The problem has been solved, thank you for the help.
Essentially, I have my onCreate() class that sets an OnClick listener on a button. Once I click it, an async task is created and executed.
This async task gets a response from a server and then sends the info to onPostExecute().
From here, if the info is valid or not, I want to toast the result and switch activities accordingly.
As of now, I have tried to do it from the onPostExecute() and it does not work. Somehow, I must get back to my main thread and do it there. How do I do this?
Here is the code:
public class Class1 extends Activity {
JSONObject jObj = null;
#Override
public void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.myLayout);
Button submit = (Button) findViewById(R.id.submitButton);
submit.setOnClickListener(new View.OnClickListener(){
public void onClick(View arg0){
(new CallAPI(restfulCall)).execute();
}
});
}
public class CallAPI extends AsyncTask<Void,Void,String>
{
private String restfulCall = "";
public CallAPI(String command)
{
restfulCall = command;
}
protected String doInBackground(Void... urls)
{
return API.getData(restfulCall);
}
protected void onPostExecute(String result) {
try {
jObj = new JSONObject(result);
} catch (JSONException e1) {
e1.printStackTrace();
}
try {
if(jObj.get("status").toString().equals("success"))
{
Toast.makeText(getBaseContext(),"Registration Succesful",Toast.LENGTH_LONG).show();
Intent intent = new Intent(Class1.this,Success.class);
Class1.this.startActivity(intent);
}
else
{
Toast.makeText(getBaseContext(),jObj.get("error").toString(),Toast.LENGTH_LONG).show();
Intent intent = new Intent(Class1.this,Error.class);
Class1.this.startActivity(intent);
}
} catch (JSONException e) {
e.printStackTrace();
}
}
}
}
use equals for comparing Strings intead of == as :
if(jObj.get("status").toString().equals("success")
instead of
if(jObj.get("status").toString() == "success")
Related
I am new to android development.
I want to perform some db operations and then, want to start a new activity. I have written AsyncTask code below.
I am getting error on startActivity call. Please help me out.
private class AsyncTaskRunner extends AsyncTask<String, String, String> {
Context mainContext;
public AsyncTaskRunner(Context mainContext){
this.mainContext=mainContext;
}
#Override
protected String doInBackground(String... params) {
publishProgress("Sleeping..."); // Calls onProgressUpdate()
try {
sql.updateRelations();
} catch (Exception e) {
e.printStackTrace();
}
return "";
}
#Override
protected void onPostExecute(String result) {
InitActivity.progress.dismiss();
Intent intent = new Intent(mainContext, MainActivity.class);
if(mainContext!=null){
mainContext.startActivity(intent);
((Activity)mainContext).finish();
}
}
#Override
protected void onPreExecute() {
InitActivity.progress.show();
}
#Override
protected void onProgressUpdate(String... text) {
}
}
If your async task is an inner class of your activity then do the below
Intent intent = new Intent(YourActivityName.this, MainActivity.class);
if(mainContext!=null){
mainContext.startActivity(intent);
((Activity)mainContext).finish();
}
Else if your async task is a separate class then try the below
Intent intent = new Intent((YourActivityName)mainContext, MainActivity.class);
if(mainContext!=null){
mainContext.startActivity(intent);
((Activity)mainContext).finish();
}
If it doesn't work please post your logs so i can be of better help.
I am currently using an AsyncTask to fetch the JSON array when pressing a button. After that i have another button called ParseJson which opens a new activity in which a list is shown with the JSONArray.
What i would like, is to have one button instead of 2, but since the getJSON button (first button above) is starting a backgroundtask which needs to be finnished first, before launching the other activity (ParseJSON button), this doesnt work in one button right now.
I heard something about using a loading dialog, but i am quite new to this and have no idea how to solve it.
This is the code i use, but i also need the the value from the Textview in the background task. I will send the value of the textview to a php file (by POST) which fetches the data from the database.
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
}
public void getJSON(View view) {
TextView txv = (TextView) findViewById(R.id.orderID);
txv.getText().toString;
//I need this value in the backgroundtask later
new BackgroundTask().execute();
}
class BackgroundTask extends AsyncTask<Void, Void, String>
{
String json_url = "MYJSONURL";
String JSON_STRING;
#Override
protected String doInBackground(Void... params) {
try {
URL url = new URL(json_url);
HttpURLConnection httpURLConnection = (HttpURLConnection)url.openConnection();
InputStream inputStream = httpURLConnection.getInputStream();
BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(inputStream));
StringBuilder stringBuilder = new StringBuilder();
while ((JSON_STRING = bufferedReader.readLine())!=null)
{
stringBuilder.append(JSON_STRING+"\n");
}
bufferedReader.close();
inputStream.close();
httpURLConnection.disconnect();
return stringBuilder.toString().trim();
} catch (MalformedURLException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
return null;
}
#Override
protected void onProgressUpdate(Void... values) {
super.onProgressUpdate(values);
}
#Override
protected void onPostExecute(String result) {
json_string = result;
}
}
public void parseJSON(View view)
{
if(json_string==null)
{
Toast.makeText(getApplicationContext(), "First Get JSON", Toast.LENGTH_LONG).show();
}
else
{
Intent intent = new Intent(this, DisplayListView.class);
intent.putExtra("json_data", json_string);
startActivity(intent);
}
}
Instead of starting the AsyncTask by a button press you code in a way by which it can be started as soon as your main activity is launched. Use onProgressUpdate method of the AsyncTask which will show some progress, once that method is finished your data is loaded. Then you use one button to parse and display the data in the list.
