CASE: I have a button and list-view in the activity. On click of the button I have added a click listener, which starts a new thread in which I update the progress bar. After the job is done i.e. progress bar is done 100%, I want to update the list-view.
final OnClickListener mStartScan = new OnClickListener() {
#Override
public void onClick(View v) {
// prepare for a progress bar dialog
progressBar = new ProgressDialog(v.getContext());
progressBar.setCancelable(false);
progressBar.setMessage(getString(R.string.text_scanning_inbox));
progressBar.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL);
progressBar.setProgress(0);
progressBar.setMax(totalSms);
progressBar.show();
progressBarStatus = 0;
Thread progressThread = new Thread(new Runnable() {
public void run() {
while (progressBarStatus < totalSms) {
// process some tasks
progressBarStatus = someStuff();
// Update the progress bar
progressBarHandler.post(new Runnable() {
public void run() {
progressBar.setProgress(progressBarStatus);
}
});
}
if (progressBarStatus >= done) {
// sleep 1 seconds, so that you can see the 100%
try {
Thread.sleep(5000);
} catch (InterruptedException e) {
e.printStackTrace();
}
// close the progress bar dialog
progressBar.dismiss();
// this method updates the list
populateList();
}
}
});
progressThread.start();
// try {
// progressThread.join();
// } catch (InterruptedException e) {
// // TODO Auto-generated catch block
// e.printStackTrace();
// } finally {
// populateList();
// }
}
};
PROBLEM: When I update the listview after completion of the task and dismissing progress bar, I get an exception which says that the view can be updated only from the thread in which it is created.
android.view.ViewRoot$CalledFromWrongThreadException: Only the original thread that created a view hierarchy can touch its views.
WHAT ELSE I TRIED: I tried waiting for the thread which is running progress bar to complete and then update listview from the main thread.
try {
progressThread.join();
} catch (InterruptedException e) {
e.printStackTrace();
} finally {
populateList();
}
However, this does not work. It does not show the progress bar at all.
I used this:
private ProgressDialog progressBar;
class MyTask extends AsyncTask<String, Void, String> {
#Override
protected void onPreExecute() {
super.onPreExecute();
progressBar = new ProgressDialog(getApplicationContext());
progressBar.setMessage("please, waiting ...");
progressBar.setCancelable(false);
progressBar.show();
}
#Override
protected String doInBackground(String... params) {
try {
// get info and set them in my model ...
} catch (Exception e) {
e.printStackTrace();
}
return params[0];
}
#Override
protected void onPostExecute(String result) {
super.onPostExecute(result);
if (null != progressBar && progressBar.isShowing()) {
progressBar.dismiss();
}
// do work in UI and set info adapter and refresh list ...
populateList();
myListView.invalidateViews();
}
}
for more information:
http://developer.android.com/reference/android/widget/ArrayAdapter.html#notifyDataSetChanged%28%29
Only the original thread that created a view hierarchy can touch its views.
Here original thread refers to the ui thread. You are attempting to update ui inside a thread which is not possible.
You cannot update ui from the back ground thread. You can use runOnUiThread .
runOnUiThread(new Runnable() //run on ui threa
{
public void run()
{
}
});
I would suggest you to use asynctask
You use use asynctask for this purpose. The onPreExecute(), onPostExecute() are invoked on the ui thread and you can use the same to update ui. You can do your background computation in doInbackground()
http://developer.android.com/reference/android/os/AsyncTask.html
Check the topic under heading The 4 steps.
class TheTask extends AsyncTask<Void,Void,Void>
{
#Override
protected Void doInBackground(Void... params) {
// TODO Auto-generated method stub
// background computation and publish progress
return null;
}
#Override
protected void onProgressUpdate(Void... values) {
// TODO Auto-generated method stub
super.onProgressUpdate(values);
// update progress bar
}
#Override
protected void onPostExecute(Void result) {
// TODO Auto-generated method stub
super.onPostExecute(result);
// cancel the progress bar
}
#Override
protected void onPreExecute() {
// TODO Auto-generated method stub
super.onPreExecute();
//display progress bar
}
}
Load asynctask on the ui thread
new TheTask().execute().
The error you are receiving is because of the fact that you are trying to change the UI components on a secondary thread. You should read this for more information on how to use threads on Android.
You can use the Activity method runOnUIThread() to call the populateList() method or whatever makes the updates on the UI(main) thread. If you read the doc mentioned above, you will find out more about this.
Related
In my application when i click on Button it sometimes shows the progressdialog and sometimes not show the progressdialog on click of button.
