I'm working on a simple I.M android app for class that makes queries to a server and displays the results (i.e messages) on a ListView. One of the requirements is that the app display an indefinite progress bar while the query is being made.
This means that I have to set a ProgressBar widget to View.VISIBLE when the query begins and to View.INVISIBLE when the query is over.
The trouble I'm having is that the query is a background function defined in a different Java class, so while I'd like to do something like this:
ProgressBar pb = (ProgressBar) findViewById(R.id.progressBar);
pb.setVisibility(View.VISIBLE);
...
...
uploader.execute(myCallSpec);
...
...
pb.setVisibility(View.INVISIBLE);
This doesn't work, because the server call runs in the background. Using this code, it's as if the progress bar was never even displayed.
How do I set the progress bar to be displayed when the service call begins and then back to invisible when the call is completed?
Go ahead with AsyncTask
class MyTask extends AsyncTask<Void, Void, Void> {
private ProgressBar pb;
public MyTask(ProgressBar pb) {
this.pb = pb;
}
#Override
protected void onPreExecute() {
super.onPreExecute();
pb.setVisibility(View.VISIBLE);
}
#Override
protected Void doInBackground(Void... params) {
//Your query here.
return null;
}
#Override
protected void onPostExecute(Void result) {
super.onPostExecute(result);
pb.setVisibility(View.GONE);
}
}
MyTask mt = new MyTask(pb);
mt.execute()
But in real project I suggest you to use something like RoboSpice. As well AsyncTask doesn't handle activity lifecycle by default.
UPD:
There is two ways to have access to ProgressBar instance inside AsyncTask:
Just declare it as inner class and save ProgressBar in field of your outer (main) class
Pass reference via constructor. (see modified example)
In your AsyncTask class in onPostExecute method you should stop progressbar
protected void onPostExecute(Long result) {
pb.setVisibility(View.INVISIBLE);
}
It call(on ui thread) after task is finished
Related
I need to process some data when the user click the button in one activity, so the screen looks like the app stops for 2-3 seconds. It isn't a lot but I want to give the user information that everything is ok and IMO the best way will be the progressbar which is visible only when data are processed.
I found the code of ProgressBar and it looks like this:
<ProgressBar
android:id="#+id/loadingdata_progress"
style="?android:attr/progressBarStyle"
android:layout_width="50dp"
android:layout_height="50dp"
android:layout_alignBottom="#+id/fin2_note"
android:layout_centerHorizontal="true"
android:indeterminate="true"
android:visibility="invisible" />
and inserted it on the middle of my layout.
And to try if the progressbar works, I put this code
loadingimage= (ProgressBar) findViewById(R.id.loadingdata_progress);
loadingimage.setVisibility(View.VISIBLE);
into onCreate method and everything looks fine.
Then I recreated the code to show this progressbar only if the data is processed.
After click the user invoke this method
public void fin2_clickOnFinalization(View v)
{
loadingimage= (ProgressBar) findViewById(R.id.loadingdata_progress);
loadingimage.setVisibility(View.VISIBLE);
// code where data is processing
loadingimage.setVisibility(View.INVISIBLE);
}
and nothing appear on the screen. I don't know where is the mistake. If I found the progress bar by id, It's strange for me that I can control it in onCreate method but in onclick method it's out of my control.
Your UI thread cannot show progress bar cause it is busy due to your data processing. Try to use this kind of code :
public void fin2_clickOnFinalization(View v) {
new YourAsyncTask().execute();
}
private class YourAsyncTask extends AsyncTask<Void, Void, Void> {
#Override
protected Void doInBackground(Void... args) {
// code where data is processing
return null;
}
#Override
protected void onPostExecute(Void result) {
loadingimage.setVisibility(View.INVISIBLE);
super.onPostExecute(result);
}
#Override
protected void onPreExecute() {
super.onPreExecute();
loadingimage.setVisibility(View.VISIBLE);
}
}
EDIT:
AsyncTask let you run code in separate thread and make app more responsive, just put time-consuming code inside doInBackground.
