponse = client.execute(getBitRates);
StatusLine bitRatesStatus = bitRatesResponse.getStatusLine();
if (bitRatesStatus.getStatusCode() == 200) {
HttpEntity entity = bitRatesResponse.getEntity();
InputStream content = entity.getContent();
try {
// Read the server response and attempt to parse it as
// JSON
Reader reader = new InputStreamReader(content);
Gson gson = new Gson();
test = gson.fromJson(reader, GlobalRates[].class);
content.close();
entity.consumeContent();
} catch (Exception ex) {
Log.e(TAG, "Failed to parse JSON due to: " + ex);
failedLoadingPosts();
}
} else {
Log.e(TAG, "Server responded with status code: "
+ bitRatesStatus.getStatusCode());
failedLoadingPosts();
}
} catch (Exception ex) {
Log.e(TAG, "Failed to send HTTP POST request due to: " + ex);
failedLoadingPosts();
}
return test;
}
#Override
protected void onPostExecute(GlobalRates[] test) {
Log.i(TAG, "Test Size: " + test.length); // Returns 158
gr = test;
Log.i(TAG, "Gr Size: " + gr.length); // Returns 158
if (dialog.isShowing()) {
dialog.dismiss();
}
}
}
#Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.posts, menu);
return true;
}
private void failedLoadingPosts() {
runOnUiThread(new Runnable() {
#Override
public void run() {
Toast.makeText(PostsActivity.this,
"Failed to load Posts. Have a look at LogCat.",
Toast.LENGTH_SHORT).show();
}
});
}
}
Here is the error Log:
04-21 20:30:01.954: E/AndroidRuntime(32595): FATAL EXCEPTION: main
04-21 20:30:01.954: E/AndroidRuntime(32595): Process: com.example.postsactivity, PID: 32595
04-21 20:30:01.954: E/AndroidRuntime(32595): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.postsactivity/com.example.postsactivity.PostsActivity}: java.lang.NullPointerException
My class partner and I are unsure as to how we can call the global array (gr) properly. I understand that onCreate is not going to wait for AsyncTask to finish. What can we do to get this to work? Thanks for the help and understanding. You guys can prove more useful than my professor...
the problem is that you are accessing array of globalrates before it was initialized in your postExecute(). There are a lot of way to do this one of which is creating an interface or creating callbacks that waits for globalrate to be initialized after ur background thread is done.
Create a Interface
public interface SampleInterface {
void globalResultBackground(GlobalRates[] gr);
}
implements the interface to ur activity
public class PostsActivity extends Activity implements SampleInterface
pass the interface to your asynctask
//in the activity
BitRateFetcher br = new BitRateFetcher(this);
br.execute();
//in the asynctask class
SampleInterface si;
public BitRateFetcher(SampleInterface si){
this.si = si;
}
pass the result of the background thread to ur interface method
#Override
protected void onPostExecute(GlobalRates[] test) {
si.globalResultBackground(test);
Log.i(TAG, "Test Size: " + test.length); // Returns 158
gr = test;
Log.i(TAG, "Gr Size: " + gr.length); // Returns 158
if (dialog.isShowing()) {
dialog.dismiss();
}
}
in the activity where the you implemented the interface and generated the globalResultBackground method
#Override
public void globalResultBackground(GlobalRates[] gr) {
//you can freely access the globalrates here because this is called when the
//background thread is done
Log.i("BitRateFetcher", "Size from onCreate: " + gr.length);
}
Pass in your activity to the AsyncTask and directly access its gr in your onPostExecute
Sample code:
private class BitRateFetcher extends AsyncTask {
PostsActivity activity;
...
public BitRateFetcher(PostsActivity activity){
this.activity= activity;
}
...
#Override
protected void onPostExecute(GlobalRates[] test) {
activity.gr = ...
}
}
In PostsActivity,
BitRateFetcher br = new BitRateFetcher(this);
Take care to attach and reAttach the activity to handle scenarios such as device rotations.
EDIT: Just noticed you've got a static, so you don't even need to pass in the activity. The same principle applies though.
GlobalRates[] gr is public and static, so you dont really new GlobalRates[] test
simply replace every instance of test with gr:
test = gson.fromJson(reader, GlobalRates[].class);
to
gr = gson.fromJson(reader, GlobalRates[].class);
if you need to access gr in Oncreate then move that logic to postExecute
Log.i("BitRateFetcher", "Size from onCreate: " + gr.length);
I've made an app that sends a request to a webserver in a specified interval and gets XML data. It then parses the XML data, gets information from the phone (text messages, contacts or something similar) and shoots it back to the server with a http post request.
The problem is that it usually takes a few seconds for the app to get the info, which often leaves the app crashing. A dialog comes up saying the app has become unresponsive and asks if i want to close the app or wait, if i press wait it eventually starts working again.
Is AsyncTask the right solution to this problem?
Another thing i don't really understand is how AsyncTask actually works. Let's say i have two methods that do a lot of work and crashes the app, can i put both of them in one AsyncTask and just call them from doInBackground()?