Asynchronous Task code is:
public class LoadData extends AsyncTask<Void, Void, Void>
{
ProgressDialog pd;
#Override
protected void onPreExecute()
{
pd = ProgressDialog.show(MainActivity.this, "", "Loading...");
}
#Override
protected Void doInBackground(Void... params) {
// TODO Auto-generated method stub
MainActivity.this.runOnUiThread(new Runnable() {
public void run() {
// TODO Auto-generated method stub
LoadActivities(); // function to load data from url
}
});
return null;
}
#Override
protected void onPostExecute(Void unused)
{
pd.dismiss();
}
}
and on button click event call this as:
btn.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
new LoadMoreData().execute(null);
}
});
the wrong think you are doing is that in doInBackground you use runOnUiThreade . just remove that from your code . It solves your problem.
never use any thread in doInBackground.
Why you have taken run method again in doInBackground, doInBackground method performs computation on a background thread, so no need to take runOnUiThread
MainActivity.this.runOnUiThread(new Runnable() {
public void run() {
// TODO Auto-generated method stub
LoadActivities(); // function to load data from url
}
});
Just write
protected Boolean doInBackground(final String... args) {
try {
LoadActivities();
return true;
} catch (Exception e) {
Log.e("tag", "error", e);
return false;
}
}
And also change new LoadMoreData().execute(); don't write null
btn.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
new LoadMoreData().execute();
}});
Nirali's answer seems correct, just to make further explaination and some edits.
Progress Dialog will be shown by the time doInBackground method returns value. and in your code it just create another thread, and completes execution, so to display progress dialog by the time LoadActivities exectues, execute this statement in the same thread doInBackground executes, so change to following:
#Override
protected Void doInBackground(Void... params) {
// TODO Auto-generated method stub
MainActivity.this.runOnUiThread(new Runnable() {
LoadActivities(); // function to load data from url
return null;
}
i got this progress dialog code:
new Thread() {
#Override
public void run() {
try {
sleep(1000);
}
catch (Exception e) {
Log.e("tag", e.getMessage());
}
// dismiss the progress dialog
progressDialog.dismiss();
}
}.start();
and i got text that will apear after some httprequest actions:
editText2.setText(stringEr);
how do i sync between them? i want that the text will be hidden untill the progress will finish
tnx!
You have to use Handlers to update your UI. A little modification here,
new Thread()
{
#Override
public void run()
{
try
{
//Instead of sleep, call your http request method here.
handler.sendEmptyMessage(0);
}
catch (Exception e)
{
Log.e("tag", e.getMessage());
}
// dismiss the progress dialog
progressDialog.dismiss();
}
}.start();
And create a handler in onCreate(),
Handler handler=new Handler()
{
public void handleMEssage(Message msg)
{
if(msg.what==0)
editText2.setText(stringEr);
}
};
i think you should use AsyncTask for that and you can hide in OnPreExecute Method i mean when asynctask in started and show in OnPostExecute method. after complete the progress.
Android skip the painful Threading concept, Use Asyntask class.
http://developer.android.com/reference/android/os/AsyncTask.html
private class UIOperation extends AsyncTask<String, Void, String> {
#Override
protected void onPreExecute() {
//show dialog
}
#Override
protected String doInBackground(String... params) {
//collect data
return null;
}
#Override
protected void onPostExecute(String result) {
//dismiss dialog
//update UI
}
}
i want to add a progress Dialog button when i click on this button before the new activity apperar, i think i don't need a thread, i did search but i find only that i need to do a thread and many other think it s not clear
i just want when i clik on a progress Dialog say to the user to wait so a few sec the other activity will appear that's all:
btn_newsfeed.setOnClickListener(new View.OnClickListener() {
public void onClick(View view) {
// Launching News Feed Screen
Intent i = new Intent(getApplicationContext(), CustomizedListView.class);
startActivity(i);
}
});
There are three different different ways in which you can use a ProgressDailog -using threads, handlers and async tasks.
here a example of async task for using a progress Dialog
private class Operation extends AsyncTask<String, Void, String> {
#Override
protected String doInBackground(String... params)
{
// code to be executed in background thread
for(int i=0;i<5;i++) {
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
return "Executed";
}
#Override
protected void onPostExecute(String result) {
// runs on UI thread and updated UI after executing doInBackground
progressDialog.dismiss();
}
#Override
protected void onPreExecute() {
ProgressDialog progressDialog = ProgressDialog.show(MainActivity.this, "Title ", "Loading...");
progressDialog.show();
}
#Override
protected void onProgressUpdate(Void... values) {
// runs on UI thread and starts first
}
}
I've developed an application that takes content from the internet and shows it accordingly on the device's screen . The program works just fine , a little bit slow . It takes about 3-4 seconds to load and display the content . I would like to put all the code that fetches the content and displays it in a background thread and while the program is doing those functions , I would like to display a progress dialog. Could you help me do this ? I would like especially to learn how to put the code in a background thread.