You're not giving the UI time to refresh. Your "data processing" code is running on the UI thread, blocking any visible changes. By the time the system gets control to refresh the display, you've already set it back to invisible.
To fix this, move your processing code to a separate thread or AsyncTask. Then you can set the progress bar to visible, start the task, and have it turn itself invisible once it's done.
I'd recommend AsyncTask for this purpose about 90% of the time on Android, since it comes stock with useful callbacks. The developer guide for it(in the Javadoc linked above) is pretty explicit, and outlines all the steps you need to take.
AsyncTask is too heavily-weighted for such task.
A better much solution
Handler handler = new Handler(getMainLooper());
handler.post(new Runnable() {
#Override
public void run() {
loadingimage.setVisibility(View.VISIBLE);
}
});
Or even simpler (does essentially the same thing as solution above)
runOnUiThread(new Runnable() {
#Override
public void run() {
loadingimage.setVisibility(View.VISIBLE);
}
});
You can try to create a global ProgressDialog not in the layout but in your activity like:
public class MyActivity {
ProgressDialog progress = null;
protected void onCreate(...) {
progressDialog = new ProgressDialog(this);
progressDialog.setCancelable(false);
progressDialog.setTitle("Progress");
}
public void fin2_clickOnFinalization(View v)
{
progress.show();
// code where data is processing
progress.dismiss();
}
}
Hope i it helps
There's a "download" button in each listview item. While the button is clicked, it will start a worker thread to down files. And at the same time, the button changed to progressbar and showing the progress rate.
So please show me some proper ways.
Use an AsyncTask since it has special methods for communicating with the main (UI) thread despite being asynchronous.
Here is an example:
http://android-er.blogspot.com/2010/11/progressbar-running-in-asynctask.html
Something like this:
public class DownloadTask extends AsyncTask<Void, Void, Boolean> {
protected void onPreExecute() {
ProgressDialog() progress = new ProgressDialog(context);
progress.setMessage("Loading ...");
progress.show();
}
protected Boolean doInBackground(Void... arg0) {
// Do work
return true;
}
protected void onPostExecute(Boolean result) {
progress.dismiss();
}
}
This should be nested in your activity class and executed like this:
new DownloadTask().execute();
You will likely need to adjust the asynctask to fit your needs but this will get you started.
I have a button, and when I clicked on it, I load other Activity, onCreate of this I call a method that fills a spinner with data from a Web Service.
Well, When I click at this button the screen stay "frozen" and then shows the Activity. So, I thought that it could be a good thing shows a progress dialog for user, and after gets the return of the Web Service, ends the progress dialog.
I tried use Handler, and now I'm trying to use AsyncTask, but, geting NullPointerException, because my program is filling spinner before web service get called.
private void fillSpinner(){
//runWebService();
new CallWebServiceAsyncTask().execute(null);
mAdapter = new PlanesAdapter(this, allPlanes);
mList.setAdapter(mAdapter);
}
class CallWebServiceAsyncTask extends AsyncTask<Void, Void, Void> {
private ProgressDialog progressDialog;
#Override
protected void onPreExecute() {
progressDialog = new ProgressDialog(PlanesActivity.this);
progressDialog.setMessage("Loading...");
progressDialog.show();
}
#Override
protected Void doInBackground(Void... v) {
runWebService();
return null;
}
#Override
protected void onPostExecute(Void result) {
progressDialog.dismiss();
}
}
because my program is filling spinner before web service get called.
you should fill data after getting data in onPostExecute Method
#Override
protected void onPostExecute(Void result) {
progressDialog.dismiss();
mAdapter = new PlanesAdapter(this, allPlanes);
mList.setAdapter(mAdapter);
}
What #SamirMangroliya suggested is correct but you even need to know where you are going wrong. When you call an AsyncTask you are asking the application to do some actions in the background which will take place in the non-UI thread. Now when you call execute() on your AsyncTask object the application code written in the function doInBackground(Void... v) runs in background and your control returns to the next statement following the call to execute() [new CallWebServiceAsyncTask().execute(null)], which in your case is the action of filling the adapter values. These values are yet to be received from the webservice. The only place where you can be sure that your background action is completed is the function onPostExecute(Void result) where as suggested you can create your adapter.