I have also implemented something similar you are trying. That is sending request to server, receive XML response, parse XML, show result. View This. I have used AsyncTask for this.
Here is how i have implemented it using AsynTask
private class AsyncClass extends AsyncTask<Void, Void, Bundle>{
#Override
protected Bundle doInBackground(Void... arg0) {
Bundle b=startProcess();
// startBundle() method do all the processing and return result in a bundle. You can as many methods from within startBundle() method
return b;
}
#Override
protected void onPostExecute(Bundle result) {
Log.d(TAG , "In onPostExecute");
dialog.dismiss();
if(result==null)
Toast.makeText(cont, "Can't process query.\nTry again later.", Toast.LENGTH_LONG).show();
else{
Intent in = new Intent(cont, QueryResultDisplay.class);
Log.d(TAG , "Displaying");
in.putExtras(result);
cont.startActivity(in);
}
}
I give you brief description about your problem.
There are many possibility that you don't get data from server
if your network speed is very slow and you try to get all the
information from server and XML data then in this case if network crash then it show you error
if you're making request to that page which is not in server
Now, if you are facing the problem in code, then I give you the complete code of AsyncTask class which I had implemented in my project and it work fine.
private class GetLoginResponse extends AsyncTask<Void, Void, Boolean> {
private ProgressDialog progressDialog;
private String email;
private String password;
public GetLoginResponse(String emailId, String paswd) {
this.email = emailId;
this.password = paswd;
}
#Override
protected void onPreExecute() {
progressDialog = ProgressDialog.show(LoginActivity.this, "",
"Loading....", true, false);
}
#Override
protected Boolean doInBackground(Void... params) {
try {
DefaultHttpClient httpclient = new DefaultHttpClient();
HttpGet httpGet = new HttpGet(url);
HttpResponse response = httpclient.execute(httpGet);
//here u can check the reponse is ok and 200
} catch (NetworkException e) {
isNetworkError = true;
}
return false;
}
#Override
protected void onPostExecute(Boolean data) {
progressDialog.dismiss();
System.out.println("lOGIN RESPONSE for email = " + email + data);
}
}// end AsyncTask
This would solve your problem.
Yes, you can use AsyncTask.
The code called in doInBackground() must not touch the UI.
You can touch the UI thread with publishProgress().
I've run into this error before, but thought it was some mistake by the strict mode system. However, it apparently was right as I sadly found out now. :(
My programm is made of one Activity and loads of Fragments. I have a NetworkWorker fragment, which starts URL requests like this:
public void startURLRequest(Fragment target, String url, String message)
{
if (asyncTask != null) asyncTask.cancel(true);
asyncTask = new FragmentHttpHelper(url, message, target);
asyncTask.doInBackground();
return;
}
FragmentHttpHelper is a custom inner class derived from AsyncTask:
private class FragmentHttpHelper extends AsyncTask<Void, Void, String>
{
//...
#Override
protected String doInBackground(Void... params)
{
if (CheckInternet())
{
try
{
URL myURL = new URL(url);
httpClient = new DefaultHttpClient();
if (this.message == null)
{
httpRequest = new HttpGet(myURL.toExternalForm());
}
else
{
httpRequest = new HttpPost(myURL.toExternalForm());
HttpEntity myEntity = new StringEntity(message, "UTF-8");
((HttpPost) httpRequest).setEntity(myEntity);
}
// and so on...
}
//catches
finally
{
// auf jeden Fall Verbindung beenden
if (httpRequest != null) httpRequest.abort();
// if (httpClient != null) httpClient.close();
}
}
else
{
showDialog(getString(R.string.net_notify_no_network), target);
}
//...
}
/**
* gets called after AsyncTask has finished
*/
protected void onPostExecute(String result)
{
if (target == null)
{
((NetworkWorkerListener) getActivity()).onDownloadHasFinished((!result.contentEquals(ERROR)), result);
}
else
{
((NetworkWorkerListener) target).onDownloadHasFinished((!result.contentEquals(ERROR)), result);
}
}
}
NetworkWorkerListener is just an interface for a callback on the Fragment which started the URL request. This class has always worked fine when I used it in my 2.2 app. I would derive it in my Activities then.
Now, if a menu item is selected, another worker Fragment starts the URL request via the above method and opens a loading dialog:
FragmentManager fragmentManager = getFragmentManager();
NetworkWorker network = (NetworkWorker) fragmentManager.findFragmentByTag(TabletMain.NETWORK);
if (network == null) return WorkerFeedback.NO_NETWORK_WORKER;
myDialog = LoadingDialog.createInstance(getString(R.string.notify_download), this);
myDialog.show(fragmentManager, TabletMain.ONETIME);
network.startURLRequest(this, someurl, null);
At least that's what supposed to happen.
Instead, when I click the menu item, my app freezes and no loading dialog is shown until. Next happening is the reaction to the end of the download (or, in my case an error message, as I am sending nonsense strings). Meaning onPostExecute() was reached.
I feel really stuck now - is it not possible to use AsyncTask with Fragments? Or did I do something wrong?
Thanks for your help,
jellyfish
Don't call doInBackground directly, call execute instead (on the async task)