You may refer this to know more about AsyncTask methods
You can have a look at the below code to understand how communication can happen between an activity and AsyncTask. For simplicity I have a count loop running inside AsyncTask which will update the progress on the activity.
Please be warned that this code communicates with the same activity which started the AsyncTask. So, if you would like to perform any such background task, you should be having the AsyncTask attached to your second activity.
public class MainActivity extends Activity {
private ProgressBar mProgress;
private int mProgressStatus = 0;
TextView percentage = null;
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
mProgress = (ProgressBar) findViewById(R.id.progress_bar);
percentage = (TextView) findViewById(R.id.percentage);
new CountProgress().execute();
}
class CountProgress extends AsyncTask<Void, Integer, Void> {
#Override
protected void onPreExecute() {
mProgress.setProgress(0);
super.onPreExecute();
}
#Override
protected Void doInBackground(Void... unused) {
for (int i=0; i<101;i++ ) {
if (isCancelled())
break;
publishProgress(i);
SystemClock.sleep(200);
}
return(null);
}
#Override
protected void onProgressUpdate(Integer... progress) {
if (!isCancelled()) {
mProgress.setVisibility(View.VISIBLE);
// updating progress bar value
mProgress.setProgress(progress[0]);
// updating progess percentage text
percentage.setText(progress[0].toString() + "%");
}
}
#Override
protected void onPostExecute(Void unused) {
Toast.makeText(getApplicationContext(), R.string.done, Toast.LENGTH_SHORT).show();
}
}
}
A full working app code can be downloaded from here and you can extend it further for your needs.
My program crashs after doInBackground and doesn't come to onPostExecute.
My activity code's related parts are like this:
public static class News {
private String title;
private String content;
private Bitmap image;
public News(String nTitle, String nContent, Bitmap nImage){
title = nTitle;
content = nContent;
image = nImage;
}
}
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_news);
final AsyncTask task = new DatabaseConnection(this, Method.GET_ALL_NEWS).execute();
try {
task.wait();
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
public final void fillListView(List<News> news){
recentNews = news;
if(recentNews != null && !recentNews.isEmpty()){
((ListView)findViewById(R.id.lvNews)).setOnItemClickListener(this);
final int size = recentNews.size();
final String newsTitles[] = new String[size];
for(int i=0; i<size; ++i)
newsTitles[i] = recentNews.get(i).title;
((ListView)findViewById(R.id.lvNews)).setAdapter(new ArrayAdapter<String>(this, android.R.layout.simple_list_item_1, newsTitles));
}
}
#Override
public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
final News selectedNews = recentNews.get(position);
startActivity(new Intent(this, ANewsActivity.class)
.putExtra("title", selectedNews.title)
.putExtra("content", selectedNews.content)
.putExtra("image", BitmapFactory.decodeResource(getResources(), R.drawable.ic_launcher)));
}
My AsyncTask code's related parts are like this:
public DatabaseConnection(Context nContext, Method nMethod){
method = nMethod;
context = nContext;
}
#Override
protected void onPreExecute() {
progressDialog = new ProgressDialog(context);
progressDialog.setMessage(context.getString(R.string.database_connection_wait_message));
progressDialog.setTitle(R.string.database_connection_wait_title);
progressDialog.show();
}
#SuppressWarnings("incomplete-switch")
#Override
protected Void doInBackground(String... params) {
if(method != Method.NONE){
open();
try{
switch(method){
case GET_ALL_NEWS:
final ResultSet rs = conn.createStatement().executeQuery("select baslik, metin, resim from haberler");
news = new ArrayList<News>();
while(rs.next())
news.add(new News(rs.getString(1), rs.getString(2), BitmapFactory.decodeStream(rs.getBlob(3).getBinaryStream())));
break;
}
} catch (SQLException e) {
e.printStackTrace();
} finally {
close();
}
}
return null;
}
#SuppressWarnings("incomplete-switch")
#Override
protected void onPostExecute(Void temp) {
if (progressDialog.isShowing()){
progressDialog.dismiss();
switch(method){
case GET_ALL_NEWS:
((NewsActivity)context).fillListView(news);
break;
}
method = Method.NONE;
}
}
I want UI thread waits until database operations finishes.