Now I am doing an Android application.In my application I have to get the data from json page.This operation is taking time delay.So I have to show a progressbar until the fetching process is completed.I used the following code to show progressbar.
public void onCreate(Bundle savedInstanceState) {
//somecode
ProgressDialog progressBar = new ProgressDialog(this);
progressBar.setCancelable(true);
progressBar.setMessage("Loading");
progressBar.show();
Thread thread = new Thread(this);
thread.start();
}
public void run() {
flag=GetFixtureDetailsJsonFunction();
handler.sendEmptyMessage(0);
}
protected boolean GetFixtureDetailsJsonFunction() {
//json parsing code
return true
}
private Handler handler = new Handler() {
#Override
public void handleMessage(Message msg) {
if (flag==true) {
progressBar.dismiss();
}
}
};
Using this code I am getting exception.android.view.ViewRoot$CalledFromWrongThreadException: Only the original thread that created a view hierarchy can touch its views.
AsyncTask is best way for getting response from xml or database. try like this,
private class DownloadQuestion extends AsyncTask<String, Void, String>
{
#Override
protected void onPreExecute()
{
pd = ProgressDialog.show(Activity_SplashScreen.this, "","Please wait...", true,false);
super.onPreExecute();
}
#Override
protected String doInBackground(String... urls)
{
//Write background code here Code
return "";
}
#Override
protected void onPostExecute(String response1)
{
//Some Code.....
if (pd != null && pd.isShowing())
pd.dismiss();
}
}
Instead i would suggest you to implement AsyncTask, which is known as Painless Threading in android.
Using this AsyncTask, you don't need to bother about managing Threads. And its easy!!
FYI, do as follows:
Display ProgressBar in onPreExecute() method.
Do long running tasks inside the doInBackground() method.
Dismiss the ProgressBar inside the onPostExecute() method. You can also do display kinds of operation in this method.
This is a bit strange way to implement this functionality. Instead of fixing that code I suggest you using AsyncTask, which was implemented right for that purpose. See here.
You are trying to access the UI View from another thread which is not eligible.In this case this is your handler.
Instead of trying to access UI thread like this you should use an AsyncTask and do your progressDialog logic in it.
Start showing the progress bar onPreExecute
doInBackground() jobs while progressBar showing
And finallly dismiss your progressBar after your doInBackground() is complete onPostExecute()
I have create the android application program.In this program i am using the progressbar..I put the code for progressbar in the xml layout. my problem is, when i click the button after that only the progreessbar is loaded ,but it will displayed before clicking the button..pls tell some idea..Thanks in advance..
Set android:visibility and android:id attributes for ProgressBar element.
android:visibility="gone" android:id="#+id/your_prg_bar_id"
For the button click add attribute. android:onClick
android:onClick="showProgressBar"
Inside your activity write the method showProgressBar to show progressBar.
public void showProgressBar(View source){
progressBar = (ProgressBar) findViewById(R.id.your_prg_bar_id);
progressBar.setVisibility(View.VISIBLE);
}
try this::
AsyncTask enables proper and easy use of the UI thread. This class allows to perform background operations and publish results on the UI thread without having to manipulate threads and/or handlers.
An asynchronous task is defined by a computation that runs on a background thread and whose result is published on the UI thread. An asynchronous task is defined by 3 generic types, called Params, Progress and Result, and 4 steps, called onPreExecute, doInBackground, onProgressUpdate and onPostExecute
private class xyz extends AsyncTask<Void, Void, Void> {
private final ProgressDialog dialog = new ProgressDialog(tranning.this);
protected void onPreExecute() {
this.dialog.setMessage("Please Wait...");
this.dialog.show();
// put your code which preload with processDialog
#Override
protected Void doInBackground(Void... arg0) {
// put your code here
return null;
}
#Override
protected void onPostExecute(final Void unused) {
if (this.dialog.isShowing()) {
this.dialog.dismiss();
}
}
}
and use this in your button click event ::
new xyz().execute();