MY CODE
public class Activity1 extends Activity
{
private ProgressDialog progressDialog;
#Override
public void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
new AsyncTask<Integer, Integer, Boolean>()
{
ProgressDialog progressDialog;
#Override
protected void onPreExecute()
{
/*
* This is executed on UI thread before doInBackground(). It is
* the perfect place to show the progress dialog.
*/
progressDialog = ProgressDialog.show(Activity1.this, "",
"Loading...");
}
#Override
protected Boolean doInBackground(Integer... params)
{
if (params == null)
{
return false;
}
try
{
/*
* This is run on a background thread, so we can sleep here
* or do whatever we want without blocking UI thread. A more
* advanced use would download chunks of fixed size and call
* publishProgress();
*/
Thread.sleep(params[0]);
// HERE I'VE PUT ALL THE FUNCTIONS THAT WORK FOR ME
}
catch (Exception e)
{
Log.e("tag", e.getMessage());
/*
* The task failed
*/
return false;
}
/*
* The task succeeded
*/
return true;
}
#Override
protected void onPostExecute(Boolean result)
{
progressDialog.dismiss();
/*
* Update here your view objects with content from download. It
* is save to dismiss dialogs, update views, etc., since we are
* working on UI thread.
*/
AlertDialog.Builder b = new AlertDialog.Builder(Activity1.this);
b.setTitle(android.R.string.dialog_alert_title);
if (result)
{
b.setMessage("Download succeeded");
}
else
{
b.setMessage("Download failed");
}
b.setPositiveButton(getString(android.R.string.ok),
new DialogInterface.OnClickListener()
{
#Override
public void onClick(DialogInterface dlg, int arg1)
{
dlg.dismiss();
}
});
b.create().show();
}
}.execute(2000);
new Thread()
{
#Override
public void run()
{
// dismiss the progressdialog
progressDialog.dismiss();
}
}.start();
}
}
Check ASyncTask, its specifically created for such tasks.
public Runnable NameOfRunnable = new Runnable()
{
#Override
public void run()
{
while (true)
{
// TODO add code to refresh in background
try
{
Thread.sleep(1000);// sleeps 1 second
}
catch (InterruptedException e)
{
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
};
now start this with
Thread name = new Thread(NameOfRunnable);
name.start();
How to work with Background Thread.
Note: Do not work with UI with this background thread.
AsyncTask.execute(new Runnable() {
#Override
public void run() {
//TODO background code
}
});
Hope this would help you.
I want show dialog after finish Thread.
In thread I am changing TextView's Value like as 0 to 100...
When TextView Value is reach 100 then i want to show dialog..
What i do for it.
Thanks in advance...
Code Snippet:
final Thread thread = new Thread(new Runnable()
{
#Override
public void run()
{
synchronized (this)
{
try
{
for(int i=0 ; i<speed; i++)
{
final int value=i+1;
wait(3000/speed);
Test.this.runOnUiThread(new Runnable() {#Override public void run()
{
accText.setText(String.valueOf(value));
}});
}
}
catch (InterruptedException e)
{
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
});
thread.start();
this is asyntask code snippet...
class setTextBackgroundTask extends AsyncTask<String , Integer, Void>
{
#Override
protected void onPreExecute()
{
}
#Override
protected Void doInBackground(String... params)
{
Thread th = new Thread();
int value;
for(int i=0 ; i<speed; i++)
{
value=i+1;
publishProgress(value);
try {
th.sleep(3000/speed);
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
return null;
}
#Override
protected void onProgressUpdate(Integer... values)
{
accText.setText(String.valueOf(values[0]));
System.out.println("Value=="+values[0]);
super.onProgressUpdate(values);
}
#Override
protected void onPostExecute(Void result)
{
showShareDialog();
}
}
This document explains how you can create dialogs.
Please note that you will have to do any dialog creation code on the UI thread.
You already have code that runs something on the UI thread, just do that outside the loop,but with the dialog creation code inside.
You should use AsyncTask: subclass AsyncTask, override doInBackground() to execute your time consuming action on another thread, and then override onPostExecute() to show your dialog.
Note that you cannot change UI elements from a non-UI (background) thread. AsyncTask takes care of that for you: it calls doInBackground() on a new thread and then calls onPostExecute() on the UI thread as soon as the background task is complete.