By the way there is no initialization problem at variables etc and database returns proper infos and my "news" variable is filled normally.
By the way again I realized it is WORKING on PHONE, STUCKS on EMULATOR interestingly (if I remove wait() method and its try-catch block on main thread code).
It's difficult to say what is crashing without the logcat output, but it would most likely be the main thread of the app because of the .wait() method you are calling in onCreate(). Your onCreate() cannot wait - it must initialize and exit, otherwise you are blocking the main thread of your app and defeating the purpose of the AsyncTask.
My MainActivity has 2 views: TextView and a Button. On button click, I am running an AsyncTask which further creates 10 new AsyncTasks for network operations. Every new task creation is delayed by 1 sec. The code is:
public class MainActivity extends ActionBarActivity
{
TextView tv;
Button t;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
tv = (TextView) findViewById(R.id.textView1);
t = (Button) findViewById(R.id.toggleButton1);
t.setOnClickListener(new OnClickListener()
{
#Override
public void onClick(View v)
{
getData();
}
});
}
void getData()
{
SuperNetworkAsyncTask s = new SuperNetworkAsyncTask();
s.execute("");
}
private class SuperNetworkAsyncTask extends AsyncTask<String, Void, String>
{
#Override
protected String doInBackground(String... urls)
{
for(int i=0;i<10;i++)
{
{
nTask = new NetworkAsyncTask();
nTask.execute("");
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
return "";
}
#Override
protected void onPostExecute(String result)
{
}
}
private class NetworkAsyncTask extends AsyncTask<String, Void, String>
{
#Override
protected String doInBackground(String... urls)
{
return String.valueOf(System.currentTimeMillis());
}
#Override
protected void onPostExecute(String result)
{
tv.setText(result);
}
}
}
I was expecting that the moment first NetworkAsyncTask execute method is called, it will start execution. But when I run it, I do not find any NetworkAsyncTask begin its execution until the control comes out of SuperNetworkAsyncTask. Is there any way to push the execution of NetworkAsyncTask thread as soon as execute method is called?
Some clarifications:
Why NetworkAsyncTask are created by SuperNetworkAsyncTask? Because If I create the NetworkAsyncTask in main thread, I get my UI freeze for some time.
Why making 10 object? The purpose of NetworkAsyncTask is to read data from a server at interval of 1 sec for n seconds, here n=10.
Part 2: Updates after doing some tests.
Observation 1:
As a fellow Brian shared a way to avoid creating AsyncTasks in nested way, I tried his code:
void getData() {
Runnable runnable = new Runnable() {
#Override
public void run() {
for (int i = 0; i <= 10; i++) {
nTask = new NetworkAsyncTask();
nTask.executeOnExecutor(AsyncTask.THREAD_POOL_EXECUTOR);
try {
Thread.sleep(1000);
}
catch (InterruptedException e) {
e.printStackTrace();
}
}
}
};
new Thread(runnable).start();
}
This freezes my UI for few seconds and then the screen is updated in a fraction of second. It is quite surprising to me too.
Observation 2:
With java.lang.Thread, I experimented to make sure that 1) The threads should be executed right away when run() called. 2) The next task will be created only after previous task is finished.
Code:
public static void main(String[] args) {
myThread m;
for (int i=0;i<10;i++)
{
m=new myThread(String.valueOf(i));
m.start();
synchronized (m)
{
try {
m.wait();
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
}
public class myThread extends Thread
{
public String name = "";
public myThread(String n)
{
name = n;
}
public void run()
{
synchronized (this)
{
System.out.println(" Thread Name = " + name);
try {
Thread.sleep(2000);
} catch (InterruptedException e) {
e.printStackTrace();
}
notifyAll();
}
}
}
Output:
Thread Name = 0
Thread Name = 1
Thread Name = 2
Thread Name = 3
Thread Name = 4
Thread Name = 5
Thread Name = 6
Thread Name = 7
Thread Name = 8
Thread Name = 9
Based in this, I updated my NetworkAsyncTask & SuperNetworkAsyncTask as:
private class NetworkAsyncTask extends AsyncTask<String, Void, String>
{
#Override
protected String doInBackground(String... urls)
{
synchronized (this)
{
return String.valueOf(System.currentTimeMillis());
}
}
#Override
protected void onPostExecute(String result)
{
synchronized (this)
{
tv.setText(result);
notifyAll();
}
}
}
private class SuperNetworkAsyncTask extends AsyncTask<String, Void, String>
{
#Override
protected String doInBackground(String... urls)
{
for(int i=0;i<10;i++)
{
nTask = new NetworkAsyncTask();
nTask.execute(url);
synchronized (nTask)
{
try {
nTask.wait();
} catch (InterruptedException e1) {
e1.printStackTrace();
}
try {
Thread.sleep(2000);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
return "";
}
#Override
protected void onPostExecute(String result)
{
}
}
With this code the wait() keeps on waiting indefinitely.
Finally I replaced:
nTask.execute(url);
with
nTask.executeOnExecutor(THREAD_POOL_EXECUTOR, "");
This worked well as expected.
The UI will be updated only at onPostExecute(). See notes on AsyncTask
Click here! And Try to avoid 10 AysncTasks, it does not make any sense.
You don't need to use a "super async task" use a runnable and then create new async tasks in parallel
void getData() {
Runnable runnable = new Runnable() {
#Override
public void run() {
for (int i = 0; i <= 10; i++) {
nTask = new NetworkAsyncTask();
nTask.executeOnExecutor(AsyncTask.THREAD_POOL_EXECUTOR);
try {
Thread.sleep(1000);
}
catch (InterruptedException e) {
e.printStackTrace();
}
}
}
};
new Thread(runnable).start();
}
Post honeycomb you can specify to run async tasks in parallel
An AsyncTask should be started in the UI thread, not on the one doInBackground runs on. You could call publishProgress after every sleep, and spawn each AsyncTask in the resulting calls to onProgressUpdate, which run on the UI thread.
I need to pass the async task result to the calling class. I have created a separate ASync class which is called from other classes. I am passing the response from Async task in "Post Execute" method to calling class method but getting null point exception. Below is my calling method in
public boolean getCategories() {
serUri = "categories.json";
WebServiceAsyncTask webServiceTask = new WebServiceAsyncTask();
webServiceTask.execute(serUri,this);
return true;
}
The method to be executed with result from below aysnc task is
public void writeJSONArray(final JSONArray result)
{
try {
for (int i=0; i<result.length();i++){
JSONObject c = result.getJSONObject(i);
String name = c.getString("catname");
}
} catch (JSONException e) {
e.printStackTrace();
}
}
WebServiceAsyncTask Class:
public class WebServiceAsyncTask extends AsyncTask<Object,Void,JSONArray> {
ROMSjson roms;
private static JSONArray json = null;
private Context context = null;
protected JSONArray doInBackground(Object... params) {
// TODO Auto-generated method stub
String serviceUrl = (String) params[0];
final HTTPHelper httph = new HTTPHelper(serviceUrl,context);
if(serviceUrl.equalsIgnoreCase("categories.json")) {
json = httph.fetch();
}else if(serviceUrl.equalsIgnoreCase("categories/create"))
{
}
return json;
}
#Override
protected void onPostExecute(JSONArray result) { // invoked on the ui thread
roms.writeJSONArray(result);
super.onPostExecute(result);
}
I am getting null point exception when roms.writeJSONArray(result) is called. The result is correctly received before this command. I checked with Log statement. Also if I write the writeJSONArray method in my Async class instead of calling class, all works fine.
I am not sure if I am missing something in passing the result or while calling methods. Please advise. Thanks.
null pointer exception
because roms is null
you are declaring ROMSjson roms; inside WebServiceAsyncTask but not initializing it !
and using it inside `onPostExecute(JSONArray result)
roms.writeJSONArray(result);` // here roms in null
so initialize roms before using it !
Here is the problem:
else if(serviceUrl.equalsIgnoreCase("categories/create"))
{
// if it falls to this condition then your json object appears to be null
}
Hope this helps.
Interface is the best way for passing data between classes.
create a public interface
public interface WebCallListener{
void onCallComplete(JSONArray result);
}
what to do in your class?
public class WebServiceAsyncTask extends AsyncTask<Object,Void,JSONArray> {
ROMSjson roms;
private static JSONArray json = null;
private Context context = null;
//update
private WebCallListener local;
public WebServiceAsyncTask(WebCallListener listener){
local=listener;
}
/////
protected JSONArray doInBackground(Object... params) {
// TODO Auto-generated method stub
String serviceUrl = (String) params[0];
final HTTPHelper httph = new HTTPHelper(serviceUrl,context);
if(serviceUrl.equalsIgnoreCase("categories.json")) {
json = httph.fetch();
}else if(serviceUrl.equalsIgnoreCase("categories/create"))
{
}
return json;
}
#Override
protected void onPostExecute(JSONArray result) { // invoked on the ui thread
//update
super.onPostExecute(result);
local.onCallComplete(result);
}
From Your Calling class.
public class CallingClass extends Activity{
protecte void oncreate(Bundle b){
new WebServiceAsyncTask(new WebCallListener() {
#Override
public void onCallComplete(JSONArray result) {
//play with your response
}
});
}
}